texts: Circuit to detect in which port sensor inserted

texts:
I want to build a Counter using a Proximity Sensor. I want to give choice for user to use either PNP or NPN. I will give two ports for the same. I am using PIC16f887 microcontroller.
How to detect that which sensor user inserted?

I dont want to miss any sample just to detect.
I dont want to put burden on user to select type of sensor from the menu.

Power supply for sensors is 12V DC.
It may be programmatically but automatically it should detect without user intervention.
Or it may be electronically , may be using Gate circuit or something.
What is confusing me more is some of them come "open collector" type. When sensor detect the object, they pull down.


texts:
I am working on my Circuits Analysis class and I came across an interesting problem. I will put it below along with my work and then explain the problem.

The current through the \$L=100\,mH\$ inductor in the following figure is
\$i=2(2−e^{−\frac{t}{100}}) \, mA\$. Use the integral of the power to find the initial energy stored in the inductor at \$t=0\$.

Using the formula \$W = \dfrac{1}{2}L\,i^2\$, you get
\$W = 0.5 \times 0.1 \times (0.002)^2 = 200\,nJ\$ of energy. This turns out to be the correct answer, but for fun I decided to do it the long way.

\begin{align*}
   P &= L \dfrac{di}{dt} i \\[1 em]
   i &= 0.004 - 0.002 \, e^{-\frac{t}{100}} \\[1 em]
   \dfrac{di}{dt} &= 2 \times 10^{-5} \, e^{-\frac{t}{100}} \\[1 em]
   L &= 0.1 \\[1em]
\end{align*}

Simplifying, you get:

\begin{align*}
   P &= 8 \times 10^{-9} e^{-\frac{t}{100}} - 4 \times 10^{-9}  e^{-\frac{t}{50}} \\[1em]
\end{align*}

By integrating P with respect to t, you can get the total work:

\begin{align*}
   W &= -8 \times 10^{-7} e^{-\frac{t}{100}} + 2 \times 10^{-7} e^{-\frac{t}{50}} \\
\end{align*}

Plugging in \$t=0\$, you get \$-600\,nJ\$ instead of \$200\,nJ\$.

Why does the longer method yield a different answer? Am I neglecting something?


texts: This clamp is being used on a piece of equipment that is a few years old. I am trying to identify the type of clamp this is.  If you the reader cannot identify it, leave a comment with something similar that will not damage thin wire when clamped.


texts:
I would like to know, what is the purpose of the special FPU unit, that is advertised with STM32F4 microcontrollers ?

To quote this website :

  " The Cortex-M4 core features a Floating point unit (FPU) single precision which supports all ARM single-precision data-processing instructions and data types. "

What would be the difference, if this unit was not present in the architecture ? Does this mean I need to use some special libraries / functions when doing arithmetics with floating point variables ? Thank you.


texts:
So, i got this Vccs opamp that I want to use. I know that the Vcontrol is the voltage that will appear in my Rsense and knowing my Rsense I can find the Ie. What I dont get is the role of the Vc and whether it determines the Ib and Ic. I got the datasheet for both the opamp and the transistor which do have the different Hfe values. I mean I will have to supply the Vc.

What I want is to know exactly the values of all the currents and voltages in paper before trying it out on the actual circuit.


texts: Role of yellow wire in 115v AC Industrial motor

texts: I am rewiring a 1725 rpm, single phase 1/3 hp AC GE Industrial motor Model 5KH39QN9397C. It has four wires: red, black, yellow and green. Label on motor states that line voltage is red-black and green is ground but does not mention the yellow wire. Resistance between the wires is red-black = 4.8 ohms; yellow-black =3.1 ohms; yellow-red = 2.2 ohms. What is the role of the yellow wire? Will connecting the red and black to line voltage cause the motor to run @ 1725 rpm? Will connecting line voltage to red and yellow or black and yellow cause the motor to run at a different speed?


texts: How to route and solder TO-263AB packages?

texts:
Am working on making a PCB and i was using RFP30N06LE MOSFET on my breadboard circuit, now that am making a PCB i want to use the other variation RF1S30N06LESM of the same component. which as you can see the datasheet does not say much on the pads, spacing, etc.

This is my first time working on such packaging so please excuse my lack of knowledge. my questions are:

Does TO-263AB packages have a fixed standard sizes, pads, etc.? I checked out other datasheets for other components and it seems that TO-263AB packages have standard measurements.
The drain pad in TO-263AB packages is quite a large pad, when routing it do i need to make a large trace for it?
Is there any special "configurations" or things i need to put in mind while working with TO-263AB packages?

Thank you and again i have never worked with TO-263AB packages and i cant seem to find much information on working with it.


texts: I can not find needed CPU (STM32F401) in IAR 6.5 list

texts:
I'm trying to start STM32 software developing using IAR 6.5 IDE. I have STM32F401C-DISCO board for developing and IAR's IDE.

It is needed to choose the right CPU in the project options menu:

However there is no such CPU available. After some search for needed packages (search like IAR STM32F401...) I have no result.

Do I need to choose nearest CPU (like STMF405)?

Or should I in some way upgrade my IAR IDE?


texts: How to determine how much current and or voltage a given circuit "needs"?

texts:
My apologies in advance if I make any wrong assumptions. Say you have an outlet that is rated at 120V and 10A. My power adapter for my MacBook says it is rated at 16.5V and 3.65A max. How was it determined that the power adapter needs to provide at most 16.5V and 3.65A? What is the process of actually figuring this out when designing electronics/circuits?

The only thing I have been able to think of so far is that based on the physical properties of a circuit, you can only handle a certain amount of current before burning out which can be figured out empirically. In addition to that maybe the amount of voltage required has to do with power efficiency and driving the max amount of current you can handle.

I understand Ohm's Law and I am not asking about how to calculate anything using it. This is more of a design question when you have a circuit in mind but need to figure out what resistors to apply and what voltage/current you will need to operate correctly.


texts:
Has anyone actually measured the maximum amount of power that can be drawn from a smartphone's (say Samsung S4) USB OTG in host mode?

I've read people suggest 100mA but can't find if anyone has actually tested it. I have seen it work with a keyboard, mouse and both keyboard & mouse but these are only around 50mA.

If I need say 1W for 2 minutes, is there any way to make it possible (without the use of additional batteries)?


texts: What is the natural frequency of a 3rd order system with 3 real roots?

texts:
I know the the structure of a 3rd order system is:

\$Q_s=(s+a)(s^2+2\xi\omega ns+\omega n^2)\$

but what do I do if I have something like this?

\$Q_s=(s+4)(s+5)(s+3)\$

How do I measure its natural frequency?


texts: LTSpice predefined components for ideal Voltage Gain and Sum

texts:
I'm trying to enter a circuit found in a Book from C.P.Basso which contains:

ideal gain stage with one input and one output (Vout=Vin*k)
ideal adder stage, which has two inputs and one output (Vout=VinA+VinB)

I could reproduce these by using ideal OpAmps, but aren't there already such predefined components in the LTSpice library ?


texts: Does my laptop need powerbank with output voltage the same like my charger's or my battery's?

texts: I have laptop (Acer Aspire 7745G) which has charger 19V-4.74A and battery 11.1V - 6,6Ah (73Wh). I'm planning to buy powerbank for it but I don't know what voltage would be okay. I'm looking to this powerbank I see that it has DC output of 12/15/19V. So, can I use this powerbank for my laptop? If yes, what voltage of output should I use?


texts: 12V relay circuit, converted to 5V relay, under uC control

texts:
Few questions about a little Home-Automation project I am trying.

Below is the schematic which I found in an article, slightly modified to suit the parts I have in hand --

Original had,

Q1 = BC548
Relay = 12V coil voltage

Mine has,

Q1 = BC547B
Relay = 5v coil voltage

Q1) Is that an acceptable conversion ?

Note: The BC547B has Vcbo:50V, Vceo:45V, Vebo:6V, where-as the BC548 in original circuit has Vcbo:30V, Vceo:30V, Vebo:5V, rest of the parameters being pretty same as per datasheet (hFE:220-450).

The relay is the SPDT PCB-mount kind (rated for 10A @230VAC), also called "sugar cube".

Q2) The load I am trying to drive is resistive (60W 220VAC incandescent lamp). What changes might I need if I would like to drive loads like --

Fluorescent lamp
Fan (220VAC, 60W)
1HP Water pump (220VAC, 800W) -- One thought is to use higher current rated (e.g. 30A) relay. But, I think I need to worry about EM feedback which might cause arcing and destroy the EM relay.

Q3) Right now I am making this on a veroboard (el-cheapo phenolic kinds). While I understand that this may be sufficient for the lamp/fan control, I am wondering if I need something better for higher loads, s.a. the Water-pump control ? What is the minimum gauge wire to be used for this purpose ? What kind of connectors (terminal blocks) could be used ?


texts:
simulate this circuit – Schematic created using CircuitLab

$$U_{DF}=0.7V$$
Calculate the currents of diodes. I've used KVL and KCL in 3 nodes, and I got
$$I_{D1}=0.2mA$$

$$I_{D2}=-0.5mA$$ but i don't think that this second current should be negative.

loop 3
$$3V - R_1I-0.7-0,7=0 $$ which gives
$$I =1.6mA$$
loop 1
$$3V-R_1I-R_2I_0=0$$
$$I_0=1.4mA$$
from KCL
$$I_{D1}=I-I_0=0.2mA$$
loop 2
$$3V-R_1I-0.7-R_3I_1=0$$
$$I_1=0.7mA$$
from KCL
$$I_{D2}=I_{D1}-I_1=-0.5mA$$


texts: Capacitor Impedance ESR vs Frequency Curve

texts:
Yageo's SMT capacitor datasheet lists the ESR vs. Frequency Curve show below:

Note that impedance (Z) is listed in units (W). How can this be understood? Why is impedance seemingly not measured in Ohms, as is customary?


texts: Calculating the DC motor fraction coefficient

texts:
So I have been designing a DC motor controller and I ran into a problem rather complicated. So for modeling the mechanical block we require motor inertia as well as friction coefficient. But my problem is that there are two different friction coefficient alike in two different equations:

The general equation for for all rotating machines:

Coefficient of friction based on inertia and motor mechanical time constant which is B=J/Taum

Now based on some calculation on the motor (its a robot. so Im guessing the motors are loaded but can figure out the load torque) this equations has been provided for me:

which is in similar form as the first equation. Based on this equation the value of B is supposed to be 4.3e-5. While if I calculate it based on the 2nd equation it corresponds to 9.67e-5 (based on the motor datasheet J=5.8e-7 and Taum=6ms).
the thing is that Im not sure which value should be used in the mechanical block in my Simulink design. Should I calculate B by substituting Tem and rated speed in the first equation, Or substituting J and Taum in the 2nd equation, Or assume B is equal to 4.3e-5 based on the equation provided in the design requirement?
(the last equation is based on practical measurement that was conducted on the robot to calculate the rolling friction, the bearing friction and the aerodynamics drag)


texts:
I understand the super node aspect of this circuit, but I'm unsure of what to do as I dont see a direct way to proceed with KCL using all of the nodes. I found the equation for the supernode, but I'm unsure of the rest.

simulate this circuit – Schematic created using CircuitLab

Supernode: 12=v1-v2
  node 1: 1=v1 + ???
  node 2: ???


texts: Square wave to DC voltage with passive components

texts:
Good day,

I have a design challenge that I have been thinking about.

