texts:
I've got this circuit. The target generates an identical PWM signal to control the intensity of 3 LEDS. But I would like to protect the output of these optocouplers with this TVS:

I'm not sure if using the TVS SMBJ78Ca is the best option: https://www.fairchildsemi.com/datasheets/SM/SMBJ100A.pdf

Max Vce [ACPL-271-500E] = 80V

The design schematic is only to distribute the PWM intensity signal to three different LES drivers.

The PWM outputs only control de intensity pin of a LED driver tps92551 [Pin3 DIM].

Best regards.

The design schematic is only to distribute the PWM intensity signal to three different LES drivers.

The PWM outputs only control de intensity pin of a LED driver tps92551 [Pin3 DIM].

Best regards.


texts: Measuring the voltage drop across electrical components doesn't match the calculated values

texts:
I have a newbie question regarding circuit analysis.

I have a simple circuit with a voltage source of +4.32V (output of a u7805C voltage regulator), an 18K Ohm resistor, a normally open push button, and a 39K Ohm resistor.

The schematic of the circuit is shown below:

simulate this circuit – Schematic created using CircuitLab

Below is a table comparing the calculated and simulated values vs the values measured with an oscilloscope.

When I measure the value across the 18KOhm resistor I get a 4.16V when the switch is open and closed. Shouldn't the measured voltage drop across the 18KOhm be the same as that in the simulation?

EDIT and new findings

This is the circuit, I am using a solderless breadboard. I am using a microcontroller development board's (MSP430FR6989) to power the circuit, the 5V and GND pins are connected to a uA7805C voltage regulator to

The schematic of the circuit is shown below

simulate this circuit

Here is a picture of the circuit

Measuring the Voltage between the rails:

Measuring the output voltage of the regulator:

Measuring the voltage drop across the 18KOhm resistor:

However, I replaced development board power and replaced it with a 9V Alkaline Battery and I got different results get any issues:

These are the results:

I think the problem was with MSP430 powering the circuit, but that is what I don't understand I am using is only to power the circuit (5V power supply), and the voltage between the 5V pin and the GND pin was 5.12V

I think I figured what the problem was

I think the problem was the ground clip of the oscilloscope was connected to a point other than the ground of the circuit.

I connected it like that:

and I got these oscilloscope readings when the switch is open:

These are the oscilloscope readings when the switch is closed:

As mentioned the Oscilloscope's ground probe should only be connected to the ground, it is not like a multimeter where we can probe a voltage with reference to any other voltage point.


texts: What is this weird behaviour I am observing with doing a loopback around MAX3232?

texts:
So this is my pretty little circuit that I made. AFAIK all connections are fine and I have tested them using multimeter for any shorts.

I was actually testing the circuit by loop back shorting J1's TX and RX line using a jumper wire. I have powered this circuit using one of my STM board that provides 3.3V.

The STM32 board is powered using USB connected to the laptop. On the J2 side, I have connected a RS232 to USB converter.

Working fine when TX and RX are shorted, until the random character started popping up as seen in the next image.

All I did was halfway while connected I took out the jumper wire from RX side and left it connected to TX and then all those jumbled characters came whenever I typed something.

Is my open RX pin working like an antenna ?

EDIT 1 :
Datasheet I referred


texts: Do VHDL for loops only allow incrementing by 1?

texts:
The VHDL for loop looks like this e.g:

for i in -5 to 5 loop
  -- Do something
end loop;

Can we only increment by 1 or have a arbitrary step size value?


texts: STM32 USART with DMA -- which interrupts to use?

texts:
I'm working on firmware for an STM32F103 which is communicating over RS232 at 115200 baud with a motor controller. The motor controller (a Copley Xenus XTL) operates on a "speak when spoken to" protocol. I'm using the ASCII programming interface in the linked documents. The STM32 always be sending the same command ("g r0x18") to poll a register, and the motor controller replies with a variable number (~4-10 bytes) of characters terminated by a carriage return ("v 12345", where the number of digits is variable). I have code to parse the response and pull a numeric value out of it. Once the response is parsed, the register poll command should be transmitted to the motor controller again. The STM32 is also reading an ADC channel over DMA in circular mode in the background.

I'd like to implement this using the DMA controller to make everything as non-blocking as possible, but I'm a bit confused as to which interrupts I should be using and when they fire. Without using the DMA controller, the parsing code currently resides in the USART RXNE interrupt. Suppose I transmit command and the motor controller starts to reply. I believe the RXNE interrupt fires for each received byte, but what about the DMA transfer complete interrupt? Is there even any functional difference in this case between using the DMA TC interrupt and the USART RXNE interrupt?


texts: Identify a component (compoent with hex screw) on a garage door opener

texts:
I'm trying to disable the receiver circuit on a garage door opener due to security concerns with the old rolling code algorithms and can't identify this component. I've seen these before but I'm not sure what it is or what its purpose is.

Regarding disabling the receiver circuit. I've already un-soldered the antenna and a resistor to the antenna with no positive results.

Thanks!


texts: IC chip identification request - Analog Devices

texts:
Please help me to identify this IC. I guess it is an Analog Devices chip

The signs say Q00 635

The oval line above with RA3 is an antenna, and this IC acts perhaps as detector (or amplifier) . The device is receive only - an electric field (EMC) meter and the displayed part is the E-field to voltage(?) converter.

Thanks


texts: How to Change PushON - PushOFF Power Button to HoldON - HoldOFF

texts:
Using the integrated circuit MC14093B (quad 2-input NAND) you can be able to convert a pushbutton to a latching ON-OFF toggle switch.

This circuit is able to do that:

simulate this circuit – Schematic created using CircuitLab

Some applications, to prevent accidental powerON / powerOFF use an HoldON / HoldOFF system.

What is needed to change the circuit's behavior to XsecondsHoldON / XsecondsHoldOFF?. Let's say Xseconds = 3-5 seconds.


texts:
I have 8 thermistors and I must make sure that each of them is inside a temperature window. They all have the same window and I don't care which or how many are inside the valid range, I just need to know if all of them are inside the (same) window or not. This is to be a hardware-only solution, so software-sequencing of ADC reads is out of the question.

My best solution currently is to use a bunch of comparator ICs and implement a separate window-comparator for each thermistor. To optimize the solution, I can use a number of quad comparators, each with an open-drain output so that I can connect them all up. Still, in essence it is the same circuit. The reference/trigger voltages I can make once, buffer, then supply to all comparators.

I do feel stupid for just simply throwing a bunch of comparators at the problem. I am not sure if there isn't any better way, I'm mostly trying to optimize board space. Is there some creative way you know? For example, select min/max voltages of all thermistors and use a single window comparator (EDIT: two comparators ofc), which IMHO would lead to a larger solution and is thus not a good answer, I'm just mentioning this for inspiration.

EDIT: I know that a software-based solution would be the best. That is why I mentioned it right in the beginning and upfront to prevent everybody suggesting it. The reason the problem is defined this way is because this is a safety circuit, and specifications require me to implement a hardware-only solution in addition to a software-monitor. So the software-based solution is already there, I "just" need to find the best way to implement the hardware-based one.


texts: What is the effect of remapping ports on a USB hub

texts:
I'm using the USB2517 for a project.  It's a seven port hub, and I'm using six of them.  I'm working through the config settings, and I'm stumped by the port remap registers.  The datasheet gives the following text (page 34 in the datasheet):

  Port  remap  register  for  ports  1  &  2
  When  a  hub  is  enumerated  by  a  USB  Host  Controller,  the  hub  is  only  permitted to report how many ports it has; the hub is not permitted to select a  numerical  range  or  assignment.  The  Host  Controller  will  number  the  downstream ports of the hub starting with the number '1', up to the number of  ports  that  the  hub  recognizes.
  The  host's  port  number  is  referred  to  as  "Logical  Port  Number"  and  the  physical  port  on  the  hub  is  the  “Physical  Port  Number".  When  remapping  mode  is  enabled  (see  PRTMAP_EN  in
  Register  08h:  Configuration  Data  Byte  3)  the  hub's  downstream  port
  numbers  can  be  remapped  to  different  logical  port  numbers  (assigned  by  the  host).
  Note:
  The  OEM  must  ensure  that  Contiguous  Logical  Port  Numbers  are
  used, starting from #1 up to the maximum number of enabled ports;
  this ensures that the hub's ports are numbered in accordance with the way  a  Host  will  communicate  with  the  ports

So, I've got seven ports, DS[1:7].  These are the "Physical Port Numbers".  The host enumerates these as a range, which we can call PORT[1:7].  These are the "Logical Port Numbers".  By writing to this register, I'm mapping DS[x] to PORT[y], or outwrite [see what I did there?] disabling it

Why would I want to remap my ports, however?  What does that gain me over letting the hub automatically handle remapping?  Is there some kind of port priority in the USB 2.0 spec that allocates additional bandwidth to lower numbered ports?  Is it just in there to keep overcautious engineers up at night?

Edit:  The hub is able to automatically remap ports to ensure contiguous logical ports if physical ports in the middle of the range are disabled if PRTMAP_EN (08h:3) is low.  Is there anything to be gained by manually remapping them in a different order than the hub would automatically do it?


texts: Using a 12VAC Transformer For a LM317T Power Supply

texts:
I have found a circuit diagram for a regulated power supply using a LM317T regulator which I wish to build as my first electronics project.

The only problem is that instead of a 24 VAC transformer I have a 12 VAC transformer and I do not have a 3300uF 35V capacitor, the highest rated one I have is 2200uF 16V.

Is it safe for me to replace these parts in the circuit with the only effect being the output will be a maximum of 12V?


texts: What is the reason of RAM modules conflicts in terms of computer architecture?

texts:
What is the reason of such conflicts?
I read a book "Computer architecture" by Andrew Tanenbaum, but didn't understand the reasons may cause conflicts with memory with different timings, frequencies.


texts: NMOS as a pass transistor showing weird behavior when VG = 0. Please help me to understand. (Newbie in electronics engineering)

texts:
I used LTspice to simulate my circuit and used the monolithic NMOS transistor in the library.

I thought the gate voltage being 0 means the transistor is switched OFF. In that case why isn't the output at B not 0?

Then I tried connecting a resistor to the output side.

As you can see when I connected a 1000K resistor to the output side, the NMOS transistor behave almost like what I want. How did this happen? My first thought was when the gate voltage is 0, the voltage at the output is floating, and therefore when I connected a big enough resistor it gets to 0. Is that correct?

Finally, in the place of the resistor, I tried connecting a capacitor of 1pF and this is how the circuit behaved. Here also when the gate voltage is 0, still there is some voltage at the output. Why?


texts:
My ADC (LTC2323, 16 bit, 5MSps, http://www.linear.com/product/LTC2323-16) has an internal reference (4.096V) which is provided at output pins REFINTx. Now I need (roughly) half of this reference voltage for the ADC driver. The reference output is buffered and referred to another pin REFRTNx - to my understanding for proper decoupling but otherwise "close enough" to GND. The datasheet does not explicitely confirm or deny that I can load this pin externally but it somewhat suggests I can. What I found in the datasheet:

REFOUT1 (Pin 12): Reference Buffer 1 Output. An onboard buffer nominally outputs 4.096V to this pin. This pin is referred to REFRTN1 and should be decoupled closely to the pin (no vias) with a 0.1µF (X7R, 0402 size) capacitor and a 10μF (X5R, 0805 size) ceramic capacitor in parallel. [...]

