texts: A question on zero crossing versus random-fire SSRs

texts:
Figure 1.

I have the above mechanism, where I control a single-phase fan motor's switch.
I mean instead of a mechanical switch, an AC/DC SSR is switching ON or OFF from a remote place by a constant DC input (DC in in figure, 10V or zero).
When the SSR is ON, it will stay ON for long time like an hour or more. I mean it is not for speed controlling itself, it should act just to turn on the fan or turn off. The speed controller in the figure is an AC phase controlled speed controller(like a dimmer for inductive loads).

Here is the speed controller regarding the above figure:
http://uk.rs-online.com/web/p/fan-speed-controllers/6685345/

As you see in my illustration when the SSR is ON, the hot line is connected to the speed controller.
The fan speed is controlled via the poti knob of the speed controller manually.

The system above works for tests until now with the following SSR (Of course I cannot see whether there are current spikes or surges during each switching).
Here is the SSR with zero crossing I have and use currently:
http://uk.rs-online.com/web/p/solid-state-relays/2181959/?origin=PSF_428032|alt

The data-sheet says "Switching Type: Zero Crossing" and "Output device: SCR"

*But I started to get worried when I read the following articels:

http://www.jelsystem.co.jp/en/product/ssr/ssr_dosa.html

http://www.crydom.com/en/tech/newsletters/solid%20statements%20-%20ssrs%20switching%20types.pdf

*They claim a zero-crossing SSR is not recommended for an inductive load.

My question is:

1-) Do I need a random-fire SSR instead of a zero-crossing one considering my illustration and the articles I read?
I'm asking becasue I thought the speed controller would be taking care of dV/dt effects even I use the zero-crossing one.
But I'm not sure its effect on the SSR's SCR or triac if I use the one I have with zero-crossing.

Here I found a random-fire switching type below:

http://uk.rs-online.com/web/p/solid-state-relays/4092851/

Its data-sheet says "Switching Type: Random" and "Output device: Triac"

Which one would you recommend in my case?

2-) This is a bit confusing for me because I cannot find any wave forms of the inner trigger circuitry(the part which triggers SCR or the triac) when there is continuous DC input for lets say minutes or hours.

What I understand until now when there is zero-crossing, the circuitry detects zero crossing points and fires each time when the voltage crosses zero point.
So what I understand is that, in one second for a 50Hz AC, the SCR fires 100 times if the DC in is constant and ON for one second . Is that right?

If above is true, my question is about the random-firing SSR. Okay in zero-crossing case the SCR detects and knows when to fire. But how about random firing case?

How is the triac inside the SSR is fired? What does firing it randomly means if the DC in constant ON all the time? How often it fires in this case and would that create some surges? Or in constant DC in case the triac is always on and there is no firing? The confusion arises because a triac is not a transistor and unlike a transistor it will not be ON when its gate is always ON right? I struggled to find an answer but I failed and had to write as a question.

I would be very glad if you can illustrate the wave form in this case.

Edit: Some simulations with LTspice:

Here is an opto-triac with zero crossing:

As you see below the opto-triac fires at each zero crossing point when DC in is 5V constant all the time. I'm asking is that the same case in zero-crossing SSRs?

Figure 2.

And below is an opto-triac this time with no zero crossing and DC in is always ON again:

Figure 3.

As you see above the opto-triac again fires at each zero crossing. What is going on here? It is not random.

Another example here. And this time again we have an opto-coupler with no zero-crossing "with an inductive load":

Figure 4.

And here an opto-coupler with zero-crossing "with an inductive load":

Figure 5.

Edit 2:

A non-zero cross optocoupler


texts: Resistors in series to increase maximum Voltage

texts:
Do the values of resistors matter when I want to use them in series to increase the maximum voltage they can handle?
So can I just use a 1 megohm resistor for example that's rated for 200 V and then add a 10 ohm resistor that's also rated for 200 V in series to get a maximum voltage of 400 V and then connect that to 350 V without any problems?
I tried googling it and found nothing.
Sorry if this is a stupid question.


texts: Understanding Source Code of I2C communication

texts:
So in my University studies we recieved few source code samples that are working with a OPT3001 Light Sensor. Our studies do not focus on engineering tasks in general, but this is a lecture that touches some of the Electrical Engineering subjects.  I study Physics if someone wondering.

I am not familiar with Electrical Engineering communication protocols but I have read few guides online about I2C communication in order to aid me to understand the given source code.
I have only some knowledge of Android programming - but also self-taught.

I would like to understand more, that is why I ask you, if you can help me. I will just copy one function of the entire code so it won't be too long and if you can guide me with some comments on each line what is happening I will be really thankful!

void UpdateLight(void)
{
    uint8_t error = 0;
    // start conversion
    I2C_Start();
    error |= I2C_Write(OPT_ADDR_W);
    error |= I2C_Write(OPT_CONFIG_REG);
    error |= I2C_Write(OPT_CONFIGURATION_H);
    error |= I2C_Write(OPT_CONFIGURATION_L);
    I2C_Stop();

    // wait for conversion
    _delay_ms(150);

    // set result register
    I2C_Start();
    error |= I2C_Write(OPT_ADDR_W);
    error |= I2C_Write(OPT_RESULT_REG);
    I2C_Stop();

    // read data and update scratchpad
    I2C_Start();
    error |= I2C_Write(OPT_ADDR_R);
    if (error == 0)
    {
        scratchpad[1] = I2C_Read(1);
        scratchpad[0] = I2C_Read(0);
    }
    else
    {
        // report error value
        scratchpad[1] = 0xFF;
        scratchpad[0] = 0xFF;
    }
    I2C_Stop();
}

Some definitions that are used in above code:

volatile uint8_t scratchpad[9] = {0x50, 0x05, 0x0, 0x0, 0x7f, 0xff, 0x00, 0x10, 0x0};   // initial scratchpad

This is not a requirement to know on my university, it is just an exercise where it is pre-made by professor and all we need to do is to use this Light Sensor to measure illumination. But I wanted to teach me something more if possible.

I am familiar with the Datasheet of OPT3001 so I do understand a bit the necessary addresses, but also not completly.

Here is a link to datasheet if someone needs: OPT3001 datasheet

Gratefull for any help / comment / input.
Hope this still applies to the StachExchange rules - did not know where else to post this question.


texts:
Possible Duplicate:
  Does the frequency of a crystal influence its height?

I am looking at s and saw that there are some odd shaped packages.  Is there a  case where such a tall  (13.46mm) would be ?

For comparison a "regular"  (3.68mm)

The specs and price between these two seem very similar.  I was just curious to know if there is a reason for such a package?


texts:
I am trying to build a pressure sensor ( PSI gauge ) that will be used to measure and monitor the pressure in a pool water filter. These generally have a mechanical pressure gauge like this....

What I want to do is use this Freescale Pressure Sensor so that I can electronically monitor the water pressure in the filter. However, it is not waterproof and would mostly certainly be destroyed in little time if used to measure the pressure of a liquid.

Anybody have any idea or experience with use such a sensor in a manner that provides accurate readings while protecting the sensor from the water?

Any other methods that work well for this sort of thing?

Cost is a factor here. I can't spend a lot of money.

Edit: might something like this water pressure sender for cars work?


texts: Why does the tank circuit of Coplitts oscillator produce 180 phase shift?

texts:
http://www.circuitstoday.com/colpitts-oscillator

I would like to understand how Coplitts oscillator works. This link says that the tank circuit of Coplitts oscillator produces 180 degrees phase shift. I Can't understand how a combination of a coil and two capacitors produce 180 degrees phase shift, Would you explain it,please ?


texts: Output impedance of differential amplifier

texts:
How do I calculate output impedance of the following differential amplifier?

Input are at the base of two BJTs.

I know that it's Rc || resistance looking into the collector of Q2, but how to find that value?

simulate this circuit – Schematic created using CircuitLab


texts: RS232 and RS422 (Isolated and ESD Protected)

texts:
I want my RS232 and RS422 to be galvanically isolated and ESD protected. I have two options to implement this requirement.

Option 1: MCU-->OPTO-->DRIVER-->ESD PROTECTION

Use MAX3232 for RS232 driver with ESD diodes near the connector and lines connecting to MCU I will isolate using optocoupler ACPL-217. Next, for power supply I will have to use transformer driver say MAX253CSA or SN6501 with transformers.

Use similar type of set-up for RS422 with MAX489, optocoupler and transformer driver.

Option 2: MCU-->ISOLATED DRIVER-->ESD PROTECTION

Use MXL1535E for RS422, with external transformer only(transformer driver is inbuilt) to implement the design. No ESD diodes also, since it is +15KV ESD protected.

Use MAX3250 for RS232 interface, with ESD diodes also.

Looking into space constraint option 2 looks better with fewer components, but please suggest your views which option is better for the good and robust design?


texts: Circuit testbench nailbed: how to test the pots?

texts:
Imagine I make an analog circuit, lets say a guitar pedal circuit (in a PCB of course).

How can I test (automatically if possible) the potentiometers functionality, when testing in a nailbed testbench ?


texts: STM32F7: activate USART Receiver Timeout Interrupt (USART_RTOR.RTOF)

texts:
I want the STM32F769NI to generate an interrupt when a pause after a received byte on USART6 was detected.

I cofigured USART6 with 9600 baud in asynchronous mode and enabled the receiver interrupt RXNE and the global USART6 Interrupt. So far this is working, on USART6 interrupt I can read the correct byte from USART_RDR of USART6.

I found the RTO interrupt in the reference manual. It says, the RTOF flag is set if no start bit is set for the number of bit times given in USART.RTOR.RTO. And the USART interrupt is generated if the RTOIE flag is set. I want to get an interrupt 100 ms after the last byte was received, so I configured:

// Set RTOR.RTO = 960 (0,1s * 9600baud = 960):
MODIFY_REG(USART6->RTOR, USART_RTOR_RTO, 960);

// Reset RTOF flag:
WRITE_REG(USART6->ICR, USART_ICR_RTOCF);

// Set RTOIE (enable RTO interrupt):
SET_BIT(USARTx->CR1, USART_CR1_RTOIE);

But the USART6 Interrupt never gets executed with the RTOF flag set.

The USART6 interrupt vector is executed if a byte was received (with the RXNE flag set). I expect the same interrupt to be executed if the timeout happens after the reception of one byte (with the RTOF flag set), but this does not happen. I tried to set a LED on, set breakpoints in the debugger, but after sending one byte to USART6, the interrupt gets executed only once and only with the RXNE flag set. I also tried to set the RTO value in the interrupt handler after the reception of one byte but this changes nothing. I also tried to set RTO = 1, also without result.

