texts: PWM DC motor speed control outputs same input voltage regardless of the potentiometer

texts:
Hi, I just bought one of these PWM DC motor speed controllers, powered it using a 24(V) 10(A) power supply and attached a high rpm DC motor to it for a few seconds, increased and decreased the speed with the potentiometer and everything worked fine the first time. The second time I did the same setup, however, now it looks like the speed control module always outputs the same voltage available to it, regardless of the potentiometer's position.

Nothing smells or looks burnt or anything, and I also desoldered and tested the potentiometer, and it worked fine. I used a multimeter and found out that the DC motor actually draws much more than 10amps - which I thought it wouldn't since the PSU's highest current was advertised to be 10amps. I don't know how it's possible though - and possibly that high current draw damaged a component. I'm a neophyte here and I need help identifying the problem, just hoping to be able to change the faulty component.

Thank you very much.

UPDATE:
this is the best datasheet I could find for the DC motor (ERS-550SM 7520): http://www.evermotor.com/link/ERS-550SM.html
Although I wasn't lucky with the PWM module and didn't find anything whatsoever.

UPDATE 2:
As dear @Bruce Abbott suggested, I checked the resistance between the pins of all three FETs (those with heatsinks!), and the one with the larger heatsink has almost NO resistance between any two pins. So I guess that's the problem, isn't it?


texts:
I do understand that similar questions and maybe even the same question has been asked before, I've found them but unfortunately as a result of inexperience on my part I have been unable to adapt the posted solutions to my design specifically.

I am currently working to build the power side of my overall circuit that uses an 18650 (3.7v, 2600mAh) battery that is charged through an MCP73833 IC. The source power for charging will be a 5V wall wart power supply. What I am trying to accomplish now is to create a path or switch that disconnects the battery when the 5V power supply is connected, while preferably allowing the the 5V to be used to power the project and charge the battery at the same time.

Based on prior answers here on EE, I've heard that two Schottky diodes can be used with a little forward voltage drop; I've also seen recommendations for FET's. I'm trying not to add any more IC's to the project if I do not need too especially since I'm hand soldering all of this (not meaning FET's, but actual IC's).

Forward voltage drop is not critical since I'll need to step-up the battery voltage anyway after this circuit (to 5V for MAX7219). So it wouldn't be a big deal to run both power sources through the same booster.

My problem is that I have zero experience with Schottky diodes and even less with Mosfets. I've been reading and trying to understand but just when I think I do, I look at my circuit and my brain turns to mush.

Obviously if you see any errors within the circuit and wouldn't mind pointing them out, I'd appreciate that as well.


texts: Do all ATmega32u4 QFN ground pads need to be connected?

texts: A QFN chip I'm working with (atmega32u4) has multiple pads connected to ground, see the picture. Is it really necessary to connect all these pads? Could I say omit one or is it really bad practice? Would it be a big deal?


texts: Ive made up a laser security sytem that uses a pnp and npn transistor. Everything is going well except for the LDR. When there is no light the led will stay off. And once there is light it will turn on. How do i reverse it? here is my diagram. Please help.


texts: Is is possible to create modular logic gates from transistors for teaching purposes?

texts:
I'd like to work through some basic logic circuits with some youngsters and wanted to build them up from scratch (transistors), not logic gates if possible.
We've done the basics: buffer, NOT, AND, OR, NAND, XOR just using NPN mosfets and resistors. We've even been able to get to D-latches. As an example, the AND gates we're playing with have been build like this:

simulate this circuit – Schematic created using CircuitLab
The problem is that as the circuits have grown in complexity, with transistor emitters feeding into other transistor bases, I've only been able to get things to work by very carefully balancing resistor values to make sure transistors are triggered when they should be.
I would like to be able to build modular logic gates, which are identical and can just be plugged into one another without needing to carefully calculate resistor values.
Another restrictions is that we currently have 200 BC547ATA NPN transistors and a big bunch of resistors, so if its achievable without buying any more components, that would be ideal.


texts:
Consider the following setup:

Capacitors C1, C2, C3, C4 where C1 = C2 = 2C and C3 = C4 = C. All the capacitors in the bank have their top/positive plate connected together at the common central node. The bottom plate of C1 and C3 is connected to a reference capacitor which is charged to 1V initially (Vr node). The bottom plate of C2 and C4 is connected to GND. There is also an input switch used to sample a voltage onto the top plates of each capacitor.

Step 1 - Sampling:

The input switch is closed and the top plates (positive plate) of the capacitors now move with the input voltage (let's say some sinusoid)

Step 2 - Stop Sampling:

We now open the input switch and a voltage (some voltage of the sinusoid) is sampled on the top plates of each capacitor. Let's call this voltage Vin.

Step 3 - Switching:

Here come's the tricky part. Let us now switch the bottom plate of capacitor C2 from GND to Vr.

The question is: What is the voltage drop on the reference capacitor?

My Solution

I analyse in two states - the first is after the input voltage Vin has been sampled and the input switch is open. The second is after the capcaitor C2 has been switched from GND to Vref. I calculate the charge in each of these cases and then equate the two, using the law of conservation of charge.

Before

After

Before I equate the two cases, I need to find a relationship between Va,new and Vr,new to ensure I have one equation and one unknown (C123 is parallel combination of C1, C2, C3):

Finally, I now equate the two cases together:

Let's do some more algebra:

Finally, I have the equation that tells me the new reference voltage. Let's try a Cref value of 1pF and a C value of 32fF with an initial reference voltage Vr of 1V:

This gives me a new reference voltage value of 1.094117647V How is it possible that the refernece voltage went up?


texts:
I recently got into arduino and salvaged some N-type MOSFET Transistors. I'm trying to power some motors with a 12v battery and control them with my arduino. I found that the transistor gate and source need to have a common ground. So instead of powering my arduino from a 5v phone charger battery, I'm powering it from a 12 volt battery and using a voltage divider circuit to cut the voltage to 6, and still be able to have a common ground with the battery and the arduino. I'm using two 220 ohm resistors in series to divide my voltage. For a few seconds they work just fine and I'm getting about 6v out of the resistors, however after a few seconds they both begin to burn up and smoke.

I'm wondering if maybe I'm doing something fundamentally wrong in the circuit, my resistors can't handle the .25 mA the arduino is pulling, or I'm just stupid.


texts: Why does Flash and SRAM have a "hold" signal?

texts:
I have read datasheets on SRAM and Flash devices. They seem to have a "Hold" signal that can be used to prevent it from registering the input data/instructions until it the hold signal is deasserted. When would one need to use such a thing?

The 23LC1024 SRAM datasheet says:
"The HOLD  pin is used to suspend transmission to the 23A1024/23LC1024 while in the middle of a serial sequence without having to re-transmit the entire sequence over again"

These memory devices also have dual and quad SPI modes in which the hold signal is replaced with a data IO signal instead. This makes me think that the hold signal is not really important or is it?


texts: Is this resistor sufficient as dummy load in an ATX 250W Dell PSU?

texts: I have attached a 20 Ohm resistor to my Dell PSU on the 5V rail since its a 2004 PSU and most of the current is on the +3.3V & +5V rail. I have seen on most youtube videos where they mention using such dummy loads but they are usually those ceramic resistors. I dont a have 10 or 20 ohm 5W one in my posession now. But I do have a 1 ohm 5W resistance which I assume isn't ideal. Just attached this resistor I had previously salvaged from an old Nokia charger. I have attached a picture below for better idea.Thanks in advance everyone.


texts: Why does PC still get a little power from power socket turned off through remote control?

texts:
I have bought a power supply device to remote-control the power consumption at home. This works very well, however the PC has a little blue power light that keeps blinking from time to time even though the power socket is turned off. You can not turn the PC on or similar, but it still seems to get some power from the supply for the light to blink. This of course does not happen anymore when I completely remove the power plug.

How can this be and is this normal for remote-controllable power supply devices?


texts: Different bulbs with different voltage ratings in the same (DC) circuit

texts:
I am new to electrical/electronics area and just started studying/experimenting.
I am trying to make two different circuits (series and parallel) with (two sets) of the following:

I have a 9V battery
I have 3 bulbs: 1.5V, 3.5V, 2.0V

Not even sure if it's possible using "series", but wanted to ask anyway.
I suspect that I would need a couple of resistors to be bought (not sure about their specs, what to buy, how/where.)  Can anyone guide me on how to achieve this?


texts: At what point in the charge cycle do lithium ion batteries draw the most current?

texts:
When charging lithium ion batteries do they draw a stable current throughout the charge cycle? Say you have used the battery until it shut down. When you put it on the charger will it draw more current at the beginning of the cycle or will it draw more as it gets close to a full charge? Or is it constant throughout the range?

And the same question regarding heat. Usually current and heat go together, but I don't know if a charging battery follows this pattern. Will the battery heat up quickly at the beginning of the cycle and stay at that temperature? Will it get hotter or cooler as it reaches full charge?


texts:
I found this Moog Prodigy synthesizer schematic that I'm trying to figure out how it works in order to learn more about how electronics work.

What do the circled symbol at the top of the schematic mean ?
What does "N.C" mean ? An example of it is located at the far right.
What does the "*" next to R2 mean ?
What does the "1%" next to R5 mean ?
What does -9V and -12V mean ?
What does the arrow next to R14 mean ?


texts:
Not actually sure if this is too simple a question for this exchange.

Just now I picked up my phone charger and unplugged it to move somewhere  and plugged my phone in to the recently unplugged (from the wall) charger, and my phone registered that it was plugged in and charging. even though it was plugged into a charger not connected to a power source.

I can understand in theory that there was some residual electric current in the charger, just enough to trigger my phone. However, I fail to understand the scale.  How much residual electric charge could be left in a 1m phone cable, and how long before it dissipated?

How does this play into the whole completing the circuit, as there was no real ground connection.


texts: Simulating FPGA design without having the actual hardware

texts:
I'm new to FPGA and currently taking HDL (Verilog particularly) class. I have sufficient knowledge in digital design like combinational and sequential circuits.

I want to create a project similar to the one shown in this YouTube video.

I also know that Xilinx ISE can process logic signals and simulate waveforms. Does it have extra capability like getting the input signals via USB, camera etc. and output it in your computer.

