texts: GPIO Button setup with switching power supply

texts:
I have a small board with 8 GPIO's, I previously had 4 buttons connected thus used 4 as inputs and 4 as outputs. I use a 10k pull-down resistor for each button. I don't have a resister pre input to protect against programming mishaps (nothing like living on the edge).

I want to connect 8 buttons now, so instead I plan to switch all 8 GPIO's to inputs and use a switching power supply to run 3v through the switches in place of the GPIO outputs.
I've actually already done this and it works fine, but I was reading a tutorial that suggested I needed to protect the GPIO because the power supply could supply up-to 1A in my case and the maximum sink current on the GPIO is 2mA.

Now I didn't think this is how current worked and dismissed it as misguided as I thought something had to draw that current from the PSU, but now it's got me worried as I am a complete amateur with electronics and don't particularly want to fry something.

There is nothing in my circuit other than Board/GPIO, 1A 3vdc PSU, momentary switch and a pull-down resistor. Does my GPIO need current limiting / protection?


texts:
I have wired some custom USB-C cables from scratch in the past, where the USB-A connector is plugging in to a host PC. If I wired a USB cable where the USB-C connector was plugging into a host receptacle (a USB-C to Mini-USB cable for example), would there be any additional wires/pins that need to be connected in order for the cable to function properly? Typically, I am using a 4-wire cable, connecting VBUS, Ground, D+ and D- pins.

Thanks in advance!


texts: PIC24f Get Clock Signal for external Device?

texts:
I have an external memory device with pin configuration:

Data Input
Data Output
Connection
System CLock
DC 24V
Ground

Here is the link

I need to design a code to communicate with this device.

I am having Explorer-16 Starter kit with PIC24FJ128GA010 microcontroller. So, I was trying to setup a test environment to check the module before proceeding with the final design.

But I am stuck with few points. Might be lacking concept.

My first requirement is to provide a System Clock Signal to the device. Please suggest me the best possible way to get/generate clock signal for the device?
Secondly, as per the memory device instruction, to start communication, Send Start/Stop cmd while clock signal is stable in the high state? How can I achieve this?

I am badly stuck with these two points. Please provide me a better solution. I am starting microcontroller after very long time. So need to brush up. Please help me with any addtional information.


texts: Is it possible to create a parallel SPI network while using only a single slave select?

texts:
My background is in mechanical design and this is pretty much my first experience with a more in-depth system control.
I am planning on creating a network of 144 different servos, each controlled by arduino nano and several sensors. I want to send commands to all of them at the same time periodically in an array format that each nano can parse through from an arduino mega, acting as a master.
Since I don't need the ability to single out each servo, would it be possible to create a parallel SPI, but with a single Slave Select? I figured since the rest of the wires for CLK, MOSI, and MISO (which I don't technically need) are shared, SS could be shared as well?
Also, when designing custom pcb, what should I keep in mind to make sure that all 144 are connected?


texts: Arduino - How do I reduce the noise in my circuit

texts:
I have a fairly simple circuit consisting of an arduino an accelerometer and an amplifier. I am collecting data from the accelerometer using I2C and playing some sounds through a switching amplifier (this).
The problem is I am getting a constant noise in the background. I am 90% sure it is because of the I2C connection between the accelerometer and the arduino.

I am using an inductor of 10mH and cap 100nF
The amplifier is connected across the capacitor and is receiving power from arduino 5 volt supply. (I didn't draw it here). Also, I am not using external pull-up resistors with the accelerometer because apparently I don't need to when working with adxl 345

How can I reduce this noise? Where is it coming from?

Edit :-

My code has if else statements that play sounds if the accelerometer value is above a threshold. I think the noise has something to do with the fact that I am polling the accelerometer all the time.


texts: Reverse-engineering proprietary magstripe cards

texts:
I imagine we've all seen those parking systems where, to enter the parking lot, you need to get, from a dispenser, a card which has a magstripe on the back, and then, when you leave, you feed it into another box which calculates what you owe. Some systems also support passes, where, in lieu of inserting money at the exit kiosk, you feed it your pass (which looks just like the other magstriped cards) and you get your pass back and are allowed to exit.

Out of boredom and hacker curiosity, I'm wondering what the format of the data on the magstripes is. They're not as wide as credit-card stripes. Because these cards are proprietary, they don't have to conform to any standard, so I'd be starting from square-one.