Is there something I am missing to configure? Do I need to set RTOR.BLEN (Block Length) to some value? But this is only for SmartCard mode.


texts: How do I solve the equivalent resistance of this circuit?

texts: How do I determine the equivalent resistance of the circuit looking into terminals A and B? I am quite stuck and the only thing I've figured out is that there are 3 pairs of parallel resistors: 90&12, 18&6, 100&150. The diagonal wires with no resistors kind of throw me off.


texts:
I'm aiming to control 4 motorized faders with an Arduino. However, I'm still trying to figure out how to best multiplex all the inputs/outputs. Each fader has two potentionmeters and one touch capacitive sensor, and even if I discard the touch sensing pin I still need at least 4 inputs per fader (16 in total). On the other hand, I don't know if it would be possible to mux the four DC motors, but I wouldn't discard reserving 4 PWM pins for each indivual motor. I've read that it is possible to achieve this with either multiplexers or shift registers: but what would be the advantage of each approach? I predict each motor would be operating at 10V@0.8A max.

EDIT: I have no actual "fixed" requirements for how fast the motors should run, I'm trying to estimate what kind of speeds I would get with each approach, and if how much I would gain if used dedicated PWM pins for each motor (besides being able to control them "simultaneously")


texts: what is a unit sample response ? It is denoted by h(n) , is it same as the impulse response?

texts: what is a unit sample response ? It is denoted by h(n)in discrete , is it same as the impulse response?


texts:
I have built a machine. The main machine shaft rotates when 4KG force is applied at a 1 foot distance from the center of the shaft. I want my machine to run at 1500 RPM.
How do I select the right motor (induction motor) size in terms of horsepower?


texts:
I would like to use a LT3080 as a current source (see datasheet page 17 in Typical Applications Section).  However, I need to be able to shut it off. Since $$I_{\text{out}}=10\mu\text{A} \times R_{\text{set}}/R_{\text{out}}$$ it seems just a matter of shorting \$R_{\text{set}}\$ with a PMOS.  The problem is that for all PMOS devices I've reviewed the best I've found for zero gate leakage current  is 1uA, and at high temperatures 10uA, so depending on the temperature it will suck all the current from the 10uA current source, thereby killing the output current when it is not supposed to.

I thought of using a PNP but the problem is that \$V_{\text{ce(sat)}}\$ will be comparable to the 0.5V-1V I intend to drop accross \$R_{\text{set}}\$, so it will not shut off \$I_{\text{out}}\$ effectively.  The only solution I have at the moment is to shut off the input voltage.  Any ideas?


texts:
When we calculate the equivalent of the capacitors that are in series and are connected to a battery we assume that the total charge on each capacitor is equal to the next one.

When I look at two capacitors in series the inner plates of the two capacitors are connected by a wire. Why the charge on each of the inner plate doesn't go through the wire in between and make the two plates neutral?


texts: Is there a PIC development tool like Texas Instruments's EZ430‑F2013 to help introduce me to PIC?

texts:
I would like to familiarize myself with Microchip's PIC product line and IDE, I don't want anything too basic or cheesy, etc. I can't seem to find a device like Texas Instruments's EZ430‑F2013 USB development kit:

The features I like about TI's board, and what I'm looking for in a PIC version, are the following: (In order of 1 = most desired to least)

Works with their IDE
Quality
The detachable PCB with chip pinout, and the size of this PCB (because it
can easily be used in a basic project...)
Size and surface mounted desing
USB connectivity
Price
Can easily be used to program other MSP430's

I also want to learn with a processor line that I will be able to use in production units. I don't know the PIC processor line differences well, but a processor in the price range of $1.80~$6 per 100 quantity, is my goal.

From a bit of research and answer's like this one I'm thinking that to best meet my desirements, I may need to get a separate programmer and dev board (like is needed/recommended with AVR's.) If so, it seems like the PICkit2 or maybe PICkit3 would be the way to go? And I don't know what dev board/processor line etc. to start with.

Price isn't too big of a deal, especially with regards to the programmer/debugger, so if there is a better option I may rather buy it. However, a cheap device like TI's is fine too, as long as it meats my processor goal, etc.


texts: A Mealy machine state diagram ( Couldn't draw it )

texts:
I want to draw a state diagram of a Mealy synchronous state machine having a single input x, and a single output y, such that y is asserted if the total number of 1’s received is a multiple of 3.

But the problem is how to get a multiple of 3 only with one input and one output ??

Help appreciated


texts:
For a complex waveform as follows:

One can find the squared rms of the complete waveform by finding rms of individual components and then square multiplying it with the corresponding duty cycle.
$$s_n = \frac{1}{T} \int_0^T u(t)^2 dt$$
$$u_{rms} = \sqrt{d_1 s_1 +d_2 s_2 + \cdots + d_n s_n}$$
EDIT1:
For example finding the rms of following waveform,

$$ I_{rms} = \sqrt{d_1 I_1^2 + d_2 I_2^2}$$
Is the above method also applicable for sinusoidal wave or any other non-linear waveforms?
EDIT2:
If I want to calculate the rms of a sine function defined from 54 degrees to 180 degrees with peak value of 27.44 I get 11.48 but the actual answer is 12.66.
$$ RMS = \sqrt{27.44^2 * 0.35 * 0.5} = 11.48 $$
here, duty cycle = 0.35


texts:
Consider this circuit.

What would I get if I measure over R1? It should be less than 12v, right? But then what volatage is LAMP1 running at? Is it still 12v, or is it the voltage I measured across R1? If it's 12v, then why didn't the voltmeter show 12v since it's connected to the supply in the same way as the lamp (IE over R1)?

I'm confused because the wiki article on parallel and series circuits states that:

  If the light bulbs are connected in parallel, the currents through the light bulbs combine to form the current in the battery, while the voltage drop is 6.0 V across each bulb and they all glow.

(The wiki article uses a 6V supply instead of a 12V for their example)

So what is the voltage drop across LAMP1, and if it is different to the measurement across R1, then why?


texts:
I want to control a fan using analog voltage instead of PWM.
I have a PWM signal from MCU. I want to use a low pass filter to convert this to analog, so 0 to 3.3V based on PWM duty cycle. This will go into a MOSFET which will drive the fan. I want to be able to control the speed of the fan in this manner. This way I control the current to the fan based on Vgs. I need this because it gives me greater control in fan speed and is cheap.
Is there anything wrong with this method?
How do I go about making this work well?
And what should I keep in mind and what am I missing in this circuit?

I need to find a transistor with a low enough Vgs to do this, but if such a thing doesn't exist is there a way to fix that?

Thanks!


texts: When is a programmable logical controller the best choice?

texts:
I am studying PLCs as a part of my Elements of Industrial Automation class. Trouble is, I can't imagine why would anyone use such a thing.

For complex tasks, microcontrollers are available. The vast majority of practicing programmers are well-versed in C, so creating a system with an ARM core (for example) is relative cheep. Furthermore, there are numerous free and tested RTOS for hard-realtime design to rest upon.

For massively parallelizable, hard realtime, low-latency tasks, there are FPGA-s. Those are a little harder to program. Yet there are many VHDL/Verilog guys out there in the job market.

Now to address the reliability of PLCs:

  the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact

The same can IMHO be acheaved (and far surpassed) by extensive redundancy e.g. 3 identical systems operating simultaniously, upon detection of a problem in the primary system, another one, located at a different place, and programmed in a different way, kick in.

Where are PLCs used in modern industry? Why are they the best solution in those situations, instead of one of the solutions above?


texts: RS232 Bridge cable stopping after some time

texts:
Im trying to reverse engineer a very old DOS program that connects with a machine using RS232, for this i setup a typical in the middle connection like this:

From Computer A to PC A connection im using a standard RS232 crossover cable with this configuration:

And feeding both lines to my PC using Serial to USB converters, for monitoring the software i'm using Device Monitoring Studio and setting it to bridge all communications between PCA and PCB

It apparently works fine but after some time the communication breaks, I have double checked the connections, the transfer options (It seems to be 9600 8N1) and redo the cable, if i try other transfer options like changing the speed or the handshake or the start / stop bits the communication wont even start

Any ideas on why the communication is suddenly stopping? what else can you suggest to monitor the communication on a Windows 7 x64 machine (or maybe linux)?

Regards...


texts: What is an example of a three-terminal current-controlled voltage source?

texts:
Dependent sources come in four flavors:

voltage-dependent current sources (e.g. a FET can act as a VCCS)
current-dependent current sources (BJT)
voltage-dependent voltage sources (OpAmp as an example of a linear component)
current-dependent voltage sources

A resistor can be seen as a special type of CCVS, where the current through the resistor determines the voltage across it.

Is there such a thing as a three-terminal current-controlled voltage source? I guess the equivalent circuit could look like this:

simulate this circuit – Schematic created using CircuitLab

The current at AM1 controls the voltage across R1, measured by VM1. But is there a single, specific component that does the same thing?


texts: How do I design a circuit to convert a 100 mV and 50 Hz sine wave to a square wave?

texts: I have a sine wave of 100 mV and 50 Hz. I want to design a circuit that converts this sine wave into a square wave as shown in a figure.


texts: Why are some products not priced openly?

texts:
OK - maybe this is meta, so feel free to move it.

I am looking for a 100 Ohm precision calibration standard. Seems a number of companies do them but all (so far) have a "Call for price". Why? Why can't they (or their distributors) actually name a price online? I find this extremely annoying, especially if I do ask for a price they assume I want to be spammed by them for all eternity. This seems typical behaviour for specialist stuff.


texts: Battery power options for ESP-01 + Sensor (Arduino Project)

texts:
I am building out my first self-designed project and am a bit unsure how to proceed with the power setup. I'm making a sensor device that will send me a tweet whenever the relative moisture of my plant gets low. I plan on making one for each potted plant in the house (a dozen or so), so want to keep things cheap and also not need to be near an outlet.
I have all the code working fine, but not sure what to do with regards to power. I am using an ESP8266-01 wifi module (this one) that has 8 pins (2 IO, TX, RX, 3.3V, GND, reset) with this soil sensor, which need 3.3V, gnd, and output connect.
I guess I don't get how I can power both the ESP-01 and the sensor. I don't want to use a full Uno or something, to keep the price minimal. So much I see online seems to say I should be able to use just these two components. But I don't see how.
I have a bunch of adafruit trinket m0 boards, which give me battery/usb in, but only one 3.3V out. So, I could set the code up to use the trinket as the control that reads the sensor and then passes the readings to the ESP-01. But there aren't enough power outs on the trinket?
Should i set up two battery supplies, one for the wifi and one for the sensor, or can I somehow combine the two off the one 3.3V output from the trinket?
Total newbie on power setup, so please forgive if these are dumb questions.
EDIT: To clarify, per the comments:
In an "ideal" world, the ESP-01 wifi module would run the code that both reads the sensor and send the tweet containing the sensor data. If I could figure out how to both power the ESP-01 and the sensor without using the trinket, that would be what I would prefer.
Barring that, I would use the trinket to read the sensor, then use the trinket to send the data re: sensor data to ESP-01 to POST the tweet. Basically making the trinket the power hub, I guess.
If I can just set up a power source and splice the wires off to the ESP-01 and sensor, great. But would that work?
I assume I would need to use the trinket if I don't want to worry about stepping down power and whatnot, so would a splice still have enough power for both the 3.3V ESP-01 and the 3.3V sensor?
If so, for the future, how to I determine that?


texts: Electronically controlled pneumatic lift, or something similar

texts:
Need to be able to firmly lift about 110Lbs (~50Kgs) weight, through a distance of upto 12 inches. The weight can be considered to be a flat & square wooden board, hinged to a flat platform, with the lifting action applied to the free end, s.t. the wooden board slopes at an angle, when a signal is applied.