Is it possible to run this project (like a simulation in computer) without buying an actual FPGA board? What I mean is, can I build, code and run that project in my computer, and just hook up my camera via USB, then let the incoming video signals be processed by HDL simulators like Xilinx ISE, etc. (w/o really buying an FPGA board and synthesize your project there, I currently do not have the budget to have one)

(What I really mean is to interface the HDLl design into real world sources, C code, etc.)


texts: Why I've weak Bluetooth signal with Sim800C and how to strengthen it?

texts:
I've designed a circuit and used SIM800C module to work with its standard Bluetooth and GSM module. GSM works well, but its Bluetooth has weak signal, which I've to stick my phone to the board.
In datasheet there are some concerns about its Antenna:
Antenna Interface:
The length of trace between pin output and connector should be as short as possible;
Do not trace RF signal over across the board;
The RF signal should be far away from SIM card, power ICs.
Is the problem because Sim800C is placed near to the power supply and GSM module and their noise interfere with the Bluetooth antenna? or what could be the problem?
Here is a picture of the board:

Updated:


texts: Can we use DC-DC Buck convert installed 3.8v battery to power Phone continuously?

texts:
I have a Windows tablet whose battery is dead and I want to convert it to without battery to use as a digital photo frame.

Table dead battery is 3.8V

Can I use DC-DC Buck convert (DC-DC converter step-down 1.23-30V 1.5A)  with input 5V regular mobile charger to power this tablet?
What about Current is it enough?

Full specs of converter:-
Input voltage: 4 – 35VDC
* Output voltage: 1.23 – 30VDC
* Max current: 3A (1.5A continuous)
* Maximum efficiency: 90%


texts: Connecting 1.8V USB and PCIe to 3.3V system

texts: I'm working with a google coral module (ASIC) that has both PCIe gen2 1x and USB 2.0. From the datasheet (https://coral.ai/docs/module/datasheet/) the I/O levels are 1.8V maximum. The problem then becomes to connect the USB 2.0 and the PCIe which instead have levels of 3.3V. How can I interface the chip with the USB and with the PCI?


texts: I have 16 PIR sensors that I’m using for a project on a Raspberry Pi. The output of the PIR sensors is connected to the 16 inputs of the multiplexer. However I don’t know what to hook up to the select input(s) to read the readings from the PIR sensors that is/are currently being tripped. Any help would be appreciated


texts: Fried Beaglebone Black - Possible Reasons?

texts:
I've fried my beaglebone while powering it from a switching regulator which gives around 4.95V , The output voltage of the regulator was pretty stable with low ripple voltage. What happened was it all started good and it was starting up , all of a sudden after 15-20 second the beaglebone turned off and it doesn't work anymore.

Here is the relevant connection I suspect which might caused the problem . I use it to monitor the error signal from another voltage regulator (The error flag output, (or power OK) is the collector of a NPN transistor, with the emitter internally grounded) .

simulate this circuit – Schematic created using CircuitLab

Also as I found in beaglebone documentation, it is stated that no pin shall be driven before the SYS_RESET line goes high , can this have anything to do with this ? I have a spare one but I don't want to risk it before I find the problem.

Addition from the datasheet:

Error Flag (Pin 3)Open collector output that provides a low signal (flag transistor ON) when the regulated output
voltage drops more than 5% from the nominal output voltage. On start up, Error Flag is low until VOUT
reaches 95% of the nominal output voltage.


texts: Explanation on why there is no feedback in the circuit for higher voltages of input signal

texts:
simulate this circuit – Schematic created using CircuitLab

I don't understand the reasoning behind the analysis of this circuit. The professor started by saying that if diodes D2 and D5 are ON and D4 and D3 are OFF than there is no global feedback in the circuit and V+ and V- of the first ideal op amp are not the same because the I1 is independent and Vo=R2*IO. Same goes for the other two diodes with the output being Vo=-R2*I0. When all 4 diodes are working then there is feedback and Vo=V2 because V+=V-.

He than proceeded to draw a diagram that is confirmed by the simulation. He also added that if there were a resistor in parallel with the I1 there would be feedback in all cases but the feedback would be weak and not much would change.

  How do I know that there is no feedback in the case where 2 diodes are working and the other 2 are off and how does that change when the resistor in parallel with I1 is added. Also how do all 4 working diodes introduce the feedback here?

  Isn't feedback a connection between the input and the output, and adding diodes doesn't seem to do anything with the input signal as far as i can see.


texts: Question on Use of Y2 Saftey Capacitor in AA5 Style Tube Radio

texts:
In a radio I am restoring, there is a 0.1 uF capacitor between B- and chassis, designated as C12. My thought process is that if this capacitor were to fail, I would not want B- shorted to chassis as this could create a significant shock factor due to the high B- voltage. My understanding is that a Y2 capacitor would fail open circuit if it failed. In this instance, while the radio would no longer work, B- would not be present on the chassis as a shock hazard.

There is an across the line capacitor elsewhere in the circuit, designated as C11, which I know needs to be an X2 safety capacitor.

My question is, does the C12 capacitor need to be a Y2 safety capacitor or can it be a regular capacitor?


texts: Is port map (A => (others => x)) legal in VHDL 2008?

texts:
I have an entity dummy with an input port signal of type std_logic_vector:

entity dummy is
    generic (
        LENGTH : natural);
    port (
        A : in std_logic_vector (LENGTH - 1 downto 0);
        Q : out std_logic);
end entity;

When instantiating dummy, is it allowed to associate A with (others => x), where x is a signal of type std_logic?

dummy_i: entity work.dummy
    generic map (
        LENGTH => 4)
    port map (
        A => (others => x),
        Q => open);

ModelSim 10.7b stops with the error message

  ** Fatal: (vsim-3420) Array lengths do not match. Left is 4 (3 downto 0). Right is 0 (-1 downto 0 (null array))

It works, however, if

I use (others => '0') instead of (others => x) (replace #1a with #1b), or
the length of port signal A of entity dummy does not depend on the generic (replace #2a with #2b).

Full MWE:

library ieee;
use ieee.std_logic_1164.all;

entity dummy is
    generic (
        LENGTH : natural);
    port (
        A : in std_logic_vector (LENGTH - 1 downto 0); -- #2a
        --A : in std_logic_vector (3 downto 0); -- #2b
        Q : out std_logic);
end entity;

architecture rtl of dummy is
begin
    Q <= '0';
end architecture;

library ieee;
use ieee.std_logic_1164.all;

entity modelsim_others_bug_testbench is
end modelsim_others_bug_testbench;

architecture rtl of modelsim_others_bug_testbench is
    signal x : std_logic;
begin
    x <= '0';