REFRTN1 (Pin 11): Reference Buffer 1 Output Return. Bypass REFRTN1 to REFOUT1. Do not tie the REFRTN1 pin to the ground plane.

Under "Internal Reference Characteristics" it is stated: REFOUT1,2 Output Impedance: 0.25 Ohm.

Furthermore:

Internal Reference: The LTC2323-16 has an on-chip, low noise, low drift (20ppm/°C max), temperature compensated bandgap reference. It is internally buffered and is available at REFOUT1,2 (Pins 12, 26). The reference buffer gains the internal reference voltage to 4.096V for supply voltages VDD = 5V and to 2.048V for VDD = 3.3V. Bypass REFOUT1,2 to REFRTN1,2 with the parallel combination of a 0.1µF (X7R, 0402 size) capacitor and a 10μF (X5R,
0805 size) ceramic capacitor to compensate the reference buffer and minimize noise. The 0.1µF capacitor should be as close as possible to the LTC2323-14 package to minimize wiring inductance. Tie the REFINT pin to V DD to
enable the internal reference buffer.

Can I load this pin externally and if yes - how much? Can I attach a resistive divider of, say 10k, to get 1/2 of the ref voltage? Or at least the input of a simple op-amp follower?


texts: Cascode Amplifier: clarifications about output resistance and working point of transistors

texts:
let's consider this cascode amplifier (here the reference):

I have the following questions:

1) Is it good as a voltage amplifier or as a transconductance amplifier?

I do not understand it because:
- voltage gain is evaluated, so it seems that it is used as a voltage amplifier
- when the output resistance is evaluated, we see that it is very high, that is not good for a voltage amplifier. Moreover, I have read in my notes that cascode is used sometimes in order to increase the output resistance in order to have a better behaviour as a current source. But if it is true, I do not understand how can it be a current source, since the load will receive a current which is not equal to the drain current, but to I0 - drain current (except the case in which the load is a short).

2) Do we prefer designing Q1 and Q2 to work in saturation or in triode? And why?


texts: Cable rating - What is the max amp for a 1.5-1.75mm cable?

texts:
I have a new hob (magnetic induction plate). It requires 7200W/32A.
The power grid's voltage is 230V (Europe).

I have already installed a thick cable and I want to use it (it would be difficult to change it). But I don't know its diameter (and at the moment no tools to measure it) but it seems to be about 1.5mm or rather 1.75mm diameter. The cable is about 3meter long and it says:

CableTeam    VDE    HAR    HD 5VV-F    301.5

What is the max amp for this cable?

I will run this cable in the back of the over. There is a 6-9 cm space between the oven and the wall. And the oven has its own cooler. The temperature in the back of the oven stays relatively low (about room temp).


texts: Does slew rate of an op-amp affect a low pass filter?

texts:
Lets say we have an active low pass filter with an OP-AMP. Does slew rate of this op-amp affect the filter? what will change? From what I understand, since the op-amp is charging and unchanging the capacitor with different currents passing through the resisor, there will a maximum rate of change in the output voltage, ie slew rate, which make the signal distorted.

Am I thinking correctly?


texts:
Assume we have an inductor with the following values:
$$B=B_0 \cdot sin(2\cdot \pi \cdot f \cdot t)$$
$$N=10$$
$$r=5cm$$
$$B_0 = 2mT$$
$$f=50Hz$$
$$R=5 \Omega $$
How much current runs through the inductor as function of time?
Well I don't know the inductance, so I tried this:
$$U=-\frac{d \phi}{dt}$$
$$\phi = B \cdot A = 2mT \cdot sin(\pi \cdot 100 \cdot t) \cdot \pi \cdot (2\cdot10^{-2})$$
$$U = -\frac{d}{dt} 2mT \cdot sin(\pi \cdot 100 \cdot t) \cdot \pi \cdot (2\cdot10^{-2})^2 $$
$$U = -\frac{d}{dt} 8 \cdot \pi \cdot 10^{-7}T \cdot sin(\pi \cdot 100 \cdot t) $$
$$U = -8 \cdot \pi \cdot 10^{-7}T \cdot \frac{d}{dt} sin(\pi \cdot 100 \cdot t) $$
$$U = -8 \cdot \pi \cdot 10^{-7}T \cdot 100\cdot \pi \cdot cos(\pi\cdot 100\cdot t) $$
$$U = -800 \cdot \pi^2 \cdot 10^{-7}T \cdot cos(\pi\cdot 100\cdot t) $$
$$I=\frac{U}{R}= - \frac{800 \cdot \pi^2 \cdot 10^{-7}T \cdot cos(\pi\cdot 100\cdot t)}{5\Omega} = -1.579\cdot 10^{-4}\cdot cos(\pi\cdot 100\cdot t)A$$

I never saw something like that anywhere else so I'm a bit unconfident if this approach was really correct. Is this correct? Is there maybe another (easier) approach?

Additional information:
After reading the comments I should add some more information.
As you may have thought, this is an exercise. Here is the full text:
A coil with N turns is brought into a magnetic field. The area of the coil is perpendicular to the field. The coil has a radius r and the field changes after [see B above]. The coil has a resistance of R.
Biot-Savart was discussed but is explicitly not necessary.
Solivng this task should be pretty easy, so I get the feeling that this task either lacks some values or I misunderstood it.


texts: Many electric stovetops are operated by an infinite switch, which pulses the current on and off for intervals determined by the dial setting. The actual control is effected via a bi-metal switch that moves as it is heated. I was wondering whether the temperature of the heating element has any effect on the timing of the switch. In other words, if I put a pot of cold water on the stove, thereby lowering the resistance of the element, will that speed up the heating of the bi-metal in the switch, causing it to stay on longer? Or is the bi-metal heated by a completely separate circuit?


texts:
I have a project where an nRF51822 (BLE Nano v1.5) is an I2C master and communicates with an Atmega328. I have communication working over I2C just fine using various pins. However, when attempting to use pin P0_10, the pin specified by the manufacturer, as the standard I2C SDA pin, it doesn't work.

I have tried on multiple BLE Nano boards and also on a BLE400 development board to no avail. As previously stated I can use other pins for my I2C bus and it will work with no issues.

I am using mbed OS with these boards. When using Arduino IDE then I2C works fine, however the entire project is written in mbed and porting to Arduino isn't an option. The mbed pin mapping for this board also specifies P0_10 as the default SDA pin.

This is a huge issue for me as I have a big batch of custom PCBs on order that use the standard I2C pins. If this issue can't be fixed in software then it means having to manually fix each individual board.

I'm really struggling with this one so any suggestions are very welcomed!


texts: audio jack ground to main earth ground, safe or not?

texts:
My audio amplifier got some unclear noise from ground. amplifier ground is connected to player, and use some decent RCA cables, also tried to add ground loop isolatior to RCA cables. None of them works. Finally, a friend recommended me to try to connect audio RCA jack ground to main earth ground, like the picture shown below.
I tried this, it works perfectly. But just wonder any potential safety issue? thank you very much.


texts: Mixing analog audio signals with resistors

texts:
I am creating a type of mixer for 2 audio inputs into 1 output so i can use 1 pair of headphones with 2 computers without buying an expensive mixer with a amp

Currently i have 1k 1/2W metal resistors on both left and right input signals and nothing on ground

It works great and i can hear both inputs fine though the headphones but it really needs a amp and isnt usable

My question is: What resistors should i be using so there isnt so much volume loss?


texts:
I do not understand why my verilog code doesnot produce output  of arbiter puf when I am trying to implement on fpga.

module arb( e,a,q );

 (* KEEP="TRUE" *)   input e;

   (* KEEP="TRUE" *) input [7:0]a;

  (* KEEP="TRUE" *)  output q;

  (* KEEP="TRUE" *)  wire [7:0] t,b;

  (* KEEP="TRUE" *)  mux m0(e,e,a[0],t[0]);

   (* KEEP="TRUE" *) mux m1(e,e,a[0],b[0]);

  (* KEEP="TRUE" *)  mux m2(t[0],b[0],a[1],t[1]);

   (* KEEP="TRUE" *) mux m3(b[0],t[0],a[1],b[1]);

   (* KEEP="TRUE" *) mux m4(t[1],b[1],a[2],t[2]);

   (* KEEP="TRUE" *) mux m5(b[1],t[1],a[2],b[2]);

   (* KEEP="TRUE" *) mux m6(t[2],b[2],a[3],t[3]);

   (* KEEP="TRUE" *) mux m7(b[2],t[2],a[3],b[3]);

   (* KEEP="TRUE" *) mux m8(t[3],b[3],a[4],t[4]);

  (* KEEP="TRUE" *)  mux m9(b[3],t[3],a[4],b[4]);

   (* KEEP="TRUE" *) mux m10(t[4],b[4],a[5],t[5]);

   (* KEEP="TRUE" *) mux m11(b[4],t[4],a[5],b[5]);

   (* KEEP="TRUE" *) mux m12(t[5],b[5],a[6],t[6]);

  (* KEEP="TRUE" *)  mux m13(b[5],t[5],a[6],b[6]);

  (* KEEP="TRUE" *)  mux m14(t[6],b[6],a[7],t[7]);

   (* KEEP="TRUE" *) mux m15(b[6],t[6],a[7],b[7]);

   (* KEEP="TRUE" *) dff d1(t[7],b[7],q);

endmodule

module mux(input a,b,s,output q    );

 assign q=s?b:a;

endmodule

module dff(input d,clk,output reg q    );

   always@(posedge clk)

  q<=d;

endmodule


texts: Differential to single ended conversion using transformer

texts:
I need to convert differential data signal to single ended signal using isolation transformer
Expected configuration is

I cannot able to measure differential signal so i have used the below configuration

The Input is fed from function generator 5V sine signal, the output is connected to oscilloscope. The same input should be displayed at output. But the output was not in the expected way. The amplitudes are changing for different frequencies, the output amplitude gets distorted for lower frequencies (i.e, 50KHz) and gets amplified at high frequencies (10MHz) .
In first images, first transformer part number : MABA-007159-000000 (link :https://cdn.macom.com/datasheets/MABA-007159-000000.pdf) and second transformer part number : MABAES0060 (link : https://www.mouser.in/datasheet/2/249/MABAES0060-961544.pdf).
Now, I am giving input(-2.5V to +2.5V sine wave , 32KHz) from function generator and the output is observed at osciiloscope.
Observations :
The signal amplitude was attenuated at 32KHz, 320KHz, 200KHz
at 5MHz the output was same as input but at >15MHz, output was amplified.
Now I swapped the input and output. same procedure was repeated , same observations were made.
can you please suggest any part numbers for achieving this application
The circuit should work in bi-directional way i.e input should act as output also and output should act as input also i.e when data is fed at data+ and data-, this circuit should convert the signal to single ended , when input is O/P in first image then it should convert the single ended signal to differential signal.
The frequency of signal is 32KHz and signal is -12 to +12V square wave.


texts: 220V 0.2A converted to 12V 5A, where are the missing amperes?

texts:
I have an AC adapter at home that reads (roughly) the following:

uses 220-240v AC 50Hz at 0.2A
produces 12V DC at 5A

I'm a little surprised that it uses 0.2 amps and produces upto 5. Here's what happens in my mind. Please stop and correct me whenever I'm wrong.