Assuming that I have access to an oscilloscope and could obtain a magstripe reader:

How would I even figure out how many tracks the stripe has? I imagine that I can keep swiping the card, offsetting the stripe from the read-head a little differently each time, looking for "twin" signals when the read-head is straddling two tracks. But what would those twin signals look like on a scope?
Are there any common encoding techniques used on magstripes (kind of akin to the way clock bits are/were kinda folded into the data on floppy disks with MFM)? Or is it standard to have a dedicated clock track? Or would there not need to be a clock track since the kiosk is in total control of how fast the stripe is swiped over the read-head?
Any tips of how to construct an adjustable reader? All of the readers I've seen for sale seem designed for credit-card form factors. Are there generic read-heads I could find, somewhere?


texts: How does this OP-AMP non-inverting amplifier work?

texts:
In this non-inverting circuit at page 6 of "A Single-Supply Op-Amp Circuit Collection (SLOA058)":

I've found out the equation to be (assuming Vcc=+5 V):

$$ Vo=(Vin-2.5)*\frac{R_{1}+R_{2}}{R_{1}}+2.5 $$

Which gives -2.78 V for Vin=0.1V .That cannot be satisfied as this is a single supply operation.

I've verified my equation with this spice simulation with various Vin voltages. It also clips if I give SINE(0 500m 1k) as Vin :

Edit: There is  a typo in the above schematic. R2 should go to Vcc/2 instead of GND.

What am I doing wrong? I think there should be a Vcc/2 bias at \$V^{+}\$. But can TI be wrong?

Also when adding a low output impedance Vcc/2 source directly at \$V^{+}\$, it doesn't give the desired effect. You have to put a little big series resistor (100K) after Vcc/2 source. Why is that?

Edit: This is because of the series resistances of the voltage sources, both Vcc/2 and Vin. The series resistances form a voltage divider in-between and preventing you to create a bias; in fact, it will create a bias and almost remove Vin. Still cannot figure out the above question, though.

Edit:

OK, I didn't want to make this a long question. However, there are misunderstandings which are normal because I was in a rush when I asked this question so I was not clear enough.

I am using a model of LM324 instead of an ideal OP-AMP.

Here is the circuit I think it should be:

Here is the circuit in TI paper:

Clearly, there is a bias error.


texts: Principle and generalization of proportional-resonance controller

texts:
simulate this circuit – Schematic created using CircuitLab

We can introduce the model of \$u(s)\$ into the controller \$K(s)\$ to realize high accuracy control.

\$u(t) = 1\$, i.e. \$u(s) = 1/s\$. We use \$K(s) = K_p + \frac{K_i}{s}\$ (PI controller) to realize zero static error.
\$u(t) = \sin(\omega t)\$, i.e. \$u(s) = \frac{\omega}{s^2+\omega^2}\$. We use \$K(s) = K_p + \frac{K}{s^2+\omega^2}\$ to realize zero static error.

Now my problem is that, does this work for any other \$u(t)\$? Such as \$u(t) = \exp(\alpha t)\$?

P.S. I learnt that the high accuracy of PI or proportional-resonance controller is high gain. I can understand this for DC input (\$u(t) = 1\$) or sine input. But if this kind of controller works for other input, how to understand the gain here?


texts:
Hope someone can help me, I am really getting confused.
So I am just getting into electronics, and a project i would like to do is to make my own LED strip lighting for a workbench.
I understand that a 12V strip needs a constant 12V supply, and if the usage is 0.900A per strip / meter and I want 2 strips, I will need a minimum of 12V 1.8A supply. I also understand that I should increase the supply by 20% so as to not over tax the unit.  So a good supply would be 12V 2.25A.
If I have a PSU that provides 12V 5A is this too much or is it safe as the LEDS will only draw what they need?
Thanks in advance


texts: How to separate the modulated signal on a DC supply into signal and power

texts:
I a have an AC audio signal modulated on a DC power rail. The AC signal might be around 0.7 V pk-pk, but on the transmission line it can be higher. The DC power supply is 30 V @ 2 A max. With the power supply, I supply 10 units, each drawing 100..200 mA.
Inside each unit, I need a 'clean' power rail and the audio signal.
The audio signal must be good enough to be able to transmit music for listening on cheap headphones. The circuit must not be the part that makes the sound poor quality.
Would a circuit like the following work?
(The point between R2 and R3 is V/2, used as the Audio Ground.)


texts: How can I convert analog voltage to PWM converter just by changing the input voltage

texts: Which is used to convert analog input signal to PWM output. How can I vary the output with the input? How I can vary duty cycle?


texts:
so I have a question to build a single stage transisitor amplifier. I know Rc/Re = gain. And the value of capacitor which is parallel to Re can be found by the formula F = 1/2piRC but I have difficulties in finding values of other resistances because there are 4 resistances in the circuit, and i only know 2. Can you explain how to get another 2 values?
Thanks


texts: How to calculate voltage after rectifier?

texts:
Well, my question is:
"Is this calculator  wrong?"
It calculates the voltage after rectifier as

  Vdc = Vac * 1.41

It seems it forgets the voltage drop on diodes (0.7V + 0.7V).

Is the site accurate or we should we take into consideration the voltage drop on diodes?