    dummy_i: entity work.dummy
        generic map (
            LENGTH => 4)
        port map (
            A => (others => x), -- #1a
            --A => (others => '0'), -- #1b
            Q => open);
end architecture;
```


texts:
I'm trying to design a simple SRAM board (using a cypress Cy7c1011cv33) to connect to my lattice machox3 starter kit's pin connectors. But I have some design questions, after reading their "SRAM Board Design Guidelines". The guideline says "PCB should be designed to inductances as low as possible", but how high can the inductance be? also is it advisable to connect two SRAMs' address and data pins together? I ask because then the vias will be longer, which goes back to my question about inductance. I made a simple board with one sram ic, but I calculated (by hand not with kicad) its inductance to be 51nH and have no idea if thats okay or not.

I plan on using the SRAM near its full speed (100MHz) and I'm using kicad to design the board (only because I can keep the track length constant without having to pay a small fortune). This is the first time I'm trying to design something that works this fast I usually stick to PICs MCUs and analog circuits so any help is appreciated.


texts:
When attempting to construct a miniature laser beam profiler with the Omnivision OV7740 CMOS detector and an Arduino Due, I am running into some problems with FIFO reading/writing. From the datasheet, it appears I can only set a FIFO speed, toggle a FIFO valid mode, toggle a FIFO manual mode, or set a FIFO delay.  The chip uses the SCCB for communication, which I understand to be very similar to I2C.

From my previous understanding of FIFO memory operation, there should be pins associated with enabling write and a FIFO output buffer clock.  To take an image one should enable FIFO writing, read pixel bytes from the output pins, and pulse the output buffer clock to obtain the next byte.  After the image is taken, the memory can then be cleared by powering down.

Am I understanding the operation of FIFO memory correctly? What strategies can I take for reading image data from the FIFO to the microcontroller with this setup?


texts:
I have a low pass filter in spice made of several stages but they look similar to this except I have a small resistor to gnd at the positive terminal:

The design was done using a positive and negative supply but I wanted to use a single supply.  So I made myself a virtual gnd with another opamp like this:

Then I made the supply pins VCC and GND, and tied the previously grounded portions of the circuit to the virtual gnd output.   When I did a bode plot of the output it looked badly distorted at high frequencies, around 30-100Mhz.  So I tried just using an ideal DC suppy in spice and everything looked perfect.

I was starting to write my question here when another suggested question about opamp decoupling made me think I should try adding some decoupling caps to the output of the virtual GND opamp.

This worked buy not as I expected.  If I place a single 0.01uF capacitor on the output of the virtual gnd opamp I still get distortion, but if I place a 10 or a 100uF cap there everything looks great out to 300Mhz.

That's counter intuitive to me since I'd think if it needs more current at high frequency then lower value caps would be what I should use.  My only thought is that the small value caps are affecting the filter response in some way.

Can someone explain why the 100uF works better?


texts: What is the general procedure for matching networks when there are multiple circuits are connected back to back?

texts: If I have two circuits like the one shown above (Rx antenna -> block1 -> block2 -> Tx antenna), where all should I add matching networks. How should I look at the impedance while doing the matching network? Let's say, if I am adding a matching network in front of Block1, do I have to find the impedance of block1+block2+antenna looking toward the output side or do I have to find the impedance of just block1?


texts: What metal is recommended for soldering iron tip wire mesh cleaner - brass, copper or steel?

texts:
There are many low-cost options out there for metal wire mesh tip cleaners. Three types of wire metal are dominant - steel, brass and copper.

I was wondering if there is a metal that is superior to others, and one that should be avoided, and why?


texts:
I am new in the world of embedded software. But I was having normal challenge in blinking LED and SPI bridge communication on STM32F0-Discovery. All this work fine. Now I was planing to go to next level, but for sure I do not really understand some things.
To program I am using STM32Cube for configuration ( 8 Bit datasize, 187,5KBits/s and MSB first) as usual.

For testing I define:

uint8_t display[8] = {0,0x7F,0xFF,0xCC,0xCC,0xCC,0xFF,0xF}; //A

For sending the data, as through the STM32Cube all the initialization is done, I wrote the following code in the while-loop:

HAL_GPIO_WritePin(GPIOC,GPIO_PIN_4, GPIO_PIN_RESET); //here is chip select
trasnmit = HAL_SPI_Transmit_IT(&hspi1, display, 8);
receive = HAL_SPI_Receive_IT(&hspi1, Rxbuff, 8);
//HAL_GPIO_WritePin(GPIOC, GPIO_PIN_4, GPIO_PIN_SET);
HAL_Delay(5);
HAL_GPIO_WritePin(GPIOC,GPIO_PIN_4, GPIO_PIN_SET);

Of course I am getting my CLK on the oscilloscope but no data at the DIN-Pin of the MAX7219 (see: https://www.ebay.de/i/273605021101?chn=ps)

While debugging, I can see that the transmit function is being skipped, what could be the cause? But the return value is always on HAL_OK.

Could somebody help me with a step by step config of the MAX7219 based on STM32, so that I can better understand where my problem is.


texts: Create a synchronous network of 400 devices

texts:
I have around 400 devices that i want to address in a star topology. Each device controls a set of LED strips (27*12 resolution). The idea is display a video animation in a good frame per second rate (at least 25fps).
I was successful controlling one set using Arduino (working code in this post). The step of transforming the video into RGB values was done with ffmpeg tool in Linux , the program then transform RGB values to a raw binary frames ready to be sent by the Arduino to the LED strip.
So to send these frames from the Linux program to all the Arduinos i have made an MQTT layer through TCP/IP where each device listen on a topic and the Linux program send according frame to it.
The problem is the heavy delay between sending the frames to all of the 400 devices and the start of the animation (trust me it seems awful resolution where each LED strips shows the RGB values in delay from the others).
I want to stay at 60fps which gives around 16ms between each frame being converted ,sent and displayed. So we are on a milliseconds tolerant architecture.
My question is how to implement a synchronized network with above considerations ?
Below a picture of a 12 pixel strip :


texts: How accurately can an ESC detect the number of RPMs?

texts:
I am working on a project involving brushless motors, so I got an ESC to power them. The problem, is that I need to accurately control the number of RPM.

Can an ESC, like this one, control the number of RPM the motor is doing? Or is it based more on percentage of throttle?

If I wanted to accurately control the number of RPM my motor is doing, would I have to get an optical RPM sensor?


texts: why is transformer not considered as an amplifier?

texts:
I know that in a transformer the power is conserved on both sides, and hence there's no power amplification as such. That's fine!

But if I instead want only a voltage amplification, then choosing proper turns ratio and connecting the load across the secondary would serve my purpose. So can you consider it as voltage amplifier? If yes, then why is it not used as one?


texts: What are the determining factors for using a polyfuse in electronics circuit design?

texts:
When designing electronic circuits (PCBs) I often wonder if I should use a polyfuse (aka polyswitch, PPTC, PTC resettable fuse) at the power inputs and outputs or not.
So basically what I am asking myself is:
"Is it worth to spend money on a polyfuse in this design?"
Guess the primary reason for using polyfuses is to protect the PCB traces and externally connected wires from melting in case of an error. Further to keep damages caused by any fault low.
Is there a more structured way to decide whether the use of a polyfuse makes sense or not?


texts: Why should we multiply Copper loss with \$ (\frac{1}{2})^2 \$, not \$(\frac{1}{2})\$ when the transformer is in half loading?

texts:
A 10 kVA transformer, its iron loss is 120 W, the copper loss is 240 W (full loading), now when the load factor is 0.9 delay, what is the efficiency when the transformer is in half loading?

The answer said \$\eta=\frac{\frac{1}{2}*10K*0.9}{\frac{1}{2}*10K*0.9+120+\frac{1}{2}^2*240}\$.

I want to ask why should we multiply copper loss with   \$ (\frac{1}{2})^2 \$, not \$(\frac{1}{2})\$.

The unit of copper loss is Watt,this means it should have a relation with real power,that is \$IVcos\theta\$, and the real power has a relation with resistor, and as  we know,the relation between resistance and power is \$P=IV=I^2R=V^2/R\$, so I wonder does \$ (\frac{1}{2})^2 \$ have relation with \$P=IV=I^2R=V^2/R\$? If not,can anyone tell me the reason of  multiplying  Copper loss with   \$ (\frac{1}{2})^2 \$ ?


texts: How to correctly wire LF356 JFET Opamp as amplifier?

texts:
I have a circuit in which a square wave with smaller amplitude should be amplified with an opamp. Before, I used a MAX492 which has G/B-product of 500 kHz. With this circuit I manage to easily amplify the signal, Vcc is single supply 3.3V:

simulate this circuit – Schematic created using CircuitLab

This gives me a nice amplification of around 5 (1 + 40k/10k) and the input is very high impedance.

Now here's my problem: I bought some LF356 Opamps with GBP of 5Mhz and tried to put it in instead of the MAX492. However, I noticed that

it doesn't seem to work below 5V at all
it pulls up the positive input to some DC voltage, overlaying the signal if I don't use a decoupling cap.

Is this how this old opamp is supposed to operate? Is this because I'm using a single supply?


texts: Need some insights regarding Shunts for ammeters

texts:
So i bought this cheap digital ammeter that can measure current from 0 - 100A:

http://www.ebay.com/itm/141196910898

I will be using this with my LM317 (1.5A max). 0-100A version was the only one left in stock. Stupid as i am i didn't read much about ammeters since i first thought that it was like a multimeter, break the circuit, put in the ammeter and you're good to go, but when i got the ammeter and i noticed how small it really was my first thought was

(there is NO WAY that this small thing can get 100A through it without melting).

So after a bit of seaching on the web i found out that you need this thing called a "shunt", Where i live shunts are pretty expensive to buy and if i order one from ebay (china) i have to wait forever for it to arrive because of the slow shipping.

I searched for different ways to make your own shunt but i couldn't really get the hang of it, so is there another solution for me to hook up this meter so that it can read up to 1.5A without a shunt? Or does anyone know a good step by step guide which shows you how to make one? Cheers.


texts: How to match impedance when driving 75ohm differential video amp with single ended RS-170 video output?

texts:
I am trying to feed RS-170 video signal from a single ended amp to a differential 75 ohms video amp. When I connected RS-170 signal to + of the differential and RS-170 return to - of differential, video had a lot of flickering and noise - maybe impedance matching problem? I think it is matched 75 ohm, but maybe I am wrong. The video amp is AD8023 from Analog Device. The two systems' GNDs are connected (driving side and receiving side) via other connection, but not shown in the drawing below.

What's the best way to connect TSG350 to 75 ohms differential video amp(37.5ohm into each +/- inputs of the amp)? Please advise.


texts: What operation could cause the inductor or the capacitor to explode?

texts:
In really early days of electronic school, the teacher used to say something about not unplug power too quickly at an inductor or capacitor and we were used to slowly turn the voltage generator from a signal generator down to zero. Something about the transients, something about the charge stored...

I'm now interested in working with a power converter, but what was said many years ago still lingers with me but I can't remember exactly what was said at that time.

Can someone please remind me what is the rule when it comes to safely handling inductors and capacitors in a (basic) circuit?


texts: Calculating the line-to-neutral voltage of a generator

texts:
A three-phase generator is connected to a strong grid with
line-to-line voltage 14 kV and frequency 50 Hz. The generator is rated
at 15 kV and 180 kVA. The resistance in the windings is 2 Ohm/phase
and the reactance is j3 Ohm/phase. The current in one phase was
measured to be: I= 1500 / -25º A.