Is there a passive and inexpensive system that I can get a square wave (frequency not decided yet, but less than 8MHz) that will output a 5V DC signal? If the input changes to a fixed voltage the output must go low.

My solution was to DC null the square wave with a decoupling cap and then smooth out the gaps in the remaining square wave with a passive low pass filter. Essentially take advantage of the capacitor to GND and allow it to charge and discharge at a frequency that will result in a DC signal.

The problem with this design that I can see is that this is wildly inefficient as the DC null will half the power and the passive LPF will also result in a loss of power.

Is there a way I could use transistors to active what I want? (I am trying to stay away from IC's)

EDIT
@Neil_UK

Thank you for your help.

This is my simulation response with a slow frequency of 2kHz.


texts: why when calculating rise time we use 2.2 × tau? (RC Low Pass Circuit)

texts: I am just trying to understand why we use 2.2×Tau when calculate the rise time. I can't find a derivation anywhere, I don't understand where this 2.2 came from.


texts: "Renaming" an output reg to another reg?

texts:
I am attempting to perform a CDC from a FIFO Generator IP to AXI registers. Forgive my lack of understanding of Verilog, I'm a VHDL guy.
What I have:
cdc_fifo_64 timer_fifo(
   .rst(reset_p), // active high
   .wr_clk(CNTR_CLK), // MUST be 500MHz
   .rd_clk(S_AXI_ACLK), // MUST be 100MHz
   .din(timer),
   .wr_en(TRIGGER_os),
   .rd_en(1'b1),
   .dout(timer_cdc),
   .full(),
   .empty()
);

cdc_fifo_32 interval_fifo(
  .rst(reset_p), // active high
  .wr_clk(CNTR_CLK), // MUST be 500MHz
  .rd_clk(S_AXI_ACLK), // MUST be 100MHz
  .din(interval),
  .wr_en(TRIGGER_os),
  .rd_en(1'b1),
  .dout(interval_cdc),
  .full(),
  .empty()
);

always @(S_AXI_ACLK) begin
  slv_reg2  <= interval_cdc;
  slv_reg1  <= timer_cdc[63:32];
  slv_reg0  <= timer_cdc[31:0];
end

I do not want the last block to add a clock cycle of delay for something as simple as renaming signals.
In VHDL I could simply assign bit fields (so I could use slv_reg1 <= timer_cdc(63 downto 32)) and have no issues with sequential/combinatorial assignments. But here, I have reg signals (and I should not be changing slv_regX to a wire or renaming it). How can I assign these so that I simply rename the reg output to a bit field of another reg?


texts: How to get a clean 50 kHz square-wave with 555 timer (Astable Mode)?

texts:
I can't get a pure square wave above a few kilohertz. Everything is fine at the lower frequencies, but I would like a clock speed of between 50 and 100 kilohertz. Unfortunately, there is a distortion on the rising edge. Is it possible? Is that the nature of this chip?
Here is 28kHz waveform example.


texts: How are function name abbreviations of a chip conceived?

texts:
The microcontroller on the Arduino has functions such as RXD, XTAL1, ADC4, AVCC, MISO. These abbreviations are quite commonly used, and often make sense on first sight. One thing I noticed, that it's not just "first letters of each word":

XTAL1: Crystal 1 input
MISO: Master Input, Slave Output of the Serial Peripheral Interface
AVCC: Voltage supply for analog digital converter
RXD: UART receive input

How are these names conceived? Is there a guideline somewhere that I can follow for my own designs?


texts: Sometimes in videos made by the YouTube creator ElectroBOOM the creator says he is using a 1 ohm series resistor to measure current. I looked it up and found some links to forums where people are saying that you can use a resistor rather than a DMM to measure current, but I can't find anything saying how to do this. Are they usimg the voltage drop across the resistor from a voltmeter or are they doing something else?


texts:
A basic nugget of info is missing in my end-to-end picture of how grounding works and why it's important. When a voltage is applied in a circuit the electric current starts flowing (or the field establishes itself). Now in an AC home circuit the current flows through the circuit like in DC, but happens to reverse directions 50 or 60 times a second too (Hz).

So why do some appliances have electric current leak onto their metallic surfaces at all in the first place. Should'nt all appliances's internals be designed so that there can never (or rarely) be any leakage of current ?

The whole point of my question is that why do we blame the lack of grounding when an appliance gives an electric shock - isn't the appliance equally to blame for being designed in a way that allows for charge leakage ?

Hence in the event of an electric shock isn't it equally important to investigate the appliance (in this case it's actually a custom assembled desktop computer) to find out why its circuit is leaking charge to its metallic body parts, instead of always expecting the grounding to remove that excess charge to the earth.

Another way to paraphrase this question is - are some appliances (especially assembled computers) likely/expected to leak charge. Hence in the event of rare shocks sometimes shouldn't it be more important to investigate the appliance itself for having the proclivity to receive leaked charge instead of blindly checking the grounding


texts: Can I add PWM timers to a microcontroller externally?

texts:
I'm doing a project involving an LED matrix, and using PWM timers to be able to control the brightness. My microcontroller has 3 timers, and I need 4.

Is there a PWM timer circuit, perhaps using a 555 that I can connect outside the microcontroller to effectively add PWM timer?

I've seen this question, whose answers recommend servo drivers for PWM. However, I'm unsure how to use this to drive my LED's, as their output is for 3-wire servos. Looking at this pinout, would I just attach the signal wire to my LED(s)?

I'm also curious if there's a simpler circuit I could use to do this, if GPIOs are at a minimum (if I want to use one pin instead of the two that i2c would require). Alternatively, could I possible use a SIPO shift register to communicate over i2c with the servo module, using only one GPIO pin?

edit:  Sorry, it's late, I just realized that using a shift register would use more pins than just using i2c would. maybe use some kind of i/o expander so that pins are no longer at a premium?


texts:
I have a multi-pin connector that I would like to be able to turn off with a single switch. How would I do that?

The situation is that there is a multi-pin connector cable (like an RS-232 connector) with two outputs. So, the cable will fork. One connector is permanently connected to a monitoring system which is always on. The other connector is free-standing and is only used for occasional test purposes.

When the test connector is used, the monitoring connector has to be turned off because otherwise it will send commands and electrical signals down the cable constantly. So, basically I need to switchover the cable from the monitoring device to the test connector.

Now, of course I could install a small switch on every wire in the cable, but it seems silly to install 24 switches or whatever. Is there a way to make all the wires go one way or the other using just one switch?

Note that it does not need to be either/or, I just need to turn off the connection to the monitoring system when required. I cannot do this by unplugging it because the monitor is installed in a panel that takes over two hours to disassemble, so unplugging it is not a good solution.


texts: Driving high current bipolar stepper motor with high voltage

texts:
I have a 3A 5V bipolar stepper motor, which I would like to run at 40V. Running stepper motors at high voltage is okay as long as the current is capped. To cap the current I need to have a chopping circuit using PWM. On top of that, since the motor's load can vary, I need to have it as a closed circuit that senses amps and changes the width of PWM.

I researched this for a while and cannot seem to find the right driver IC to use for this. The highest rated ones I found are 2.8A. I am okay with using Arduino to control PWM and building a custom driver using the likes of TIP120s.

Does anyone know of a driver IC that can do this, or suggest a schematic? Thank you.


texts: Who can identify the IC with marking code "L7" with design SOT25 and IC with marking code "TY4iC" with design SOT23-6L?

texts:
To create a schematic I need the datasheet for the two IC's with the markings "L7" and "TY4iC" which can be seen on the picture.
The IC "L7" could be an amplifier for data signals, the IC "TY4iC" is probably responsible for a 5V power supply.
I didn't find the markings in the internet and also in the relevant SMD books and tables.
I would be very pleased about an answer and thank you in advance
WolleP


texts: Should Kirchhoff's Law be changed to account for information removal?

texts:
If I have a simple DC circuit consisting only of an LED output, how does Kirchhoff recognize the fact that information has left the loop?

Since, in accordance with relativity(?), you can't have information without the loss of energy.

I presume the loss is negligible down to some small voltage like 10^(-20)V or something, but still...


texts: Dry solder joints - what exactly happens?

texts:
This Wikipedia article on soldering and this previous question explain basics of dry joints.

But none explain:

why moving the contacts while the solder cools creates dry joints
why the result creates poor physical and electrical properties
to what degree, and in what way the joint is weakened in those respects

I am not asking about techniques etc, but for a deeper understanding that if necessary enables further reading. (This would be better asked on physics.SE except I'm only asking about electrical usage scenarios)


texts: Switching a 3V led series with an Arduino uno with 5V supply

texts:
just to verify my idea. I'd like to switch on and off a series of led supplied with 2 AA batteries with an Arduino uno.
I'd like to use an 2N3904 transistor.
The collector of the transistor will be connected to the series of leds and to the 3V led voltage supply, the base will be connected to an arduino GPIO trough a resistor. The emitter will be connected to ground. Is this a good schema?

simulate this circuit – Schematic created using CircuitLab

Thanks,
Giuseppe


texts:
What techniques are there to "prototype" a component like a MC68020 processor? Since the pins are in a 13x13 geometry standard bread boards will not do. Are there something like bread boards for this type of application? Should I go with wire wrapping the MC and connect it to a components on breadboards using wires and band cables?

New to this, I have quite some experience in OS development as well as low level programming and compiler design. Not as much in hardware design. I thought I sink my teeth into a fully fledged nerd project with an old MC68020 from eBay and make it a really long-time project, taking my time.


texts: Using Solicore flexible batteries as replacement of CR2032

texts:
A device that I am using (Gimbal iBeacon series 10) uses 1 CR2032 battery that lasts for 3 months.
I am trying to find out if I can replace it with a flexible unit from Solicore.

CR2032 spec from Energizer
Solicore flexible batteries spec

Questions:

Which Solicore battery (if any) can I use as replacement of CR2032
If it can be replaced. How many of the Solicore batteries do I have to have to extend the life to 1 year?


texts:
Consider the circuit above. I'm struggling to answer the following question:

  Suppose the source of “Analog In” to your sample and hold has a
  Thevenin output  resistance of 10K and you want to keep the sample
  time (when “In 1,3” is high) to a  maximum of 1uSec . Is this a
  problem? Why or why not? If it is a problem, how do you  fix it? (Make
  sure you do not increase voltage droop with your fix.)

I've been staring at the question and don't even know where to start. The only thing I can think of is an op amp buffer, since they seem to fix every problem related to impedance.

Note that this is homework, I'm looking for hints that could point me in the right direction and/or a deeper understanding of this circuit.


texts: Translating a 1.8 V FPGA pulse to 24 V pulse to power a solenoid

texts:
I am designing a board that will interface between a FPGA board and solenoid that powers a pneumatic system.

The signal coming from the FPGA is a LVCMOS 1.8 V signal. Current from the FPGA signal is approximately 10 mA. I desire the output of the designed board to be a 100 mA 24 volts to power the solenoid. My initial thoughts are using a BJT transistor to accomplish this task.