Amperes is the measure of current. It is measured in Coulomb/s: 1A = 1C/s
1C is a fixed number of electrons (can't find the number again, what was it?)
Therefore, 1A is a fixed number of electrons that flow through a wire per second.

So, if 0.2C/s go in my adapter, how can 5C/s go out? Does this have something to do with AC versus DC?

As most writers below answered, these numbers are wrong. In reality, the adapter outputs 5v at 2A... my bad. However, the point is the same, it provides more Amps than it eats.


texts: Function generator in the nano or micro volt range

texts: I'm looking to get a hold of a wave function generator that can produce signal in the micro or nano volt peak to peak range.  The lowest I've been able to find is in  the millivolt range.  Do these exist?


texts: I wanted to confirm that my approach is correct for wiring multiple devices together communicating over I2C when each node is utilizing DC\DC converters. Should I be including a ground connection over the I2C cable (#1) or would that cause a ground loop with the main 20 foot GND connection.


texts: Thevenin equivalent of the input of an op amp?

texts: In the image above, the subcircuit in the box in the top circuit is reduced to the subcircuit in the light box below it using Thevenin's Theorem. I don't really see how to get a Thevenin equivalent out of the first circuit. I spent a while on it to no avail - could someone please give me a hand? How can you make a Thevenin equivalent of the subcircuit highlighted in the top circuit?


texts:
I had a LiPo battery with specifications of 14.8 V, 2200 mAh, 23.6 Wh with 25 C rating.
Can any one tell me how to calculate the resistance value.
Current= 25C x 2.2 A= 55 A
Power P = VI = 14.8 V x 55 A = 814 W
P= I X I X R
R = P/(I x I) = 814 / (2.2 x 2.2)  = 169 ohms
This is what I got. Could any tell me whether the calculations are correct or wrong


texts: Problems with Switching a Solenoid Valve with a Relay

texts:
I've been trying to switch a solenoid valve using a relay controlled by a signal from a microcontroller. The circuit works fine when connected to a normal load like a light bulb, but some random behavior (of the digital circuitry) was observed when connecting the circuit to the (highly inductive) solenoid valve. The problem was reduced to some degree by adding a snubber circuit between the terminals to the load and increasing the decoupling capacitor for the circuit to 1000uF. Although the circuits works now (with the occasional randomness, about 1 in 100 false trigger of the relay), there is one more persistent problem. The relay contacts close with a very large noise (almost like a crack of a whip). The contacts open with no problem. The relay also switches normally with a lightbulb load. Does anyone have any idea why this is and how I can fix it?

The circuit I used is shown below.

The valve used is a 230V Danfoss solenoid valve.


texts: How do I calculate parameters of LC filter from component values?

texts: I have found this schematics and want to know corner frequency and characteristic impedance of this filter. How do I calculate it?


texts: What is the "short-range outdoor model (ITU-1411) with a distance-dependent path-loss" mentioned in this paper?

texts:
I am reading the paper Graph Embedding Based Wireless Link Scheduling with Few Training Samples, and trying to reproduce some of its results. This paper aims to solve the wireless link scheduling problem, by building a neural network that takes geographic data as inputs (distances between transmitter-receiver pairs). You can skip to my questions if you are already familiar with this problem.

Model and Problem Formulation

Suppose there are \$L\$ pairs of transmitters and receivers. Let \$h_{kj}\$ be the channel from transmitter \$k\$ to receiver \$j\$. Then the SINR (sum to interference-plus-noise ratio)  of the \$j\$-th pair is
$$SINR_j=\frac{x_jp_j|h_{jj}|^2}{\sum_{k\neq j}x_kp_k|h_{kj}|^2+\sigma_N^2}$$
where \$p_j\$ is the transmitting power of transmitter \$j\$, and \$x_j\$ denotes whether it is activated or not. \$\sigma_N^2\$ is the power of additive white Gaussian noise. The problem is to maximize the sum-rate
$$\sum_{k=1}^LB\log(1+SINR_k)$$
subject to \$x_j\in\{0,1\}\$, where \$B\$ is the bandwidth.

My Questions

The authors propose a neural network architecture to solve this problem, based only on the geographic data, i.e. distances between the transmitters and receivers, and uses no CSI (channel state information) as input. However, to train the network, I have to generate training samples, which can be computed via a classical algorithm for this problem (e.g. FPLinQ), which requires CSI.

This is where I run into trouble: How should I generate the training samples? The paper says to generate the geographic points uniformly randomly, which means no CSI is generated during this stage. However, to use FPLinQ, I must have CSI to begin with. So I deduce that there must be some way to calculate the CSI using geographic data, transmitting power, and some other information.

In particular, if I am understanding this correctly, then I need a formula to estimate \$|h_{kj}|\$ at distance \$d\$ from a transmitter, when other parameters like the transmitting power, carrier frequency, bandwidth, antenna height, etc. are given. There is only one mention of this matter in the paper, and I quote as follows:

  We use the short-range outdoor model ITU-1411 with a distance-dependent path-loss as the channel model.

There was also a reference to this recommendation (no longer available):

  Recommendation ITU-R P.1411-8. International Telecommunication Union, 2015.

Is there such an estimation for \$|h_{kj}|\$ in ITU-1411? If not, is there other reasonable way to find \$|h_{kj}|\$? Note that you may consider the following information as given:

location coordinates of each transmitter and each receiver.
transmitting power
noise spectral density
bandwidth
carrier frequency
antenna height

As I am not a professional in this field, I'd appreciate it if you could explain to me (briefly) some other concepts:

What does \$h_{kj}\$ mean, physically? What is its unit?
Is \$\sigma_N^2\$ precisely the noise spectral density? Should I change the unit of \$\sigma_N^2\$ and \$p_j\$ to Watts-per-Hertz before plugging them into the expression of SINR?


texts: Connecting all grounds directly to the supply's ground?

texts:
I currently have this layout on my PCB:

As it appears, the grounds from the different components are connected to each other and then connected into the supply's ground.

In the context of amplifiers, an answer from one of my questions explains that small signal grounds should be separated from large signal grounds to prevent distortion because of the signals mixing within the PCB traces. I did that on one of my amplifier boards and it worked.

Questions:

What happens if I separated all of the grounds from the components and directly connected them instead into the supply's ground?
Is this technique better than just separating the grounds into small and large signals before connecting them into the supply's ground?


texts: How does the shape of the coil relate to the magnetic field around it?

texts: I want to know if the shape of the coil affects the path of the magnetic fields around it. The two different shapes that I have are Helical coil and a spiral coil (in a plane).


texts: Reduce a noisy 14vdc to 12v dc 3A with linear regulator or a switching regulator

texts:
I would like to build a very simple constant current and constant voltage power circuit to power a net book at 12V 3A from my car supply that has lots of ac ripple in it from alternator that I cannot seem to fix. It's an old ford focus so I'm just looking to use parts from old power supplies and a few other boards like an lcd monitor board  with functioning starter thingy. Not sure what it does but looks like all possible parts may be just on one bored waiting to be recycled.

So to be clear
car supply with engine off 12v
engine on 14vdc fluctuating with rpm to 15v with ac ripple
want to get 12vdc 3 Amps no matter what rpm the engine is at.

Ps I know I should fix the source of the issue but I cannot find any grounding issues anywhere

I made a choke/ inductor but it does not seem to have made any difference. Where should I look for grounding issues ?  I mean I have cleaned the ones I could see in the engine bay but could it be an issue with a ground wire of the lights at the back of the car?  Also  from memory inductors are rated in James's or Henry or something similar. So how do I select a correct inductor value from scrap parts so may not have that specific part. What voltage should I use for the cap to get rid of the whine?  I used same method as mentioned here http://www.instructables.com/id/Car-Radio-Noise-Eliminator/


texts: RC high pass Circuit Step Input why C Initially acts as SS

texts:
In an RC high pass circuit, when you apply a step input, the capacitor doesn't have any drop initially. My professor's explanation for this was that the capacitor doesn't change voltages instantaneously. He presented the formula \$ V= \frac1C\int_0^T idt\$.

Could someone explain to me why there is no drop across the capacitor? I didn't understand the explanation given by my professor.


texts: How to calculate voltage in an open resistor circuit

texts:
I have an open circuit that looks like this:

I can measure the voltage at these points using a voltmeter:

A -> D: 4.65V (the batteries)

B -> D: 4.3V

C -> D: 4.23V

Say I did not have a voltmeter: What formula would I use to determine the voltage between B -> D and C -> D?


texts: Two different circuits on one SPDT switch?

texts:
I have an air condition condensation pump that has a float switch which interrupts the control signal from the thermostat to the outside aircon unit if the water level in it gets to high - i.e. if the pump fails for some reason.  That's wired into the NC half of the float switch.

What I'm hoping to accomplish is to wire a small battery powered siren through the NO side of the switch so that if the float switch is triggered, the aircon is powered down (which is already it's current behavior) and the siren starts sounding, letting me know I have an issue.  Is it a problem to have the common used for two completely different circuits?  I'm thinking not since I'm just using the switch to complete circuits, but I'm not entirely sure and don't feel like burning up a control board somewhere.

Here's my diagram if it helps explain it better.

simulate this circuit – Schematic created using CircuitLab


texts: Protective measure against powering inductive loads

texts:
From various chip manufacturer articles and other post in this site, I still have doubts on my circuit for switching inductive loads.

I have two setup here that both switches an inductive but using diferent MOSFET one is a P-Channel and the Other is N-Channel. A zener diode is placed on the Gate and source of both, the value for this zener is calculated to be greater than your typical Vgate voltage and less than the Fets Maximum Vgs rating.

The best suppression for inductive seems to be a Schottky and zenner parrallel to the inductive load. Schottkey should atleast handle the full current of the inductor (1A to 2A which is pretty common). For the Zener selection is seems to be  geater than supply voltage yet less than the fets Vds(max).

As for my questions:

When the coil collapses, are there danger of the current going back through the mosfets?
For the NMOS setup in blue line is there danger of it going back to the power rails? I do not want to stress my PMICs
For the PMOS is that ground safe to be connected directly to the logic grounds? I would like the setup to be able to have an alternate function where it can power digital ICs where having the same ground is important


texts: Sequence of capacitor's charge and discharge in voltage quadrupler

texts:
I was taking a lecture about diode and ended up stuck on understanding voltage quardupler below:

On first positive (+) half cycle, C1=VM.
On first negative (–) half cycle, C1 is discharged, and together with induced voltage provide C2=2VM.
On second positive (+) half cycle, C2 is discharged and with induced voltage provide C1=VM and C3=2VM.
On second negative (–) half cycle, C1 and C3 are discharged and with induced voltage provide C2=2VM and C4=2VM.