Also, I need that the lift should be proportional to signal duration or strength (voltage), ideally not be jerky (or be minimally be so), and it should be possible to reduce the lifted height as well.

Would like to understand the potential options available for the required mechanical action, on application to electrical current. Few things on my mind are electronically-controlled pneumatic lifts, gear-and-pully with stepper motor. An indication of the relative costs (amongst alternatives), would be of great value.


texts: I am having trouble identifying the socket type of the power connection on an old voltmeter I purchased. It did not come with a cable, so I am trying to find a new one which will fit in the socket. It has two pins near the bottom of a circular hole, and a plastic ridge at the very bottom for alignment.


texts:
I have a linear regulator with three pins. It's identifier is LM7805.
I've taken a look at it's datasheet and it looks unlike linear regulators I've encountered.

Is the the op amp circuit included in this schematic?
There are segments of the block diagram I am sure surpass your standard linear regulator with an open op amp and a transistor. What segments of this schematic compose the Thermal Protection? The Safe Operating Area Protection? Other blocks?


texts: Different models of mcp23017 for raspberry pi

texts:
Im about to order an mcp23017 for getting more pins to my Raspberry Pi.
I got a bit confused. At the place where I order there multiple models of mcp23017. I guess they are about the same, just different manufactures. Or are there any difference between these two:
https://eu.mouser.com/ProductDetail/Adafruit/732/?qs=GURawfaeGuDsiwNCtfEn8A%3D%3D
https://eu.mouser.com/ProductDetail/Microchip-Technology/MCP23017-E-SP/?qs=usxtMOJb1RyESXZDw7ia5A%3D%3D
I guess not?


texts: Understanding balancing resistor in bipolar op amp

texts:
I just can't understand compensation resistor in bipolar op amp. And reading other answers in Reason behind choosing the compensating resistor for input bias current in op amps
 or How does the compensating resistor act in op amp haven't cleared my confusion.

Is the "input bias current" the current generated from external power source or some unwanted current resulted from within the op amp circuitry when the op amp is powered? In my learning of BJT, input bias means setting the Q-Point by coupling a DC voltage to the base of a transistor. So my assumption of input bias in op amp is the DC part of the input signal, but elsewhere they state the input bias is due to transistor mismatches within the op amp circuitry - hence the bias current is an "unwanted" current induced from within the op amp. But if it's an unwanted current needing to be gotten rid of, it can't possibly be called an input bias - it's neither a meaningful input for any operation nor a bias to set a system up to center an amplified signal. Neither of my interpretations is correct. What exactly is input bias current?
In the diagram, when there exists a potential difference between \$ V_- \$ and \$ V_+ \$ then an \$ I_{OUT} \$ will be generated to zero out the input potential through \$ R_2 \$ and \$ R_1 \$ voltage divider. \$ V_+ \$ is grounded to 0V regardless of the size of \$ R_3 \$. And seeing from the op amp circuitry, the inverting input's emitter sees \$ {R_2 \parallel R_1} \over \beta \$, and the non-inverting input's collector sees \$ {R_3} \over \beta \$. So the op amp behind the inputs sees a total resistance of \$ {R_2 \parallel R_1 + R_3} \over \beta \$. Adding the compensating \$ R_3 \$ only adds to the resistance seeing from the op amp, how is it balancing or compensating anything?


texts: What amount of noise on Vcc is acceptable?

texts:
I have added a .1uF decoupling capacitor between Vcc and GND on a TMS9118 (this is an old video display processor).  When I measure the voltage at Vcc with my oscilloscope, I read a pk - pk of 1V.  Is that noise level way too high?  This is related to a previous question of mine regarding a noisy composite video out signal from this chip: Lack of color displaying composite video

I would also like to note that I'm using a very clean bench supply for power.  Pk - Pk on the bench supply is 60mV.


texts:
I do not know much about antenna's. A wire broke off of a Wifi antenna, being part of a video transmission unit of a quadcopter.

The short grey colored wire on the right side of the picture broke off.
I simply tried soldering it back on. But that does not seem to work. The range of the antenna now is not even 2 meters. The thick shrinkwrapped black part of the antenna is a holow metal tube.

I assume that the center of the antenna is going through the tube, while the outside of the antenna should be attached to the tube. But this is just a guess of mine, I have not much knowlegde about antennas.

The black antenna wire is so small that I can not see a distinct core or shield.
Is this a coaxial wire? How should it be attached to the metal tube? In other words: How could I fix this antenna?

Thanks.


texts: Is there an easy way to multiplex the state of multiple switches in an AC circuit?

texts:
If I had a circuit like this...

*Blurple boxes represent unknown devices/circuitry

What would be the simplest way to transmit the states of the switches, using only a single wire?

In essence I'm trying to control three light bulbs (loads) using three switches, trouble is there's only one conductor (wire) between the switches and the bulbs. So I have to transmit the state of the switches; an undetermined distance (less than 500 ft.), using only a single conductor (wire).

I was thinking either phase modulation or frequency modulation, but I'm not exactly sure how to implement either. I want to make this as simple, and as small as possible. I also want to avoid micro controllers, and other such things.

The idea is that whichever switch is closed, the corresponding lead on the other end will be energized. For example...

Contact A Closed

Contact B Closed

Contacts A and C Closed
*Orange in the diagrams represents the flow of electricity.
*Blurple boxes represent unknown devices/circuitry

So the truth table would look like this:

A   B   C   |   a   b   c
0   0   0   |   0   0   0
1   0   0   |   1   0   0
0   1   0   |   0   1   0
1   1   0   |   1   1   0
0   0   1   |   0   0   1
1   0   1   |   1   0   1
0   1   1   |   0   1   1
1   1   1   |   1   1   1


texts: Hotplug li-ion in parallel for a custom battery pack

texts:
I'm designing a custom battery pack for a computer with 2S1P alignment. However, I want to be able to add batteries on the fly, as the computer is designed to be working at all times without reboots.
Say, I have 3 (for two cells in series) pins to which I can connect an external battery pack for the computer, making the whole arrangement 2S2P. However, I know that voltage difference shouldn't be too low, else the batteries with highest voltage will charge those with lowest with no current limiting whatsoever. So how could I design such a battery pack? Is there something I can do, like circuit which connects the hotplugged batteries through a resistor for some time, or something MOSFET-controlled?
Ideally, my concept would be 4 sockets for removable 18650 cells (2S2P) which I can either remove or add on the fly without interrupting power supply, so I can replace them - or even add an additional battery pack in parallel through a connector - but I somehow have to take into account the possible problems of interconnecting a 3.5V discharged cell with a 4.2V charged one. Any guidelines on what's the simplest way?


texts: Can I use 1N4148 diodes instead of a 1N4001 diode for reducing the speed of a 5V 1.8W fan?

texts:
Looking at this 1N4148 datasheet, it seems that the forward continuous current is 0.3A, thus 300 mA. So if I add two in series, I will get 600 mA.

I want to use diodes to reduce a 5V 1.8W fan speed. The current through the fan is P = V * I <=> I = P / V = 1.8 / 5 = 360 mA.

Can I use two 1N4148 diodes in series, resulting in a voltage of 5 - 0.7 * 2 = 3.6 V (having thus about 72% fan speed), because 360 mA < 600 mA?

(note: I know a 1N4001 is better, having a 1A limit, but I don't have them yet).

Or did I make a mistake in my calculation or is there another effect why two 1N4148's cannot be used?


texts: I'm wondering if it's possible to drive an 0805 SMD red LED directly off of an ESP32 pin with a 150ohm resistor. I heard they have max 10mA on each pin.


texts: Two diodes in parallel for over-voltage protection

texts:
I've got a power supply circuit that needs the input to be protected against some pretty big voltage spikes.  To do this, I need a really beefy clamping diode (D1) that will handle the voltage and current associated with those spikes.  I also have a second diode in parallel with less current/voltage handling capability, but with a higher breakdown voltage (D2).  My thought was that the secondary diode might react faster, but the primary diode would do the real voltage clamping.  The circuit below is a simplified version (not including additional bias components).

My hope is that the two diodes will provide the response as shown below.  Is this a bad idea?  Any cautions or warnings for this type of implementation?


texts: What are the underlying physical principles of a constant current power source?

texts:
I´m currently looking for a led driver to drive a 34,25 W High-Power LED at 38.06 V / 900 mA. Browsing trough various online shops i found a constant current source and i don`t get how it works.

The datasheet says the rated output voltage is 27 to 54 V, the rated output current is 1050 ma. What are the physical principles, that would allow this device to drive my led ? I don`t understand how the voltage would adapt based on the needed voltage of the LED.


texts: Harmonic analysis of an electrical circuit

texts:
I am having troubles trying to figure this out.
I have a complicated electrical circuit and I would like to compute the spectrum of some voltages of interest. Below is an example of what I want to do on a simpler circuit . My two voltages of interest here are those in red. V1 and V2:  V2 which could be computed easily as in the pictures. Where Vi is the spectrum of the input voltage and Zc is the impedance of the circuit which could be computed using an .ac analysis in LTSpice. Values (or rather the vectors -harmonics-) V1 and V2 could be computed using Matlab or python.
My question is the following: For very complicated circuits, pen-and-paper is basically impossible, do you guys have an suggestions on how I can go about it?
PS: All the parameters (R1,Cm1,L1,etc...) are frequency dependent. I have fitted them and deduced their rational approximations.
Happy new year and thanks in advance :)


texts: Establishing common ground between attiny and 24v motor, and between attiny and 12v logic circuit, without connecting 24v motor and 12v logic grounds

texts:
I have a coin hopper which has a 12V logic circuit and a 24V motor. It also has 2 brass plates which sense the amount of coins in the unit, one plate has high voltage, and second has low. These plates are connected to the 12V logic.