What is the line-to-neutral voltage of the generator, |Ei|=____ kV.

Hi, I've got issues understanding what I should calculate and what "Ei" actually means?
I tried to calculate the I(phase)*Z(polar) to get the Ei(line-to-neutral), which gave me 5408,32V. Which is wrong.
Then I tried to take the V(line-to-line)/sqrt(3) to get Ei, which gave me 8082V which is also wrong.
How am I supposed to do it?


texts: Soldering back the disconnected wires from the charger board

texts: The attached link images are the front and back photo of the board inside my charger. This charger is used to charger my son's toy car. Unfortunately, the wire soldered on this chip got disconnected. Now I have 2 wires red and black. Kindly help me in finding the exact location, where these 2 wires should be soldered. Thank you all in advance.


texts:
I am looking at installing some LED lighting which requires a 12v DC 10 amp power supply. The question which I cant seem to find an answer for is this...

I live in the UK which uses a nominal 240 v AC mains power, so what would the power draw be on the power supply? ie. what would the input amperage be at 240 v AC ?

The reason I need to know, is that I don't want to overload the domestic lighting circuit in the house but I can't find any definitive answer to the above. I understand that there's a direct relationship between volts, amps and watts but is it transferable from AC to DC?

Am I right in thinking that the power supply would supply around 120 watts (12v x 10A) so that would infer that the supply would be 120w / 240v, around 0.5A plus a bit for losses?


texts:
So I'm doing first order circuit analysis and I stumbled upon a circuit which had this as a voltage source:

When would this voltage source be active?

For example in this circuit:

The current source on the left would be active at t>1.
The one on the right is active at t>0.

What about that voltage source though?


texts: No communication with SIM900A using Arduino Uno

texts:
I am using Arduino Uno and trying to connect to a SIM900A GSM module using serial communication. I am not receiving anything from the module at all. The module powers on and has another LED flashing at 800ms

I have connected the following

5V from Arduino to 5V power supply input on GSM
GND from Arduino to GND power supply input on GSM
Pin 2 (Rx) from Arduino to Tx serial on GSM
Pin 3 (Tx) from Arduino to Rx serial on GSM
GND from Arduino to GND serial on GSM

Breakout-board schematic from this page.

I have tried both Arduino's built in serial comm and also software serial using pins 2 and 3.

Information about SIM900 can be found here.

The code that I am currently running, using software serial:

#include <SoftwareSerial.h>

SoftwareSerial mySerial(2, 3);

const int baud = 9600;

void setup() {
  mySerial.begin(baud);
  Serial.begin(baud);

  while (mySerial.available() < 0) {
    mySerial.write("AT");
    delay(2000);
  }
}

void loop() {
  if (mySerial.available() > 0) {
    Serial.write(mySerial.read());
  }
}

I have also tried different baud rates but still haven't received anything from the module at all.


texts: Is it bad if I held solder with my mouth?

texts:
When soldering, I have on a few occasions, used my teeth to hold a strand of solder while my hands were busy. I do not do this frequently, but sometimes I forget that solder is made of lead and I instinctively use my mouth.

How bad is doing that for my health? Is it very dangerous?

I use manly lead based rosin-core solder.


texts: How can I reuse an AC speaker amplifier board with DC?

texts:
I'm planning to reuse this board powering it with a computer 12V DC power supply.

It gets 9V AC 200mA from its own 220V AC transformer.
I have basic understanding of electronics, so I've been searching about AC to DC conversion.
I found https://www.instructables.com/AC-to-DC-Conversion/ and Powering AC Appliance with DC, but I'm not sure how to apply it.
The specs for the TDA2822 stand that it operates normally on 12V and at an absolute maximum rate of 15V.
Measuring with a multimeter on the capacitor I get 13.90V DC. But I'm not sure if I have to get the measure there, or somewhere further on the circuit.
Is it right to just plug 12V from my power supply on the capacitor leads? Or I must remove it along with the four diodes?
Can somebody point me into the right path?
Thanks.


texts:
I know this question has been covered multiple times already; but as far as my reading goes I couldn't get any clear answers yet.

I am building a circuit based on a LiPo input source (4.2V to 3.3V) and I plan to shut-off any power withdraw at 3.3V in order to save the LiPo lifetime. (using voltage comparator on EN pin). The maximum current draw is around 500-600 mA, but for 80-90% of the time, the system will be on lower power mode (around 100mA). The operating voltage is 3.3V for as long as possible; until the LiPo voltage reached 3.3V (bottom discharge limit)

Therefore the dilemma and if I got my reading correct, so far this is what I understood. Under high load it is not favorable to use an LDO because of the increase of drop-out voltage; however it seems that a DCDC step-down would do the job perfectly. But according to my case I would like to have a second opinion; is there any reason to use one or another ?

LDO : http://www.ti.com/lit/ds/symlink/tps737.pdf

DCDC Step-down : http://www.ti.com/lit/ds/symlink/lm3671.pdf

edit : In addition; what do you think about the benefit of using an LDO that would not track bellow 3.3V and therefore get rid of the voltage reference? As opposed to the DCDC that will track voltage well bellow 3.3, hence the need to shutdown system.

Thank you.


texts: Is information lost when you downconvert an RF frequency?

texts:
I am trying to work out what happens when you downconvert an RF signal, such as what happens in an SDR device when tuning to a given frequency.  For example if a device using a Zero-IF is tuned to 399MHz, then whatever signal you see at 400MHz will appear at 1MHz where it is then digitised.

Now imagine at 400MHz you see a signal consisting of just a carrier, which switches on and off very rapidly.  On for one cycle, off for one cycle, on for another cycle, off again.  If you assign a binary 1 to the 'on' cycle and a binary 0 to the 'off' cycle, I believe this would allow you to transmit 400,000,000 bits per second.

Now what happens if this signal is downconverted to 1MHz ready for the SDR to digitise?  If the 1MHz carrier switches on and off at a rate of one cycle at a time, there will only be 1,000,000 transitions, although the original signal had 400,000,000 transitions in the same time period.

So what happens in this case?  Does the 1MHz carrier cycle on and off at the original 400MHz frequency?  Does that allow you to transmit your original 400,000,000 bits per second on a 1MHz carrier frequency?  Or are the extra cycles lost somehow?  What would the resulting signal at 1MHz look like?


texts: Evaluation of input and output impedance of a RF amplifier

texts:
I have a doubt about the meaning of input and output impedance of RF amplifiers. I'll take as example the amplifier CMA-252LN by Mini Circuits .
In its datasheet it is not clearly written their input and output impedances' values, but I think they are equal to 50Ohm since this is specified under the main properties of the amplifier, as you can see:

Now my question is: how are input and output impedances evaluated and what do they represent for this kind of amplifier?
For instance, I have always evaluated both of them by using Thevenin theorem. For instance, with respect to the following BJT common emitter amplifier we evaluate its input impedance by short circuiting the power supply and by evaluating the ratio between input voltage and input current (while the output port is open), while we evaluate the output impedance by short circuiting the power supply and the input signal generator, and by putting a voltage source at the output port and by evaluating the ratio between output voltage and output current.

So, for istance for evaluating the output impedance, the input voltage Vin is shorted (so the input port is shorted). Is this the same procedure through which the output impedance of an RF amplifier is evaluated? Or is its input port closed on a 50Ohm load?


texts:
How would I make a Zener diode current source? Something like this?

I don't know how to figure out what resistors/transistors/diodes I need.

I guess what I'm asking is, how do I calculate what resistors I need, and the rating for the transistor and the diode (I don't know how to tell if the circuit will burn them out).

Edit:
I want the load to receive 1 Amp, the resistance of the load is 0.97232Ω, and I am supplying the circuit with either 8.4V, or 9.6V probably 9.6V.

What I'm looking for, is a set of equations to find values for the resistors. I(believe) I can assume that nothing in the circuit will experience current more than my target current of 1Amp? If that's true, I can get parts rated 1.5-2 times my target current.

Schematic of the circuit I want.

simulate this circuit – Schematic created using CircuitLab


texts:
I have two motors in series that are connected to a 36v speed controller. They are identical motors, 12vdc, 30000RPM.

My problem is when applying power, 1 motor slowly drops in voltage until it reaches zero. At the same time, the other motor slowly speeds up.

If I apply full power, the motor that went to zero will then spin but no where near the same speed of the other motor. My DMM confirms the smaller voltage at full power on the slower motor.

I've also tried another motor to replace the slow one but still same result.

What could be happening here?

Could it be that the faster motor is actually different in some way?

EDIT:

I've now wired the motors in parallel and they work perfectly but now I have another thing I'm confused about...

In parallel, the motors should now see the full voltage of the battery which is around 31.5v (8s lipo at 50% charge) but both see half that?? what is going on now?

EDIT:

Attached is a crude drawing of the current setup.

For clarification, both motors now work at the same speed and the shifter works perfectly in so far as i can change the polarity with a flip of the switch. The problem now is both motors only see half the voltage each from the battery.

I've confirmed that when disconnecting 1 motor, the other motor reaches the correct voltage....as soon as I reconnect the other motor, both motors go back to a voltage of 15.5. could this be a current limiting issue?

The controller can handle around 25a and the battery, 90a.
Both relays are also rated at 40a @ 12vdc. At 31.5v it should handle around 15a.
Both motors were pulling around 4a @ 15.5v.

EDIT:

sorry for all the edits, I'm learning more crap all the time!

I've found another symptom/issue...Not only does the voltage half for each motor but it slowly drops!? Now i'm more confused than ever!. i've uploaded 2 videos showing this issue. 1 video shows 2 motors running together and the other, just 1 motor running. DMM is connected to the same motor on both videos.

https://www.youtube.com/watch?v=4M-1r9IBKuU (parallel motors)
https://www.youtube.com/watch?v=uO_2VKqxTaA (single motor)


texts:
I want to start learning Hardware design, and I want to start parcticing with PADS, is there any student version for this SW, if yes please tell me where I can find it.
thanks in advance.


texts: Which switch/amplification method described is better for accurate reading of variable voltage using ADC?

texts:
I'm trying to design a relatively accurate variable power supply with 2~24V output voltage controlled from an MCU using off-the-shelf parts.

For the MCU to be able to read the whole range of voltage, the simplest approach was to use a voltage divider to map the scale of 0~24V into 0~3.3V for the ADC unit. Considering noise and ADC precision, for desired voltage resolution of 10mV, the accuracy is low, so I came up with 3 remedies.

I'm a bit lost to find out which gives a more stable reading. The approach itself is my concern. The values provided (e.g. input voltage) are not that critical.

Assumptions:

The input, unregulated voltage is 25V.
The output voltage is variable from 2~24V.
Desired voltage resolution is about 10mV. (e.g. a reading of 7.24V. It's not strict if it's not reachable.)
Digital parts and op-amps have a linearly regulated supply of 5V.
The main adjustable regulator which the output is concerned is a LM2596 with datasheet designed circuit.
ADC is 10bits with a 3.3V reference from an STM8S MCU.
The analog mux can be either CD4051 or 74HC4051 based on the switch voltage range.
Software calibrations are applicable.

The methods:

A: Variable gain op-amp using analog switches.

In this design, the input voltage is divided so the whole range of input is scaled to ADC input., but for accuracy, a simple op-amp is placed with a MCU controlled analog MUX to select various resistors for selective gain. Corrections and calibrations are possible using software. The MCU starts with the lowest gain, adds up gain until a good value is reached.

B: Multiple dividers, series resistors for protection