Doing some simple online searching I found this DIY project that is translating 3.3 V to a 5 V signal. I assume I can use this as my basis using BJT transistors, though my knowledge on electrical engineering is limited.

Is this the appropriate approach to take mimicking the DIY project, or is the voltage and current difference too large? If the simple design is okay, how do I go about selecting the correct resistor values and BJT transistors?

Any help is greatly appreciated! Thank you!


texts:
No, I'm not asking you about my whole design - just one little bit of it.

I have SMT devices, and I am currently pushing 8 pins on each side of some chips (SO24) straight through to the other side of the board with vias:

Having so many vias so close together - is it really a good idea?

Should I be staggering them more, or spacing them out a bit?  Will this make the board too weak?  The board itself is designed to be plugged in and out of breadboard many times, so may be stressed quite a bit.

Btw - same area as it would look after fabrication:


texts: Integrated H-Bridge (ST VNH3SP30-E) suitable for low-side current-sensing?

texts:
For motor control, I need to monitor its current. Can a simple low side shunt be used for measurement, or will the offset voltage (no direct GND connection) cause problems?

http://www.st.com/internet/automotive/subclass/1039.jsp


texts: Designing a non-inverting amplifier with a gain of 2

texts:
Quetion:

  Design a noninverting amplifier with a gain of 2. At the maximum output voltage of 10 V the current
  in the voltage divider is to be 10 μA.

I can easily understand the first part of the problem .

Here, gain = 1+\$\frac{R_f}{R_1}\$ , To make  gain = 2, \$R_1\$ should be same as \$R_f\$
But what is meant by current in the voltage divider in the second part of the question?


texts: Identify DC motor parameters using Least Squares Estimator

texts:
I'm not new to the concept of Least Squares, however, I find it difficult to figure out how to make it identify the transfer function for my motor. I will have my input voltage and an optical encoder to measure the error.

I'm attempting to control its velocity.

Also, I will be using Arduino UNO to send the encoder data to MATLAB. Any ideas?


texts:
Pretty simple answer to this, but I have managed to get myself into a lot of confusion

Can you work out real power by taking the average of several measurements of instantaneous power?

I was hoping that it is the case that way I would not need to measure the phase difference between the voltage and the current.


texts:
What are the advantages and drawbacks of each op-amp attenuator topology ? Which one would you use ?

Resistor divider followed by a buffer :

Inverting op amp attenuator :


texts: ANT-MMCX and Microstripe line and UHF RFID module circuit designing

texts:
Below, you see the only schematic of a 6 pages-datasheet of an UHF RFID module (working frequency = 840...930 MHz):

There are three questions:

What is that ANT-MMCX? I search it in Google and I found two components named ANT-GPS-MMCX and ANT-GSMQB-MMCX-ND. Which one is appropriate for this module?
The antenna is connected to the module with a 50Ω microstripe line. The question is "What is this microstripe line?". I must design and build it myself or there are created ones in the stores? What happens if I connect the antenna to the module with a simple wire?
Will the above circuit works properly if I use a 5V mobile phone charger as the power supply (let assume it can provide the require current) and connect RXD and TXD to my computer's serial port and also put all the circuit on a simple bread board? or there are a lot of points in high frequency communication circuits that I must consider and apply to the board design that are not shown in the image? (If so, let me know the most important ones).


texts: output offset: dual supply opamp running on single supply

texts:
I'm running a precision rectifier circuit on TL082. http://www.ti.com/lit/ds/symlink/tl082-n.pdf
supplying dual supplies (+/-12V) has it working correctly, however a single supply(0-12V) does not. I'm guessing that the asymmetrical supply has ground at midrail, or 6v. However, offsetting the input does not correct behaviour. I'm sure there is something simple I don't understand here.


texts: How could have Banksy kept an RF receiver running for 12 years?

texts:
I'm talking about Banksy's "Girl with balloon" painting that shredded itself at auction.

I think the general consensus is that he didn't, and that it was set up before the auction (or a couple years ago, not 12 years). But lets say he did, how could he have made it keep its power for that long? What sorts of RF receivers run on such low power? What batteries can withstand a 12 year low-but-constant-load life?


texts: Powering a small generator with a contactless rotating plate

texts:
My goal is to contactlessly power a small generator by rotating a steel plate underneath it.
Specifically, I have mounted 6 permanent magnets (rectangular shaped) on a shaft, which is mounted on ball bearings that make it spin freely (rotor.) All around it are the armature windings.
Now I know that it is possible to make the magnets spin with a conductive metal plate rotating underneath it (the plate is spinning freely at very small distance from the magnets) because of the generated eddy currents. This would work fine with an aluminum plate as I have already tested it.
In my case the spinning plate has to be steel and the main problem is that the magnets on the shaft won't turn because of the magnetic attraction of every single magnet with the steel plate. I tried different rotating speeds and distances between the shaft and the plate but nothing helps. Even with rounded shaped magnets it seems to make no difference
Do you have any suggestions how and if this could work? Maybe some sort of coating for the steel plate?


texts:
What is the 'sense' pin on an op-amp for and how is it used?

What are some circuit examples that that use the sense pin?

Here is an example of an op-amp with a sense pin: http://www.ti.com/lit/ds/symlink/ina137.pdf


texts:
This my first experiment trying to make a PCB circuit.

My main problem is that I want to make a project comping those four simple circuits in one or two pcb's (as I never try to something similar to that ) is it possible to do that and how?

T the schematic captures is ready, but I found the PCB difficult to use protest as every element has many types. For example: if I want a 100 k resistor I have to choose between a loots of kind

I have four circuits that I should print on A4 paper to transmit it to the pcb board.

[![enter image description here][3]][3]
[![enter image description here][4]][4]


texts: Need help with communicating with card reader!

texts:
For my school project I'm using the MFRC522 card reader and an FPGA with VHDL. I'm using SPI lines but I can't understand how am I supposed create a communication with it.

From what I've understand so far I have to sycnhronize both with the same clock (which I did and checked). Then... I don't know, am I supposed to send an address every time to get card information?

Isn't the card reader supposed to send me the information stored in the card when it reads it?

What do I have to do to get the card reading?

If I have to send an address every time, what address do I have to send? I've checked registers but I couldn't make sense of any of them.


texts: An electromagnetic wave incident on a closed loop

texts:
Consider the following diagram :

Both the electric and magnetic fields will induce a voltage in this circuit. In more details, the component of the electric field that is in the plane of the circuit, perpendicular to them and directed upward or downward is the component that will induce the voltage  and the component of the magnetic field that is perpendicular to the plane of the wire and directed into or out of the page is the component that will induce also the voltage. Therefore, from this diagram the component of the electric field that will induce the voltage is 10cos(3). For the magnetic field, according to the solution of this question, it states that the magnetic field is totally perpendicular to the plane of the circuit so all of it will contribute in the induction of the voltage due to the magnetic field and this magnetic field will be equal to 10/120*pi. My question is that not all the magnetic field is perpendicular to the plane of the circuit since the wave is titled by 30 degrees from the axis of the circuit and therefore the component that will contribute to the induction of the voltage ( normal component) will be 10cos(30)/120*pi ????


texts: Why do laser diodes need temperature controllers? Why not just cool them?

texts:
High quality laser diodes often require temperature controllers plus a "TE" (thermoelectric unit) that cool the diode and maintain it at a particular temperature using a Peltier cooler.

Why not just cool the diode without a controller? Is there some problem with the diode being too cold?


texts:
I recently purchased a bare-bone ESP8266-12E module but am having major issues with stability. Here is a schematic of what I am using.

I am able to program the ESP using Atmel Studio and the Arduino IDE with no issue after putting the chip into program mode by connecting GPIO0 to ground. The problem is the code never executes. I get the message:

 ets Jan  8 2013,rst cause:2, boot mode:(3,6)
 load 0x4010f000, len 1384, room 16
 tail 8
 chksum 0x2d
 csum 0x2d
 v09f0c112
 ~ld

Indicating that the chip has entered the proper boot mode and the code should be running, but the chip freezes, doing nothing. Note: Boot mode 1 is programming mode and boot mode 3 is boot from internal flash. I assumed this was me setting up the SDK wrong or using a version with errors so I flashed the latest AT command firmware to see if the problem was in the hardware. The chip gave the same problem. A normal boot message followed by nothing. Occasional, after resetting the chip, I'd receive a stacktrace like this:

Exception (0):
epc1=0x4022c0e0 epc2=0x00000000 epc3=0x00000000 excvaddr=0x00000000 depc=0x00000000

ctx: sys
sp: 3ffff850 end: 3fffffb0 offset: 01a0

>>>stack>>>
3ffff9f0:  4022c0e0 00000004 3ffee734 00000001
3ffffa00:  00000001 19161310 24221f1c 2e2c2927
3ffffa10:  00002f49 3ffee6b8 4022dff4 3ffee688
3ffffa20:  3ffee688 00000000 3ffee734 3ffee688
3ffffa30:  3ffee688 3ffee734 3ffee688 00000000
3ffffa40:  3ffee688 60000600 60000200 3ffffa70
3ffffa50:  40229c2b 00000000 3ffee688 00000000
3ffffa60:  40105f02 60000e00 00000008 3fffff10
3ffffa70:  4022eda6 3ffffa80 00000008 4021e332
3ffffa80:  00000000 00000000 00000017 88a020a6
3ffffa90:  00000000 b20017e3 0000712a 3fff0b2c
3ffffaa0:  00000000 40201dcd 3fff0b2c 3fff0b2c
3ffffab0:  3ffee1fe 40233310 00000001 00000000
3ffffac0:  00000001 3fff0b2c 000002f4 003fc000
3ffffad0:  40105666 00000002 3ffee1fe 4021aebb
3ffffae0:  4021b534 60000e00 3fff0b2c 4021b50f
3ffffaf0:  40104eac 000003fd 00000002 60000200
3ffffb00:  3fffff10 c235e4f1 108275c5 7f3da5d8
3ffffb10:  ffff02fc ffffffff ffffffff ffffffff
3ffffb20:  ffffffff ffffffff ffffffff ffffffff
3ffffb30:  ffffffff ffffffff ffffffff ffffffff
...

During this time I am also aware that the chip was throwing off a lot of RF interference as every time this stack was printed, every device connected to wifi within a ~10m radius of the chip was disconnected and could not re-discover any network for around 10 seconds.
Is it possible this chip is simply defective? Is there an issue with my power supply? I am providing the 3.3v regulator with a 5v 2A USB power brick. All of the capacitors are electrolytic.


texts:
I'm designing a PCB board (low current, low frequency) mainly consisting of low frequency SPI and analog sensors.

Are wider traces better or does it not matter?

And which is better, consistent trace width or varying (to its maximum at its location)?

Also, is wider spacing between two traces better or does it not matter?


texts: Testing a power chain with a microcontroler

texts:
A microcontroler is powered by a double power supply.
Each of them is composed by a battery, a voltage regulator, and a diode to avoid current flowing from one side to the other.
Here's a schematic. Microcontroler is connected to net "5V".

Now I want to monitor all the elements of this chain for diagnostic purpose:

Batteries, not show on the drawing, are monitored with an voltage divider connected to an ADC
Voltage regulator is monitored the same way (VReg5V1 and VReg5V2 on the drawing)
I can not find a way to measure if each diode is "alive" or dead. I think the best way is to measure the voltage between each diode pads but I don't know how to interface this idea with the microcontroler.


texts:
My understanding of current noise is that you multiply the current noise by the input impedance and that gives you the noise level in volts.