And here are my questions:

On first positive half cycle, can induced voltage VM charged on capacitor C3 or C2 instead? If diode D1 is conducted, then D3 should be conducted as well as it shares same bias. Is this due to KVL or currents tendency to flow on short circuit then opened capacitor due to constant voltage difference?
On first negative half cycle, how to set up KVL? After C1 is discharged and C2=2VM, I tried to set up KVL just to make sure. But since C1=0, I could only find -VM and 2VM from induced voltage and C2. What did I do wrong?
On second positive half cycle, how did 2VM from C2 transferred to C3? Although D1 and D3 are currently conducted, that doesn't mean reverse bias can now pass through the conducted diode like forward bias do. Did current somehow passed through D2 from C2 to C3 despite capacitor's polarization? Or did it went through inductor without affecting C1?
On second negative half cycle, how did voltage got distributed C2=2VM and C4=2VM? Why not C2=3VM and C4=VM if total 4VM is supplied from C1 and C3 with induced voltage?

I did asked to professor, but he kept saying that current and voltage behave differently, which I couldn't understand what he was trying to say here.


texts:
I have designed a PCB which has LM1117 (for 3.3V), Micro USB connector, MCP2200 usb-to-uart bridge, 12 MHz SMD crystal and few passive components.

We have been observing the PCB for some weeks and observed that the PCB doesn't work everytime. When I connect to any system, sometimes system throws an error "USB Device not recognized" (in windows) or "Device read/write descriptor failed" (in Linux) and then it doesn't work for hours and start working after sometime. I have reviewed my circuit and didn't have any solution to solve this issue. After resoldering the board and replacing old components several times, we have ruled out soldering/component issue. I think somehow the crystal is not able to start or there could be some race condition between voltage at Vcc and RST pin but I am not sure how to find the real problem and solve it with MCP.

The schematic of MCP2200 is shown below:

The layout of my PCB: (MCP2200's Pad is in green and left side of the picture with USB connector at top left corner)

EDIT:

The crystal that I am using is this.


texts:
Busses provides to IC the ability to communicate to each other. But this communication can be blurred due to noise coming from or outside the circuit. I know there is ways to lower the impact of perturbation:

Differential bus line. The information is bring from one IC to another thanks to two twisted wires. Since these two wire are very close to each other, they will both be impact by the noise. The receiver compute the difference between the two voltage to get the real value. The CAN bus use this technique :

Some protocol can trigger error in the bus and some times even "repair" it.

Is there other methods to improve the quality of communication use by busses?


texts: Why is my LC filter Bode flattening out to 20dB/dec in my Simscape simulation?

texts:
I just made an LC filter Matlab Simulink simulation and I don’t know why the Bode diagram is flattening out.

After the resonance it falls steeply, but after that it sets at 20dB/decade. Shouldn't it be 40dB/decade?

It is a second order filter.
The inductance is 1.6uH and the capacitance is 330uF.

I checked at 150kHz the input and ouput signals. Accordin to my calculations it is -35dB. It is the samme on the Bode diagram


texts: I'm going to design amplifier, requirement is that impedance for in should be more than 20kohm, impedance for out should be less than 50ohm, and voltage gain should be more than 200. So I'll make cc-ce-cc amplifier, but how can I choose transistor for each cc, ce, cc? And is it better to chooose transistor first and after that choose Rc, Re...and then R1, R2...etc? Or is there any other better way(order) to design it? Any guide will be appreciated. Thanks


texts: Strange oscillation when drving motor with PMOS

texts:
I am trying to drive a 24V DC motor with IRF5305 PMOS. I am generating ~300Hz PWM signal with an AVR microcontroller and level-shifting it to 12V-24V signal to drive MOSFETs gate.
I need to use a PMOS because this will get added to an existing machine.

I am also measuring current tru the motor with ~1 Ohm resistor on the source. But am getting some weird measurements. MCP6022 op amps are powered from 5V so I need to reduce the voltage then get the difference across the resistor (24V is not totally stable) and then amplify the difference by the same amount which then gets feed to a comparator. Also inverting and non-inverting inputs on OA1 have clamping schottky diodes to 5V.

This is how I got everything set up:

simulate this circuit – Schematic created using CircuitLab

And these are the results I get when driving the motor:

Blue trace is MOFETs gate which gets a nice 12-24V signal. Pink is connected to the MOFETs drain pin where these oscillations occurs. And yellow trace represents output from AO1 the differential amplifier, weird shapes.

I was expecting to see a sawtooth yellow trace without these giant bumps and peaks. Also the pink trace looks a bit weird, when the blue trace is high (24V) shouldn't the pink trace gradually approach ground (as the power is dissipated by the diode)?

What is going on? How can I fix it?

P.S.

I have to admit I've used a 12V motor connected to 24V line but it was under no more than 50% duty cycle and I turned it off more or less as soon as I got the readings. Did I damage the motor? (it looks like it is spinning ok)


texts: What is the purpose of resistor Ra in this simple vaccum tube voltage amplifier circuit?

texts:
Came across this in a book, there's a brief explanation of why there's said resistor in the circuit:

" ... it should be obvious that if we apply an audio
signal voltage to the grid (i.e., vary the grid voltage)
then current in the valve is bound to vary too. We can
put this current variation to good use by putting a
resistance in series with the valve so that a
corresponding audio voltage is generated across the
resistor, which is also called the load. "

Yet I can't quite understand the need for the resistor to be there in order to create the second amplified voltage signal, won't the amplified voltage signal be there anyway whether there's a resistor or not?


texts: What is the typical delay relative to to the maximum delay?

texts:
I have a board with a number of ICs, an FPGA, and some flash and RAM devices.  The board is designed based on worst case conditions, as it should be.  The critical combinatoric path has a maximum delay of 100 ns (as an example).

A few number of these boards are to be used in the laboratory for an application where it is required the that actual combinatoric latency is shorter than 100 ns.

The conditions for the boards running in laboratory are expected to be typical device process, typical supply voltage, and room temperatur (ambient).

What can be expected as typical delay of the combinatoric path, relative to the maximum delay?

I know there will not be an exact answer, but maybe there is some rule-of-thumb for what to expect.

Update: For a start I looked into delay for 7483 and 7496 where there was some datasheet showing both maximum and typical delay, and the typical delay for these range from 55% to 75% of the maximum delay.  I think at least it quantifies the area to expect.


texts:
I'm trying to make a negative voltage power supply, mainly for opamps. I did some googling and found a circuit I like, so naturally before making it, I wanted to simulate it first.

It has 12V on the input and inputs around +12 and -12V or there about if you take the diode voltage drops into account. However LTspice just calculates that there's 12V at the output and the -12V output is at 0V as is the gnd. I've no clue if this is a bug or if I'm doing something wrong. I've tried electrolitic and nonpolarised capacitors and the default diodes as well as some randomly picked ones and some 1N4007 ones. The output is always the same apart from the +12V which obviously changes with the different voltage drops across the diodes.
Does anyone know what's going on and why?
Here's a picture of the circuit as well as the output I measure at the supposed -12V

P.S. I've tried another simulation software and it worked properly.

Here's a picture of the circuit working properly with a 12V DC supply. The points measured are the two wires.

Here's a link to a video where a guy builds the circuit and it seemingly works.
video
He measures DC volts, but I'm not sure if he actually uses a DC source. That's why I wanted to simulate it.


texts: Interfacing Vector(VN1610) CAN Simulator with an OBD reader (Freematics One+ B)

texts:
I am using a Freematics One+ B for my project and to avoid developing and testing in a car, i would like to simulate ODB messages. I already have a Vector CAN emulator (VN1610) which creates proper CAN messages.

The problem i am facing is, the CAN emulator i have just provides a GND,CAN_ HIGH and CAN_LOW. On the other hand, the ODB scanner (Freematics One+ B) has  more pins that connect with the actual Car ODB port, namely:

4,5 : signal ground and chassis ground (i will hook them together for now)
6,14 : CAN_H, CAN_L (goes to corresponding can pins)
7,15, ... : Other vendor specific pins such as IS0 9141 (not related)
16 : Battery Voltage 12V

My question is, do i also need to hook up an external 12V battery to Pin 16 for this to work, or is there something i am missing and its not even possible to do this.


texts:
I'm a software guy and am dabbling a bit with arduino recently. I don't understand many things when it comes to taking a circuit board schematic and doing it in real life.

For instance, at this tutorial: http://blog.makezine.com/projects/make-34/the-dryer-messenger/, I don't understand what to do with this: (that is how I build out the circuits that he's describing in these bullets or in the schematic attached to the post.)

Since the dryer runs on AC, current flows in both directions, causing the voltage to swing positive and negative. The Arduino can only sample positive voltages, so I used a voltage divider to bias the sensor’s output. The volt- age divider uses two 10K resistors (R1 and R2) to obtain 1.65V from the 3.3V supply.
The current sensor has a fairly linear output up to 1V at 30A, which means the Arduino will read 0.65V or 2.65V when the sensor sees 30A. Capacitor C1 goes between the sensor and the Arduino to filter out noise.

I would really appreciate a simpler schematic and some understanding of what's going on.


texts: How do I power many devices off of a low voltage microcontroller?

texts:
I'm new to electronics.
I have a GENIE 08 microcontroller, and I want to control multiple LEDs from one pin, and a few buzzers from another, and an LCD from one too.
I am worried that the power supplied from the output pins will not be suitable for this.
I am going to be running the controller from a 3V supply.
Is a relay with another supply going to be the best option for this project?
Any help in understanding this would be appriciated


texts:
I'm using an Arduino to read an analog signal from an electret microphone.
Here is the circuit:

But I will be powering it with 5V from the Arduino,

So would this work okay?
Thanks!


texts: Why is a voltage across emitter and base required in a bipolar transistor?

texts:
I read the reply to this question but I cannot really make sense of it:
In an NPN transistor, why doesn't current flow without applying a base voltage?

if I have a npn-transistor and and apply a voltage between emitter and collector which is let's say 10 V , why is no charge flowing from emitter to the base already?

As I understand the pn junction between base and collector, it is in reverse bias due to the external voltage and will not allow any holes from the base or electrons from the collector to cross the barrier. If due to a voltage between base and emitter bigger than 0.7 V however electrons flow into the base they can drain through the collector.

Now, why can't the applied emitter-collector voltage cause flow of electrons into the base (in a sense of pushing the electrons from the emitter over the potential barrier just as in a forward biased diode?) Then we would have free electrons in the base that could then flow to the collector.