In this design, I just used various dividers for analog zooming (is that correct ?) I used series resistors for the case the input voltage is high so the divided voltage (which maybe still bigger than the input tolerance of MCU)  goes through internal protection diodes and doesn't damage the MCU. This method needs 3 ADC inputs (also an analog switch is applicable.)

C: Multiple dividers, analog switch and comparators for divider selection.

I  this one, in case the B method is not applicable, I added voltage comparators and an analog switch to select the divider based on the input voltage range. It doesn't need the input resistors or 3 ADC inputs used in B.


texts:
I'm looking for the right circuit to connect my piezo buzzer to MCU (STM8S in my case). I don't have a partnumber\datasheet for my particular buzzer, but I've found a number of similar schematics in datasheets:

Some of them also have a protection diode (like described in this question) What's the function of the diode in this driver connected to a piezo buzzer?

My buzzer works when connecting directly to MCU pin (measured current is about 3mA).

So here comes questions:

Do I really need a transistor if current through buzzer is so low?
What is a good circuit to connect a non-piezo (magnetic) speaker to MCU? I've tried 8Ohm speaker with 500Ohm series resistor -- the sound is very low.


texts: why is a crystal needed to program microcontrollers

texts:
I'm making a programmer for the AT89s52 in parallel mode so that I can program other micros as well. I had bad luck using the spi interface with my computer.

I am able to flawlessly program an at89c4051 with the pc parallel port without adding a crystal.

I've seen numerous of circuits that the at89s52 and even at89c51 show a crystal attached for prograamming.

Why does the at89x5x series of chips need a crystal for programming when parallel mode (not spi) is used?


texts:
Designing a 4-layer board (signal+pwr, gnd, signal+pwr, gnd), and I have some newbie doubts about the best option to connect different connector's pin or IC's pad to power lines, or sometimes to different signals.
Board has different parts: Power, MCU & RF.

The main issues I have:

Power at connectors. Which is the design guideline to right connect these pads? Will this type connection create EMI which affect to RF module?

Power planes instead of traces. Which is the design guideline for routing at this situations? I think plane, instead of traces, will be better to reduce EMI and impedance, but I'd like to have a second option due to I'm worried about how it would affect to RF.

Best layer for planes. I would have to create several planes to connect different voltages on top layer, is this suitable? On the internal signal layer, there's only a power plane and trace.


texts: How did they get the formulas for Av, Rin, and Rout for this problem?

texts:
How did they get the formulas for Av, Rin, and Rout for both problems?
I understand how they solved it. I just want to know where they got the formulas because I can't seem to find them anywhere. Thanks!


texts:
I'm new in this field and I'm working with ardupilot APM 1 (atmega1280), and I got this

  error: avrdude: stk500_getsync(): not in sync: resp=0x00

while I was uploading.
I've read so many articles on internet and I tried everything to make the board working. I've started having problem three months ago and I always solve it in maximum six days, but now the problem is more frequent and I can't solve it anymore.

These were the things that I tried:

arduino IDE 1.0 setting the right board and port
List item
arduino IDE1.0.5 setting the right board and port
windows 32 bit
windows 64 bit
Atmel Studio 6
Software reset
reset connecting the GND RST pin
configuring the FTDI cable like in the third immage https://code.google.com/p/ardupilot-mega/wiki/MPInstallation1
http://forum.arduino.cc/index.php?PHPSESSID=ajlu19m9jj1kqfekn3mrj7v... (but I have a doubt about which TX and RX pin because the board scheme doesn't have  TX pin (Digital Pin 1) to the RX pin (Digital Pin 0))
restarting the system, taking off all cable, resetting the board and trying again

Does anyone have some idea?

Is the board broken?

Is an hardware problem?

EDIT:
Verbose of the upload:

avrdude: Version 5.11, compiled on Sep  2 2011 at 19:38:36
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2009 Joerg Wunsch

         System wide configuration file is "C:\arduino-0100-relax\hardware/tools/avr/etc/avrdude.conf"

         Using Port                    : \\.\COM20
         Using Programmer              : arduino
         Overriding Baud Rate          : 57600
avrdude: Send: 0 [30]   [20]
avrdude: Send: 0 [30]   [20]
avrdude: Send: 0 [30]   [20]
avrdude: Recv:
avrdude: stk500_getsync(): not in sync: resp=0x00

avrdude done.  Thank you.


texts: Fan speed controller according to temperature using arduino

texts:
I am working on a project to control fan speed according to temperature using arduino,  according to the above circuit all the connections have been made , but the speed of the fan does not change , I am new to this electronic field so please help me out
. I am using LM35 sensor for sensing the temperature


texts:
Does ALM mean "Adaptive logic module"?

www.altera.com/literature/ds/ds_nios2_perf.pdf
Jul 1, 2013 -

  One ALUT is equivalent to about 1.25 LEs.

Does LE mean logic element and ALUT means adaptive look-up table?


texts: The reason of ripple on output of isolation amplifier

texts:
You can find schematic below. I have seen ripple (apapproximately 184mv) on output of isolation amplifier so I can not read output voltage of amplifier on my ADC.

What is the purpose of ripple on output of isolation amplifier? Do you have any advice for it?

By the way, I added 1k resistor to schematic. It's for high voltage. This situation has no effect on the problem.

You can find datasheet of AMC1301 in here: http://www.ti.com/product/AMC1301


texts: How much effort goes into designing and laying out a PC motherboard? By this, I do not include Intel's IP etc, but I do including having to read all the documentation concerning the chipsets. And getting it to work, if not 100% tested


texts: How do you calculate the voltage between two phases?

texts: If I have two hot wires at given voltages and phases (for example 120v 0deg and 120v 120deg), how do I calculate the voltage between the two wires?


texts:
I'm trying to calibrate the IC ATM90E26. This is an energy metering IC, it measures current through a shunt resistor and voltage through a voltage divider circuit. The IC will be part of a 220V AC circuit, with a maximum current of 0.7A.
The thing is that in order to calibrate this IC you need, according to datasheet, to:

Calibrate gain at unity power factor
Calibrate phase angle compensation at 0.5 inductive power factor.

And here is where I get a bit lost. To achieve a power factor of 1 the load in the calibration circuit has to be purely resistive, this I can get with a light bulb (non-LED).
But to get a power factor equal to 0.5 I'm no really sure how.
So here comes the question, how can I make a test / calibration circuit that generates a power factor equal to 0.5? I mean with what type of every day use device can I achieve this? will a common fan(220V AC) do the trick?
My current set-up for measurement of electronic "things" consist of: 2-channel oscilloscope, multimeter (a regular one, and a amp-clamp one), and a variable DC power supply (30V - 5A max). How can I measure the apparent, real and reactive power to calculate the power factor?
I've been reading a lot on this subject on the internet but I get a bit confused on how to make the circuit and how to do a proper measurement of it.
Thank you for your time :D


texts:
I am trying to learn electronics with the help of the Art of Electronics From Horowitz and Hill.
I am working on transistors and amplifiers and I am currently working on problem 2.16: Design a tuned common emitter amplifier stage to operate at 100kHz. Use a bypass emitter resistor and set quiescent current at 1mA. Assume Vcc is 15V, L = 1mH and put a 6.2k resistor across LC to set Q=10. Use capacitive input coupling.
There is already a question asked here about the same problem, but here I would like to have someone check my design process and see if I am doing things in the right way.
So this is what I did:

I calculated the value of the capacitor \$C_2\$ in the resonant circuit to resonate at 100kHz. That turned out to be $$\frac{1}{2π*f_c*\sqrt{LC}} = 2.53nF$$
I set the emitter resistor \$R_3\$ to be 1kΩ to give enough feedback; at 1mA emitter current \$V_E\$ is set at about 1V and \$V_B\$ at about 1.7V;
I set the emitter bypass capacitor \$C_1\$ to be 3.3μF, which gives me a reactance at 100kHz of about 0.5Ω (I wasn't sure how to set this value differently, so I just aimed for a reactance below 1Ω).
Knowing that the impedance looking into the base of the transistor is \$βR_E\$, I set my bias resistor network to be \$0.1βR_E\$ = 10kΩ (I assumed β=100 and omitted the intrinsic emitter resistance) . For \$V_B\$ of 1.7V, the ratio between \$R_1\$ and \$R_2\$ turned out to be \$R_2\$ = 0.128 \$R_1\$, and I calculated \$R_1\$ to be 88.1kΩ and \$R_2\$ to be 11.3kΩ, which gave me the required parallel input resistance looking into the base of 10kΩ
I selected \$C_3\$, i.e. the input coupling capacitor value calculating the total parallel resistance into the base of the transistor given by $$\frac{1}{R_B}=\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{βR_E}$$ This turned out to be about 9kΩ. Given that Q=10 gives me a bandwith of the resonant frequency +/-10kHz , I calculated the value of \$C_3\$ at 90kHz and -3dB to be approximately 200pF

Below is the circuit. I set the load \$R_5\$ to be 100kΩ to not load the transistor output (\$R_{load} >> R_c\$).
When I simulate the circuit, it seems to work; however, I get an 18Vpp waveform at 100kHz (0.4Vpp input sinewave at 100kHz). How can that be higher than 15Vcc? The bode plot looks also very ugly... why?
Is my approach to designing a circuit correct? Would this design be OK for the purposes of the exercise?
Many thanks!


texts: Raspberry Pi and FFT (Fast Fourier Transform) -- Using MCP3208

texts:
EDIT:  I've made adjustments based on your answers, while I couldn't get it to be evenly spaced, I managed to get a better curve with more samples per cycle. Turns out I need to remove the print function from my program so that the Pi could focus more on reading and plotting.

See ((Final adjustment)) at the bottom

Question:

Thanks for reading this. I'm doing a project using Raspberry Pi and MCP3208 (ADC) and currently, I'm testing my program with NI myDAQ's function generator to supply a 10Vpp to the ADC at 50Hz. I've tried using NumPy and managed to get some readings. However, when I got to my supervisor I noticed that my frequency reading is not exactly at 50Hz. Then I tried to change the input to 25Hz to see if it works at a lower frequency. Proceeding to 10Hz, I noticed that it is true! It is more accurate at a lower frequency.

My friend tried using another ADC chip and it worked accurately (or at least more accurate than mine) so I am wondering where did I go wrong with this? Below are my results and I've placed my code underneath.

READING AT 50HZ

READING AT 10HZ

FINAL ADJUSTMENT


texts: How would you jerry-rig an android phone for continuous autonomous operation?

texts:
I want to use an android phone as dash-cam with GPS tracking capabilities.
It is supposed to run 24 hours a day, 365 days a year.

If the phone / app hangs, the user cannot be expected to troubleshoot it. (This is the most important requirement). So I want to have a self recovery mechanism to recover from software glitches.

I am thinking of adding a MOSFET between the positive contact on battery and the corresponding pin on the phone. The MOSFET would be controlled by a micro-controller which acts as a watchdog. Additionally, the micro controller may also pull up/down the POWER-ON pin on the phone to turn on the phone.

I am concerned that the device's life could shorten due to exposure to higher than normal levels of heat and vibration. But apart from that I don't see any reason for this to not work.

Has anyone tried doing something like this before? What are some mistakes one can avoid?


texts: When drawing a circuit a resistor looks like this. How would a Microprocessor look? Microphone? Webcam?


texts: Best way to structure Verilog module to allow for simulation clocks

texts:
Quick question that I am likely missing an obvious solution for. I have a relatively simple Verilog design which I'll call taco, where the top-level design entity is taco_top (because I'm writing this before lunch).

It's the only module in the design with all relevant logic contained in taco_top. The design targets the ever-popular Lattice iCE40 UltraPlus FPGA. In taco_top, I'm using the iCE40's low-frequency and high-frequency oscillators to generate 10kHz and 6MHz clocks. There are no external clocks in the design; taco_top's ports all correspond to physical I/O pins on the FPGA and the clocks I need are sourced from these internal oscillators.