I’m looking at the LMC6001 opamp and it states in the spec sheet “low current noise... adds only 1 dB at 100k ohms, .1 dB at 1 megaohms, and .01 dB at 10 megaohms”.

Why are they saying the noise goes down with higher input impedances?  That’s the exact opposite of how I’ve been working with these.


texts:
I'm looking at building an inductive charger (based on the design at http://people.oregonstate.edu/~watersal/documents/uhc_awaters.pdf), and there are a few components they use that are surface-mounted as opposed to the kind you can use in a breadboard (no idea what the name is...). I need help finding equivalents I can use in a breadboard. Any suggestions?

Here are the ICs in question:

LT6106 (high-side current sense amplifier)
TPS62000-05 (low-voltage step-down converter)

Any ideas whatsoever (or for that matter any suggestions for how to use surface-mounted ICs on a breadboard) would be tremendously appreciated.


texts: Two sine wave of 0 to 5V,with a frequency of 500Khz. How do I find the phase difference between the two sine wave

texts:
I have two sine wave with a frequency of 500Khz, and voltage range of 0 to 5V.
I would like to detect phase difference between the two sine wave; especially, when the phase difference between the two sine wave signal is zero.
I can think of PPL (Phase Locked Loop) but I am unsure.
Any help is appreciated.


texts: What is causing the input to my buffer to be damaged?

texts:
I have recently been having issues where the buffer of the circuit below has been damaged. The output pin (2) does not change with changes to the input pin (1). I sent 2 of these ICs to Fairchild for FA analysis, and their report indicates that there was an Electrical Overstress (EOS) condition at the ESD circuitry of pin 1 which caused metallization.

Could this be due to too much current going into pin 1? I have checked the circuit many times, and do not see anyway for the input pin to be damaged.


texts: Replace button by a component/circuit in 555 diagram

texts:
I need your help im crazy with this, i already tried many ways to do it, i need to replace the push button in this circuit by a component or circuit to be activated for a signal of 5 v such as a microcontroller one, please help me, could you draw a diagram for me with this.

Thanks in advance!


texts: So I have this circuit. I've been trying to figure out Vout. I couldn't find a specific formula for this situation. Can anyone help me figure out the formula? Thank you.


texts: How is a transmission line with a different characterisitc impedance shown on the smith chart?

texts:
A transmission line can be shown on the smith chart as a clockwise rotation, each 180 degrees corresponding to a quarter wavelength. But this is when the characteristic impedance (Z0) of the transmission line is equal to that of the smith chart (for example, everything is in the 50 ohm system and the characteristic impedance of the transmission line is also 50 ohms).

My question is, how is a transmission line with a different characteristic impedance shown on the smith chart? For example, how to show a quarter-wave transmission line with Z0 = 100 ohm on a smith chart in the 50 ohm system?


texts:
I want to connect my circuits together, but the problem is that the distance they have from each other are longer than my jumper cables can reach. So I had the idea to use a Category 5 (Ethernet cable) to connect my circuits over longer distances. How long can I have the cable go before problems will arise, such as voltage drops?

The distance between my circuits are at maximum 1 meter apart. And there are several circuits branching out to distances. The longest circuit will have 9V, and the other, shorter ones will have 5V. I am very noob with electronics, so please tell if there is anything else I should be aware of.

EDIT:

The data i am transmitting through the short wires are serial data, and the longer cable is a DC output to a motor. So the longer one is constant on or off, and serial is... Well, serial (Tx / Rx).

Baudrate for the serial communication is 115200


texts: What is the best sensor to use in a wearable device to monitor body temperature on a continuous basis: Thermistor, RTD or a semiconductor device?

texts: Most wrist-worn wearables on the market today don’t seem to feature body temperature sensing which makes me wonder if all these sensors are inadequate in some ways.


texts: Is ESP32-Pico D4 Kit able to charge batteries out of the box?

texts:
I was looking at this:

https://www.digikey.in/product-detail/en/ESP32-PICO-KIT/1904-1030-ND

I read somewhere that Dev boards like this have the ability to charge batteries (LiFePO4) when connected to USB and run of the batteries when not connected to USB.

Is this true? Does that mean that you just connect the battery to 3v3 & GND, and charge via USB? But then how will I know the charge level etc?

I tried going through the Datasheet, but couldn’t figure this out. There are a number of tutorials which describe how using an external module, you can charge the battery, but if there is already some circuitry built-in, I would prefer to use that to keep my footprint small.

Can someone point me in the right direction?

Edit: the getting started guide says that only one of the 3 mutually exclusive options (usb,3v3,5v), can be used at a time, so I guess the other poster was incorrect. If I’m wrong please let me know.


texts:
I am trying to interface an FPGA to a DAC device. The DAC has a JESD204B interface so the data clock is embedded in the serial data lane (it uses the 8B/10B encoding).

The DAC still needs a clock input, CLK, (LVDS) to drive the DAC sample rate clock. It can actually be a lower clock rate as the DAC has an internal clock multiplier. I think the lowest clock rate I am required to achieve would be about 65 MHz. Obvious the FPGA needs the same root clock to generate the samples at the same/correct rate.

I am trying to decide if I can simply use an FPGA pin to generate this 65 MHz clock. I'm generally not sure if this is a good idea or not (would jitter be particularly bad?). Also, I'm not sure what is the best method to achieve this. Do FPGAs have internal constructs specific to generating clocks on output pins, would I utilizes a simple DDR output block, or would it be best to consume a SERDES or GTX?

I guess the alternative is to use an external clock synthesis chip. Two output clocks can be generated, and one is sent to the FPGA for DAC sample production, and the other is sent to the DAC for sample consumption. I don't think the phase relationship between the two is critical.


texts: Digital Potentiometer (MCP4131) with Raspberry Pi

texts:
I'm very new in electronic stuff. I'm used to develop for desktop and mobile applications not for hardware products.

I try to wire up my Raspberry Pi board with an MCP4131 digital potentiometer. But it's not very easy to understand. I tried to build the projects from this previous thread. But Chris (the original posted in that thread) hasn't supplied a schematic of the wiring nor the successful running source code - so I tried my best to find out by myself:

What's the meaning if P0A, P0W, P0B? I tried to measure the voltage across P0A and P0B but it's always 0V. To which connectors should a LED, buzzer, ... be connected to regulate? (P0A-P0W or P0B-P0W)

My Python code look likes the following (tried to adapt the hint with writing out eight 0's before the value):

import time
import RPi.GPIO as GPIO

SPI_CS_PIN = 17
SPI_CLK_PIN = 23
SPI_SDISDO_PIN = 22 # mosi

GPIO.setmode(GPIO.BCM)
GPIO.setup(SPI_CS_PIN, GPIO.OUT)
GPIO.setup(SPI_CLK_PIN, GPIO.OUT)
GPIO.setup(SPI_SDISDO_PIN, GPIO.OUT)

def set_value(value):
    print "here"
    GPIO.output(SPI_CS_PIN, True)

    GPIO.output(SPI_CLK_PIN, False)
    GPIO.output(SPI_CS_PIN, False)

    b = '{0:016b}'.format(value)
    for x in range(0, 16):
        print 'x:' + str(x) + ' -> ' + str(b[x])
        GPIO.output(SPI_SDISDO_PIN, int(b[x]))

        GPIO.output(SPI_CLK_PIN, True)
        GPIO.output(SPI_CLK_PIN, False)

    GPIO.output(SPI_CS_PIN, True)

while True:
    for level in range(0, 128):
        print 'level:' + str(level)
        set_value(level)
        time.sleep(0.1)

    for level in range(127, -1, -1):
        print 'level:' + str(level)
        time.sleep(0.1)

Is there an easier way to use the MCP4131? I know the RPi supports the SPI protocol, but I'm not sure how to handle the multiplexing, because the RPi has one dedicated pin for SDI and SDO.


texts: XL6009E1 boost converter weird +40V voltage spike when feeding in 3V

texts:
I'm using a DSN6009 boost converter which uses the XL6009E1 chip, with the following specs:

3-30V input voltage, with an optimal range of 5-30V input voltage
5-35V output voltage, with a maximum current of 4A

I noticed that when I give an input voltage of around 3.33V, the output voltage spikes to 40+ volts and I don't understand why.
I get that this is outside of the "optimal" range but why would it do this? When the voltage sink under 3V the output voltage simply decreases but just around this 3.33V point, it goes crazy high.
I was planning to use it to increase the output voltage of a solar panel plug into a MPPT board which minimum input voltage is 6V, but without some kind of over-voltage protection I'm worried it will just fry my board...


texts: When I update the PCB layout from the schematic, it will place some room on the PCB editor for each sheet. How to remove this all in once ? Is there are a way to select them all in once and to delete them?


texts: Can someone explain how this bias circuit works to output only positive voltages?

texts: This is confusing me because there are two power sources in this circuit. (120 V AC and the 5V pin from the Arduino which is DC.) The output is measured at the point all the way to the right (Arduino Uno). Thanks in advance


texts: How to calculate reduction of inductance eddy currents in ferromagnetic core?

texts:
Suppose you have a LC circuit. Now at high frequency the core loss of the inductor meaning hysteresis and eddy current loss will increase. When this happens the frequency increases while the inductance will decrease.
Now how can one calculate the decrease of inductance due to the eddy currents?


texts: What is the performance tradeoff of using different resistors with the LM317. For example using a 300 Ohm and 400 Ohm resistor vs. using a 3k and a 4k resistor. Specifically I am interested in knowing power consumption, available current, and percentage of error, and what causes these to change, if they change.


texts:
I'm moving my project from the Uno to the smaller ATTiny85, and I'm having some problems. It builds and uploads just fine, but I think I've messed up the serial communication somewhere along the way.

What I have is a cheap RF link and a Dallas 18B20 temperature sensor. When I moved to the ATTiny the compiler stated it could not find SoftwareSerial.h, so I'm using TinyDebugSerial.h instead.

I connected the RF transmitter on the pysical pin 2 (or digital 3 / analog 3) but nothing happens. Anyone have a clue?

The code: http://pastebin.com/m0W1SNuY

The wireless transmitter: http://www.dx.com/p/433mhz-wireless-transmitter-module-superregeneration-for-arduino-green-149254#.VJqsZl4AQ

The temperature sensor: http://www.dx.com/p/ds18b20-temperature-measurement-module-blue-215793#.VJqsq14AQ


texts: calculate the ouptut of two operational amplifiers in a series

texts:
i want to calculate Vs which is the output of this circuit

simulate this circuit – Schematic created using CircuitLab

so i just want to equation that can help me find Vs.

please help me, because i have an exam tomorrow, and i am frustrated.
thanks in advance


texts: Understanding this IBD to make a Guess Game in VHDL

texts:
I am given an assignment of making a guessing game for a Cyclone II FPGA in VHDL.

I have the following IBD diagram about the game:

The purpose of the game is to guess a secret number that the opponent has entered.

The description of the game says the following:

  After entering the guess, a press on a button will evaluate the result
  as “Hi”, “Lo” or “–”.  The secret number is entered manually by your
  opponent.