Update:
For 12Vac I get 15.9Vdc after the rectifier (4x 1n4007 & 470uF capacitor, no load).


texts: Why does PCB copper surface oxidize when I apply flux on its surface?

texts:
I had to create a printed circuit board for a project, using the home method (PCB developer solution, iron chloride.) At first, after the PCB was etched, I cleaned it very well using paper towels and isopropyl alcohol.
The PCB looked like this:

Then, I applied a thin layer of flux, hoping the soldering process will be better and the board will be protected a little. I used a flux dispensing pen because I didn't have any other kind of flux.
Here's the flux dispenser pen type I used:

Here's how the board looked after I applied the thin layer of flux:

I let it dry over night.
The next day, when I wanted to solder the components, I noticed that the soldering material wouldn't stick to copper, so I applied some more flux. Apparently, it worked, but some minutes later, the copper surface where I applied the flux turned green, with a dirty aspect:

Can someone help me with an answer, why did this happen? I assume it's the flux, but I'm not sure why.
Will the board be affected and in the end the traces will be destroyed?
Is there a solution to clean the dirt and protect the existing board?
Later edit:
I tried to fix the damage already done by cleaning the PCB with isopropyl alcohol as well as I could, and it turned out pretty well, in my opinion. Here's a photo of the cleaned PCB:

It's been over a month and the board works well, I had no problem with the connections. The project I used the PCB for is an UV exposure box. I've put the PCB inside a plastic case, and the plastic case is inside a bigger wood case, also protected with extruded polystyrene. I hope this way the PCB will be protected from humidity. Also, the humidity in the laboratory where the PCB is located is controlled, always under 40%.
Thank you for all your help and good advice, I learned a lot from your answers.


texts: Need help in designing a BJT Amplifier with Avnl = 100

texts:
For our final project, we need to design a "single-stage BJT-based highpass amplifier using voltage divider configuration".
The amplifier has the following requirements:
\$V_{CC} = 12V, f_L = 300 Hz, Vs = 300 m V_{pk-pk}, and A_{VNL} = 100 to 300 \$.
I decided to use a 2N3904. And the following is what I have so far
I set the voltage at R2 to 6.35 to have the maximum swing for the output. I set R2 to 10k ohms and R1 needs to be 8.87k ohms to set the voltage divider.
\$ 6.35 = 12 \times \frac{10k}{10k+R1} \$
Next, I set \$I_C = 10 mA\$. Then \$R_E = \frac{6.35-0.7}{10mA}=565\Omega\$.
For the gain to be 100, \$R_C = 100\times re = 100\times\frac{26mV}{10mA} =260\Omega\$
For the capacitors, I use the formula \$1/(2\pi\times R\times300) \$ and then
increase it a bit more.
The problem is then I can only get a maximum of \$2.39V\$ and a minimum of \$ -3.439V\$. I don't what else I can do.
Thank you for the help.
EDIT:
Here is the result of the DC point analysis:

Based on my understanding, the DC point analysis looks good to me. That being said, I still do not know what I am missing to make it work.


texts: Truth table with logical gates for a traffic light

texts:
I want to create this truth table:

So I tried this but I was not able to get the last row, which is:
 While a =1 and b =1 ,yellow = 1  red = 0 and green = 0.
This is my design for it, but I could not make the last row.

Does anyone have a sample or a tip about what I can do to fix this?
Thanks!


texts: Arduino Nano - USB not present after reboot

texts:
I do have an Arduino Nano (v3.0) board and to my surprise the USB (and communication with board) is disabled after I restart the PC.

If I do unplug and plug the USB cable the USB port becomes available.

Is this an Arduino Nano "feature"? (As I see that my other Arduino UNO board works fine after a reboot)


texts:
How do you properly monitor supply voltages for digital circuits (microcontrollers, FPGAs, RAM)? (I stumbled upon this question when working on safety critical systems)

What I have seen a lot is to have ADCs which measure the supply voltage regularly, but these kinds of circuits perform weakly against glitches as most of the time the ADC is not measuring at the right moment. Glitches can lead to memory corruption, which can be catastrophic.
Furthermore, having a look at http://www.analog.com/media/en/technical-documentation/product-selector-card/Supervisorsfd.pdf it seems like some resilience against detecting glitches seems even desired. What makes sense, because as long as a glitch does not have a certain width or depth, it has no impact.

But I have also stumbled across some ICs (an RTC for example) which besides their normal brown-out circuitry have some edge detection to detect sudden rises or falls on the supply voltage.

To summarise, isn't it desirable to have beside the normal "static" voltage monitoring (with things like ADCs or comparators) some circuitry which can detect glitches (of a big enough width of depth to have an impact)?


texts: ATmega48PA: can not run PWM on OC0A and OC2A pins

texts:
I have some troubles trying to run Fast PWM on OC0A and OC2A pins.