Thank you for your help!


texts: Connect a bipolar stepper motor to a breadboard

texts: I would like to connect a bipolar stepper motor, with a connector as the one in the picture, to a breadboard. Is there any adapter I can use?


texts: Can any one explain why the direction of H is -Z and +Y ? once I do the cross product and multiply it by -100 , I get -Z and -Y as directions.


texts: I have three DS18B20's. I can't tell if any of them are working correctly

texts:
I have three DS18B20's (or I believe at least two of them are DS18B20's). I am currently reading them through an embedded Linux board (Raspberry Pi in this case).

I have two of the sensors in a breadboard, they give seemingly accurate temperatures. The third one is one of those DS18B20's enclosed in a "waterproof" cable from Ebay like this:

When I read the sensors I get the following readings:

pi@raspberrypi:~ $ cat /sys/bus/w1/devices/28-*/w1_slave
45 01 4b 46 7f ff 0b 10 84 : crc=84 YES
45 01 4b 46 7f ff 0b 10 84 t=20312
57 01 4b 46 7f ff 09 10 c7 : crc=c7 YES
57 01 4b 46 7f ff 09 10 c7 t=21437
60 01 80 80 1f ff 80 80 2e : crc=2e YES
60 01 80 80 1f ff 80 80 2e t=22000

So what this command does is simply get all the sensors and read from them. Pretty simple. Divide t=20312 by 1000 and you get 20.312°C

But the odd thing is that the third sensor will only ever give temperature measurements that are to within 0.5 degrees, whereas the other two are capable of measuring down to what seems to be 0.1 degrees. At first I thought that the third one was broken, but when I checked the datasheet it clearly specifies that the part is accurate to ~0.5 degrees.

I have made a table of the values I'm getting:

Breadboard Sensor #1 | Breadboard Sensor #2 | Cable Sensor
21.937                 21.562                 22.00
21.812                 21.562                 22.00
20.468                 20.478                 22.50
19.584                 20.201                 27.00
19.625                 19.687                 28.00

So now I'm totally confused. Are the breadboard sensors broken, or is the cable? If they are all working, they why is that two of them seem to have a higher resolution?

Edit: I've been searching around more and it seems that there a few people who have encountered this, and other people have suggested that they might be fake chips!

Update: The device driver for the sensors (https://www.kernel.org/doc/Documentation/w1/slaves/w1_therm):

  The driver also doesn't support reduced precision (which would also
  reduce the conversion time).


texts:
So, I got my 74190 counter shows number like this
 9-8-7-6-5-4-3-2-1-0-5-4-3-2-1-0-5-4-3-2-1-0-5-4-3-2-1-0 and so on.

My questions:

What can I do to change the output count down into 5-4-3-2-1-0-5-4-3-2-1-0 and so on?
When it changes 0 into 5 it moves so fast. How could I fix this one?


texts:
I'm having trouble with a boost converter I made: it outputs 1.2V with no load and 2.4 with one. I expect to draw 0.25 Amps MAX with Roughly 0.2 Amps continuous. My battery pack is 2P2S NiMH with the cells having 2.4AmH capacity

Code:

byte val=127;

void setup()
{
  analogReference(INTERNAL1V1);
  pinMode(A3,INPUT);
  pinMode(4,OUTPUT);
  analogWrite(4,val);
}

void loop()
{
  if(analogRead(A3)>512)
  {
    val-=1;
    analogWrite(4,val);
  }
  else if(analogRead(A3)<512)
  {
    val+=1;
    analogWrite(4,val);
  }
//endif
  delay(1);
}

Schematic:

simulate this circuit – Schematic created using CircuitLab

No, I will not buy something off of the self. I want to learn my mistakes and correct them.


texts: circuit analysis to find current and then voltage across resistors

texts:
This was one of my assignment questions, I am on it since last 3 hours but not able to solve it. Here the source voltage in the circuit shown in Fig. is 100 V.

I need to find reading in each meter. I don't know what I am doing wrong in applying KVL here. Please give your solution.


texts: Is there a GPIO IC that has a parallel interface?

texts: Sorry if this is an obvious question, I come from a software background and don't know the names for a lot of components. I am designing some custom hardware based around a W65C02S processor (a modern version of the classic MOS 6502). This processor (data sheet here) has only a 16 bit parallel bus for talking to other chips but to interface with modern peripherals I need GPIO functionality. Are there any ICs which would provide setting/reading a GPIO line state by communicating with the parallel pins on this chip?


texts:
This is a board from a Johnny Lightning V-bot, it has these SMD 6 pin components that just have a M03 and a dot on one of the terminals. Does anyone have a datasheet or any idea on how to ask for one to replace it? It helps with switching direction on a motor that transforms the upper half, and it's right on top of the hip motor connector.

This is the component, roughly 2.9 mm by 1.5 mm:

This is where it goes:


texts: What causes the increased power consumption of a window air conditioner in the afternoon?

texts:
I installed a new 8000 BTU window mount air conditioner on the weekend on a wall that is west facing. I plugged it into a Kill-A-Watt to monitor its power consumption and noticed in the morning, when the house and the outdoor temperature is at its coolest, it consumes 620-640 W. In the afternoon when the sun is on the unit, it consumes ~750W. Since the air conditioner is way undersized for the space it's trying to cool, it runs at max for the whole day (we shut it off at night since it's in our room and it's crazy loud).

In the morning, the indoor temperature is probably ~22ish C and the outdoor temperature is around 20C, and the afternoon the outdoor air temperature is around 29 C.

It didn't sound like the cooling fan had multiple speeds to account for an increased power consumption when the fins are hot. Is there anything else (electrically related) that could be causing the power consumption to increase by about 100 watts in the afternoon?


texts: Single input impedance of long-tailed pair

texts:
I have following circuit:

and I'd like to know input resistance of single input Ui. I tried to calculate it like this:
if I increase Ui by little, there's some voltage drop on base-emitter junction (which determines my emitter current), and also some drop on both R1 and R2. Here, I don't know what to do with the other transistor - from the point of view of input, it can be represented as emitter-base resistance of Q3 and also some voltage drop. But as base of Q3 is always on +2V, voltage drop is equal to Ube of Q4. So, if I'm correct:

$$
r_{in} = \frac{U_i}{I_{b_{Q4}}} = \frac{U_{be_{Q4}} + U_{R1} + U_{R2} + U_{be_{Q3}}}{\frac{U_{be_{Q4}}}{r_{be_{Q4}}}} \\
U_{be_{Q4}} = U_{be_{Q3}} \\
U_{R1} = U_{R2} = (I_b + I_e)R_1 = \frac{U_{be_{Q4}}}{r_{be_{Q4}}}(1+\beta)R_1\\
\\
r_{in} = \frac{2U_{be_{Q4}} + 2\frac{U_{be_{Q4}}}{r_{be_{Q4}}}(1+\beta)R_1}{\frac{U_{be_{Q4}}}{r_{be_{Q4}}}} = 2r_{be_{Q4}} + 2(1+\beta)R_1
$$

So, finally, it's equal to two times input resistance of common-emmiter stage (with emitter degeneration)? Thanks for help.


texts: Altium: How to change designator font when creating new library?

texts: I am creating a new schametic library in Altium Designer and wondering how can I change the text font of designators, pin names and pin numbers for all components in this library.


texts: Is this a safe design for an input at a 74HCT165

texts:
I'm new to designing my own circuits so please be kind and tell me if I'm right with my thoughts or if I have errors in it. Thanks!

The purpose of the 12V is to compensate the resistance of long wires (up to 60m). S1 will be normally closed. As long as S1 is closed Q2 should connect ground to Q1 and light up LED1 and pull D7 high.

R1 = Resistor for the LED and limiting the current through D7, R2 = Limit the current through Q2, R3 = Pullup-Resistor for Q1, R4 = Pulldown-Resistor for Q2

Are my suggestions right? Thank you for your answers!

Greetings, Christopher


texts: Why does the current still flow through the collector eventhough the transistor circuit has no Vcc

texts:
I came across a tutorial where I thought the above BJT NPN circuit is wrong because of the conclusions made.

But when I simulated this circuit I found out the conclusions were true.

I was completely puzzled and seems like I have some fundamental misconception about transistor behavior.

The above circuit is not powered. There is no Vcc.
There is an input voltage Vin which is increased from zero to 1V.

Below is the plot of the output voltage Vout with respect to Vin:

And here below plot is the current through the load I(Rload) and the collector current Ic with respect to Vin.

Question:

My confusion is how come any current forms and flows through collector and Rload when there is no potential difference between the transistor's collector and emitter terminals.

According to the plot it seems KCL is satisfied because I(Rload) + Ic = 0.

But what I don't understand how does the current forms and flows this way.

If someone would ask me I would say: "The current will flow from the base to the emitter hence to the ground. There will be no current through the load and there Vout will be zero."

I'm completely puzzled with this circuit. Obviously something is wrong in my view. Why does the current loop that way?


texts: What's wrong with this modified 12-pulse rectifier topology?

texts:
I added two capacitors downstream in order to absorb AC component from rectifier current. Both Subsystem blocks are meant to form "triangular" currents in order to have these currents at both HV windings and thus a nice sinusoidal current at AC bus. At least that's the theory.

So, the idea of both capacitors, additionally to maintain a stable DC-link voltage, is to absorb AC component from this triangular-like currents. With component values like the picture I'm getting this results.

EDIT: For the record, both subsystems are just to represent why I need two capacitors at that location but scope results are from a simulation without those subsystems (as you can see, both sub-blocks are not connected to anything, those small circles indicate an open circuit. Nevertheless, the next figure shows the circuit I'll use to follow that triangular reference I told you before.


texts: Drift and "flipping" in Instrumentation Amplifier reading thermistor

texts:
Disclaimer: I only have about 2-3 months of semi-intensive electronics experience.

Note that the chip (to the left of the Arduino, is Analog Digital's AD623 Instrumentation Amplifier) Datasheet here.

Note that the Potentiometer VR2 sets the gain in the circuit (according the the AD623 datasheet I should be getting a gain of around 5).

The thermistor (RT1) I am using is just a normal NTC thermistor that is quite stable.

I am having the following problem:
The voltage I am reading between the Output of the AD623 and the Arduino Ground (The same as the REF Pin of the AD623) seems to fluctuate in a not random but unusual way.

It used to jump around wildly but I re-soldered some connections and that seems to have gone away, what I am seeing now is the slow drift over a range of 1-2 volts of the signal. (Note I am trying for a dynamic range of about 4 volts, so this is quite large). It is almost as if the Instrumentation amplifier just has a really really bad slew rate. Then once it seems to have settled it slowly moves on (randomly) up or down by about a volt the same way, this then repeats.

I realize that this is very similar to the thread voltage fluctuations in Arduino opamp thermistor circuit (I do in fact work with that OP - on a somewhat different problem), and I found the answers to her question very unhelpful.

I have considered that this drift could be something as trivial as room temperature and air currents but my reference thermometer often (but not always) seems to track inversely (and other times somewhat linearly) with the voltage I read between the output and ref.