  Design a game with an interface as shown in the IBD.

  It needs the following functionality:

  With no keys pressed, the displays show the current input value.
  With “Set” button pressed, the input value is stored as the secret number.
  With “Show” button pressed, the secret number is displayed.
  With “Try” button pressed, the guess is evaluated and the result is displayed as “Hi”, “Lo” or “–”. The IBD shows the overall building
  blocks in the design.

My question is...

How would it be possible to use the "try" input that goes into the "Compare Logic" entity, when "try" is only a std_logic and not a std_logic_vector to make a guess about a number when it can only be 1 or 0 (on or off)?


texts: Instrumentation amplifier for load cells

texts:
In the most part of tutorials I see they use INA125 as the instrumentation amplifier for load cells.

Is it ok to use another cheaper amplifier as the AD8237? Or is there a specification or peculiarity that I need to consider?

I want to use a gain of 1000 (as the load cell rated output is 1mV/V) and the power supply can be 3.3V or 5V (I am still deciding). It is possible to get an output equals to the power supply with these amplifiers?

Thanks


texts: Single-Phase to Three Phase Cycloconverter

texts:
When my classmate report about cycloconverters. He discussed about different classifications and types of cycloconverters. He also discussed how Single-phase to Single-Phase Cycloconverters operate. But when he approached Three-Phase to Single-Phase and Three-Phase to Three-Phase Cycloconverter's operations, he discussed it not very well leading to a lot of confusions. Almost all of the answers to those confusions was answered through Internet except one:

    Is there any Single-Phase to Three-Phase Cycloconverter existing? How does it operate?


texts:
We are using RF radiation in between 0.3 and 100MHz for evaporative cooling of Rb87 atoms in vacuum. For example, in one application we ramp our frequncy in a three-part linear ramp from 80 to 1MHz during 8 seconds.

What would be the ideal antenna design for this frequency range?

Currently we are using a coil antenna with 3 windings of copper wire (1mm diam.) with a diameter of 4cm. We have no R or C present, our antenna is directly connected to an RF amplifier (Mini-Circuits ZHL-3A +).

The efficiency of our cooling depends on the RF power we can deliver to our atoms (Rb87). So far, we have measured a strong dependence of efficiency vs. distance (the closer the better, roughly linear dependence), but we are limited to ~3cm distance by our vacuum chamber. We have not observed any strong efficiency dependence on the angle of the antenna axis w.r.t. to the atoms. It seem the antenna is radiating, roughly speaking, homogenously in all directions (c.f. near field?).


texts: Communicate PIC with digital scales/DMMs

texts:
Is it possible for anyone to make a PIC(I'm thinking of using 16F628/16F628A) communicate with another device, in this case a digital scale or industrial digital multimeter using USART/serial port communication?

I know that connecting digiscales to PC and reading data thru serial ports is possible (I've done this before so I know I could). I was just wondering if anyone has ever tried to use PICs or any microcontrollers in place of PC. The change is needed since where I am going to implement this thing, the PC option can't be used(it's not there), and using PIC is much much cheaper.

I got codes for a 16f84 communicating to a PC with me(got it off electronics-diy.com, somehow blocked now), gonna try converting it to 16f628A compatible first. Anyone who has ideas do share.


texts:
I can understand some of the electronics concepts and components, like diodes, resistors, thyristors, capacitors, inductors. But transistors I still fail to grasp the way they work and what role they play when in a circuit.

Can I understand them only reading theory about them, without hands-on lab experiences?
What good literature (preferably on the Internet) can you recommend to me about transistors, for a person that understood a broad area of other components, but transistors still are a big enigma?
Is there some free online simulator where I can place circuits including transistors and after see the electrons fluxing,immitating a real-life circuit?


texts:
I'm looking for a way to completely shutdown power supply to two Modules (UltraSound HC-SR04 and a 433 MHz transmitter unit) while the ESP8266 Module is in deep sleep mode.
I bought some MOSFET IRF740 units because they were recommended by the clerk in the electronics store for that kind of undertaking.
I wired everything the way I think It's supposed to:
Gate = GPIO 14
Drain = Ground of HC-SR04 and 433 MHz
Source = Minus From the Circuit
The Whole system is powered via 3 1,2 V Batteries so there's 3,6 Volt

Problem:
I defined the ping as output and set it to low to test the whole thing but there was still a reading from the HC-SR04 Module although this should only be possible if the ping is HIGH?

Question:
Is my setup wrong... Did I misread the purposes of a MOSFET? Is 3,6 V not enough to switch the system from Power On to Power Off?

I edited the code a bit and found out that it works if I putting the Pin on LOW twice ... ?
So like this:

const int GATE_PIN = 14;
digitalWrite(GATE_PIN,LOW); //SensorPower --> OFF
digitalWrite(GATE_PIN,LOW); //SensorPower --> OFF

this sets the Pin to low and the MOSFET switches


texts: why need to connect ESD diode close to the connector?

texts:
It is noted that TVS should be placed close to the connector.
What is the significance of placing close the connector?

Added the snapshot for reference


texts: Is there such a thing as analog and digital compatible cmos or ccd sensors?

texts:
I'm way over my head with this one but I am trying to learn about cmos/ccd(preferred) sensors in order to build my own camera. Looking to get analog video from a sensor in a very small package size <7mm.

The sensors I've come across all list digital specifications but from my understanding imaging sensors are inherently analog.

For example this is a cheap inexpensive sensor I've found.

https://www.arrow.com/en/products/ov05695-ga4a-1b/omnivision-technologies

Do I only need an analog compatible video driver?


texts: Can I use an ATmega328P without Arduino, just using it in a breadboard for projects?

texts:
I am thinking of using ATmega328P for a project so can I use it without using an Arduino board, just in a breadboard and use other programmers to burn and use Atmel Studio and C to program it.

Is ATmega328P a good choice for this or do I need to use another microcontroller? Please suggest me the name of another microcontroller.

My project needs to use LCD, ADC, and IR sensor circuit. Can you also suggests programming material for ADC and LCD interfacing with ATmega328P in the C language?


texts: Creating a +5V/-4V Clock with a PIC Micro

texts:
I'm working on a project to drive a CCD array which needs a particular signal with a high of +5V and a low of -4V, changing fairly rapidly. I'm using a PIC18F4620, which as far as I'm aware, looking at the data sheet, cannot produce a negative signal directly.

Above is the design I did a while ago with the components I had available. The inverter is quite slow, so I used a transistor with a switching signal from the PIC. Another signal is output at 0V/5V from the PIC. The two signals alternate so that at any one point, either the negative signal or the positive signal will be sent to the CCD.

Is this the right kind of idea? I tried using a diode to ensure the signals aren't going the wrong way (instead of going to the CCD), but as one is negative and the other is positive, this doesn't work. I feel like there must be a much simpler way to do this. Any help?


texts: TXE Interrupt is not generated ARM STM32F103C6

texts:
I'm trying to write a class to have the possibility of sending data using UART by TXE (TDR is empty) Interrupt. The class uses only USART1. The class has a ring data buffer to send. I have written a similar class for AVR (ATmega) and I would like to repeat such functionality.

At the moment I don't have the hardware (STM32), but I am using Proteus v.8.6. The start of sending is to enable TXE Interrupt. The main problem is TXE Interrupt is not generated. If I enable RXNE Interrupt and send one byte to the STM32, I will see all my data (from sending buffer) correctly are sent. Hence I can enter in USART1_IRQHandler only due to RXNE Interrupt. I'm not sure, perhaps it's a simulation problem. Also I use Atollic TrueSTUDIO v.9.3.0. I'll try to provide comprehensive information about my code. Sorry for my question, I'm a novice with STM32.

main.cpp

usart_transmitter UsartESP; //Usart class object declaration
int main(void){
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  UsartESP.ini();           //USART1 Initialization
  UsartESP.print("Hello from class!");
  while(1){}
}

stm32f1xx_it.cpp

extern usart_transmitter UsartESP;
void USART1_IRQHandler(void){
    //If Interrupt due to TDR is empty
    if (USART1->SR & USART_SR_TXE){
        UsartESP.handlerTDRE();
    }
}

usart_transmitter.h

const uint8_t BUFFER_SIZE = 100;    //Size of sending data buffer
class usart_transmitter{
  private:
    char _Data[BUFFER_SIZE];  //Data buffer
    uint8_t _PushIndex;
    uint8_t _PopIndex;
    uint8_t _IsOverflow;

    void push(char symbol);
    char pop();
  public:
    void ini();                 //Configuration Usart1
    void print(char* message);  //Put string message to sending buffer
    void handlerTDRE();         //Interrupt TDR is empty handler
};

usart_transmitter.cpp

void usart_transmitter::ini(){
    for (uint8_t i=0; i<BUFFER_SIZE; i++){
        _Data[i] = 0;
    }
    _PushIndex = 0;
    _PopIndex = 0;
    _IsOverflow = 0;

    RCC->APB2ENR |= RCC_APB2ENR_USART1EN;
    RCC->APB2ENR |= RCC_APB2ENR_IOPAEN;
    //Tx - Alternate function push-pull
    GPIOA->CRH &= ~(GPIO_CRH_CNF9_0); //CNF9[0] = 0
    GPIOA->CRH |= GPIO_CRH_CNF9_1;    //CNF9[1] = 1
    GPIOA->CRH |= GPIO_CRH_MODE9_0;   //MODE9[0] = 1
    GPIOA->CRH |= GPIO_CRH_MODE9_1;   //MODE9[1] = 1

    //Rx - Input pull-up
    GPIOA->CRH &= ~(GPIO_CRH_CNF10_0);  //CNF10[0] = 0
    GPIOA->CRH |= GPIO_CRH_CNF10_1;     //CNF10[1] = 1
    GPIOA->CRH &= ~(GPIO_CRH_MODE10_0); //MODE10[0] = 0
    GPIOA->CRH &= ~(GPIO_CRH_MODE10_1); //MODE10[1] = 0
    GPIOA->BSRR |= GPIO_ODR_ODR10;      //PxODR = 1

    USART1->CR1 = USART_CR1_UE;  //Usart1 Enable
    USART1->BRR = 16;            //4500000 baudrate

    USART1->CR1 |=
    (USART_CR1_TE) |    //Enable Transmitter
    (USART_CR1_RE) |    //Enable Receiver
    (USART_CR1_RXNEIE); //Enable RXNE Interrupt

    USART1->CR2 = 0;
    USART1->CR3 = 0;

    NVIC_EnableIRQ(USART1_IRQn);  //Enable USART1 global Interrupt
}

void usart_transmitter::push(char symbol){
    _Data[_PushIndex] = symbol;  //Put character to buffer
    _PushIndex++;
    if (_PushIndex > BUFFER_SIZE-1){
        _PushIndex = 0;
        _IsOverflow = 1;
    }
}

char usart_transmitter::pop(){
    char data = _Data[_PopIndex];
    _PopIndex++;
    if (_PopIndex > BUFFER_SIZE-1){
        _PopIndex = 0;
        _IsOverflow = 0;
    }
    return data;
}

void usart_transmitter::print(char* message){
    uint8_t i = 0;
    //Placing string to buffer
    while(message[i] != '\0'){
        push(message[i]);
        i++;
    }
    USART1->CR1 |= USART_CR1_TXEIE; //Enable TXE Interrupt
}

void usart_transmitter::handlerTDRE(){
    char byte = pop();
    USART1->DR = byte;
    //Checking criterion to stop sending
    if (_PopIndex == _PushIndex){
        if (!(_IsOverflow)){
            //Disable TXE Interrupt to avoid circularity of interruption
            USART1->CR1 &= ~(USART_CR1_TXEIE);
        }
    }
}


texts:
Question is :

The answer I attempted is below:

Is this correct, or did I make a mistake somewhere?


texts: How to determine the length of the last data field in a SDO block transfer?

texts:
I've got a problem with the implementation of the CANopen SDO Block Transfer. The transmission is ok except the last block:

...
TX:  "     618   [8]  5B 65 73 74 0A 44 69 65"
TX:  "     618   [8]  5C 73 20 69 73 74 20 65"
TX:  "     618   [8]  5D 69 6E 20 54 65 73 74"
TX:  "     618   [8]  DE 0A 00 00 00 00 00 00" //last block (5E | 80 = DE)
RX:  "     598   [8]  A2 5E 00 00 00 00 00 00" //ACK from Server: last block 5E

The data is a file which only contains Dies ist ein Test\n (engl: This is a test\n) several times. So the last byte that contains data is the 0A of the last block but an SDO has to be always 8-Byte, so the rest is filled up with zeros.