In simulation, I want to replace these with simple dummy clocks with the appropriate period since I can't simulate the LFOSC and HFOSC primitives. So, I've created the appropriate simulation only clocks and kludged them into my design with `define which is not particularly elegant.

In writing a testbench, I would normally instantiate my taco_top module and feed it the appropriate stimuli, but those sim clocks are buried inside / not exposed at the top-level.

What's an elegant way to structure my design such that I can easily feed those clocks in simulation and maintain their behavior in the synthesized design?


texts: Solar Li-Ion battery charger at low light

texts:
typically a MPPT ic such as the LTC3105 is directly connected to the solar cell. To charge a li-Ion battery, a li-ion charger ic is connected to the output. This charger ic e.g. a MAX1551 has a fixed or programmable maximum load current.

I am asking myself, is there any intelligent li-ion charger ic which auto-adjusts the maximum load current based on the maximum current available from the MPPT ic?
If there is low light, the MPPC ic will deliver e.g. +5V but with only 10mA. If the battery is almost completely empty, the charger ic will try to load the battery with the maximum current.
As the MPPC will act as an step-up, the output will collapse.

Is there any solution available?
Setting the maximum load current of the charger to e.g. 1mA is not an option as when not having low light, most of the available energy is vanished.

Thanks.


texts: How does multi-voltage power supply work?

texts:
So I was looking at this USB power supply by Xiami, and I noticed in the specs, it says:

Input voltage     12V/9V/5V
Output voltage    12V/9V/5V

So how is it able to achieve that? I understand there might be some circuitry that would convert between the voltages, but how does it know which voltage is needed?


texts:
I am working on an old PCB that uses a lot of the TI IC's for performing its functions.

It's essentially a power management board that takes a DC input and charges 12 batteries connected to the circuit. It has a power on/off button and a status LED light to show the overall battery level. It's a really old design. Instead of reverse engineering this I would now like to prepare an alternate design with similar or better functionality. Basically, to power networking devices over PoE. So the board must have at least 5 PoE ports and be able to power a load of 15W for up to 80 hours. This should be enough to help us narrow down on the battery capacity and requirements.

Wondering if anyone has any tips on how to get started on a circuit like this? I did robotics and specialized on the software side and wish I paid more attention in my electronic classes as well but it's never too late to learn and would appreciate all the help I can get to help make building a circuit that achieves or exceeds this.


texts:
After assembling a simple emergency light kit, it's time to build the battery charger.

Details: Most of the time, the battery won't be used and the circuit will be always connected to the energy source. It's necessary to avoid overcharge.

The circuit has educational purpose, so being simple is a must. I'm also trying to build it only with components that I already have (a bunch of resistors, capacitors, transistors and none IC).

Circuit

This schematics is completely based on this text.

By the author of the text, R1 is set as:

  P2 [here, R1] is set such that at 14.6V (across the battery terminals) the base LED becomes very dim, hardly visible, and at 12.5V it's brightly lit.

Doubts

Do you think that this is a good approach to this problems (considering the limitations)?
Wouldn't it be better if I just kept the voltage in 7v?
What is the best way to test this circuit? I'm not sure that I understand the potentiometer role.

As always, any kind of suggestion or critic will be appreciated!


texts: What physical construction features in a transformer control the dot polarity?

texts: As we know, the dot convention is used on transformer symbols to denote whether the transformer "inverts" the signal passing through it or not.  However, I am not clear on what in the physical construction of a transformer determines the dot polarity -- is there something physically different between two otherwise identical transformers that have opposite dot polarity conventions?  (I.e. one has the dots on the same side and the other has the dots on the opposite side)  Or are these two transformers physically identical and interchangeable?


texts: I was recently in Hong Kong and decided to purchase a knockoff Airpod to tear it down and see how it was engineered to help me in my own design process. I got to the mainboard and found the single chip which runs the operation marked "AC1815E8K193-9A0" (It may also be "AG...") and uses a logo which looks like the Pi symbol. A search turns up nothing and I'm struggling to find anything online about this model. Any ideas of where to search or any leads would be much appreciated! I'd also be glad to provide more pictures if desired


texts: How can I achieve symmetrical analogue low-pass filtering?

texts:
I am experimenting with VCFs for an analogue music synthesiser. Initially I tried a 3-stage low-pass filter based on the sinewave-generator circuit in the LM13700 datasheet but having removed the oscillator, as per schematic below:

I find that its effect on a squarewave, as the filter frequency is swept, is not symmetrical. A series of scope traces shows the effect of the sweep:

If the low-pass filter is meant to attenuate higher harmonics, I would expect to see the square soften to a sine whilst retaining its symmetry. Using a Max293 active switched-capacitor filter does give a more symmetrical sweep (ignore the apparent clipping, it's due to the input running to the rails):

Question:
Can anyone explain in simple terms why these filters have different effects on the waveshape symmetry (I assume it's something to do with phase shift in the analogue circuit) and whether the asymmetry can be avoided by using a different analogue design rather than having to use an active filter (with its associated downside of the clock frequency breaking through)?

Thanks


texts: How can I build a switching circuit that scales several 12v signals down to <5v?

texts:
Let me start off by saying that I know just enough about electronics to be dangerous (how to solder, follow a simple schematic, and check for connectivity problems and usually figure out what each wire is for).

I've installed a cruise control kit in my car, and I want to use a set of Honda steering wheel controls instead of the stock controls from the kit.  The cruise kit controls are expecting 12 volts, but I'm not comfortable running any more than 5 volts through the small steering wheel wires next to the airbag wiring.  I'd prefer even less, like 2-3 volts.

So I need to build a switching circuit that will provide the 12 volt signals to the cruise kit.  I was thinking of keeping it solid-state, since I don't know of any relays that will switch on 2-3 volts.  However, if there's a good reason to use relays then I can.

Here's a rough drawing of what I need:

How can I get started with this project?


texts: Is my lookup table with 50,000 entries too big for MCU memory (dsPIC33EP256MC506)?

texts:
I want to implement a 2-input 1-output fuzzy logic controller using lookup table on the dsPIC33EP256MC506 microcontroller. I am comparing the lookup table and actual fuzzy logic controller side by side in Simulink. In order to minimize the error between the lookup table and actual controller, I am having to generate a huge table, having around 50,000 entries. The input 1 range is -5000 to 5000, input 2 range is -1000 to 1000 and output range is -9999 to 9999. I am using Simulink code generation.

I went over the datasheet's memory section, but still need some expert guidance in relating the lookup table size to the program memory size.
My questions are: how can I find out if this lookup table will fit into the program memory? How can I estimate the approximate size of the lookup table? What are key things to look for in datasheet or the lookup table from practical implementation viewpoint?


texts: What is this symbol on the Arduino Uno schematic?

texts: These look like capacitors, but they're not labeled and I'm not quite sure what to make of them.


texts: Getting +/- voltage from a benchtop power supply

texts:
I have this benchtop PSU which I got from some dude on Craigslist:

I need to power a circuit that requires +12v, -12v, and a ground reference. Currently the way I do it is to use one channel of the power supply to provide 24v, and use a simple voltage divider on a breadboard to provide a fake ground. But that is not a very good long-term solution.

I figured I could get a -12v out of the second PSU channel by just hooking up + and - backwards. Would that work? How would I make a ground in that case?


texts:
it's the first time I encounter this in a schematic, and I'm wondering at how to reproduce this in Eagle.

So first number 1. As per description, the volume pin is "Internal Gain Setting Input
Connect to VDD which Set Max. Gain = +20dB ", this is the first part I didn't get along with that schematic symbol. Do I have to connect a button there? If so, how to connect a pair of buttons to increase/decrease volume?
My educated guess is that it means it's a potentiometer? (Maybe I could use a digital pot here then if that is really the case)

Now, number 2 seems to me even more strange, there isn't a node connecting the lines, and again that arrow. Is there a button here again to switch modes from BTL to SE? (If that is even possible to be switched like that...) and as the arrow goes through, is it still a pot? What is that?
Also it's description is "Output Mode Control Input
High for SE Mode and Low for BTL Mode ", so it pretty much is a pot right?

Thanks everyone! Tried to be as clear as possible here, let me know if I forgot something.

PAM8900's datasheet here:

https://www.diodes.com/assets/Datasheets/PAM8009.pdf

Edit:

Looks like BTL are speakers and SE are headphones, so how exactly is that part of the schematic going to be hooked up to choose between the two of them? At first I thought that simply by hooking up the headphones the IC would switch to SE mode...

Edit 2:

I think I may be overthinking this, would a simple jack like this and the PAM 8407 I was using do the trick of disconecting audio from speakers?


texts: Input impedance of common-collector configuration

texts:
We have been asked to find the input impedance of the given circuit (above)
I've done the small signal representation of the circuit which is as follows
The question is :
I tried to solve it i'm getting this result :
Rin= ( rR2+[(R3//R4//R5)(B+1)R2])÷R2+r


texts: How the current from circuit cross a capacitor dielectrics?

texts:
I've intensively studying electronic circuits there are few months and this is the first time I feel my brain stuck.

How can the current coming from the circuit cross a capacitor to the other side if there is a dielectrics layer between it? Even if it is AC it doesn't make sense to me.


texts: There are a few thing that can run directly off of AC power like incandescent light bulbs and and electric motors but it stops there. Most electronics need power converted to DC before it can be applied to a circuit. Is there a fundamental reason why logic circuits that use AC power directly haven't been developed or is it just a lack of ingenuity?


texts: I have a single phase induction motor, with no capacitor, and can't see the shaded pole. Can you help me understand how it starts or should start?

texts: I have a small single phase, induction motor with no capacitor. It's not missing, so this has got me thinking it should be a shaded pole. However, I don't see the shaded pole and my motor is just humming. If I try to manually spin it, it's very difficult while powered up. What am I missing?


texts:
I was reading about the Input bias currents for an op-amp.
And I had a question regarding the ones internally compensated for.

So in general if I was to use an Op amp for any particular application and I have an op amp with the internal compensation for the bias currents, then do I ever have to worry about the bias currents or connecting resistors to compensate for the design ?

Also if the answer is yes to the above question, then why don't people just use the internally compensated ones ?


texts:
I have this 433 MHz transmitter attached to my Arduino 5v Vcc pin.

I asked this question so I could deliver 12v to the transmitter chip, effectively boosting the transmitted power output, allowing me to reach the furthest corners of my house.

To prevent continually powering the transmitter; transmitting 433Mhz low level noise all the time around the house I have added the box outlined in yellow. This yellow box contains a very simple circuit with one transistor that only turns on power to the transmitter when the arduino 5v datapin goes high.

Can anyone suggest what the simple circuit in the yellow box should look like, particularly which transistor.