I have an ATTiny85 which controls the 24V motor via a BJT transistor which controls a MOSFET, which requires the motor and ATTiny to have a common ground afaik.

The problem occurs when I want to read the voltage level from the 2 brass plates. For this, I believe the ATTiny would need to have a common ground with the 12V logic, but when common ground is established between the motor and logic, or in this case, motor, logic, and ATTiny, the motor suddenly is energized. I'm not sure why this is happening. In the datasheet, it says the motor and logic grounds are isolated in the unit.

Any idea what I can do to measure the voltage level with my ATTiny and be able to control the mosfet, without allowing both the motor and 12V logic circuit's grounds to be connected? Thanks.


texts: Quick JFET Datasheet Comparison/Analysis

texts:
In a previous question I asked for a replacement for the J402/LS3954 dual JFET that has gone out of production and increasingly expensive. (Mouser has them for $23 right now, what a deal) and I came across the BSR58 single JFET which is on average about $0.10 from China. I don't mind electrically matching the two with a multimeter since the application isn't crucial (to me, anyways).

Comparing the two datasheets, is the BSR58 a suitable replacement for the J402? I'm not at all familiar with FETS or their specs so any help is appreciated.

BSR58

2N3954


texts: Need help setting up 7X6 Piranha LED Matrix with Arduino

texts:
I need help correctly getting my parts list for a 7X6 matrix that will be part of a electronic outdoor scoreboard.
Here is my parts list so far but I am stump whether the arduino is powerful enough to power these LEDS in a matrix.

42 X Piranha Super Flux LEDS (~2.1 forward voltage) (~5000 mcd)
4017 decade counter
7 X 2N3904 transistors
74HC595 shift register
7 X 1KOhm resistors
6 X 150 Ohm resistors
4 X pushbutton switches (The matrix is going to be controlled by the 4 pushbuttons.)

I have the coding down I just need help setting up the arduino to power these high powered LEDS. If I am missing something from my parts list please let me know. Thank everyone in advanced! External battery will be used to power the LEDS.

This matrix will be powered by a 12 volt rechargeable lithium battery.


texts: Electromechanical or Semiconductor solutions to control chandeliers and homes stuff

texts:
I've been designing some wireless modules and finally got them to work and now I have a network of them and want to use them for home automation purposes. Controlling stuff like chandeliers, heating, and even simple lamps and so on. The load voltage is 220VAC and the current is normally up to 1 or 2 or in some cases 3 Amps I guess.

Now I'm wondering what is the best way to control those stuff? Electromechanical Relays or Semiconductor solutions like SSR, Triac, MOSFDET, ... ?

I'm not sure which solution is the best. The thing is Since I want to install this system into other peoples homes I want it to be safe, very reliable, perfect and without any problems or dangerous in long term uses. You see I don't want to blow their homes! That's why I'm asking you guys.

On the other hand I sort of have a limitation for space considering I have to implement this system into a wall switch or the top of a chandelier somehow (for now I'm not sure which one to go). As always there is other limitation as well, Money!

Now what I think is that electromechanical relays do not generate too much heat in the load side. They are also simple to use. Although there is the contact sound.

But the thing about using relay is since I have 5V or even less trigger signal with not too much current I have to use small signal relays (right?). The latched version of these relays does not draw much current in the control side considering it latches its state. But unfortunately they don't switch high currents. Apparently up to 2.2A which maybe enough for me in some cases.
But about the long term use that I mentioned, I'm not sure electromechanical relays take care of that.

Now there is semiconductor solutions like SSR, Triac, MOSFET, and ...
They don't generate sound as opposed to electromechanical relay.
I don't know about the size considering I've never used a SSR before and a discrete opto-triac and Triac (and probably a heat sink) may take too much space.
Plus I know SSR probably costs too much as opposed to other methods.

So with all the stories I just said what do you think would be my best option?

1-Simple Electromechanical Relays

2-Small Signal Relays

3-SSR

4-Opto-triac + Triac

5-MOSFET

or something I'm not aware of.


texts: Phase difference between source voltage and inductor voltage

texts:
What will be the phase difference between the source voltage and the inductor voltage? Will the two voltages be in phase or will be out of phase. How much out of phase they will be?

Note that there is no resistance in the circuit


texts: Using a Contactor or Relay to switch between two DC power sources?

texts:
I want to power a motor with a battery, however the complication arises as I want to have two power sources and be able to switch between them. The context of this problem is for an electric vehicle. Sensing circuitry on the vehicle will measure speed and driver input and decide which of the two batteries to use under the conditions. i.e. when acceleration is needed the higher power battery is selected and power is drawn from that. When the vehicle is driving at slow speeds or at constant velocity the so called "cruising battery" will be switched to and used to power the motor. Both batteries will be at 48V and the motor power will be at a maximum of 5kW giving a maximum current of around 100A.

The above two circuits were suggested to me as possible ways of switching between the two batteries. I believe that a Schottky diode or capacitor of the correct rating can be found for fairly cheap however the main problem I seem to be facing is what type of switch to use and how to control this switch. On the circuits I have drawn a relay however am I right in thinking a contactor would be needed for a high power application such as this? In this case is it reasonable to control a contactor with a MOSFET as shown in the diagrams?

If anyone has any suggestions or advice for components that would be really useful, as well as suggestions for controlling the MOSFET/contactor. Using my current circuits the system would require 4 power sources, 2 for the motor, one for the contactor and one for the MOSFET!

Apologies for my inexperience or any unclear parts of my question.

Thanks!


texts:
simulate this circuit – Schematic created using CircuitLab

I inherited the top circuit from a previous designer on my robotics team. The circuit uses two ferrite beads, a zener, a TVS and a capacitor to filter incoming power. The incoming power comes from batteries. Along with the digital circuitry the batteries have large motors connected to them making for a very noisy environment.  My understanding is that with the help of the ferrite beads the zener and TVS suppress any spikes. Then the large capacitor holds up any droops. This circuit has worked well so far.

My question is whether replacing the ferrite beads with a common mode choke improve the filtering or if it's not broken don't fix it?

(I just used generic components to give the general circuit layout, the top is the current circuit and the bottom is my proposed change)

Additional info
The circuitry is going into a robot. The robot is made out of extruded aluminum (not grounded) and the whole thing is clad in clear acrylic. The whole thing is powered by a 24V 8 cell lithium iron phosphate 20Ah 10C battery. The digital circuitry draws about 1A. The motors are two wheel chair motors. The motors are rated at 60A max but they are never driven that hard, usually around 50% or less. The motors are driven by Vex Victor H bridge motor controllers.


texts: Line/load matching for electric power transmission

texts:
Impedance matching is a critical topic for microwave engineering where the signal wavelength becomes comparable to the physical sizes of components. Substitution of distributed component models for standard lumped component models leads to circuit equations involving wave reflections, VSWR, s-parameters, and all that fun stuff.

Do these topics translate to the electric power industry where voltage and current waves must travel over extremely long lengths of power lines? It seems to me that these topics are not very prominent in power engineering, or am I mistaken? Consider a very simple model of a generator connected to a step-up transformer, which connects to a load through a step-down transformer by means of many kilometres of power line. It's impossible for the designer to predict the load at the end of the line, unlike in microwave engineering where the load is practically guaranteed to be 50 Ohms. So, how can the designer perform impedance matching to eliminate reflections? If this is a non-issue in the power industry, why is  it a non-issue?


texts: High current, high frequency IC PWM switching with MOSFETs

texts:
I'm designing a circuit for an automotive application (chassis ground) that has a number of MOSFET outputs to drive large LED arrays and smaller motors (application tends to favour non inductive modes, but it's still an important consideration). One of the goals here is to be able to PWM switch a 300W LED light using a MOSFET or similarly appropriate transistor.

I'm trying to understand now how to understand requirements and limitations of MOSFETs in high frequency switching. I'm targeting a switching rate of 20khz such that it's outside of the audible range as some of the cheaper LED lights i'm trying to switch use inexpensive filter caps that tend to mechanically oscillate at the input frequency.

I've drawn up a very simple circuit in which a simple NPN BPJT (BC848) is used to invert the positive 3.3V output from a micro controller and drive the gate on a low Rds power FET like the IRF5305.

My understanding at this point is that the goal of the driver here is to saturate the FET as fast as possible such as to minimise the Rds as it's turning on; and to do this with some sort of capacitive driver. (I'm new to this and my knowledge is coming from unverifiable sources).

I've read into some of the merits of gate driver IC's which seem to tick many of the boxes (other than cost, but that's a sensible sacrifice to make here) though I'm having a hard time understanding how to indentify the associated rise and fall times required from an application (20khz @ 0-100% duty cycle, 40Khz??) and what that does to the gate at any specified current. If I were looking to drive a FET at:

20KHz PWM
Logic voltage drive (3.3v)
0-100% duty cycle
20A load
12-24V

How would I determine an appropriate FET and how would I determine the driving requirements?


texts: How can I prevent my multi-meter fuse from blowing with a brief 120VAC surge?

texts:
I wanted to test how much power a GFCI outlet uses while idle, so I hooked up my multi-meter to test the current flow.  I put my test lead in the amp socket, and confirmed the current was on the order of a milli-amp, so I was safe to plug my lead into the milli-amp socket.
After doing so I measured a current of a few milli-amps.  But then suddenly through testing I got a sudden current spike, and blew my 400mA fuse.  I'm not sure what caused the spike...  maybe tripping the GFCI, etc, but some GFCIs seem to operate this way.
Is there some way I can even this out, and absorb whatever the spike current is for that sub-second that it spikes protecting my fuse and multi-meter, but still be on the milli-amp scale?  I know conceptually this is what a capacitor does, but I also know you can't simply hook a capacitor up in series and expect to get any current flow.
I'm thinking maybe there's some simple circuit, or inexpensive device I can hook up between the GFCI and my multi-meter that'll prevent the fuse from blowing, but I don't know enough about electronics to know if this is possible, or where to even begin.
EDIT:
Another possibility is some sort of solid-state, fast trip 300ma circuit breaker that I put in series, before the multi-meter that'll trip before I blow the fuse?  Does such a thing exist?
EDIT2:
How about something like a Inrush Current Limiter?  https://en.wikipedia.org/wiki/Inrush_current_limiter
On the face of it, it sounds like the solution to exactly the problem I'm having.


texts:
I need to compare and contrast a CMOS IC with a TTL IC. I've chosen a quad 2 input NAND gate IC, 7400 for the ttl version and 4011 for the CMOS. I'm having a bit of trouble with 2 of the requirements.
I need to:
compare the power consumption
compare the input and output impedance
I've got all other required comparisons but these 2 are upsetting me.
I'm using the following datasheets
http://web.mit.edu/6.131/www/document/7400.pdf
and
https://www.futurlec.com/4000Series/CD4011.shtml

Can I calculate the power consumption and input/output impedance from these data sheets? If so, can someone please explain how? I've tried datasheets from other manufacturers but it's the same information. I know it's probably a bit of a hand holdy question but I've been reading up on this for 2 days now and really need some help
Thanks


texts: STM32F407ZET6 and nordic nrf24l01+ communication with interrupt driven SPI

texts:
Currently working on STM32F407ZET6 MCU. I am trying to generate an interrupt based SPI communication with nordic nrf24l01+ chipset. The MCU is in Master mode. I am able to establish an SPI communication but looks like it is using polling method.