On a SDO Block the first Byte counts the actual Block (max 7fh=127d). The MSB of the first Byte marks the end of a Block Download.

In this example the SDO-Block sequence no is 5E and it is the last block so the MSB has to be marked as 5E OR 80 = DE. But the last block has to mark the size of non data bytes, see [1].

So I didn't find any documentation which describes how the first byte has to look on the last sequence in block mode. In a 'normal' SDO the 2nd and 3rd bit masks the data. A good explanation can be found in [2].

My Question is:
Please, can someone explain how this first byte on the last sequence has to look like? Which bits must be set in this example?

[1] CIA 301, Chap 7.2.4.2.11 Service SDO block download end
[2] byteme, chap. Expedited Read Dictionary Object


texts: A question about sizing and placing fuses

texts:
I will make a circuit used with two DC power supplies. And I plan to put everything in one plastic or metal enclosure. I will mount an AC socket to the enclosure box which will supply AC input for DC power supplies. Something like below:

If I want to limit the max total current sourced by the power supplies, should I add one fuse to AC line or plus terminal of DC power supplies?

Let's say I don't want both PSU1 and PSU2 to exceed 500mA. Should I put 1A fuse to AC socket and 500mA fuse to each DC outputs? Or should I use a fuse with a higher rating? And the types of fuse matter? I don't know the common practice and believe some experienced answer help.


texts: how to design power for arduino and servo

texts:
I'm designing a system where an arduino (3.3v) will run continuously, and occasionally turn a MG996R servo - this servo is pretty strong and can draw more than 2 amps.

The servo runs fine off 4 AA batteries - I want to make the arduino run off these batteries as well.  Is this a good idea? Or should the servo and arduino batteries be separate?

If possible, I'm guessing I'll need a capacitor from what I see in other posts.  If so, is there a formula for a capacitor size that I need for this kind of servo?

Thanks for your help, any tips or pointers would be greatly appreciated


texts: How am I able to jump my car when I ground one of the jumpers?

texts:
Electrically, when I think of jumping my car, I visually see basically putting a stronger voltage source in parallel with a weaker voltage source (see http://imgur.com/qz8jX). However, on every car forum, they say to ground out the negative jumper on the engine-block of the dead car (see http://imgur.com/6RPYB)

All I hear is "there's gas that's formed when a battery dies, and there might be a spark that causes an explosion", that makes reasonable sense and all, but aren't we opening the circuit? Is the car's negative technically "ground"? (I reference this post: When a battery is your power source, what is ground?)

If we've defined (as described in the other post) the engine block as ground, is there actually a potential formed between the car and earth-ground?


texts:
I am trying to get more familiar with using a 74HC14, as an experiment I have an ldr set up in a voltage divider configuration and the center tap goes to the input of the 74HC14 input 1.  I have all of the other inputs tied to ground.  Everything is soldered together on a perf board.  I have a .1uF, .01uF, .001uF, .0001uF cap on the power pin (probably overkill).  Input voltage is 5v.  The voltage divider and the IC are both powered off the same rail

The IC triggers as expected when light is shined on/removed from LDR.  Below is the waveform I am getting for the falling edge, it is very consistent from test to test.

What I don't understand is why the signal is dropping to -2.4 or so when triggered then staying below 0.

The rising edge has an overshoot to about 6v but is smoother. Any information/guidance would be appreciated.

https://drive.google.com/open?id=1oG6Eh2Gwj9bf4IXGBJ9i5LoJoLvwybN6


texts: What are the two components of this waveform generated by a MS-15 hall effect current sensor?

texts:
I am doing a lab write up for school in which we measured the output of a current sensor which was part of a power supply we are using with our ELVIS boards. Here is a schematic of the basic design showing a transformer at the top and the current sensor/source at the bottom. I highlighted the wire where we took our data.

We then used an oscilloscope to capture the output waveform. Here are the results from the data

Part of my assignment is describing "both parts" of the waveform. I believe this is referring to the peak and then the following square wave. Me and my partner believe that the square wave is generated as a result of the hall effect, but to be totally honest we do not know. Nothing so far in our class or research has indicated to us what could be causing the peak.

Any clues? Sorry the question is somewhat vague, but I have not been able to find any information regarding the waveform.

Thanks guys!


texts:
A friend of mine purchased a pack of little ball shaped widgets from Banggood. Each contains an RGBA LED with a integrated timing circuit inside the LED lens itself. The ball flashes in different colors, and different patterns in sequence.

When opening one of the widgets, it simply contains an RGBA LED, which has only two leads for connecting the battery.

Does anyone know where one can purchase one of these LEDs or possibly know of the whereabouts for a datasheet for this product?


texts:
As I understand it, digital multiplexers contain multiple inputs (2^N), one output, and N selector lines. The selector lines are used to select which input is mapped to the output line. I then understand that a demuxer takes a single input line and based on the selector lines maps the input to one of multiple outputs.
So, assuming the above is correct, my question is how does using a mux/demuxer pair to change 16 line parallel communication signal to 1 mux'ed signal, then back to a 16 parallel signal work? How would the demuxer know the selector signals to use to change the mux'ed signal back? Do you need to run the mux'ed signal line with the selector signal lines together so that the demuxer knows the proper mapping?


texts:
I know that it is possible to generate higher voltage from lower voltage source, I just don't know how ...

Anyway, few days ago I got this:

http://www.ebay.com/itm/260922050640?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

As you can see, it's volt-meter and that's the mistake I've made. I just needed some kind of analog display that I could control (I want to make something else, not volt-meter). And now I know that I should have bought ampere-meter display, so that I could control it using current, and not voltage.

So, my question is, can I control that 30V volt-meter using 5V components (any ideas are welcome) ?

If there isn't any way (or any practical way), how can I generate 30V from 5V ? Will that be linear ? I mean, will the output voltage linearly depend on input voltage ?

In the end I would want to be able to control that volt-meter display using PWM signal.

Thanks :)


texts:
I have a PIC18F1330 which does not have native USB capabilities (see datasheet). I am planning to load it with a bootloader using my PICkit the first time and then programming from a USB port after that. I have a Micro-B USB jack and an FT232 (datasheet) to allow me to program it using the RX/TX pins on the PIC (RA3 and RA2 on the 28-pin QFN). However, I am not very familiar with this method of programming micros so I'm looking for some verification. Here's the schematic I have so far:

Is it as simple as connecting pins 24 and 25 on the FT232 to pins 7 and 8 on the PIC? Or must I use some of the other connections as well? I have not found much information for programming PICs through an FT232, mostly AVRs.

You can ignore some of the net labels that don't make much sense, they are used for other parts of my project.

EDIT: This post is asking about the connection between the FT232 and the PIC18F1330. I am NOT asking about the bootloader.


texts: Elegant naming convention for pins with (many) multiple functions in gEDA

texts:
I use gEDA suite for schematics and PCB layout and I sometimes need to create new components (i.e. symbols) for gEDA library is rather generic. Not a problem to me. But with the advent of micro-controllers it's not uncommon to have pins with many alternate functions.

In general pins are named against their functions, for instance SDA or SCL, RESET, Vcc, Vdd, you name it. But what do you do with pin names such as PC1 (PCINT13/ADC10/ICP1/SCLUSCK/XCK1) on the ATtiny1634?

Not only do I find such names ugly and impractical but they also tend to inflate the symbol, turning it into a fat block instead of an elegant rectangle... (Golden Ratio anyone?) Moreover extremely long pin names also clutter the PCB layout:

Now I want the symbol to carry all the alternate functions but hidden, preferably. Ideally in gEDA the pin name would look like pinlabel=PC1. But how do you add the rest? I could only think of adding [hidden or not] pinlabel attributes.

  pinlabel

  This attribute labels a pin object. This attribute is primarily used by gnetlist to support hierarchical designs.
  This attribute must be attached to the pin and be left visible. Please make this attribute green (instead of the default attribute yellow).

But gEDA documentation isn't clear; my question is: does it allow for multiple pinlabel occurrences?


texts: Power off/ failure to trigger NO state on resumption

texts:
First of all I am no electrical engineer (would love to be one!) so apologies upfront if this question is only fit for the sci-fi section. If it is, I'd still like to see a solution to this:

Appliance is connected to switch X which is plugged into mains AC socket. Switch is set to ON, but appliance stays off. Upon a power failure, switch X detects the power loss and upon power resumption, becomes "active" and allows power to flow through, powering up the connected appliance. Possible reset of switch X through second power off and on at the AC socket or a button push.

Is this available/ possible?

I want to hook up a vacuum pump to an aquarium sump set-up but don't need that appliance running 24x7. Upon a power failure, the sump will fail. When power resumes, the sump will still not work, requiring the vacuum pump to draw water into the pipes, hence the need for this relay.

Thanks in advance!


texts: Solenoid Valve blowing power LED - how can i protect the LED?

texts:
I have this simple circuit setup and working well to turn a solenoid valve on (close it) and off (open it again) for a watering system I use.

missing is an on/off switch before the VCC.  However, I have an LED connected to indicate when I have my switch on (system ready/on).  If I leave the relay in the "ON" position (so the solenoid is powered), switch the system off, then back on again (powering the solenoid on, because the relay is latching and left in the on position), sometimes the LED blows (i.e. stops working and i have to replace it).

I want the feature of leaving the relay in the on position (why I chose a latching version), but how can I protect the LED from whatever is happening (I assume a negative over voltage is being created by the solenoid??).


texts: Protecting current measuring shunt resistor from overcurrent

texts:
To measure the current "drawn" by a 12V PTC heater element and to be able to switch it on and off from an AVR micro controller, I have come up with the circuit below.

The PTC heater element has about 2 Ohm cold and 8 Ohm at steady state and is powered by a 12V 10A switching power supply.

I tested the circuit and it works okay, I can measure the expected 600mV (cold) and 150mV (steady state) across the 0.1 Ohm 9W shunt resistor.