texts: Simulation in Altium Designer: how to simulate multi-sheet schematics?

texts:
I'm starting to simulate a complicated schematic in Altium which looks in LTSpice like this:

In Altium I can split this scheme into several sheets to make it more convinient to work.

So I make part of the scheme (generator.SchDoc):

And a simple root document (top.SchDoc):

So I assumed that this should work fine. However, simulation works well if I press the "Run active simulation" button in the Generator sheet. If I do this while I'm in the Top.SchDoc - the simulation result is a horisontal line (dispite that I have netC1_2 net displayed in both cases).

Looks like Altium did not figured out the ierarchy right.

How do I fix that out?


texts: Some op-amps are marked for audio applications, what makes them diferent from "regular opamps"?

texts: Datasheets for opamps for audio applications contain many example circuits that have nothing to do with audio applications at all. But anyway, what makes an Audio Op-Amp an Audio Op-Amp?


texts: Typical Resistance Temperature Coefficient Variance between a reel of same value resistors

texts:
I have a resistor divider, I'm interested calculating the drift of the divider over temperature and if possible minimizing it.
I was wondering if both resistors in the divider have the same value picked from the same reel, can I assume that the temperature coefficient of both resistors cancel each one out? if not how much variance can I expect between the temp coeffs?
I know this relies on resistor types and ...., I just want to know if anyone has tested this and knows a ballpark for typical resistor values laying around with temp coeffs around 200ppm


texts: Does the formula \$Av\times \left( v_{in-}-v_{in+}\right) \$ of opamp applies also for DC voltage input?

texts:
For a two-stage Miller op-amp, if I only apply DC common mode input, the vout is obviously not zero, since there is a voltage drop across M7.
So does this mean that the formula Av*(v_in_plus-v_in_minus) applies only for sinusoidal v_in_plus and v_in_minus? If this formula does apply for DC input, why am I not getting a zero vout when v_in_plus is equal to v_in_minus? Thank you.


texts: Ghetto crimping tool for FCI "Clincher" connectors?

texts:
After much experimentation and some helpful answers here I've decided that FCI "Clincher" (.pdf link) parts are the right answer for adding connectors to the ends of flexible ZJ168 RGB LED strip.

The parts themselves are cheap enough (< $2 each) but the crimping tool appears to cost almost USD$2500! I certainly can't afford that and in any case Element 14 here in Singapore (from whom I got the connectors) don't have any crimpers in stock and can't hire/lend me one.

I've had a modicum of success crushing the crimps down with the tip of my pliers but can someone suggest something more elegant and/or foolproof? Are there any un-obvious flaws with attempting to crimp these without the proper tool?


texts: Can I use the Coulomb Counting Method to estimate the SOC of a battery being charged by PV panels?

texts:
I have seen a couple questions about Coulomb Counting, but I have not found anything defining an "outside source" providing the current to the battery, this questions might be close, How to estimate Li Ion Battery SOC?.
I am wondering if what I am doing is possible in order to produce a simple SoC estimation of a lithium ion battery being charged by PV panels. The lithium ion battery is basically an energy storage system, maybe something like a Tesla power wall.
I am using the Coulomb Counting equation (Section 3.2.1 of the paper,  https://www.hindawi.com/journals/isrn/2013/953792/). I have implemented the equation in the following way:
soc = soc[-1] + ((irradiance * self.solar_panel_size)/(pv_volt))/(c*60)*dt

Units

irradiance: W/m^2 (changes between 0 and 1000 depending on time of
day)
solar_panel_size: m^2
pv_volt: Volts
c: Amp-hours (60 is to convert Amp-hours into Amp-minutes)
dt: Minutes

I believe the typical size for a solar panel is about 1.635m^2 (https://us.sunpower.com/how-many-solar-panels-do-you-need-panel-size-and-output-factors). I also believe the voltage coming from the solar panel changes with the irradiance, but I am hoping maybe 5 volts would be a good number to use for pv_volt (https://www.altestore.com/howto/solar-panels-pv-and-voltages-a98/).
Things I am assuming:

Not taking into account cycling, inefficiencies, temperature, different charge rates depending on SoC
Assuming a linear charging rate

I am trying to use the equation for a battery with a rating of 8kWh and power rating of 2kW. The battery can be fully charged/discharged in 4 hours (I know a battery would never be charged "100%", or discharged to "0%", but for the sake of simplicity, I want to assume this is the case). I would think that at 1000 W/m^2 irradiance, based on my equation, the SoC would increase by 25% in 1 hour.
I think my main issue is the "PV portion" of my equation, right now it basically depends on the size and voltage of the PV panel, I am not sure if I can do it this way, or if there is a more "optimal" way.
If I can use the Coulomb Counting equation as I am using it, then I guess my question is, what values can I realistically use for c and pv_volt to obtain a "realistic" SoC rate at every time interval?


texts: Using an Opto-Isolator to change an Op-Amp's Amplification

texts:
Consider this circuit, which is a standard non-inverting amplifier with an amplification of A = 1+R1/R2.

I now want to be able to change this amplification value dynamically, using a microcontroller pin. I came up with this solution, which basically modifies the value of the feedback resistor by inserting another resistor in parallel:

I think that the new amplification (with the opto-isolator turned on) is

A = 1 + (R1||R3)/R2
  = 1 + (R1 R3)/(R2(R1+R3))

Would this solution actually work the way I intended? I'm especially worried that the phototransistor's saturation voltage may influence the op-amp in some way. If so, is there an alternative solution to this problem?


texts: Is electric charge a state variable since derivative of charge flow is defined as current?

texts:
\$ i=\frac{dq}{dt} \$

Is 'q' a state variable in general?


texts: What to change when migrating designs from Altera DE2 to DE2-115?

texts:
I'm migrating a working design from Altera DE2 to Altera DE2-115 and I'm running into problems. First everything works with DE2 just like mentioned in the exercises doing what is instructed. Now I want the designs to work also with DE2-115. So I make new designs with the chip that is for the DE2-115 (Cyclone IVE EP4CE115F29C7). But besides changing the chip to Cyclone IVE EP4CE115F29C7, I don't know what other changes to make. So I download the design (the mux4to1 mentioned in the text) to the board and it's not working. I didn't run a simulation with this project but it compiles and it's basically a copy in Quartus II of another project that was for DE2 and I just did a new project for the Cyclone IV chip and copied over the sketch. Now I wonder what I'm doing wrong since the design downloads fine in Quartus Programmer downloading to the board but the it doesn't run like it's suppossed to, the board is simply "locked". Do you have any ideas what I should do? I can provide more details if needed and I asked about this before and then the answer says that the "pin mappings differ" between DE2 and DE2-115.

Upgrading from Altera DE2 to DE2-115

So can you tell me where I can find what the pin mappings are and what I should change them to?


texts: Verilog - Synthesize High Speed Leading Zero Count

texts:
Using Verilog how do I synthesize the fastest leading zero count on a 64-bit number?

Initially I went with a CASEX(..), with a lot of 01xxxxx, 001xxxxx lines but I understand this synthesizes a barrel shifter which I'm not sure is quick.

My ask is this, what's the fastest way to get to output... what would the gates look like?

I finally came up with this solution but not sure if it will synthesize to something quicker than the above.

The answer to leading zeros in a 64 bit number is either the number of leading zeros in the first 32 bits (if any is a non-zero) or it's 32 + the number of leading zeros in the lower 32 bits.  That gives you the answer to the 6th bit of the answer.  You then need to find the number of leading zeros in the 32 bit number, so apply the same rules.  I had to do an If/else to deal with all zeros.

VERILOG:

// Leading zero count of Sj
  if (Sj_int[63:0] == 64'b0)
   tmp_cnt = 64;
  else
   begin
    tmp_cnt[6] = 1'b0;
    tmp_cnt[5] = (Sj_int[63:31] == 32'b0);
    val32 = tmp_cnt[5] ? Sj_int[31:0] : Sj_int[63:32];
    tmp_cnt[4] = (val32[31:16] == 16'b0);
    val16 = tmp_cnt[4] ? val32[15:0] : val32[31:16];
    tmp_cnt[3] = (val16[15:8] == 8'b0);
    val8 = tmp_cnt[3] ? val16[7:0] : val16 [15:8];
    tmp_cnt[2] = (val8[7:4] == 4'b0);
    val4 = tmp_cnt[2] ? val8[3:0] : val8[7:4];
    tmp_cnt[1] = (val4[3:2] == 2'b0);
    tmp_cnt[0] = tmp_cnt[1] ? ~val4[1] : ~val4[3];
   end
   o_Si <= tmp_cnt[6:0];
 end


texts: Can you place two boost converters in series to boost 3v to 180v?

texts:
I am looking to build a power supply for a NIXIE tube. They need to output 180v at 4ma but will run off of a 3v lithium battery. The battery can take the current requirements for the input, but at the moment I am struggling to make a single 3v to 180v boost converter. I wondered if you can have one that boosts the voltage to say 30v and then a second that takes it up to 180v.

As well as that I don't want to use an off the shelf converter chip, I want the PWM to be created by a microcontroller (probably a PIC). Is this possible? and is it the best way around the problem?


texts: My question is simple, why are we still using relays ? Can't we say that MOSFET are the future of relays?


texts:
Is there a processor that do arithmetic operations on a stack and not on registers? To keep performance, of course, that processor should cache top block of a stack in the same type of memory that is used for registers.

I read in a paper (David R. Ditzel, H.R. McLellan. Register Allocation for Free: The C Machine Stack Cache.) that a cache is slower 2 times than registers because of:

indirect addressing during every access to the cache;
cache miss when the stack grows.

The paper is old. Maybe, improvements of processor design appeared that makes stack cache viable? I feel that it will reduce complexity of compilers and optimize copying between registers and the rest of memory.

Update 2012-10-18. Because this concept was well-known (not to me), I change the question to “… Modern processors?”

Update 2012-10-18. I feel I must say explicitly that I'm not talking about “zero address machine”. Caching and “zero address” are orthogonal. My hypothetical processor may have even 5-ary addition like “r3 := r0+r2+r11+r5+r8”. “r n” means the memory cell at sp+n, where sp is a stack pointer. sp changes before and after a code block. A very unusual program changes sp at every arithmetic operation.


texts: Balancing Power in a Simple Circuit When not all Wattages are known

texts:
I am having trouble solving the following problem. I understand that the net power should be 0, but it seems that there is no way to determine the power of elements 2, 3, and 5. How would one go about solving such a problem?

Find Ix in the circuit when P1 = -18.0W, and P4 = 13.0W, using the passive sign convention and power balance. The rectangles containing numbers represent arbitrary circuit elements.


texts:
Below is the issue I am facing, any help would be really appreciated.
Please note I am a rookie in the field of electronics so forgive me if I haven't provided enough information, I am happy to provide any additional information.

My Goal

I would like to use a RaspberryPi to open a door by controlling the doors buzzer.

My Problem

As soon as I connect both wires of the buzzer to the optocoupler, the buzzer activates, regardless if the RaspberryPi (the LED) is on or not.

It is my understanding however that the buzzer should not activate until the RaspberyPi is on.
I.e. the problem is, is that the buzzer's circuit closes as soon as I connect it to the optocoupler.

My Setup

A RaspberryPi and a door buzzer circuit are coupled together using this optocoupler. By turning on a pin on the RaspberryPi, the LED lights up and the optocoupler should close the buzzer's circuit.

Credit for the image goes to user daniel-crane created the diagram for question
 #213621. It has been slightly modified

What I have tried

Instead of the buzzer, I have used an LED (power source and ground are provided by the RaspberryPi using a different pins. In this case, the optocoupler works as it excpected; i.e. the LED replacing the buzzer will only light up if the RaspberryPi's LED is on.

Please help!

Dan


texts: What are the components symbolized in these 4 highlighted areas of this schematic?

texts:
I am a beginner and I understand only the most basic portions of this schematic. Could someone smarter please help me understand the highlighted areas?

Source: Schematic was copied from page 4 of the manufacturer's product datasheet.