I do not so much care what the relationship is between the voltage read between the AD623 output and ref as long as that relationship is constant, so that I can calibrate it and trust that the calibration will give me the correct temperature when I read off the voltage.

UPDATE:
With everyones help (Especially Olin Lathrop) I think the problem has been fixed. I had been trying to use the AD623's 2 inputs to compare the resistance of a thermistor (RT1) to the equivalent resistance of the thermistor at room temperature. (Making VR1 look like RT1 at Room temperature) (circuit shown above) The problem was that I had my REF output from the AD623 tied to ground. However what I was actually doing was trying to set VR1 so that the voltage between OUT and REF would be just above the bottom supply rail. NOTE: This is not equivalent to making VR1 look like RT1 at Room Temperature. I did this to maximize the dynamic range of the output, however in doing so I also had to increase the gain (set by VR2). Such a high gain amplified the internal voltage offset of the AD623 (This voltage offset can itself fluctuate, leading to the symptoms I described above).

That said here is the schematic that seems to be working for me (compare to the starting point above).


texts: Two NPN Transistors in C-E to C-E Series?

texts:
Background: Trying to modify a cheap Digital Picture Frame. Since I don't enough enough about it to modify it's firmware, I need to take a more roundabout route. I will be including a msp430 to automate some things.

One of the main parts I need to change is the backlight control. For the most part, it is controlled with a single NPN transistor from the DPF's controller. Without modifying the transistor itself or the controller side operation of it.

So the question is, can I put two NPN transistors in series, C-E to C-E, to function like an AND gate? If not, Why not? Will it damage anything?

While the schematic below is simply representative, a major question would be the different voltages present. The Backlight might be 12v or 5v, and the DPF's controller might be 5v or 3.3v, while the MSP430 I will be using is only 3.3v. The Backlight might be up to 1A in current draw.

The second major question would be if anything would change if the existing transistor is being enabled by PWM instead of simple on/off. If my added transistor is off, will there be any negative effect on the first transistor being pulsed?

simulate this circuit – Schematic created using CircuitLab


texts: Picking out correct MOSFET for solenoid PWM control?

texts:
I'm attempting to control an automotive solenoid with PWM at 1250hz. At peak, the solenoid draws 3.75 Amps at 14.4 Volts. The specific problem is that any MOSFET that I've tried gets too hot and destroys itself as I increase the PWM frequency. The fastest that I can successfully control the solenoid is 40hz with the BUK9275-100A. I designed a test PCB to isolate the solenoid, CMS04 freewheel diode, MOSFET and MCP1402 MOSFET driver.

Here are the MOSFETs I've tried:

BUK9275-100A
NTD4855NT4G
IPD040N03L G
NTD4804NT4G
IRLR2705PBF

QUESTIONS:

What MOSFET characteristics should I be looking at besides RDS(on) to successfully control this solenoid at 1250hz?
Will I need to move away from the DPAK form factor to control the heat? I have up to 11 sqin of PCB surface to dissipate the heat.
Is there anything potentially incorrect with my PCB layout for the driver? I plan to use the same driver layout for the MCP1402 in the production board.

I've added the schematic:
http://www.firepunk.com/albums/About-Me/mosfetbreakout.png


texts: How to select the right HV pulse capacitor?

texts:
I'm planning to discharge a 1500VDC 150uF~250uF capacitor into a coil 20 times per second. I've found a few capacitors that might do the work, but I have some questions about their charge/discharge frequency capability.

This is one that I think would work.

It seems to be designed for DC links and not for pulses. Is there any way to know if it can handle the charge/discharge pulses in 20Hz? Maybe its dV/dt parameter?

Another one that looks promising is this.

Since it's designed for filters, I suppose it's more suitable for high frequency charge/discharge. Does it make sense?
Both are gonna work current and voltage wise, but how about frequency?


texts:
When a MOSFET is working in its saturation region, it might be used as an amplifier. But, as far as I understand, the more you increase vGS (voltage between the MOSFET's gate and ground) the less output voltage you get, which is the opposite of amplifying. Let me explain:

Having this (supposed) amplifier:

when it is in saturation region, it behaves as a VCCS, which, apparently, leads to an amplifiers' behaviour:

In the above picture, vO will be VS - eL, if eL is the voltage drop in RL. Following the iD equation, the more vIN incrases, the more voltage drop you will have in RL, right? That means that the more vIN increases, the more vO decreases. That isn't amplifying, but the opposite.

What am I missing?


texts: Help choosing switch for on/off timed circuit

texts:
I'm a beginner so sorry for such a simple question. I have a microcontroller connected to a 5V powerbank. I need a circuit to switch everything off 10 seconds after the press of a button. To turn it on, another button is used to reactivate the circuit. The code is no problem for me, I'm just struggling with the circuit.

I made a simple schematics with my idea, it's just missing the correct switch (S2). I tried with a relay, but with no success. Maybe a transistor could do the job, but I'm not sure how to use a transistor to switch off the positive lead and what type I should use.

Please see the image below, any help will be appreciated!


texts: Crackling sound when connecting camera to Raspberry Pi circuit

texts:
Ok so hopefully I can get this to make sense. Basically I have a Canon EOS 1D camera. What I want to do is to be able to apply an accurate time-stamp to each image so I know when each picture is taken.

To do that, I hook the camera's external flash to the input of a S-R Latch. The output and reset signal are then connected to the GPIO pins of a raspberry Pi. The Pi senses the latch, grabs the GPS time from a 72 byte UDP packet across the local network, and applies the accurate time-stamp in a text file. It then sends out the reset signal to reset the latch. I have drawn a circuit below.

simulate this circuit – Schematic created using CircuitLab

So I am under the belief that the external flash trigger on the camera is a contact closure switch. So when the camera takes an image, the switch closes and the latch triggers. The latch is powered by the Pi from one of its USB ports. This is the IC that I am using for the latch. There are also pull down resistors on the input pins so that everything stays low when it needs to and the latch works.

So here is my problem. Everything works fine. The latch works fine without the GPIO pins hooked up to the PI and with the GPIO pins hooked up. EXCEPT as soon as I hook up the camera I hear a cracking noise coming from the end of the wire connected to the camera (The other end is an audio jack) and the pwr LED on the PI no longer remains a constant red.

What could be causing this? The only places that the PI is connected to the circuit is through 2 GPIO pins and through the USB that powers the circuit. I have already wrecked a Pi from this and I don't really want to wreck another one. Please help


texts: Are Tunnel FETs (TFETs) already employed in some real world application?

texts:
I recently learned about the existence of such beasts as TFETs.

I searched the Internet and it seems to me that this device is still under heavy lab research and I got the impression that industrial development has not started yet, let alone its use in a real world application, albeit experimental or high-end.

Am I right in thinking so? Has anyone any clue about whether TFETs are already being manufactured industrially, either as discrete parts (maybe unlikely) or as part of an IC design?

I'm interested in industrially or commercially available parts, but I'd also like to know about prototype devices used in  actually deployed equipment (maybe some gazillion-dollar gizmo for a super-exotic application).


texts: pull-push gate driver for H bridge circuit

texts:
To drive power MOSFET following circuits with different pros and cons has been used
type A

type B

type C

type c which is called pull-pusher gate driver  can used either P or N mosfet

in h-bridge driver, mostly used type A and B for controlling one side P and N type mosfet (as per following image), whereas (for example) signal driver of up left P mosfet linked to signal driver of down right P mosfet, hence when this link set to high (or low) both FET turn to high (or low)

my question is:
Will the type C mosfet driver for all 4 h-bridge mosfets get a benefit from its fast switching performance? If they link together with a driver type  of A or B they can not drive those linked mosfet with same logic

following schematic is the  my preliminary design for using 2 pull-push gate driver for h-bridge circuit


texts: HX711 on-chip analog supply regulator, my mistake or datasheet mistake?

texts:
Most HX711 boards use an external transistor to supply regulated power for the load cells, the voltage output (called VAVDD) is calculated using this formula from the datasheet: VAVDD = VBG*(R1+R2)/R1

Consulting this schematic from Sparkfun (image bellow) we can see that R1 = 20K and R2= 8.2K, given that VBG is 1.25v, the formula comes to 1.76V which is not the real output, the output is around 4.3V (my own board outputs 4.5V with R1= 4.7K and R2= 1.8K).

Am I missing something or is the formula mistyped and should read: VAVDD = VBG*(R1+R2)/R2?

Using the formula above you get the correct voltage output, also it can be derived using the 1.25V reference and the voltage divider:

1.25 = VAVDD * R2/(R1+R2) <=>

VAVDD = 1.25/(R2/(R1+R2)) <=>

VAVDD = 1.25 * (R1+R2)/R2


texts:
I was reading an old copy of Horowitz and Hill's The Art of Electronics and I am trying to wrap my head around operational amplifiers in negative feedback circuits.

As the book explains, as the op-amp sees a positive voltage at its inverting input relative to its non-inverting input, it drives its output strongly negative, which effectively sets up a voltage divider along the resistor between the signal source and the op-amp's inverting input, and the feedback resistor running between the op-amp's output to the inverting input. The gain will be such that the voltage at the inverting input is the same as at the non-inverting input, which is typically ground. Hence the inverting input in a negative feedback circuit is sometimes called a virtual ground.

Now if this is the case, and the inverting and non-inverting inputs are brought to the same potential, won't the op-amp stop amplifying? I mean, there's now no voltage difference, so there's nothing to amplify.

I suspect that this is actually occurring, but as the op-amp stops amplifying, the output voltage moves up toward zero, which raises the voltage at its inverting input, which triggers amplification again until the virtual ground is re-established and the cycle repeats.

Wait, did I just say the cycle repeats? This implies is that the output voltage is actually oscillating at (probably) a very low amplitude and very high frequency, which for all intents and purposes for common circuits is stable. Is my understanding correct?

I bet if I used a capacitor to introduce a delay in the reaction of the op-amp, I could get oscillation at a lower frequency.


texts:
I've been searching for a replacement for a Toshiba K2961 MOSFET for a few days, but I can't seem to find any.
The datasheet for it is available here:
http://pdf1.alldatasheet.com/datasheet-pdf/view/213272/TOSHIBA/2SK2961_06.html

Perhaps someone can help me find an equivalent model of MOSFET to replace it?
Thanks in advanced, any suggestions are appreciated!


texts: How do I detect servo stall with an Arduino?

texts:
I am controlling a standard 5-volt servo with an Arduino with PWM.

My objective is to rotate the servo until it physically gets stalled (feels resistance) and then stop. Then I want the Arduino to store the degree at which the servo stopped at.

To do this, I have this idea in my mind...

A variable (servoPos) is declared.
Arduino increments servoPos one degree at a time and writes it to the servo.
Arduino simultaneously reads the current drawn from the servo.
IF the Arduino sees a current spike, then it stops the servo.
The Arduino stores the servo position in a new variable.

I am doing this for a project that emphasizes on low-cost. Therefore, I want to refrain from using motor encoders, op-amps, or any proprietary component.