The code is the following:

TCNT0 = 0;
TCNT2 = 76/2;
OCR0B = 76;
OCR2B = 76;
OCR0A = 10;
OCR2A = 10;
TCCR0A = 0b11000011;
TCCR2A = 0b10000011;
TCCR0B = 0b1010;
TCCR2B = 0b1010;

So I assume that timers will run with 1:8 speed from 0 (and 38 for Timer 2) to the top defined by OCRxB registers (76) and will change pins state on TOP (76) and OCRxA (10).

That's not work: the pins OC0A and OC2A connecting to the timers (as I can not change their state by putting 1 and 0 into respecting PORTD and PORTB bits) but there is no PWM signal.

However if I try to use OC0B and OC2B pins - everything works:

TCNT0 = 0;
TCNT2 = 76/2;
OCR0A = 76;
OCR2A = 76;
OCR0B = 10;
OCR2B = 10;
TCCR0A = 0b00110011;
TCCR2A = 0b00100011;
TCCR0B = 0b1010;
TCCR2B = 0b1010;

Need to note that in this case OC0A and OC2A pins can be driven directly by changing the pin state (which proofs that I don't have any schematic flaws).

I tried to replace the values of OCRxA and OCRxB in first code but that didn't help:

TCNT0 = 0;
TCNT2 = 76/2;
OCR0A = 76;
OCR2A = 76;
OCR0B = 10;
OCR2B = 10;
TCCR0A = 0b11000011;
TCCR2A = 0b10000011;
TCCR0B = 0b1010;
TCCR2B = 0b1010;

Any thoughts?

UPDATE 1

Sorry for omitting part of the code. The ports definitions goes before the main code:

DDRB =  0b00001010;
PORTB = 0b11110101;
DDRC =   0b0000000;
PORTC =  0b1111110;
DDRD =  0b01101000;
PORTD = 0b10010011;


texts: Comparator - Short circuit indicator. Possible to design a bi-color LED version?

texts:
Recently, I began work on a adjustable regulated power circuit in search of a short circuit protection / indicator add on. A fellow forum user issued a solution that involved an LM321 as a comparator in the image below:

As a possible solution as a short circuit protector, the output of the LM321 is to be connected to the gate of an SCR. The SCR's anode will be connected to the regulator's adjust pin and short it to ground thus rendering the output of the regulator to as little output as possible. (I'm not sure if the SCR part is relevant to my question yet so I included it's purpose to the comparator for now).

The current design has two LED's. The Green LED is active when the load is within specified parameters. The Red LED will activate when LM321's output is high indicating that Voltage (load) drops below Voltage (ref) or that too much load is present. With the SCR in place, the regulator's output drops off this deactivating the Greed LED. The Red LED will be active. My question is, is it possible to design a bi-color LED (two-lead or three lead) version of this?  Any help is greatly appreciated. Many thanks in advance.

Edit: Not sure why this got down voted. Question was pretty straight forward. What was wrong with the question? :/


texts: Could a china ST-Link have bricked my STM32F4?

texts:
I have built several boards with STM32F405 on them and I have been flashing them with a cheap china ST-Link knock-off from eBay which worked perfectly for many months now.
However, I now noticed, that my STM32F405 board is no longer accessible through the ST-Link (No Target Detected with ST-Link utility and STM32CubeIDE). However, the code runs fine on it! The LEDs are blinking and output is written to the SD-Card.
I am not able to do a chip erase on ST-Link Utility, because for that it needs to be connected. The issue exists on three of my boards, which have previously been flashed with the same cheap china ST-Link. I suspect that the boards have entered memory protection level 2 (RDP), thus no longer accessible via SWD, and thus bricked. ST-Utility does however not tell me that there is read out protection enabled (I don't know if it would..) it acts as if the SWD line is not connected, but I checked with a multimeter and they are... I enabled "connect under reset" and I see that the STM32 is resetting, but nothing else happens, still no connection established...
I also ordered a genuine ST-Link, and the issue appears the same.
Since I do not see any other common link between the three boards (2 have similar software, but the third has a really different software on it, the only thing in common is the drivers for the I2C and SPI sensors that are attached to the chip), I suspect that the problem could come from the cheap china ST-Link. Is that a known problem? Or do you have any other inputs? I am certain, that I did not set the memory protection flag when flashing the chip (I actually don't know how I would do that with STM32CubeIDE).
When I last flashed the board with the cheap china ST-Link I was using STM32CubeIDE on my macbook pro. ST utility was used on a virtual machine running windows 10.
All three custom STM32 Boards failed on the same day, two of them are physically the same, but running slightly different software, the third one has a much different schematic (but all use an STM32F405)
BOOT0 and BOOT1 are connected to ground through a 10k resistor, the board gets a solid 3.3v from the ST-Link. Crystal is connected with capacitors but not configured in the software. The SWD pins are not configured as anything else in software, I used the STM32CubeIDE graphical configuration tool and used them for debugging.
Thanks!
EDIT:
Conditions when it failed: High humidity (10 °C and up to 80-90% humidity) in a tent during one week (though other boards survived without any issues). Board has no conformal coating.
Schematic of one of the boards is attached.
EDIT 2:
The third board is not actually broken, it works with the genuine ST-Link but not with the replica one, however the first two boards do not work with either of them.. so there is definitely something wrong with the replica ST-Link..