I use the api uint8_t SPI1_send(uint8_t data) to send and receive data with SPI.

Need help with generating code for Interrupt driven SPI. If I use the interrupt driven SPI, do I still need to use the SPI1_send() API that I mentioned?

void init_SPI1(void){

    GPIO_InitTypeDef GPIO_InitStruct;
    SPI_InitTypeDef SPI_InitStruct;

    // enable clock for used IO pins
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

    /* configure pins used by SPI1
     * PA5 = SCK
     * PA6 = MISO
     * PA7 = MOSI
     */
    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_7 | GPIO_Pin_6 | GPIO_Pin_5;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_Init(GPIOA, &GPIO_InitStruct);

    // connect SPI1 pins to SPI alternate function
    GPIO_PinAFConfig(GPIOA, GPIO_PinSource5, GPIO_AF_SPI1);
    GPIO_PinAFConfig(GPIOA, GPIO_PinSource6, GPIO_AF_SPI1);
    GPIO_PinAFConfig(GPIOA, GPIO_PinSource7, GPIO_AF_SPI1);

    // enable clock for used IO pins
    //RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE); COMMENT THIS LINE AS PORTE IS NOT NEEDED NOW

    /* Configure the chip select pin
       in this case we will use PE7 , NOW PA4 */
    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_4;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_OUT;
    GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_Init(GPIOA, &GPIO_InitStruct);

    GPIOA->BSRRL |= GPIO_Pin_4; // set PE7 high; NOW PA4

    // enable peripheral clock
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE); // 84 Mhz

    /* configure SPI1 in Mode 0
     * CPOL = 0 --> clock is low when idle
     * CPHA = 0 --> data is sampled at the first edge
     */
    SPI_InitStruct.SPI_Direction = SPI_Direction_2Lines_FullDuplex; // set to full duplex mode, seperate MOSI and MISO lines
    SPI_InitStruct.SPI_Mode = SPI_Mode_Master;     // transmit in master mode, NSS pin has to be always high
    SPI_InitStruct.SPI_DataSize = SPI_DataSize_8b; // one packet of data is 8 bits wide
    SPI_InitStruct.SPI_CPOL = SPI_CPOL_Low;        // clock is low when idle
    SPI_InitStruct.SPI_CPHA = SPI_CPHA_1Edge;      // data sampled at first edge
    SPI_InitStruct.SPI_NSS = SPI_NSS_Soft | SPI_NSSInternalSoft_Set; // set the NSS management to internal and pull internal NSS high
    SPI_InitStruct.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_4; // SPI frequency is APB2 frequency / 4 = 84Mhz/4 = 21Mhz
    SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_MSB;// data is transmitted MSB first
    SPI_Init(SPI1, &SPI_InitStruct);

    SPI_Cmd(SPI1, ENABLE); // enable SPI1
}

/* This funtion is used to transmit and receive data
* with SPI1
*           data --> data to be transmitted
*           returns received value
*/
uint8_t SPI1_send(uint8_t data){

    SPI1->DR = data; // write data to be transmitted to the SPI data register
    while( !(SPI1->SR & SPI_I2S_FLAG_TXE) ); // wait until transmit complete
    while( !(SPI1->SR & SPI_I2S_FLAG_RXNE) ); // wait until receive complete
    while( SPI1->SR & SPI_I2S_FLAG_BSY ); // wait until SPI is not busy anymore
    return SPI1->DR; // return received data from SPI data register
}

The above code is self explanatory, it has init SPI function and Send/Receive function. I can add how I call these functions in main() also. When I need to send or receive data through SPI to nordic chip, I use the function SPI1_send(). As I said, If I use interrupt mode, do I still need to use the function SPI1_send() as ISR will take care of sending/receiving I suppose.


texts: Suppose we have a closed loop with two resistors in series and at particular moment in time the induced emf was two volts .i want to know why do we use ohm's law in calculating the induced current ?


texts: Is there a special way to solder to these LED thermal pads?

texts:
[I don't know the correct names for these things, so please correct my vocab as needed.]

I just tried to solder a wire to the one of the rectangular contact areas on this LED. I'm a beginner hobbyist with a radio shack soldering iron, but usually I can solder wires okay.  But in this case the solder just balled up on the surface and refused to bind to it.  Is there a trick or a special way to connect these to wires?

Actual part is here


texts: Optical quadrature encoder goes out of sync at higher speeds

texts:
I'm trying to get a microcontroller (stm32) to read a quadrature encoder, but running into an issue when at higher speeds line 1 seemingly gets narrower pulses until it gets out of sync with line 2.
In other words, line 1 starts off fine, but as speed picks up it gets shorter pulses. Eventually, with cycle time of ~150usec, it starts dropping off at the wrong time of the cycle, confusing the counter. See image below for the logic analyser view.
I'm not sure whether the problem is with hardware (misaligned detectors? although I don't see anything obvious) or with electronics and would really appreciate advice. Unfortunately I'm a noob with electronics and won't vouch that this simple circuit is enough to handle faster rotations. In particular, many schematics I found on the web use an op-amp, which I don't: example
Below is the schematic, followed by the logic analyzer output. Finally motor and encoder look like this.


texts: 1n4007 Bridge Rectifier at 220 Volts AC?

texts:
So, I just started getting into electronics, and I have built a bridge rectifier using the 1N4007 diodes.

So far I have been using this rectifier with a 24 volts step down transformer, but now I need a higher voltage for other purposes.
The AC current in my country comes at 220 Volts, 50 Hertz, so my question is: Can this bridge rectifier be directly connected to the AC mains, or do I have to get a transformer?

If you have links to other sources, please post them.

If you don't but you have experience, please answer anyway.

Thanks!!


texts: How do I get a sharper off time curve on my Led driver output?

texts:
I designed a pcb with the following dual led circuit based around the TPS92518:

I would like to turn on and off the Powerleds in the <1ms range.
At the moment our camera stills sees the leds a bit glowing.
When I measure on the scope, my output shows a very slow off time curve.

How do I get a sharper edge?
I played around with changing Cboot values, but higher then 100nF doesn't have a positive effect.

Can it be the N-MOSFET? PSMN019-100YL
Total gate charge is 72.4 nC


texts: Design for a balanced (positive and negative) HV DC regulator

texts:
I'm trying to design a high voltage DC regulator for driving a PZT that will provide both +200 and -200 V outputs referenced to ground. The input is a rectified AC waveform that will provide UK mains voltage (230 V ac r.m.s.). Since it's driving a capacitive load only, the current requirement is small (less than 15 mA per rail).

I've got a few ideas for how to do this, but the problem is that they are based on positive voltage regulator designs. I'd like to build something that works for both positive and negative rails of the input.

The most promising idea I have is to take a good design for a positive regulator and convert it into a negative one, and pair them up with a common ground. I am thinking of basing it on the "Maida" style floating regulator. Pete Millett has provided an updated version of this design that uses a high voltage MOSFET and LM317, freely available on his website:

The rectified, filtered mains is input to the MOSFET to perform coarse regulation and fine regulation is performed by the LM317 which only sees a fraction of the total input voltage due to the zener diode D1. The design shown is only for a positive voltage, but I would like both positive and negative varieties. I imagine that it would be possible to adapt this circuit to instead work for negative voltages simply by using a P-type instead of an N-type MOSFET and an LM337 instead of an LM317.

Can anyone think of a reason why the above idea might not work? In particular, I wonder if any difference in the time it takes for each rail to come up to full output (given tolerances of capacitors, differences in attached load impedance, etc.) would have any damaging effect on the sensitive components such as the MOSFET. Will the suppressor diodes in parallel to the MOSFET and LM317 prevent such problems (e.g. by blocking a reverse current)?

I'm happy to hear any other ideas. The output doesn't need to be regulated heavily so perhaps there's a simple approach I'm missing.


texts: I was wondering if anyone had ever heard of an IC that monitors USB traffic.  For example, allowing one to man-in-the-middle a USB joystick.


texts:
We are implementing a 2.4 GHz RF link using a TI CC2541 chip (http://www.ti.com/product/cc2541) and we are new to RF design. We want a robust, low-bandwidth, low-latency link. We were thinking of using DSSS and GFSK.

It does not appear to implement hardware-based DSSS. Will I still get the same benefits of DSSS if I perform the sequencing in software? (i.e, I could transform 1 => 0011110000101011 and 0 into 0111010000110011 and then transmit the transformed sequence) Will I still achieve interference rejection? It seems that someone could simply transmit 10101010... on my frequency at a higher power and jam my signal before it gets to the demodulator. It seems to me that the spectrum reconstruction has to occur in an analog stage.

Can someone explain why or why not the software-based would work? If it won't work, what's different about the hardware-based system. If it does, what's the mathematics behind it?


texts: Replacing Electret Microphone with Dynamic in Velleman Voice Changer Circuit

texts:
I am attempting to build this circuit:

https://www.velleman.eu/downloads/0/minikits/manuals/manual_mk171.pdf

the MK171 Velleman voice changer, but with a 1/4"mic socket for a dynamic mic instead of the electret microphone which is attached to the board as standard.

I've done some googling and apparently omitting R6 will mean that the mic no longer gets the power that the electret mic needs, but the dynamic mic does not.
However the googled answers seem to suggest it will still not be ideal - without offering any means to improve it. I'm not sure if there is anything that can be done, or indeed what (if anything) I need to consider here? Do I need to amplify the signal via an op amp or similar? Or something else that needs to be modified to supply the right signal to the IC?