Please show me how I can detect servo stall with an Arduino by reading the current. If you have a better/cost-effective idea, that would be appreciated too!

Thanks in advance!


texts:
In this related question I show data collected from a 6.5 hour run from NMEA sentences from a u-BLOX NEO-6 GPS module (datasheet, protocol spec) with an active external antenna via Raspberry Pi.
I'm looking at the value called C/No. (dBHz) which is reported together with altitude and azimuth for each GPS satellite used in a solution.
If I estimate the bandwidth of a given GPS signal to be about 10 MHz and my data scattered around 25 dBHz, that puts "dB" at -45. That's way too large to be "dBm" of the raw signal at the antenna, though I'm using an external active antenna, so "dBm" is plausible for the input to the module.
So far I haven't found a definition for C/No but it is mentioned in Section 7.4 of u-BLOX's Application Note RF Design Considerations for u-blox GPS Receivers

7.4 Sensitivity test
Check the C/No values in the $GPGSV or the UBX-NAV-SVINFO messages. Under open sky a good design should reach up to 50 dBHz for the strongest signals. If it reaches 45dBHz it can still be acceptable but the source of the reduction should be investigated (e.g. small antenna, ...).
Designs with maximal signal strengths below 40dBHz usually provide degraded performance (long TTFF times, lower coverage, accuracy, dynamic).

Question: What exactly does C/No (dBHz) mean in u-Blox GPS data? How is it defined?
update: This document gives a partial description, but I'm not confident that I understand it exactly. NEP would be power per square root frequency, but is the ratio total carrier power  divided by NEP x 1 sqrt(Hz)?

5. Signal Loss and C/No
In recent years, clever techniques have been developed to extract tiny GNSS signals from the background noise. But, the fundamental limitation to what can be achieved is limited by the ratio of the gain of the antenna element to the total receiver noise, referred to the input, or “G/T”. This is an absolute indicator primarily of antenna-plus-front-end performance, and determines the ultimate value of C/No for a given signal level. C/No is the ratio of carrier power to the noise power mixed with the signal, in a 1Hz bandwidth. This ultimately defines a limit for the GPS receiver sensitivity. So, simply put, antenna gain should be maximized (the “G”), and LNA noise figure minimized (“1/T”); a complicated way to state the obvious.
If the C/No ratio is diminished by any cause, be it bandwidth limitations or increased LNA noise figure, GNSS sensitivity will be reduced by the same amount. Once impaired, there is no way to recover C/No for a given receiver. Even additional gain does nothing because C and No are amplified equally, and so is to no avail.


texts: DIY uninterruptable power supply (UPS) for Raspberry Pi Zero with power supply selector

texts:
Foreknowledge: This post is the extension of a previous post (DIY uninterruptable power supply (UPS) for Raspberry Pi Zero), but due to the community rules I ask it as a new separate question. It is good to read the previous post.

I have several pi-zero boards and I utilize them to monitor environmental conditions (such as humidity, temperature and intrusion) of each room in home.

For continuous operation, I want to eliminate power blackouts. So, I decided to make a basic UPS for pi-zero boards. (need to be as small as possible)

I can not use combo boards of battery charger and booster, because they are expensive and hard to collect (for me).

Here is my new design: The relay selects the power supply dynamically depending on the status of the main power supply (which is AC/DC adapter).

AC/DC adapter powers the battery charger and the relay coil.
Also the adapter's (+) output pin (named as V1) is connected to the relay's normally open (NO) pin.
The battery charger charges the 3.7V battery.
Also the charger's (+) output pin (named as V2) is connected to the relay's normally closed (NC) pin.
The relay's common (COM) pin is connected to the step-up converter's (+) input pin.
The pi-zero is powered with the output of the step-up converter.

My questions are;

Is there any unsafe point similar to the issue stated in the previous post?
Even the relay is not driven by any NPN or PNP transistor, is it required to connect a diode to the relay coil in parallel?
What kind of capacitor should be connected to the load in parallel to prevent momentarily power cuts at power supply changes?


texts:
I'm trying to build a regulated power adapter using LM7915.

Before everything, I built on a protoboard the schema included on the datasheet (from ST). But, instead -15v, the output is -19v...

I'm using a 18+18v/500mA transformer. After the diode bridge (1n4007) the measure is -17.7v.

Into the input (-Vi) I'm using an electrolitic capacitor of 2200uF (50v). And into the output (-Vo) I'm using an electrolitic capacitor of 10uF (63v).

After wiring everything, measuring pins 1 (ground) and 3 (out) my voltmeter shows -19v...

I did the same experiment with a LM7815 and it worked nicely, so I don't think that I missed something.

Please, could you advise how to debug the circuit? Or point me out what I did wrong?

EDIT (solution?):

I managed to solve(?) the problem. I did not posted it as an answer since I don't know if it's only a coincidence or not... I've attached a picture.

The "problem" was that I wired the transformer 0V to the 7915 ground (pin 1). As you can see into the picture, the transformer has 3 wires: 2 purple and 1 black. Measuring each purple with the black, I found 19vAC, and after the bridge, -18vDC. So, as instructed here, here, here and here, I did the same on my circuit...

But, when I removed the  ground wire, I got the correct measures: The 7915 pin 2 (in) showed -19vDC and pin 3 (out) -15vDC (in fact a little bit more, close to -16vDC). If I put it again, the measures goes back to the values that I informed before...


texts:
This question might fly close to the rule about asking to select parts. What I'm really asking is what parameters of a PTC Fuse I should be looking for. Or even should I be using one. [Software head, so not classicaly trained] I'm not sure where I got the "inspiration" for the below circuit, I'm using it as a high side switch to power a USB Host connection. As a result I've got fairly strict 5V output requirments. Now there's two diodes which both drop 0.3V so the output from my power supply has to be raised to 5.6V and that's taken care of. (Maybe I don't need the one after the P Channel Fet, possibly belt and braces)

My problem is that the PTC fuse, (MULTICOMP  MC33189) which is meant to stop more then 500mA going to the USB Device connected. It is dropping voltage as a function of the current passing through it. As a result I can't simple add on voltage to compensate for it.

simulate this circuit – Schematic created using CircuitLab

So my question is should, or even can I use a PTC Fuse in this application or are there selection parameters I should be looking for? When the fuse I'm using gets close to the 500mA it starts heating up and gradually dropping the voltage more and more well out of spec. About 1.2 V up at 500mA and raising.


texts: Serial adder using one's complement arithmetic

texts:
The Apollo Guidance Computer (AGC) used one's complement arithmetic. The following clip from Frank O'Brien's book on the Apollo Guidance Computer (2010) offers a partial justification for this engineering decision:

  Key to the simplicity of such adders is the requirement that numbers
  employ one's complement for their representation.

Question:
Why is one's complement representation key to the simplicity of a serial adder?

Here is the clip in context from The Apollo Guidance Computer: Architecture and Operation (http://amzn.to/2EfVFla):


texts: What're the benefits of checking electronics in person over the exclusive online stores?

texts:
I found a few specialized electronic parts that I am interested in buying from eBay and/or Alibaba. However, knowing that I will be traveling to China soon, I felt checking the purchase in person would lower my risks of getting a lemon. What do you think and why?

Thanks in advance.


texts:
I have trouble understanding why Joule heating is called ohmic heating.
Also the joule heating effect establishes direct relation between current and resistance(as more current more collision more resitance more heat) while Ohm's law establishes inverse relationship i.e I=V/R why is that so?
I know I am missing something,but I can't specifically identify it.


texts: Correct way to drive an LED using 74HCxx logic

texts:
What is the correct way to connect an LED to a logic circuit?

The obvious thing to do is this:

simulate this circuit – Schematic created using CircuitLab

I have two concerns:

Can the logic gate's output actually deliver enough power to drive the LED? (Sure, LEDs are very low-power. But so are logic gates!)
Will the load from the LED distort the output so much that I can't connect it to any other gates?

The second problem looks like it ought to be trivial (if inconvenient) to solve:

simulate this circuit

Now only the output of the buffer has to deal with the load from the LED; the AND gate is blissfully unaware that anything has happened.

Trouble is, I'm planning to use 74HCxx logic running at 5 V, whereas it looks like most LEDs want to run at ~2 V. Also, it appears 74HCxx can only supply up to 4 mA, whereas most LEDs seems to draw drastically more current than that.

So now what?

Perhaps I could use a resistor to work around the voltage difference. (My knowledge of analogue electronics is far too weak to know if that would work.) Alternatively I could just run all the logic at 2 V instead. (The 74HCxx series seems to support that.) All of which does nothing to solve the current problem.

Do I need one of the level-translating logic gates? Or do I need to build something even more elaborate than that?


texts: Can a logic level converter be used as a replacement for a relay for detecting if a buzzer is currently active?

texts:
I have a small microcontroller (VoCore, runs Linux, has wifi and GPIOs) and i want to use it to hook into another system (basically a doorbell) to make the state of the doorbell-buzzer available over the network.

The system I want to hook into runs on 8V DC, there is a buzzer in it which normally doesn't get any power, if somebody rings the doorbell it gets 8V.
My board runs on 5V with a 3.3V GPIO logic level, so i have a DC-DC converter which transforms the 8V to 5V, that the things i want to connect already share a common ground-level.

I am unsure of how I can hook into / "read" the state of the buzzer-line. It should still work as it does now.
I had the following 2 ideas:

First I thought that I'll have to use a relay which is connected in parallel to the buzzer and is thereby switched with the buzzer, then simply connect a GPIO from my microcontroller to the output side of the relay and connect it to V+ from the microcontroller via some resistor. Basically like swithing a relay with the microcontroller only that the relay is put in "backwards".
When I looked around for parts I saw that logic level converters (e.g. for TTL lines) are often cheaper as relays and would probably have some other advantages because of the lack of moving parts. If I can find one which provides 8V to 3V (or simply uses reference voltage lines), I would assume that it can be used instead of a relay to read the state of the buzzer.

So my question is: Is my second assumption true? Can logic level converters be used like relays for "detecting" voltage on some line? Or am I on the wrong track from the start - how is detecting voltage on some line with different voltage than my microcontroller typically done?


texts: How can I safely connect both Arduino and a 120V 10A circuit?

texts:
I'm building a thermostat, and the idea is to have it fire one of two 120V 10A circuits (one to heat, one to cool). I have two of these modules for the relay and I understand how to connect both of them.

Here is a picture directly from the site I purchased it from:

However, I still have a couple of questions:

Is it safe to connect from an Arduino pin directly to the signal pin on this block or is there some way I should be 'protecting' the Arduino?
I eventually want to put this whole project in a single box and hopefully only have one power cord going to it. What's the safest way to power both the Arduino and the 120V 10A circuits (note that only one of the 120V 10A circuits would ever be on at a given time;never simultaneously)?


texts: Disentangling ratsnest: reassigning pins

texts: I've got a few digital pins that control various features of a MAX5318 DAC connected to headers. EAGLE makes a spaghetti nest out of the wiring, but I think I can make the wires not overlap each other if I reassign which pin goes to which pin on the header. Is it a worthwhile use of my time? I don't want my hard work to be wasted when I hit "ratsnest" again!


texts: ATtiny2313 accidental wrong fuse settings with crystal

texts:
I wanted to add external 12.000 MHz crystal to ATtiny2313.