texts: Cheap and powerful stroboscope: Turning a floodlight into stroboscope?

texts:
I would like to build a Stroboscope with the most cost-effective and less time-consuming approach. I would like to be able to control and know the frequency of operation, which should be at least of 50 Hz. I would like it to be able to illuminate an entire room (20 squared meters).

A little bit of context, so far the options I've seen have been:

Buy a pre-made one:

Although I've not found any cheap plug-and-play stroboscopes, we may take advantage of "disco" products like this (LED) or this (Xeon).

PROS: Cheap (<10$), fully assembled. CONS: Low max frequency (<15 Hz). Low brightness (LED case).

I do not know if it would be doable to modify the circuitry of these products to make them flash at higher Hz.

There are also some interesting timing lights from the car-industry that could also serve.

PROS: Fully assembled, high frequency operation. CONS: Low power, need for external battery, more expensive.

Create your own:

In that case I've seen several interesting schematics online. However, I would like to avoid doing PCBs in favor of a minimal modification of an existing design. It was at this point were I thought that floodlight lamps are cheap yet powerful (50 W for under 20$), and maybe they could be driven by a simple MOSFET controlled by an Arduino. However, I've not been able to find any example of this design in Internet.

Is that really a bad idea? Can the AC to DC transformer (the LED driver), be damaged by high rate switching? Would a large capacitor at the output of the driver help on that?

Thanks,


texts: After all the transients have settled down what would be the output voltage

texts:
Vo(0)=5 , what is Vo(infinity)
Can you please explain to me how i can get the answer.


texts: How to select a Relay that can handle a load of 42V, 3A DC?

texts:
I want a relay that can be controlled by a Raspberry Pi and can handle a load up to 42V and 3A DC. I was looking at this: relay which is rated at DC 30V/10A. Although, 30V is less than 42V but I was wondering if this could still work as I found a website that explains how to select a relay:here.
According to this, power rating of the relay is 30V x 10A= 300W whereas power rating of the load is 42V x 3A=126 W which is within the limit of the relay. Based on this, does it mean that the relay I am looking at would work?


texts:
I need a mathematical description of what happens to the spectrum of a signal when that signal is processed to divide its frequency.

As an example, construct an input signal as the sum of two sine waves of different frequencies (as commonly used in a "two tone" test). Processing this signal with a buffer that changes state at the rising zero crossings of the input signal produces a squared wave whose frequency can be divided by a flip-flop:

The spectrum of the the input signal comprises tones at 102kHz and 105kHz:

"Squaring" the input preserves the two equal tones, albeit with added side tones (spaced at the difference between the two original tones) that result from removal of the amplitude envelope and added harmonics from the squaring:

Passing the squared signal through a flip-flop produces a second square wave which in which the two-tone nature is no longer present:

The single dominant tone is at 1/2 the frequency of the higher of the original two tones, while the spacing between the peaks continues to be the spacing between the two original tones.

Passing the squared result through an LC low-pass filter produces a sine wave with cycles that are half as frequent as the input:

with the same general spectral distribution as the squared output:

Can someone, please, explain what happened to the other tone?


texts: I'm trying to simulate a circuit for a design I'm making. In a few parts of what I'm interfacing with uses relays that when closed will short a few power supplies to the chassis ground and in LTSpice and Circuit lab there is no "chassis ground" or "earth ground" just one ground. It doesn't short the rest of the circuits with power supplies tied to their own grounds just a few spots these relays are used. I've been trying to find the answer on here and elsewhere and found Need help modelling the circuit with parasitic capacitance of a power supply in this scenario in SPICE where he just hand drew it but is there a way to make it with subskt or is there a proper way to simulate this that won't skew my sim in weird ways?


texts: How different is the Arduino language than Atmel Studio language?

texts:
I see that on the official Arduino website, the reference page contains the functions and vales you would use specified to the Arduino compiler.

http://arduino.cc/en/Reference/HomePage

What would you use instead, if you are working with Atmel Studio?


texts:
I'm trying to use a MAX541 DAC (datasheet here) with a Tiva LaunchPad (TM4C123G).  I've gotten this to work with other DACs, the problem is that that those DACs required 3.3 volts and the MAX541 requires 5 volts.