I also want to add a "line out" socket - Looking at the circuit, I think I should be able to omit the amplifier section entirely and just take my audio connection from the op amp side of C3, where it would usually go to pin 3. Does this seem correct?

thanks in advance for any help offered, much appreciated.


texts: How to measure/use s-parameters for gating deembedding

texts:
I asked this question and one of the answers suggested using gating technique for deembedding purposes. I've created a script to transform S-parameters to time domain.

S_ifft = np.fft.ifft(S11)
plt.plot(abs(S_ifft))
plt.show()

When I plot it, it looks like this

Well, that looks like gibberish to me. The board itself is merely a trace with two connectors. The measured data goes from 20 GHz to 28 GHz.

My question is what measurements do I need to take to get a good time domain plot so I can identify the signal of interest? Or how do I analyse this time domain signal to see the connectors?


texts: How to deal with low pass filter questions if Fourier transform of signal does not exist?

texts:
I found this question in a previous test paper:

I'm having a few confusions:

1) Low pass filters are supposed to block signals below a certain frequency. Here that certain frequency is \$w_c=a\$. I'm not sure how to approach this problem. What would be the frequency of \$v(t) = e^{-at}\$?  Wolfram Alpha says that the Fourier transform of functions of the form \$e^{-at}\$ do not have any closed form. Also, Fourier series of the signal wouldn't exist since it's not periodic. So, how should I find the energy dissipated in the resistor?

2) In the second part of the question, what exactly is meant by \$h(t)\$ and \$y(t)\$, any idea?

Please note that I've read the answers to How Fourier transform be able to deal with transients?, but it doesn't really answer my question.


texts: Difference between Blocking and Non-Blocking assignment in VHDL

texts:
I started reading about Blocking and Non-bocking assignment with reference to verilog. But when I switched to VHDL its confusing.

What I felt is, in VHDL other than to visually differentiate  variable and signal assignment there is no significance for blocking and non-blocking assignment. Am I wrong?


texts: Problem initializing SPI TX interrupt in STM32F103

texts:
I am trying to establish SPI communication from master to slave. I am able to send bytes over to slave, and is now trying to send when the TX interrupt is triggered.

Below is code I used for master side, on STM32F103;

void spi_init() {
    GPIO_InitTypeDef GPIO_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;
    SPI_InitTypeDef SPI_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2, ENABLE);

    NVIC_InitStructure.NVIC_IRQChannel = SPI2_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13 | GPIO_Pin_15;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOB, &GPIO_InitStructure);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_14;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_Init(GPIOB, &GPIO_InitStructure);

    SPI_I2S_DeInit(SPI2);
    SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
    SPI_InitStructure.SPI_Mode = SPI_Mode_Master;
    SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;
    SPI_InitStructure.SPI_CPOL = SPI_CPOL_High;
    SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;
    SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
    SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_4;
    SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
    SPI_Init(SPI2, &SPI_InitStructure);
    SPI_Cmd(SPI2, ENABLE);
    SPI_CalculateCRC(SPI2, DISABLE);
    SPI_SSOutputCmd(SPI2, DISABLE);

    SPI_I2S_ITConfig(SPI2, SPI_I2S_IT_RXNE, ENABLE);
    SPI_I2S_ITConfig(SPI2, SPI_I2S_IT_TXE, ENABLE);
}

void SPI2_IRQHandler(void) {
    if (SPI_I2S_GetITStatus(SPI2, SPI_I2S_IT_TXE) == SET) {
        //Send from buffer
        SPI_I2S_ClearITPendingBit(SPI2, SPI_I2S_IT_TXE);
    }

    if (SPI_I2S_GetITStatus(SPI2, SPI_I2S_IT_RXNE) == SET) {
        //Receive
        SPI_I2S_ClearITPendingBit(SPI2, SPI_I2S_IT_RXNE);
    }
}

The problem is that the program always crashes within the spi_init() function. When I comment out either the NVIC_Init command and the SPI_I2S_ITConfig(SPI2, SPI_I2S_IT_TXE, ENABLE) command, it will not crash. But it will just not work with the two together.

Any help on what is causing the problem is appreciated.


texts:
I have designed and built a buck converter based on the TPS54331 which oscillates at 5.4kHz with an amplitude of 700mV peak-to-peak under a 1A load. I want to remove these oscillations.
Here is a scope picture of the problem (yellow = switch DC, blue = Vout AC):

The circuit has the following schematic:

What should I be looking for to solve this problem?
Update: Here is the relevant part of the PCB layout (back side is an uninterrupted ground plane):

Update 2: Labeled L1 in the PCB layout
Update 3: I also removed the load to bring the it into DCM mode and it produces the following saw tooth wave at the output (yellow=switch, purple=Vin, teal=Vout):


texts: Earth Fault in a TT Network: Current loop, or charges flowing from one grounding to the other?

texts:
There are serveral things I (yet) don't understand about the T-T-earthing system. The most important one is that I don't understand which way the the current takes in case one of the conductors (for example L1) touches the chassis of the device.
There are two options I can think of:
a) There is a flow of charge out of the earth at the first grounding, through the Resistance RB, through the coils of the transformator, through L1, through the chassis (at the location of the fault) , through RA, into the ground at the location of the grounding of the device.
There is not a closed current loop. Instead, ground just works like a really big capacitor (with a very big capacity), so draining charges out out of the earth, or putting it in, will not change the potential of the ground at all.
b) There is in fact a current loop in case of a faulty connection between L1 and the chassis of the device, starting at RB, through the coil of the transformator, through L1, through the Chassis, through RA and back to RB.
This would mean there actually is current flowing through the earth (which I find hard to believe since there are parts of the earth that have a very high resistivity.
Which of the two options I suggested is true? Or does it indeed not matter how to model this, because the values of RA and RB can account for the different ways of modelling this?
Edit: I come from another field (physics), and while I have a good understanding about electric potential an electrodynamics, I'm neither familiar with the concepts used in electro-engineering, nor with the terminology. That's where this question stems from.


texts: Purpose of Having More ADC channels than ADC Pins on a Microcontroller

texts:
I have been doing some work with the TMSC5515 DSP chip and noticed in the process of configuring ADCs for potentiometer control that the chip supports 6 ADC channels (VIN[5:0]), but only has 4 pins that can perform the conversion (GPAIN[3:0]). I've noticed this on other embedded processors as well.

What is the point of doing this? If the chip is only capable of reading 4 values at a time, the extra ADC channels don't seem like they would serve any purpose.

Discription of ADC on TMSC5515: http://www.ti.com/lit/ug/sprufp1c/sprufp1c.pdf


texts: What if I try to connect a 12V@0.16A computer case fan to my USB port?

texts:
What happens if I try to connect a 12V@0.16A computer case fan to my USB port?

Purchased a USB laptop HDD enclosure lately but it coming with no fans.

So I thinking of putting fans around enclosure opening for keeping cool.

12V@0.16A = 1.92W

So if I providing fan with 1.92W it not care if source voltage not 12V but maybe less?

Like, if connecting to 5V, it draw 1.92/5 = 0.384A or say 0.4A that most USB hardware port able to source?

Am I taking risk or doing my calculating correctly and so nothing to worrying about?

There is similar question, but I also interest in knowing why a 12V fan might not start up at 5V EVEN if I able to supply it same power?


texts: What happens if a 3.3V supplied IC pull-up to a 5V with resistors?

texts:
We had to make the PIC's supply voltage 5V. Previously was 3.3V. SHT21 also works with 3.6V at most. We couldn't change it.
Sht21 broken? Will i2c work correctly?
Note: There is no place to put an additional component such as level shifter and it's the final product.


texts: Power requirements for offset motor or other forms of vibration

texts: I need to generate vibrations to provide tactile feedback.  The device has minimal power available.  What type of power do offset motors require?  Are there other forms of vibration that can use less power?


texts: How would one go about finding the Norton equivalent current for this?

texts:
I have found the equivalent resistance, however, I am finding trouble as to how I should go about finding the equivalent current source.

The answer stated that the 12 ohm resistance was shorted, and that from "the load's perspective", the current through the 20 and 5 ohm resistors were found (each to be I1 = 72/20 = 3.6 A and I2 = 72/5 = 14.4 A respectively). Using that, the answer claimed that the norton current was the algebraic contribution of I1 and I2 - where I (norton) = I2 - I1 = 14.4 - 3.6 = 10.8 A.

While the answer is correct when simulated using software, I do not understand the reasoning behind why each step was done in the answer.

Any help would be greatly appreciated!

EDIT: Initially, I thought of using nodal analysis to find the output voltage, which I could convert into a current source (the Norton current source) to find the answer. However, the method used by the answer seemed much more trivial than mine, yet I do not understand how the method produced the same answer (like why the 72V was considered to be the voltage drop across both R2 and R4 when treated individually, and why the 12 ohm resistor was shorted).

EDIT 2: Modified Circuit:


texts: Relationship of Slip and Angle Between Rotor and Stator Flux for Induction Motor

texts: I know how slip and flux angle individually affect torque of induction motors but I can't understand the relationship between slip and flux angle in terms of torque. Do they both have different effect on torque or one cause the other (linked to each other)?


texts: Need a Negative to Positive Level Shifter

texts: I did a simple differantial amplifer for 0-3.3V output. But, as you see I got -3.3V output because gain. I need a shifter circuitry for non-negative output. Can someone help me? Thanks a lot.


texts: Does LED brightness change with voltage?

texts:
When I was young and learning about electricity, a fabulous tool for understanding voltage/current/resistance was an incandescent lightbulb (in my case it was a small 3V bulb). When you doubled the voltage by putting two batteries in series, it glowed 4x as bright, but heated up more and was more prone to burning out. When you put two lightbulbs in series, they glowed 1/4 as bright. When you put them in parallel, they glowed normally, but drained the battery twice as fast. Etc.

This day and age however incandescent bulbs are on the way out, and LEDs are replacing them for a good reason (like not burning out every few months or so). But LEDs are different and follow different rules, which I don't understand myself very well.

I was wondering - can LEDs be used in the same way? I know that for a LED to be usable in a similar way as a classical lightbulb, you need to put it in series with a resistor, otherwise it draws too much current and burns out. I think you can even buy LEDs with built-in resistors. But would they work in the same fashion? Would changes in voltage be accompanied with corresponding changes in brightness?


texts: How should I connect batteries in parallel?

texts:
I have a pair of these Li-ion batteries. I'd like to couple them so that I get double the current. However, I realize that this could be a Bad Idea™, as the charge could flow in a loop through both batteries.