Zhengzhou Winsen Electronics Technology Co.,Ltd
The circuit design is for a gas detection sensor element. As various levels of the gas being detected is sensed the output voltage should vary on one of the pins. Unfortunately I need this design converted to a PCB that the sensor element plugs into. I have the circuit half done, but the highlighted areas I am confused about.
I will likely have a couple follow up questions because as I said I want to understand this circuit, not just get an answer. For example, the block at the top middle, is that a voltage divide circuit? Thanks everyone. :)


texts: I am pretty new to electronics, and have mainly worked with DC circuits. I'm majoring in Computer Science, but I also find electrical engineering interesting, so I am learning as much as I can. Well, my multimeter measures about 0.050 to 0.100mV when not connected to anything. As soon as I move close to the wall outlet, it creeps up to 0.1 volts, then 2 volts, then when I am pretty close to it, it reads about 4 - 6 volts. Also, when I plug one lead into the hot or neutral, why does it read 6 volts or more? And between neutral and ground, it usually reads 0.4 volts when there is minimal load on the outlet. I heard that that is normal, but is 4.4 volts from neutral to ground normal when a 1300W heater is running? Thank you for your help. I'm still learning, so these questions may sound stupid. And yes, I am taking safety precautions so that I do not get shocked.


texts: How to connect a "touch sense" pin to a analog or digital input

texts:
I'm using a motorized fader that has a "touch sense" pin (see this data sheet), which should be able to detect when someone touches the fader. I want to use it to stop the motor and switch from setting to reading mode. I'm using a Netduino Plus 2 to read the value of the potentiometer and a motor-shield to control the motor (that part is working perfectly).

I have been told that the touch sense pin is to be used to measure capacity in order to detect touching. I was hoping to just connect it to a analog input but was warned that it could potentially damage the Netduino.

How would a typical "touch sense" circuit look like when connecting to a analog or digital input? (The Netduino Plus 2 measures voltages between 0 to 3.3V).


texts:
I am trying to understand the SPI serial interface between a Master MCU and a (Single) Slave ADC. Do we have 8-bits or 16-bits data word communication in SPI? Or is it un-bounded and I can send any number of continuous bits between master and slave in SPI communication?
I have used I2C bus which works in command-response cycles. Do we need to give command to SPI slave to get data from it or do we only need to assert its CS' (Chip Select) line and provide it with serial-clock pulses to start receiving data from the slave.
My ADC is AD7622 (16-bits ADC) or AD7641 (18-bits ADC)


texts: Darlington biasing design error in a commercial frequency counter oven control circuit?

texts:
I am repairing a commercial frequency counter (brand to remain anonymous) that had the crystal oven visibly overheat.  There is a small PCB in the oven that holds the crystals, the oscillator circuit, four diodes connected in series whose voltage drop changes with temperature, and a 220 ohm 1 Watt resistor whose voltage is modulated to provide the heat.
When looking at the circuit to repair it, I think I found a serious design error that explains why it overheated.  See schematic below, I may have drawn the diodes on the wrong input - it doesn't matter for my point.  Also, ignore the 'Rmissing' for now - that is my proposed solution, it is 'missing' from the manufacturer's design.

simulate this circuit – Schematic created using CircuitLab
I think the minimum voltage the TL061 output can reach (it is not a rail-to-rail op amp) is dangerously close to the minimum 'turn-on' voltage of the Darlington pair, meaning given tolerance overlap it is possible the op amp could never shut off the Darlington pair, leading to the heater staying on.
I simulated this in LTSpice and it confirms my suspicion.  I also confirmed that adding some resistance from the base of the Darlington pair to GND, that is the 'Rmissing' 100k resistor, creates a voltage divider and pulls the base voltage comfortably into the off region of the Darlington pair when the op amp is pulling its output low, yet still allows plenty of base voltage when the op amp output is at max output voltage.
Thoughts on my theory?
(Edit #1: My apologies, I completely missed the shorted inputs.  I fixed that plus added the exact input circuit and all component values.)


texts: Newton Raphson Load Flow of a Power System with Transformers

texts:
I have a 13 bus system that I want to apply Newton Raphson to. 3 of the buses have generators. So that makes 1 slack bus and 2 PV buses. 6 of the buses are connected to loads (PQ). 5 buses have transformers. I have no clue how to handle transformers when doing load flow analysis. I converted them to impedances in pu. I'm not sure what the next step is.

The circuit and specs are shown below...


texts: I am trying to count the number of times a motor rotates for a fatigue test machine I am building. What type of sensor/electrical component is needed to count the rotations? I plan on having it connected to an Arduino mega and the outputting the number on a basic LCD screen.


texts:
Possible Duplicate:
  Name of this component

I've noticed that on many home electronics there are sometimes power supplies that have a bulky unit attached to the cable. I don't even know what these are called to be able to search for them.

What are these called?
What purpose are these for and why do some gadgets have them and other not?

Below are are some examples highlighted in red


texts: Brushed DC motor with incremental encoder-- How do I use it?

texts:
I have come across large brushed DC motor, a Dunkermotoren GR 53X30 with an incremental encoder attached. Here are the spec sheets for the motor and the encoder:

http://www.dunkermotor.com/data/technical_data/motors/pdf/121005_GR53x30.pdf#page=1
http://www.dunkermotor.com/data/technical_data/servocomponents/pdf/Inkrementalgeber_RE.pdf#page=1

I'm fairly new to the electronics tinkering world and have a few questions about controlling it. I have a few microcontrollers lying around, a TI MSP430 and an Arduino UNO, and a 30 V, 5 A variable powersupply. I'd like to play around with the motor a bit, and possibly use it for a project I'm working on. My questions:

What purposes does the encoder serve?
What kinds of control is this motor capable of (i.e. braking, reverse, etc)?
Is my power supply able to provide enough amps to use it properly or is there the possibility of damaging it?


texts:
In theory, for an op-amp in inverting design, the voltage gain is \$\dfrac{R_{f}}{R_{in}}\$.

For example: for a \$gain=10\$ we can use \$R_{f}=100\ \mathrm{k\Omega}\$ and \$R_{in} =10\ \mathrm{k\Omega}\$. The same gain can be obtained from \$R_{f}=1\ \mathrm{k\Omega}\$ and \$R_{in}=100\ \mathrm{\Omega}\$. What is the difference and which value is best suited?

A config like this:


texts: 3.3M resistors not registering on multimeter - are they faulty?

texts:
Please keep in mind this is my very first electronics project so it’s entirely possible I’m doing something wrong. Here’s the deal: I’m building a contact microphone from a kit that came with four 150R resistors and four 3.3M resistors. My digital multimeter shows a correct reading for the 150R resistors but does not react at all when I test the 3.3M resistors. To cover my bases: I have the red lead plugged into VΩ and the black lead plugged into "COM". I have the dial set to "200" when measuring the 150R resistors and set to "2M" when measuring the 3.3M resistors. I have touched the leads together before each reading.

When I touch the leads together at 2M the display changes from "1" to ".000". But when I touch the leads to the resistors, the display simple reads "1".

Any help is much appreciated!


texts: Development board or Individual Microcontrollers?

texts:
I am an electrical engineering student and my planned career path is embedded systems. To get slightly ahead of my peers, but also for my own interests, I am learning embedded programming as well as purchasing some hardware to tinker with (possibly make my own smart devices or things of that nature).
Obviously, equipment such as an IDE, resistors, breadboards, wires, and other components are needed. And these things I have (I am using Keil MDK as my IDE). However, I would like to know the distinguishing factors between a development board, most likely a TI board like this one, and separate microcontrollers that can be purchased for under a dollar in most cases. Which option is more cost-friendly but also allows me to work on various projects? For example, one of the first projects I want to do is a motion sensor light for my kitchen pantry. Obviously, an entire development board is not necessary for this, but can I accomplish this with a simple $0.80 microcontroller?


texts:
Once I mistakenly placed a via on 0603 pad and didn't have any problem on soldering. I am routing another board now and I could save some space by placing some vias (0.3mm) on a 0603 pad. I wonder if it is a used technique or is it a bad practice? Would it cause PCB or PCBA production, or performance problem?

The via connections are low frequency (max 1.2 kHz) and related connections looks like this.


texts:
I am building a setup to make more inputs on a composite monitor (in fact it's a VGA monitor with a composite-to-VGA converter on it but the overlay needs to be composite) and everything will be controlled via a microcontroller.

I want to be able to show a menu that will tell me what source is selected. I made everything and it does work, but when I open the menu the whole screen does blank and only my menu works (witch is normal because it currently have it's own composite signal and when I open it up the relay of the input is turned off to turn on the one of the menu).

Can anybody guides me in the process?

The cheaper working solution will be the best one.


texts: nRF24L01+ RX in pulsed operation to save power?

texts:
I'm considering building a handheld radio receiver based on an nRF24L01+ and an ATtiny chip. It needs to receive "continuously", to receive a control signal that might operate some attached LEDs or make a tone from the PWM controller. However, due to power concerns of being battery-operated, I wonder if it makes sense to operate the receive in pulses, instead of continuously.

For example, I could have the receiver enabled only 1msec, every 20msec, thus reducing its power requirement to approximately 5% (with a slight hit on the ATtiny of running a timer to perform this, but that's still an overall net saving). This gives a worst-case latency of receiving a signal at around 20msec, which is fine for my purposes of controlling an LED. It means the transmitter should run a strategy of something like transmitting a packet every 500uSec for 25msec, but that's OK because this transmitter is mains-powered so there aren't such concerns of achieving low power there.

Is this a sensible plan? Am I actually likely to achieve a good power saving by such a strategy, at the additional cost of code complexity on the ATtiny, and added on-air congestion from transmitting the same packet 50 up to times?

(See also my related question How does the nRF24L01+ performance degrade with supply voltage?)


texts: How to identify the serial console port pads on device

texts: I want to identify the serial console port pads on the board. The place for male header connector(yellow arrow) have 6 pads. Usually it’s not difficult to identify Rx, Tx, GND pins with a multimeter, but here I'm not sure about the purpose of 4-pin square connector on the half of connector. There are two square pads to indicate pin number 1, so it looks like there are two different conectors combined within one header. Can anybody clarify this?


texts: How to choose or design a suitable single board computer (SBC)?

texts:
Programmer here, making my first foray into anything hardware-specific.

I need to deploy my software on dedicated hardware to around 1000 sites as part of a research project. The hardware is required to:

Run a local, lightweight web-application.
Push data over the internet to our central server.
Monitor a set of 5 local sensors.
Have Ethernet access to the local network.

Currently this runs fine on 1 remote site on a RaspberryPi 3, interfacing with our central server. Checking remotely, I can see that typically around 330-350MB of memory is used (free -m). top -i shows typical usage of between 1.0-10%. I am not keen on deploying this to 1000 separate Pis, but I am having difficulty researching information about choosing the correct alternatives for me.

Are there any good commands or tools that can provide me a better understanding of how much/what RAM/CPU/etc my software requires?
Is it worth considering designing a custom SBC?
Assuming I am buying a cheap SBC or hiring an engineer to design a suitable one, what information do I need to do write a good specification for this?