The Tiva LaunchPad outputs 3.3V.  I've purchased this RECOM ROE-3.305S DC/DC Converter which is supposed to convert 3.3V to 5V.  However, when using it with the 3.3V input, it's outputting 6.35 volts and not the 5 volts that I need.

The DC/DC converter simply has four pins that plug into a breadboard: -Vin, +Vin, -Vout, +Vout.  I simply plug the ground of the Tiva LaunchPad to the -Vin.  The 3.3V power from the Tiva LaunchPad to the +Vin.  Still I get 6.35V and not 5volts.  Am I doing something wrong?  Anyone?


texts: Modeling small signal equivalent circuit of a transistor circuit

texts: For this homework question, I have to model the circuit and find output impedance.  The question states that the capacitors can be modeled as short circuits.  As I think I understood it, the resistor R1 can be modeled as being in parallel to the other resistors and in parallel with R2, Re and Rl.  Is this an accurate simplified model of the transistor circuit?  If not, why?  By the way, the capital Ib and ib in the diagram are the same, I just realized I accidentally drew it with that inconsistency.


texts: Bidirectional DC-DC converter, 12V - 300V, 1 kW?

texts:
What DC-DC converter topology would you recommend for a device that supports bidirectional power flow of up to 1kW with 300VDC on the high-side and 10-15VDC on the low-side? I want to use it to connect a 300VDC motor/generator to a 12VDC lead-acid battery.

In particular I need a device capable of maintaining the high-side voltage according to a given set-point, irrespective of the power flow direction.


texts: How to replace microswitches with electronic switches in a voltage / resistor ladder circuit

texts:
Hello everyone,
              I am relocating a pair of transmission control levers to a different location within a car. At present each lever actuates a pair of SPST microswitches (at the same time) in a voltage/resistor ladder circuit. The diagram is below:

The outputs from the circuit are up, down, and a standby line which is used to provide fault tolerance. It is connected to a gearbox ECU and the replacement circuit must match exactly the existing voltage outputs.

There are some constraints I must work with in the new location:

There are two wires between the old location and new. A VBATT and ground do exist in the new location;
The two levers in the new location each operate a single SPST switch.

I came up with the idea of using the new switches to operate a pair of solid state relays, i.e.:

However this was before I realised there is a voltage drop across the load side of SSRs which means the circuit wouldn't work, because the gearbox ECU would not see the voltages it was expecting.

I am now scratching my head and seeking ideas. Any help appreciated.


texts:
I'm using iCircuit to simulate this circuit:

I set the the threshold voltage as 0.7V. Here's my simulation result:

It says the nMOS is in saturation mode. Since Vgs < Vth, should it be in off condition? Why did my circuit simulation apps says it's in saturation mode?


texts:
What dielectric materials are used to make film capacitors in hybrid integrated circuit?

Unfortunately I can not find a definite answer to my question in the textbooks on electronics materials.
To calculate the film capacitor, I need to choose a suitable dielectric material. This capacitor should be used in a hybrid integrated circuit.
I need to choose a material that is close in value of the dielectric constant to 4.7.

Can I use a polyvinyl chloride with a dielectric constant of 3.1–3.4 for the manufacture of a film capacitor in a hybrid integrated circuit?

If not, what material is best for this?


texts:
I have the good old problem of converting a 3.3V logic voltage to a higher voltage.
Higher means everything between 12 and 20V. With 15V being used most of the time.
The highest frequency I use now is 5kHz. I don't want to redesign this if it's 10khz in the future.
It is prototyping hardware to simulate some rotary encoders with errors. I will build 6-7 boards with 8 channels each. So I would prefer IC's over discrete builds.
The logic input should be (way) below 1mA per channel. The circuit will need to deliver 20mA max, some headroom would be nice. I have build one with SN74. Which works ok up to 14-15V. Now I'm looking forward to use CD40109BE.
Does anyone want to share some experience in this regard? My current research is:
Discrete: doable but too much work on PCB / soldering
OPAMP: haven't found a good one
Schmitt trigger: works fine but higher voltage seems to be a problem
Optocoupler: difficult with speed and channels
Buffer IC: CD4050B / CD40109BE
Gate Driver: very robust maybe UC17/27/37 from TI?
I kinda like the idea of the Gate Driver if I need a variable Power Supply somewhere down the road. But I think the right Schmitt Trigger or Buffer IC does the job perfectly fine. Just need to find the one IC ^^


texts: Well why the depletion region of the pn junction is decreased in forward bias condition and not minimized? Current will start flowing neutralizing all donor ions and so there will be no depletion region left.


texts: How to switch on/off ungrounded circuits using a transistor

texts:
I want to switch on/off the shown parts of a circuit using a transistor, which will  controlled by an Arduino, please see the picture below - the yellow marked ones. The circuit is build around a XR2206, which is a function generator IC.

The left side controls the range the function generator is working in, by adding different capacitors between pins 5 and 6 of the XR2206.