What is the best way to prevent this?
Should I add diodes in series with each battery? (if so, what type and value?)
Should I put a resistor in series with one of the batteries?

Or is there a better way?


texts: Can I use foil as a wire for my project in tight spaces?

texts:
I am building a project that I can put a AA battery into a little compartment. The battery fits fine without anything else in it, but when I put a wire in, it gets tight. A solution that might work: aluminum foil.

I measured the resistance with a multimeter, and it is about the same as a wire. Is this a bad idea? (Besides the low durability of the foil) I am planning to wrap the foil in some electrical tape or similar to insulate it, except for where I am going to connect to the battery. Will it carry enough current without overheating and melting the plastic? 100mA max with LEDs, only on for 1/2 of every minute I would say during use. Fairly standard plastic, I would say and operating in a house.

P.S. The battery is 3.7v 1200mAH and a Lithium rechargeable, but may be a bit more/less voltage.

Also, I only need it for one of the two sides (+/-), and is one better to use than other?Should I change my circuit, or am I just paranoid?


texts: What are the functions of the ULN2003A and HCF4094 within this circuit?

texts:
We are building a wordclock and want to know what the following components do within the circuit:

ULN2003A driver IC
HCF4094 shift register

This is the schematic:


texts:
Trying to understand the physical layer of CAN.
Most images that I see of a CAN network has the main network bus and then nodes that come off of this bus at a T for CAN_H and CAN_L it what I commonly see referred to as nodes.
Do these "nodes" need to have the same cable differential impedance as the main network bus? (Which I'm assuming is 120ohm in most cases)
I also have seen a lot of answers on StackExchange that describe using a daisy-chain architecture for CAN, however, I am yet to see an image of how this would look like?
Thank you for any assistance.


texts: How to terminate a coax connection into a receiver for best common-mode rejection?

texts:
I am designing a simple HF receiver as a hobby project. The design is similar to the SoftRock Lite II, and the antenna input looks like this:

The SoftRock design doesn't really say how the inputs are connected (it just provides two holes on the PCB), but I will be connecting them to a BNC connector which could be isolated from the metal chassis, or not.

Obviously this transformer has some essential functions with the double secondary windings and is forming part of the filter, but let's assume I find other ways to meet those needs. The radio I'm designing will have three such antenna inputs, and it's important that I maximize isolation between each input. This is an SDR design, and each antenna, after going through a coherent mixer, goes to an ADC and antenna phasing happens in software.

My question is this: if my objective is maximum rejection of common-mode currents on the antenna feedline, what's the best way to accomplish that?

if I'm not mistaken, if I use a connector that is not isolated from the chassis, then common-mode currents should just flow around the chassis, so does the transformer add anything?
would a common-mode choke be better, or worthwhile?


texts: "Hot-knife"/Thermal cutter power supply design

texts:
I'm undertaking a DIY rope cutter project to avoid paying for the ~$150 store bought ones.

Many resources online told me to use a light dimmer + transformer configuration and I had planned to go a step further and build the dimmer too,  using the circuit from this site: (replacing the light with a transformer)

http://www.electronicecircuits.com/electronic-circuits/filament-light-dimmer-circuit

However, upon reading a few posts here it has been suggested that dimmer circuits don't mix well with inductive loads such as transformers so I'm looking for alternatives.

I played around with a current division circuit using parallel resistors and a variable resistor however the high power would fry the resistors by a long shot.

Unfortunately this is where my education draws a blank and I open it up to any suggestions from those more educated than myself.

On a final note, please don't suggest using a bench power supply as this is not financially viable at this point in time, also needs to run off 240VAC (Australia.)

========================================================
EDIT

Blade arrived in the post today, it is advertised as a 60W but I would like to test it.

I also bit the bullet and grabbed a benchtop power supply, 0-30V 0-20A.

I thought I could find the current-voltage combination by connecting the blade across the supplies terminals however when I do so the voltage refuses to climb above 0.6V (pushing current up to 20A)

Using P=VI this means I can't get the power above 12W, much lower than the ~60W needed to heat the blade.

I'm inexperienced with benchtop supplies, is this normal? Are there any workarounds?


texts: Changing battery from 12v SLA to 12v Lithium, how can i accomplish this setup?

texts:
I am thinking of more speed for a kick scooter project.
I have a 800w hub motor for this scooter but at only 40Km/h i am thinking of making it go faster.
Now I know that increasing the voltage from 48 to 60v would do,
But what would happen by using a 1800w controller, would the increase wattage make it go faster?, is increased wattage going to make it faster?.

Here is controller and 800w hub.

http://www.aliexpress.com/item/Regen-braking-BLDC-48V-1800W-18-mosfet-top-quality-sine-wave-controller-high-power-e-scooter/32607657598.html?spm=2114.01010208.3.128.F7JNr3&ws_ab_test=searchweb201556_9,searchweb201602_1_10034_507_10032_10020_10017_10005_10006_10021_10022_10009_10008_10018_10019,searchweb201603_7&btsid=0bd124bf-0c76-4de8-be01-5960288c65d6

http://www.aliexpress.com/item/10-800W-48v-electric-motor-skateboard-electric-motor-scooter-electric-brushless-gearless-hub-motor/32649887917.html


texts: Linear Rise exponential fall pulse generator

texts:
For a neutrino detector related experiment, I need to design a circuit which generates the pulse similar to the detector. This is required to test the front end electronics.

Here are my final goals:

  Pulse shape: Linear rise exponential fall,  Rise time: 1-3nS,  Pulse
  width: 10-20nS,  frequency: 100Hz-10kHz (user control/ random
  distribution),  amplitude: 0.05-15mV (user control/ random distribution)

But to start on a simple note I am trying to generate a simple linear Rise exponential fall pulse. Currently I am able to generate 1nS to 10nS square pulses (using FPGA), which mimics the linear rise part due to slew, but I need some circuit suggestion for exponential fall part. I tried to go with capacitor discharge but it seems that even RF switches are not that fast in terms of switching frequency.

Any suggestion is welcome.


texts:
What is the transmission bandwidth for  a BASK (Binary Amplitude Shift Keying) signal?
Shouldn't it be infinity as short periods of sinusoids are used to depict 1 and 0 to depict 0?


texts: I am working on a PLC program (using CodeSys) consisting of several SFCs. One SFC is counting rising edges of a button. I want to be able to reset this counter even from anther SFC. How can I do that?


texts: Using Eagle: How do I have separate parts in the schematic, but a single socket in the board?

texts:
I have a schematic that looks like this:

In reality, this is basically 16 SPST switches with LEDs in them.
What I would like on the PCB is for each pair of switch+LED to end in something to which I can solder something like this:

4 pin JST connector (I think that's what it's called)
How would I go about doing that? (Right now the board view displays LEDs and standard prototyping momentary switches.)


texts: CPU/Processor error rate in calculations

texts:
Does Intel or AMD publish specifications about the rate at what failures in calculations can be expected on their CPUs? I would suspect it would be very age and temperature dependent, but surely there must be some kind of numbers available?

I'm not interested in obvious manufacturing errors (where a whole lot is defective or something). I'm interested in spontaneous errors due to physical phenomena not related to design error. Whether the error originates in the CPU or some other chip on the system is also of interest (for example a momentary voltage failure to the processor would also result in errors).

I'm curious, but my net searching isn't yielding what I want. I just want to get rough ideas of it I left my program running for X hours how many spontaneous errors I could expect to have.


texts: What causes the opamp to become warm in this charger? [question updated]

texts:
UPDATE

I just realized that I posted the bad version of my circuit. I now swapped the + and - input of IC5A using a utility knife and short wire on my PCB after realizing that I was making the reference input indirectly connected to + instead of -. But the warming problem exists after the changes.

END OF UPDATE

Here's my circuit.

I attempted to make a charger for two 3.6V NiCD batteries. In my circuit, all diodes are 1N4007, and the opamps come from the LM358 package. Each resistor value is in ohms. All electrolytic capacitors are 22uF 25V. The capacitor closest to 4.7K resistor is 2.2nF and P8 I might make that value as well to further filter out ripple at high speed.

I tried this charger using a 6VDC wall supply with and without the batteries attached (to the jumpers next to 3.9K resistor). Here's what I find surprising:

The Lm358 opamp is luke warm to the touch. When I disconnected all power supplies from the circuit, the opamp returned to a cool temperature (same temperature as the rest of the components).

The NiCd batteries never blew up nor did they appear to malfunction.

The voltmeter was accurate in reporting that the battery voltage is about 7.2, however when I directly measured the wall adapter voltage, the voltmeter reported between 8.5 and 9 when it should have reported 6.

What's even more interesting is that the output (to the far right) when tested showed a very accurate result. the voltmeter reported 5.08 volts.

The right-most square is the 7805 voltage regulator since I want this charger/battery unit to provide a constant 5V when either it is plugged in or the battery has a good charge.

The reason why I use opamps is because I want the charger to cut-off as much as possible when the batteries are fully charged. Eventually I will use 12VDC as my adapter instead of 6VDC.

I thought of some ideas to solve my problem but I don't know the best solution.

I can either:

Increase/Decrease 10 ohm resistor
Change the diode feeding NPN's base to a resistor. Question is how high/low?
add resistor to -ve input of comparator (but that means I have to redo my PCB which is what I don't want to do)
Change voltage divider resistors for either opamp or regulator (but I wouldn't understand why).

What should I do and why?


texts: Divert excess PV energy to floor heating in off-grid cabin?

texts:
I'm building an off-grid summer cabin with a solar PV system. I'm planning on using this equipment:

3 kWp PV panels
BlueSolar 150W/70A MPPT charge controller
Victron Multiplus 3000W inverter
4 x 303 Ah AGM batteries (probably as 48 V)
A 2 kW water heater (100 liters / 25 gallons) using normal 230 V AC energy (*see below)

When the sun is shining and the batteries are full, I'd like to divert excess energy to bathroom floor heating. It would keep the bathroom a bit more dry, and feel nice. So, it's mostly a nice-to-have feature.

Is there a relatively inexpensive and simple way to build this behavior? I'd prefer a solution that would not stress the batteries. Can I use low-voltage DC (eg. 48..54 V) floor heating? How should I connect the system?