Now I suppose I should protect the shunt resistor from overcurrent, i.e. in case the PTC heater element has a short circuit.
In code I'm switching off the relay when the measured current exceeds 9000mA and there is a 10A fuse in series with the heater and the shunt.

But what if for some reason the power supply "delivers" only, say, 8A? In that case, neither the software protection nor the fuse will kick in, and the shunt will be severely overloaded. Am I right?

If yes, how would I solve this? Would I have to add some thermal protection for the shunt resistor?


texts:
I want to build a spot welder but I do not have a microwave transformer or any other big one, so I decided to make my own toroidal core by rolling a thin steel sheet.

1- Can I use galvanized steel or it must be only steel.

2- Do I have to  varnish the sheet before rolling it to isolate the layers as in EI cores?


texts: Are there errors in the CD4013B datasheet by TI?

texts:
The CD4013B datasheet by TI contains the following statement:

  Setting or resetting is independent of the
  clock and is accomplished by a high level on the set
  or reset line, respectively.

Table 1. Function Table in the datasheet matches this statement.

The datasheet also contains the following Logic Diagram (the colored alterations are mine):

It seems to me that the datasheet contains at least one error and one contradiction:

(a) Inverter (A), or any one of the series inverters in the Q circuit, should not be there. As drawn, the Q output will be a copy of the Q̅ output.

(b) The transmission gate (B) makes sure the RESET input will only take effect when the CL input is low (or high? I've never seen TGs denoted with such symbols and not sure what exactly "p" and "n" mean here). This is in contradiction with the statement above and the Table 1. (Meanwhile the SET input does work independently of CL, according to the diagram).

Main question: are the (a) and (b) above correct? (or am I -crazy- missing something obvious)

Additional question: can I consider the diagram illustrative and just ignore it, assuming Table 1 is normative? Or should I consider the details of the RESET function unreliable and design around them? (assuming I'm stuck with this chip)


texts: PCB with multiple Arduinos and onboard hub

texts:
I'm designing a PCB for an astronomical observatory which needs several Arduino Micro to control different devices. Since the circuit must fit a very small space, I'm putting an onboard USB hub to connect all the three ATMega32U4 (instead of putting 3 full Arduinos, hub and USB cables). There will be one micro USB connected to the PC. Something like this:

However, I'm confused about:

How to connect the various D+ and D- pins of the AVRs with the DP and DM pins of the Genesys GL850G USB 2.0 Hub Controller I'm using. Which shall be connected where? (I fear exchanging them)
Whether or not I really need all the capacitors, ferrite filters and inductors shown in this example of GL850G usage: what are they used for? Why so many capacitors in parellel on the 3v3 line instead of one bigger capacitor? And why is +3.3V needed?
Is this a valid circuit for a simple ATMega34U4? Same here, why so many capacitors in parallel (between VCC, AVCC and GND)?
The hub and the whole circuit shall be powered by a bigger 5V power supply instead of the USB standard 500mA. Is it a good practise if I just leave unconnected the PC USB power and give the circuit another +5V?


texts:
Consider the linear constant coefficient difference equation

$$
  y[n] - \frac{3}{4}y[n-1] + \frac{1}{8}y[n-2] = 2x[n-1]
$$

Determine \$y[n]\$ for \$n \ge 0\$ when \$x[n] = \delta[n]\$ and \$y[n] = 0, n < 0\$.

The answer is

$$
  y[n] = 8[(1/2)^n - (1/4)^n]u[n]
$$

My question is how do they get that? I can manually calculate the first few values of \$y[n]\$:

\begin{align*}
  y[0] &= 0 \\
  y[1] &= 2 \\
  y[2] &= 3/2 \\
  y[3] &= 7/8 \\
  y[4] &= 15/32 \\
  y[5] &= 31/128 \\
\end{align*}


texts: Are bypass diodes in low voltage solar panels with parallel cells really needed?

texts:
I have 5 solar cells, ~3W ~3.3v 900mA each, a total ~15W, connected in parallel.
Considering the low voltage and current involved, do I still need a diode attached to each cell?
Will I still risk damage if one or more cell are shadowed or will I just risk power drop?


texts:
Q. Write the MU0 register transfer level organization by adding index register. Give the control logic for the following instructions and explanations.

LDA S,X ; A:=mem((S)+[X])
STA S,X ; mem((S)+[X]):= A
INX ; X:= X+1
DEX ; X:=X-1

This is the control logic table without adding index register:

This is the RTL design without adding index register:

The question here is to modify the RTL organization shown to include the X register, indicating the new control signals required and then modify the control logic in the table to support indexed addressing.


texts: Ceramic Capacitor value for 24v 10A DC Motor

texts: I'm running 24v 10A DC motor in my robotic system. For eliminating the EMI, I need to use ceramic capacitors at the terminals on motor side. Can anyone suggest me the the capacitor value to be used at the motor end.


texts: Floating Voltage to Bias a P-Channel Mosfet without Exceeding Source-Gate Max Voltage

texts:
I'm not sure if this is what you'd call "floating voltage" or not.  I'm lacking on some terminology so bear with me.  Here's the circuit with explanation below:

The premise of the circuit is this:  I want to power L1 coil with square pulses.  You can see I've got a freewheeling diode to handle the back emf field collapse to protect the circuitry.

From previous experiments and talking to others on here, I learned that using an N-channel mosfet on the high side of the coil like this doesn't work because the large negative voltage during the back emf coil collapse puts negative voltage on the mosfet source which causes the gate (at zero volts) to turn on while the field is collapsing.

I experimented with BJTs and they make it easy to fix the problem, but they also get hot.  I really want to use mosfets for the ability to pass a lot of current with minimal resistance.  So I've switched to a P-channel mosfet in the circuit shown.  This seems pretty simple but I'm adding a level of complexity.

I want to have arbitrarily high voltage in the main circuit -- 80volts shown here but it could be more or less.  Since the voltage is prone to change in use conditions, the circuit design must be agnostic to the actual main power voltage .  In the 80 volt example shown, since the p-channel mosfet requires 80volts at the gate to turn it off, I have added a small resistor network to supply the required voltage from the power src.  You can see I'm using a 555 and some BJT's to pull down the gate voltage to turn it on.

Now the tricky part.  From my understanding, I can't drop the mosfet gate all the way to 0V because that would make an 80volt difference between the Source and the Gate which would destroy it.  I need to make sure the gate drops to about 12 volts less than the Source but drops no further.  THe solution I've come up with is to add a 12 volt zener diode and adjust the resistances accordingly so once the gate starts to become more than 12 volts less than the source, the diode will reverse bias and bring the gate back up.  It should stay right around 68volts if the power supply is 80 volts -- as long as the BJT is biased on anyway.  Once the BJT turns off, the gate will recover to 80 volts and shut off the mosfet.

So my question is simply this:  Am I doing this right?  Am I over-engineering it or perhaps doing something wrong?  Let me know.  Thanks!

Jim


texts: Identifying a component on the circuit board of a mobile phone

texts: I need to identify this component which I found on a circuit board inside a mobile phone.


texts: How to calculate gain of wheatstone bridge+differential amplifier?

texts:
Can someone help me solve this task?

The schematic shows that the sensors are connected in series parallel and that the measurement is done using a Wheatstone-Bridge and a difference amplifier.

A) Create a Wheatstone bridge by Circuitlab or by hand and balance it with a resistor of 330 Ohm and a voltage source (DC) of 5V for 23 degrees! Write down calculations.

B) Use Op-Amp AD8615 and create a differential amplifier that provides (near) 0V at the output for 23 degrees and (near) 5V for 100 degrees.


texts: I recently bought an old coffee maker but it doesn't work. Everytime I switch it on my earth circuit breaker goes off so my whole house doesn't have electricity. I already looked on google to find something similar to it. I think it might be a thermal resistor, but I don't know how to test it and if it's broken how to get the right part again because I can't read what was written on it.


texts:
Does the solder pattern on these huge pads indicate what might be going on ?

The parts would not work about 80% - 90% of the time. I am trying to follow the ramp_up-soak-reflow-ramp_down curve to the best of my ability. Using a standard 2-speeds hot air gun with no temperature control and set on the second speed as the first speed won't melt the solder. Using various quantities of leaded solder paste (and sometime a bit of flux if I find the paste too dry).

My previous design has had the landmark pad dimensions almost the same as the actual component feet dimensions - caused a great deal of solder bridging, but with these extra long pads no more shorts. However, they still won't solder fine...


texts:
I'm using Max4080 to measure the current:

simulate this circuit – Schematic created using CircuitLab

The problem is it can't detect short circuit because when RS- is connected to ground, Rsense will be at low-side. Max4080 is a high-side current measurement chip...

Is there anyway at all to make this chip to detect short circuit(with extra circuitry)?
Can I use this chip to measure the current and then detect the short circuit with something like this?

I know measuring current at low-side is easy and I'll eventually going to use it if I can't find a solution(easy/cheap/accessible) to measure the current at high-side.


texts: What could be this component and what is its work? Is it a fuse or may be a protection resistor?

texts:
I opened before some laptop batteries. But this is the first time I see it. This is an IBM ThinkPad cell battery.

See picture below, the two pins to the left are connected, resistance between left-right pins is around 46 ohm (45.9 & 45.3).

What could be? What it does? What the main benefit of using it here?

The way it was mounted on the top of transistor, may be indicate something.
As requested by PlasmaHH. Resistance raise with temperature, I used a cigarette lighter, 45.9 → 46.6 & 45.3 → 45.9 . Not much change in the freezer, 45.9 → 45.8 & 45.3 → 45.2 .

Closeup:


texts:
Sorry, I know this is a very basic question, but I've already searched a few universities' sites and through my books but none of them are giving me a direct answer.

If you specify the terminals that a circuit element is connected to( like V(bc)) but not the + and - signs, can the voltage of that element be interpreted anyway you want or do you assume that the positive end is the first terminal specified and the second terminal is the negative end. For example you are asked to find V(bc) is it assumed that the positive end is b and and the negative end is c or can you interpret it anyway you want?


texts:
I am currently redesigning a circuit to switch a spring applied brake using an Arduino Micro.
The current circuit looks like this (please excuse if I'm using wrong symbols, I'm learning by myself):

The the important part is the right half, BRAKE1 is the spring applied brake with a resistance of 137 Ohm. This is the datasheet and the brake is found on page 84 MCNB 2GR.
At the moment I am using a 2N3904 transistor to switch the 24V which is generated from a Mean Well RS-100-24 DC power supply.
I have found an issue with the circuit that I have soldered where when connecting the GND from the 24V DC source to the GND of the Arduino, I get a voltage of ~1.9V on my digital pins on the Arduino. If I disconnect the GND cable, the 1.9V are gone. (during this test, the 24V positive cable was disconnected)
I have also noticed that connecting an oscilloscope including its GND will remove the 1.9V.
From my research it leads me to believe that it might be a ground loop problem.
As such I would like to electrically isolate the Arduino and the 24V circuit using an optocoupler to switch the 24V on and off with a 5V digital signal from the Arduino.
There is so much information on optocouplers and here in chapter 3 I read that the available output current with an optocoupler is limited to small values. From the break datasheet I gather that it takes 0.175A of current which seems to be too much. How would I redesign my circuit to include an optocoupler and which optocoupler whould be necessary, considering I'm not sending data but only an on-off signal that doesn't need to switch back and forth too frequently?


texts: DRV8833 does not work with output of hobby RC receiver

texts:
I'm trying to drive the DAGU robot chassis with Pololu engine drivers. Driver requires - at minimum - the following connections:

VIN (for the motor)
GND
AIN1
AIN2
AOUT1
AOUT2
GND (for the logic)

I have made the following connections:

LiPo 2S provides ~7V, which is converted by unused ESC with BEC to 5V (powers up everything) (After connecting, I'm getting around 4.5V under load, maybe it's important)
FrSky X8R receivier acts as PWM generator; 1st channel is connected to AIN1, AIN2 is shorted to GND to provide logical 0; RX is powered from 5V, GND is common;
AOUT1 and AOUT2 are connected to the engine
VIN and GND of the driver are connected to 5V provided by the ESC and GND, respectively

Specific parts I've used are:

Pololu DRV8833
Dagu DG012-ATV
Taranis X8R RX

After powering the whole thing up and turning TX on, I only hear low buzzing noise from the engine, which changes a little when I push the TX stick up and down.