The right side just switches between triangle or sine wave generation, by adding some resistance between pins 13 and 14 of the IC.

Now, I can easily switch circuits which are connected to ground using NPN, but I fail to come up with a solution for this problem.

I am ready to accept any laughter. If I am using wrong terms etc, please give me a pointer to the right one. In the old times I would have used relays to achieve this, but I get this is too much old style and overkill for this issue here.


texts:
I have created a bandpass filter with an LMC660CN chip, as shown in the image below.

However, in regards to just the high pass filter section, the filter's AC response is set so that at Vout a high pass filter is created with 1 kHz as the filter cutoff point, and it then has unity gain set by RF and RG. I also coupled RG to a 2.5 V voltage reference, in hopes that the output would oscillate about 2.5 V. That has not happened.

V1 in the schematic is a simple piezo disc in a black plastic case. It is AC coupled to the + input of the LMC660.

When the piezo is "at rest", the filter gives no output. When the piezo is slightly stimulated by the water pipe it is resting on, and vibrates at about 2.5 kHz, the filter begins to oscillate at about 20 Hz, and on each oscillation it reaches the positive power rail, 5 V. Also, this filter oscillation is also detected in the signal line of the piezo, probably from the + input interacting with the op amp's output.

Can anyone suggest why the filter begins to self-oscillate when the piezo creates a 100 mVpp at the + input? I am wondering now if it is connected to RG being coupled to VREF.


texts: How to convert a CD player's coax diigital output to a Toslink?

texts:
My question is essentially the same as this one, except my signal flow is in the opposite direction: Connecting an optical transmitter to a S/PDIF coaxial output

I'm not sure of the optical transmitter's part number because I am reusing one from an old satellite TV set-top-box.  I know this makes it hard to give an accurate answer, but I'm not worried about what happens to the gear I'm using in the event of a catastrophe. Anyone's best guess is better than mine, and I don't mind gambling!


texts: Can I use a ST-LINK V2 as a universal JTAG or TTL serial interface?

texts:
I have a ST Link V2 as pictured below. I would like to use it as a general purpose JTAG and or Serial TTL USB interface for communicating with a wide variety of devices. The documentation claims it supports SWM, which appears to be JTAG, but it's unclear if it is a vendor specific version of the standard.

Since the ST Link V2 has built-in firmware to function, I'm assuming its not just a dumb interface and may require additional steps to make it work.  Can this be used for my purpose or should I just get a general purpose JTAG cable?  If so, what's entailed?


texts: I'm using an LM358 to learn how to use op amps, I asked a question and everyone referred me to books so I've been reading up on that, but whenever I try to use them I never actually get a boost. Today I tried using this setup below but I only got -(1/2)Vin = Vout. I don't have much to work with so I'm using Vcc+ = 2.4v and Vcc- = -2.4v. RG = RG = 10K Vin = 1.2v. In this case Vout = -.6v, when I tried other resistances it didn't really match the -RF/RG equation. I'm probably not reading the data sheet right or the resistances aren't high enough. Not sure what's wrong.


texts:
Having started to learn Verilog there was this doubt that crept my mind which is as follows:-

1)   Consider the following Verilog code with 3 modules. Module 'Clock' that simulates a clock, module D Flip Flop and module JK Flip Flop:-

module clock(clock_out); //Clock Module
output clock_out;
reg clk;
wire clock_out;
assign clock_out=clk;
initial
    clk=1'b0;
always
    begin
    #200    clk=~clk;
    end
endmodule

module d(q,q1,d,c); //D Flip Flop
output q,q1;
input c,d;
wire c;
clock clock1(.clock_out(c)); //clock module instantiated
reg d;
reg q,q1;
    initial
       begin
           q=1'b0; q1=1'b0;d=1'b0;
      end
    always @ (posedge c)
       begin
         q=d;
         q1= ~d;
         d=~d;
        end
endmodule

module jk(q,q1,j,k,c);   //JK Flip Flop
output q,q1;
input j,k,c;
reg q,q1;
wire c;
clock clock2(.clock_out(c));// another clock module instatiated

initial begin q=1'b0; q1=1'b1; end
always @ (posedge c)
  begin
    case({j,k})
         {1'b0,1'b0}:begin q=q; q1=q1; end
         {1'b0,1'b1}: begin q=1'b0; q1=1'b1; end
         {1'b1,1'b0}:begin q=1'b1; q1=1'b0; end
         {1'b1,1'b1}: begin q=~q; q1=~q1; end
    endcase
   end
endmodule

2)   In this setup having instantiated a clock module each in the D and JK Flip Flop module can I expect the clock (output signal generated by module clock) in sync in both these modules or should I expect a lag equal to the delay of actual instantiation of the clocks when the simulation started?