*) Why use electricity to heat water? Yes, the efficiency is poor, but PV panels are cheap and I want to have 3 kW for other purposes anyway. Compared to solar thermal panels, this system is a lot cheaper and simpler - and fulfills my needs. (And why use 230 V and not low-voltage DC for it? I'd like to use off-the-shelf hardware, for eg. insurance reasons.) I also plan on having the system switch off the water heater circuit when there is other load in the system (eg. a washing machine).


texts: I have 5 different designs in Altium Designer, each with a PCB. I would like to put all PCBs together in a single panel, how could I do that?There are examples for Kicad, however I use Altium Designer.


texts: What would be a modern Programmable sound generator?

texts:
Not 100% sure if sourcing components is on-topic here, but if it is:

For a hobby project, I'm trying to find a readily available (that is, ideally sold on Mouser or Sparkfun) programmable sound generator, essentially like the sound chips in old computers or game consoles (e.g., the C64 SID, the TI SN76489 used in a lot of 90's consoles or the General Instrument AY-3-8910) and that comes in a DIP Package.

I have trouble finding any sound chips, so I wonder if I'm just looking for the wrong thing? I guess that the truly modern way is to use sampling and FM synthesis and I guess I can always go truly low level by building my own circuit with wave generators and oscillators, but an IC would be ideal :)


texts: Why current switch packet mentioned of voltage and ampere?

texts: Current switch doesn't generate any electric power, so what is the use of voltage and ampere details on its packet?


texts:
I am having trouble with a RF relay module that I bought off eBay, which I am using to control a 30A automotive relay to turn a 12V 20A trolling motor on/off. I’ve attached my circuit diagram below. When everything is hooked up the motor runs, so it seems to have continuity, however clicking the momentary switch on the transmitter doesn’t turn the motor off and back on like I believe it’s supposed to. When I click the transmitter switch the LED on the transmitter turns on, however I cannot get the LED on the receiver to turn on. There is a momentary switch on the receiver right below the LED, when clicked this doesn’t cause the LED to turn on either (I assume this switch is for programming). None of the connections are labeled NO,NC or C, but I assume C is the middle one and I also assume if I’ve wired it so that motor turns on then I’ve connected to the NO. When wired to the other connection the motor won’t turn on (and I can’t hear the 30A relay clicking on/off when disconnecting the battery, which happens on the other connection), so I assume this is the NC?
I’m wondering if the unit has a problem and isn’t receiving the RF transmission, or, am I making some obvious mistake? I’ve tried all possible wire combinations on the RF module, but haven’t touched the 30A relay because I’m relatively confident that is done correctly.
Thanks in advance!


texts: I want to run an 8x8 led matrix by using a darlington transistor arduino and decoder. for some reference I was looking at this previous question(Darlington Transistor Array). Each of my Leds draws 100mA, I know that the objective of using a darlington transistor is to supply a high current to the pins but how is this doing so if the darlington is being turned on to ground the Led and the decoder to give the Led voltage. Am I going to draw too much current from the arduino pin? How is the darlington working in this case to prevent from drawing too much current from the arduino?


texts: Automation/Sensors: Reading electrical switchboard press for turning lights and fans w/o relays

texts:
To reduce power consumption I am implementing a control system that uses some computer vision to validate presence in a room and eventually control the lights & fans. For comparison purpose, I want to measure power consumption before automation and I don't have an electrical meter.

How can I read the ON/OFF events (fans and lights) at the switchboard? Any specific sensors that I can use? I can always open the switchboard to use the sensors in such a case.


texts: What is the ATmega8L fuse bit setting for an external crystal of 8MHz?

texts:
I want to operate an ATmega8L from an external crystal of 8MHz and I'm planning to change its fuse bits as follows:

High fuse = 0XD9
Low fuse = 0XFF

I just wanted to know if this is correct or not? Since I don't want to clock from the chip now.


texts: How to test capacitors of non working circuit board using capacitor meter?

texts:
I bought broken sega megadrive 2 clone console. Something wrong with 7805 IC supply (I changed to another, but no result). But now I want test electrolitic capacitors and resistors, because I thing somewhere short/open circuit exits. I have chinese made capacitor meter. If I measure some capacitors with meter it show good capacity. But if measure some other so tester shows "1". But if i remove that capacitor tester shows correct capacity. So how realy test capacitors in board? I need to buy other equipment ? Or something else ?

Megadrive 2 circuit board:

My capacitor tester:

I'm trying to test 100 uf electrolitic capacitor with 200 uf setting set on tester.

Thanks


texts: Flip Flop circuit - what is high in relation to?

texts:
I am reading about "flip flop" circuits (and I've bought one as an integrated circuit to mess with). When it says that when the SET goes high, then Q (output) will be high, what is "high" in relation to? Could I feed in -5v and call that low, while 0v is high? Or connect +5v and call that high and 0v low? Or are flip flops usually biased so that they expect a positive or negative voltage at their terminals?

The IC that I bought has the following terminals: SET, RESET, DATA, CLOCK, Q and Q(with bar over it).


texts: If Infrared not visible, why the red LEDs?

texts:
If infrared light is not visible to the human eye, why do most tv remote controls and security cameras appear to have a visible red colored LED lit when the infrared light is being emitted?

Is that visible red light present as a convenience (introduced by grace of the component designer?) or as a by-product of emitting actual infrared light?

Is it possible to have infrared light emitted without this visible red color?


texts: state transfer in FSM, written in verilog

texts:
The code :

module demux(   input clk, rst_n, NewPacket,
    input [7:0] DataIn,
    output reg[7:0] Dataout0,Dataout1,Dataout2,Dataout3,Dataout4,Dataout5,Dataout6,Dataout7);

reg[1:0] state, state_n;
reg[7:0] Data_temp1;
reg[3:0] packet_size;
reg[2:0] outport;

parameter   S0 = 2'd0,
            S1 = 2'd1,
            S2 = 2'd2;

always @(posedge clk)
if(!rst_n)
    state <= S0;
else begin
    state <= state_n;
    Data_temp1 <= DataIn;
    if(packet_size > 0)begin
        packet_size <= packet_size - 1;
        outport <= outport + 1;
    end
end

always @(state, NewPacket, packet_size) begin
state_n = 2'bx;
case(state)
    S0: if(NewPacket)
            state_n = S1;
        else
            state_n = S0;
    S1: begin
            packet_size = Data_temp1[3:0];
            outport = Data_temp1[6:4] - 1;
            state_n = S2;
        end
    S2: if(packet_size > 0)
            state_n = S2;
        else
            state_n = S0;
endcase
end

always @(posedge clk)
if(!rst_n)
    {Dataout0,Dataout1,Dataout2,Dataout3,Dataout4,Dataout5,Dataout6,Dataout7} <= 64'b0;
else begin
    {Dataout0,Dataout1,Dataout2,Dataout3,Dataout4,Dataout5,Dataout6,Dataout7} <= 64'b0;
    if(state == S2)
        case(outport)
        0:  Dataout0 <= Data_temp1;
        1:  Dataout1 <= Data_temp1;
        2:  Dataout2 <= Data_temp1;
        3:  Dataout3 <= Data_temp1;
        4:  Dataout4 <= Data_temp1;
        5:  Dataout5 <= Data_temp1;
        6:  Dataout6 <= Data_temp1;
        7:  Dataout7 <= Data_temp1;
        endcase
    end
endmodule

The testbench:

    `timescale 1ns / 1ps

module demux_tb;

// Inputs
reg clk;
reg rst_n;
reg NewPacket;
reg [7:0] DataIn;

// Outputs
wire [7:0] Dataout0;
wire [7:0] Dataout1;
wire [7:0] Dataout2;
wire [7:0] Dataout3;
wire [7:0] Dataout4;
wire [7:0] Dataout5;
wire [7:0] Dataout6;
wire [7:0] Dataout7;

// Instantiate the Unit Under Test (UUT)
demux uut (
    .clk(clk),
    .rst_n(rst_n),
    .NewPacket(NewPacket),
    .DataIn(DataIn),
    .Dataout0(Dataout0),
    .Dataout1(Dataout1),
    .Dataout2(Dataout2),
    .Dataout3(Dataout3),
    .Dataout4(Dataout4),
    .Dataout5(Dataout5),
    .Dataout6(Dataout6),
    .Dataout7(Dataout7)
);

initial
    forever #10 clk <= ~clk;

initial
begin
    clk = 1;
    rst_n = 1;
    NewPacket = 0;
    DataIn = 0;

    #20 rst_n = 0;
        #60 rst_n = 1;

    #20 DataIn = 8'h73;
    NewPacket = 1;

    #20 DataIn = 8'h11;
    NewPacket = 0;

    #20 DataIn = 8'h22;

    #20 DataIn = 8'h33;

    #20 DataIn = 8'h44;

    #20 DataIn = 8'b0;

    #20 DataIn = 8'h02;
    NewPacket = 1;

    #20 DataIn = 8'h88;
    NewPacket = 0;

    #20 DataIn = 8'h99;
end

endmodule

The waveform:

In my mind, state_n should change to 1 first and the next clk state change to 1 and state_n change to 2. But in waveform, state_n change to 2 from 0 directly, Why ?


texts: Does the physical size of electrolytic capacitors affect how they perform?

texts:
I have two 100uF electrolytic capacitors. Same voltage rating and same temperature rating, yet one is 8 times larger than the other one, being 2x longer and having 2x the diameter.

If I want to use one of them as a filter capacitor, will the physical size affect how good a job it does getting rid of high frequency noise?


texts: How is clock signal edge detection done / pros and cons of different approaches?

texts:
I'm currently learning about flip-flops, and I'm curious about the different ways in which the clock signal is handled. So far I've come across 3 different techniques:

AND-ing the clock signal with the inverted clock signal (relying on the gate delay of the inverter to detect the rising edge of the signal).
Using a capacitor and a resistor to detect the rising edge
Using a MS configuration like this, which I've seen referred to as 'pulse triggered' instead of 'edge triggered', I guess because the clock has to go high and then low in order for the output to change.

I am wondering which of these approaches is typically used in practice, or if they're all used just in different situations? In the latter case I'd really appreciate an overview of when one might favour one approach over the other (and why). I'm sorry if this is very simple stuff, I tried a bunch of different searches before asking, but wasn't able to find anything that really answered my question.
Thanks!


texts: How to estimate the settling time of the rotor of a stepper motor?

texts:
I'm trying to estimate how long I need my stepper's pulses to be to ensure I don't miss steps and assess how big the vibrations will be because of the ringing (i.e. how fast it can be, considering a fixed end-of-step precision requirement).

I've tried to start from:
$$\tau=J\frac{d²\theta}{dt²}$$
Where J is the total inertia (with load).

However, I think that for one step, the torque is $$\tau=cos(\theta)$$
And I don't know how to solve that... I can't take the small angles approximation, otherwise it never stabilizes.

Then how? I've looked everywhere for the equation of the time history of the position of the rotor for a single step, but never managed to find it. That's kind of the fundamentals though, right?