You can hear the buzzing on the video:
https://www.youtube.com/watch?v=oQYu7ONXzVo

I replaced the engine driver with another one (identical) with the same effect.

What am I doing wrong? Why isn't the engine turning?


texts: How to increase output voltage of an op amp well above the supply voltage

texts:
I have a circuit which produces a (not high speed) signal between 0 and 9 volts with an adjustable slope, and I would like to increase this output voltage to between 0 and 200 volts, which keeping it ground referenced.

Currently, I am using a PNP transistor connected as a common emitter, which is controlled by an NPN transistor and the output of the lmv358 op amp (the spice model I'm using comes from this website. Here is the schematic in LTSPICE:

Everything works as expected when I run an operating point simulation, but when I try a transient simulation, I get huge oscillations and the simulation rarely has time to finish:

(this is the voltage accross R3; it should be 4 volts).

What have I done wrong? I haven't been able to find similar circuits online, which suggests that maybe I'm missing something sort of obvious. How is something like this usually done?

Thanks!


texts: DW01A not allowing power in TP4056 circuit

texts:
Edit: Used wrong resistor at R_BAT1. The schematic was correct, the part I used was wrong.
I am using the following charging circuit. It is the standard circuit taken from the datasheets. But it is not working.

The line on the right leads to an LD3985M33R LDO and then to a microcontroller. All the other components are working fine, if I bypass the DW01A by shorting the battery ground and common ground - the TP4056 charged both my 18650 batteries fine and stopped charging once it was done, the switching circuit with AO34021A works fine, the LDO regulates perfectly and the microcontroller works fine as well. If I remove the short, the battery gets disconnected.
I bought a blue TP4056 module  that has the same circuit (I traced the leads with a multimeter) and it works fine without bypassing DW01A. I took the DW01A and the C_PROT1 capacitor from that board and used it in my board. My board still does not work. I placed the DW01A and C_PROT1 from my board on the purchased TP4056 module and the module works fine.
I am stumped and unable to figure this one out. I am probably missing something obvious. Could you please help me? Thanks in advance.


texts: High current buck converter has excessive ringing and poor regulation

texts:
I am designing a power supply to power two fiber-coupled diode arrays for a solid state laser. The diode arrays need a current controlled source of about 50 A and will have a voltage drop of < 2.2 V. The diode wavelengths drift with temperature so I need to be able to control the current output from diode tasing threshold (~12 A) up to the max of 50 A.

My prototype for this uses a MAX20096. This part at first look seems ideal: dual synchronous buck drivers with external MOSFET control and a SPI interface for control of driver current and status.

My design parameters are:

VIn: 8 volts nominal (range 7.3-8.4 V)
Vout: 2.2 volts
Current set: 50 A
Input ripple: 1%
Output ripple: 1%
Switching frequency: 500 kHz

My schematic for this is below. My calculations were actually based on the MAX20078 data sheet - this is a single channel version of the same part and its data sheet was more comprehensive. The MAX20096 data sheet focuses mostly on the SPI interface. I built a prototype board so the crucial parts (mosfets, inductors) are on a circuit board and not a breadboard to minimize noise and allow me to take reasonable thermal measurements:

For a load, I have two high power diodes in series with a 100 mohm resistor. I have built a simple program on an Arduino to communicate with the MAX20096 and this seems to be working fine.

The MAX20096 allows me to set current as a % of maximum. I've set for about 2 A current to test and the results are not what I expect:

The whole circuit rings like crazy.  Noise shows up everywhere and is so bad it swamps the serial connection between the Arduino and my laptop so once I start it I can't reliably read status from the chip.
The switching frequency is way off.  I designed for 500 kHz but I'm measuring 100 kHz. And the frequency isn't stable enough to get the scope to lock into it (maybe confused due to the ringing?). I have measured the values of the R/C network forming the frequency selection and they are within tolerance.
No matter what % of maximum current I choose I always read an output of 3.1 A from a connected ammeter and the duty cycle is the same. The 3.1 A varies if I change the load, so this isn't regulating at all.
When I can read status from the SPI interface the current readings from the MAX20096 randomly go from 0-9 A. This is probably periodic but I'm not reading fast enough.

Here is an example of the ringing. The top yellow trace is the output, reading about 2 V. The bottom trace is the input to the inductor at about 8 V.  Frequency here is about 96 kHz (the scope frequency readings are confused by the ringing):

A closeup of the ringing part of the waveform shows it's ringing at about 4.5 MHz:

Any idea what's causing this?

Also, I have some specific questions about the MAX20096 if anyone has experience with it:

The chip uses independent oscillators for each channel and I'm concerned this could set up a beat frequency on the input supply that could require a bigger input filter. Would I be better off using a chip with a single oscillator that runs the channels out of phase? I am considering using the MAX17559ACJ+ and re-configuring it for current regulation. This would require more parts to interface with a microcontroller.
These synchronous converters rely on the body diode for some conduction in the lower MOSFET to prevent shoot through. At high currents, would I be better off using a large external diode in addition to the MOSFET?
Why is the switching frequency so far off?
Why is the current read-back from the SPI interface so far off? (I'm wondering if the excessive ringing is causing noise back to the current sense inputs. I'm not using a kelvin connection to the current sense resistors and could be picking up junk here).
Voltage read-back from the SPI interface is also way off. I even read random values from channels when they are off. Might also be due to noise here.

Anyway, any ideas that could nudge me in the right direction would be greatly appreciated. This is my first buck converter, so I'm sure I made a whole bunch of newbie mistakes.


texts: Help on ID for SMD component (probably diode)

texts:
I recently smoked a DC motor control board and need help identifying the wounded component.

before picture (H2 and sideways 3)

and here it is, wounded

It looks to me like a resistor SMD; but, of what type/value?

Thanks and regards


texts: Is there a Smart Meter simulator which generates data

texts: I am working on a Smart Grid project and we want a real-time smart meter data. Because of the difficulty of getting this real-time data we want kind of software simulator that generates this data? Is there any helpful application like this?


texts: Some characters are not transmitted correctly from mega32 to ESP8266

texts:
i recently bought an ESP-01 for a simple wi-fi project reading the temeprature from a website .

First i wired the ESP-01 directly on the TTL converter (cp2102) to read the temperature and everything worked just fine at 9600bps with  the AT commands etc.

Then i created a program with winAVR for the mega32 to do the same thing using uart at 9600 bps (UBRRL = 0x68; ( or 104)  for Fosc=16MHz) but it didn't work.

So i used a logic analyzer to check what went wrong with the characters i sent .

The result was very strange since some of the characters (of the AT commands sent) going from mega32 (Tx) to ESP-01 (Rx)are not transmitted correctly .

I tried to decrease the baudrate of the ESP-01 down to 4800 but the lowest baud is 9600. I don't know if some firmware version has the option for lower baudrate.

For some reason mega32 cannot accurately transmit all the characters and I cannot understand why this happens. Maybe it has something to do with crystal but when i changed it the same thing happened. I put some delay before the faulty characters which fixed a few  but not all of them ( 1 or 2 out of 10+) (bad method, i know).

Also my i have connected my Tx pin (mega 32) to a voltage divider to convert it to 3.3v for the Rx pin of the ESP-01.

After lots of struggling i decided to ask for some help.

I attached my code and a snapshot from the logic analyzer for the AT command AT+CIPSTART=0,"TCP","api.thingspeak.com",80  (the corrupted one). The other two AT commands i use in the code before CIPSTART are transmitted almost... fine (the '\r' or '\n' are not transmitted correctly but somehow the ESP-01 accepts the commands).

The full code can be seen below

#define F_CPU 16000000UL
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include "LCD4BIT.h"
#include <stdlib.h>
#include <stdio.h>

unsigned char interface_var = 0;
unsigned char counter[34];
unsigned char var = 0;

void usart_init(void)
{
    UCSRB |= (1<<TXEN) | (1<<RXEN) | (1<<RXCIE) ; //  enable receive transmit of usart
    UCSRC = (1<<UCSZ1) | (1<<UCSZ0) | (1<<URSEL);
    UBRRL = 0x68; //  baudrate = 9600 , Fosc=16MHz, UBRR value = 104 (0x68)
}
void usart_send( unsigned char ascii)
{
    while(!(UCSRA & (1<<UDRE)));
    UDR = ascii;

}
unsigned char usart_receive(void)
{
    while (!(UCSRA & (1<<RXC)));
    return UDR;
}
void send_AT( unsigned char message[])
{
    unsigned char i=0;
    while(message[i] != '\0')
{
    usart_send(message[i]);   // This sends data to esp-01
    i++;

}

int main(void)
{
    //OSCCAL = 0xA9;

    unsigned char AT[] = "AT\r\n";
    unsigned char CIPMUX[] = "AT+CIPMUX=1\r\n";
    unsigned char CIPSTART[] =  "AT+CIPSTART=0,\"TCP\",\"api.thingspeak.com\",80\r\n";
    unsigned char CIPSEND[] = "AT+CIPSEND=0,110\r\n";
    unsigned char GET_DATA[] = "GET https://api.thingspeak.com/apps/thinghttp/send_request?api_key=xxxxxxxxxxxxxxxx\r\n";
    unsigned char SEND_DATA[] = "GET https://api.thingspeak.com/update?api_key=xxxxxxxxxxxxxxxxxxxxxxx=50\r\n";

    //_delay_ms(200);
    LCD_init(); // intitialize LCD
    usart_init(); // initialize usart
    _delay_ms(500);
    sei();

    _delay_ms(200);
    send_AT(AT);

    _delay_ms(2000);
    send_AT(CIPMUX);

    _delay_ms(2000);
    send_AT(CIPSTART);

    while(1)
    {

    }//while(1) close

}// main close

ISR(USART_RXC_vect)    // Every time an AT command is sent correctly type OK on the LCD (Logic analyzer works better though :-p)
{

     unsigned char a = 0;
    //LCD_data(a);

    a = UDR;

    if(a == 'O')
    {LCD_data('O');}
    if(a == 'K')
    {LCD_data('K');}
    if(a == 'd')
    {LCD_data('d');}
    if(a == 'L')
    {LCD_data('L');}

}