I connected it (both crystal pins to ground using 0.1μF capacitor) and flashed fuse bits.

avrdude -P /dev/parport0 -p t2313 -c bsd -U lfuse:w:0x64:m -U hfuse:w:0xdf:m -U efuse:w:0xff:m

After flashing fuse bits, ATtiny2313 didn't start up and avrdude won't read it either.

What should I do?


texts: Nucleo STM32L476 and Arduino TFT shield pin mapping

texts:
I want to use an Arduino TFT shield (ILI9341) on a Nucleo STM32L476 developement board. This shield use 8 bits MCU mode and work well but the pin implantation for the Arduino connector on the Nucleo is not very convenient.

The data bus pins mapping is actually :

TFT    |  7  |   6  |  5  |  4  |  3  |   2  |  1  |  0  |
NUCLEO | PA8 | PB10 | PB4 | PB5 | PB3 | PA10 | PC7 | PA9 |

To write a byte on TFT bus i need to do a lot of shifting, masking, etc ...
This produce an overhead on the TFT communication bandwidth.

Is there a way on the STM32L4 to remap the GPIOs and PORTs into a sort of "virtual parallel port" where, after configuration, i can just write my byte on a register and the the hardware wire this register into the specified GPIOs/PORTs ?


texts: How to choose Li-ion or other battery for uC (packed into thin small device) and connect

texts:
Can we connect Li-ion batteries to microcontroller?

If yes how? How to choose a battery - what are the requirements? Are there battery chargers seperately for Li ion?

I am aking a small device which has to be thin, and uses only LCD and a small optical sensor: can we go for watch batteries, AAA batteries, what else?


texts: finding the gain of a two stage voltage amplifier

texts: i currently do not know how to approach this question, in terms of simplifying the circuit and which formulas to use in order to find the gain


texts: How does this OP amp circuit with a transistor work?

texts: I've got a question regarding this schematic. How exactly does it work? I've heard that this could be a current-voltage converter. Is this correct? How do I calculate the voltage on the emmitter if the shunt is e.g. a 3mOhm resistor with a current of 10A?


texts:
In our area, all of us have a set-top box with RCA output (red, yellow, white) and I've a spare lcd monitor which has VGA input. I want to connect them to each other.

As RCA sends analog signals and VGA receives digital signals, can I make any kind of circuit so that it'll work?

I have basic knowledge of ICs but don't know which to use or even tried to Google with no luck. Can anyone help?


texts: Multiple Avalon Data Master in Nios II Custom Instruction Crashes CPU

texts:
I am attempting to make a Nios II Custom Instruction which performs the function of summing a floating point array, given the array pointer and length. The custom instruction component has an Avalon Data Master, which is used to read a 'burst' of data from some SDRAM.
In the Signal Tap Logic Analyser, I can see that the custom instruction performs correctly, accessing the appropriate memory and presenting the correct result whilst asserting the done pin. However, at this point, the Nios processor crashes, and the result is never returned to the program.
After further inspection of the Logic Analyser, I can see that this is because the CPU Data and Instruction masters are no longer responding to requests (the waitrequest pins are stuck at high, signalling that the memory controller is not responding). Seemingly after my custom instruction data master is used, the 'control' is not given back to the other masters by the switching fabric.
Here is the Logic Analyser results after the instruction is completed:

And the Avalon Data Master interface, within the custom instruction component of the Nios platform:

Does anyone have any idea of what might be causing this, or how to fix it?


texts: Finding output voltage in Mosfet circuit

texts:
How to find out Vout in the following problems?

The threshold voltages are given as Vt.

My approach :

In the first problem, I assume two possible ranges of Vout - - -
Vout>0.7 and Vout <0.7. Now if Vout >0.7V, the device will be off since Vgs will be less than 0.3V in that case. So, the output will stick to that voltage (some voltage above 0.7V).
Now if Vout<0.7V, the device will be on. Now since nothing else is mentioned about the remaining circuitry to which the device is connected, I assume that there must be some stray capacitance at the output port, which will start charging by the drain current and Vout will increase. Now as soon as Vout exceeds 0.7V, the device becomes off and thus Vout will stick to that voltage i.e 0.7V. Here the second assumption i.e Vout<0.7V seems more accurate to me. But I am not sure about it.
In the second problem, since
|Vgs|>|Vt| for the lower pmos, it will be on. So, the same voltage 1V will appear at the drain terminal of the lower device or equivalently source terminal of the upper device. By the same argument we can say that the upper device is on and thus Vout will be 1V.
These are my approach for the above two problems. Let me know whether they are correct or not.


texts: Can I safely balance a series/parallel cell circuit to power a 12V soldering iron?

texts:
I want to power a 12V soldering iron with 2x 21700 '40T'batteries and 3x 18650 '25R' batteries with a torroidal rheostat between them.
The 3x25R batteries will be in parallel.
The rheostat will balance the resistances on a 6.4:3.6 ratio
with 2x40T batteries in series.
The available apparent power of the 40T batteries (rated 30 amps) in series will come to
root(2, 30^2 + 30^2)
=42.4264068711929 volt-amperes.
With concern for exciting current between this value and that of the 3x25R parallel pack in the series, I will include a rheostat to accomodate for differing resistances.
The 3x 25R (rated 20 amps) parallel pack will share the loads amp stress.
1/((1/20) + (1/20) + (1/20))
= 6.6• amps average stress.
(It would be great to know how to calculate volt-amperes apparent power across the parallel pack. I imagine this calculation would help to prove efficiency of the circuit. For now I'll assume peak efficiency can be based on the a healthy draw from the parallel pack.)
The parallel pack will have a combined capacity of 7500mah (25R 2500mah each), while the 40T series batteries have 4000mah each.
6.66 amps are drawn from the parallel pack (7500/6.66=1125) and 3.25 amps are drawn from both '40T' batteries (4000/3.25=1231).
Stress over the 40T to 25R batteries will be 1125:1350 when the soldering iron demands 54.54 watts
( = 3.25x8.4 = 6.6x4.2).
All batteries in circuit will be 4.2V fully charged. They will exert the lowest frequencies over the rheostat and the load when fully charged.
(The following calculation is not sequential from the last).
When the rheostat will balance the operational amplitude of the 4.2 volt 2x'40T' batteries with the 3x '25R' pack at a ratio of resistance 6.4:3:6 because the shared stress of the 25R parallel pack will equal the volt-amperes of the 40T series apparent power stress. (6.4x6.6a= 42w/~va).
resistive ratio * avg current:(resistive ratio * avg current)/parallel cells = 11:14
I imagine that this is a negligible difference.
I assume that I dont have to add resistors; relay resistors at the inverting input; or include a ground; that the soldering iron will work at around 55 watts until the circuit pack voltage goes beneath 12V and no battery will be damaged or exhausted beneath 3.2V.
I would greatly appreciate a more experienced estimate and any explanation in terms.
After consideration of 'hijacking' somebody elses post, I should ask specifically for some-body to confirm for me that my circuit will be safe and efficient. This is in the interest of a rubric for myself and others. I have put dissimilar 18650 batteries in series before and damaged batteries.
The rheostat I plan to use is rated to 25w and is 20ohms. The soldering iron has a power switch. I don't intend to leave the soldering iron on for very long at a time, enough to damage the rheostat.


texts:
I would like to generate custom waves in the gigahertz range. With beginner FPGAs like the DE0-Nano or microcontrollers like the Arduino, I can only generate waves up to the kilohertz range.

What tools or boards should I look into to start generating at this frequency?


texts: Master switch to turn on and off independent lights

texts:
i am adding some led lighting to a dolls house where each room can be turned on and off independently but i would like a master switch which turns all lights off(simple) but should turn on all lights even if they were off before. I just can't figure how to get this to work.

Example

With 2 LEDs in the system.
When the master switch is turned on all LEDs turn on.
Led1 is switched off, led2 is kept on.
-When the master switch is turned off all LEDs turn off.
And then when the master switch is turned on all LEDs are turned on.


texts: Flyback Converter Transformer Leakage Inductance

texts:
We are in the process of designing an inverter , in which designing a step up flyback converter is crucial.

The problem, we initially faced was there were more step down transformers available than step up. So we planned to turn around the transformer and use it. Usually the manufactures give leakage inductance ratings for the primary side , now that we have inverted the transformer , we have ratings for the secondary. How do we use LT spice to find the desired leakage inductance. Is there any other way we could do this ?


texts: Got an old 12V UPS battery, a sealed lead acid 17.2Ah battery. Quite a nice YUASA battery. Unfortunately it reads 9.92V so has been discharged badly. Is there any chance of salvaging it?


texts: Is powering a sound system from a computer's power supply a bad idea?

texts:
While this answer over on Super User looks like it would work, would it be bad for the computer power supply to be the power source for a sound system? Would it cause power fluctuations that would interfere with the other computer components?

The question specifies the following power requirements for the sound bar:

    Power requirements: DC 12V +/-5%, 1.0 A
    Total power output: 10 Watts continuous average power

The power supply PSU provides 12V DC to disk drives, etc., and that line can be tapped for power to the sound bar.


texts:
I'm looking for any resource that can help me build a very very basic RC circuit. I'm talking as simple as using RF to turn on/off an LED. The purpose of this circuit is for research and education. If anyone knows where I can get parts for simple RF circuits or even a tutorial or schematic that would be really appreciated.

From what I've gathered, (and I'm an absolute noob to this) I will need a transmitter and a receiver... is that correct?

Honestly guys, I know you are all probably annoyed with this question and trust me, I wouldn't bother you all if I could find my own way into RF for beginners but really I'm having the toughest time finding good resources for RF circuit building. All I'm looking for is something to get me started in the right direction and then I can go from there.

I've googled about a thousand things to try and find info on this but all I end up getting are a bunch of RC planes/boats sites. Nothing for just regular basic do-it-yourself circuit building.

Please no infrared. I'm only interested in radio control. Thanks!


texts: PROTEUS ARES PCB double side Layout - Force bottom side lyout for selected devices

texts:
I want to make a double side PCB design in ARES ( I have the desing in ISIS and I know how to do it), but for some specifics devices (Integrtate Circuit Socekts DIL16 and DIL28) I don't how to force ARES auto-rute to make these connections on the bottom side layer of the PCB.
I have try to eliminate the top layer of each pin of every socket but when I call the auto-route I get a lot of errors/warnings from the program, becouse ARES calculate many routes on the top side over the pin holes of the sockets (see picture area into the green line ).
Any idea how to config ARES for the right calculation?


texts: Sorry if this question is in the wrong community but anyway, why don't people use foam aluminium for capacitors? Its got a large surface area to my understanding (however probably not as much surface area as activated carbon) which should give it a good capacitance, right? Thanks for reading.