PS: Please let me know if I have not been able to explain myself. Didnt want to lengthen the post than required.


texts: What are the most widely used circuit simulators in industry?

texts: I was wondering if anyone knows what the most widely (not favorite) used circuit simulation tools are in industry. I have a couple options here at the company I work at, but I still like to use LTSpice for most of my work. I'm pretty fresh out of college so I haven't had a very good chance yet to see what the industry is like.


texts:
I want to repair my computer mouse cable which has become disconnected from the PCB.
The wire is insulated with enamel and I have to remove it before soldering it back onto the board.

How should I remove the enamel?


texts: Why is the cost of microcontroller lesser than microprocessor

texts:
I was learning today about 8051 and I encountered a point which said microntroller generally costs less than a microprocessor.

I didn't understood why is it so since microcontrollers have RAM, ROM, internal oscillators, ADC convertors, comparators and so on on a single chip but microprocessors dont.

I also know that microprocessors have a bigger ALU part compared to microcontrollers but can this only reason increase the cost of microprocessor?


texts: Design Question: Precision Current Source

texts:
I am attempting to design a voltage-controlled bidirectional current source that will drive an inductive load. The current source needs a range of 100uA to 200mA, and it needs to work with precision of about 100uA at lower load currents, with lower precision acceptable at higher load currents. It needs to be able to output sinusoidal, (approximate) traingle and (approximate) square waves over frequencies from 1Hz to 1kHz (I understand I'm driving an inductor so perfect square and triangle waves are impossible), and ideally with as low an operating voltage as possible, as the system will be battery-powered.

Here is what I have tried so far:

I tried designing this circuit I designed based on instrumentation amplifier feedback, but it's unstable and oscillates at around 130kHz. I considered using the circuit below from this TI document, but it introduces excessive series resistance with the load and does not have easily-adjustable current precision.

For the same reasons I've decided against using an op-amp with the load in the feedback loop. Does anyone have suggestions?

In case you're curious, this is the load, a Helmholtz coil I 3D-printed and wound which will be acting as a magnetic field generator.


texts:
Hey guys I'm new here and just need some help with a problem for my EE class. I need to find the maximum power that can be delivered to the variable resistor R.

If you could walk me through the steps of finding R-thevenin and what not in order to get to the final answer that would be extremely helpful.

Thank you.


texts: PIC24f: How to Generate Start condition using SPI for I2C device?

texts:
I am trying to communicate with the device having internal communication as I2C while externally it has two different pin for Input & Output along with a separate pin for Clock. Here is the link.

I am using SPI to communicate with this device. But I am unable to generate START/STOP condition to communicate with I2C device.

Can I get some suggestion to overcome this issue ???

I am using C Coding.

I Tried Bit Banging as follow

Dont know if any logical error.

Here is the Start Condition I m trying to implement :

bool generateStartSeq()
{
    SPI1STATbits.SPIEN      = 0;    // disable SPI port
//    SPI1CON1bits.DISSCK       = 1;    // Internal SPIx clock is enabled
//    SPI1STATbits.SPIEN        = 1;    // enable SPI port, clear status

    AD1PCFG = 0xFFFF;               // Convert IO pin to Digital
    TRISFbits.TRISF6 = 0;           // Configure RF6 pin as output;
    TRISFbits.TRISF8 = 0;           // Configure RF8 pin as output;

    LATFbits.LATF6 = 1;             // Make RF6 pin high

    LATFbits.LATF8 = 1;

    Nop;
    Nop;
    Nop;
    Nop;
    Nop;

    LATFbits.LATF8 = 0;

    //    writeSPI1(0xFF);                // SDO send data High
    //
    //    Nop;
    //    Nop;
    //    Nop;
    //    Nop;
    //    Nop;
    //
    //    writeSPI1(0x00);

    SPI1Init();

    return true;

}

Any suggestion will really help me to correct the logic.


texts: Is the voltage divider in this circuit backwards for what I'm attempting to achieve?

texts:
This circuit is from another post (from long ago) where a user helped me build a circuit which would use a BJT as a switch.

simulate this circuit – Schematic created using CircuitLab

The problem was that I needed to lower the voltage on the base pin of the BJT so the user suggested I add the voltage divider (R2, R3).

Target

The original target was to apply 0.5 - 0.7 V on the base pin.

Should Those Resistors Be Flipped?

I've recently begun looking at the circuit again and I now believe that the two resistors should be flipped.

It looks to me like this might put 4.54 volts on the base pin (instead of the @ .5 volts) that the user was trying to get onto the base pin.

I used the AllAbout Circuits voltage divider calculator and it seems to back this up. But, maybe I'm not looking at that properly?

Logically, it seems like you'd have the larger drop connected directly to the base pin too?

Should those two resistors be switched or is this correct?  If they are correct, can you please provide a bit of explanation of how to think about this the correct way?


texts: how to bumplessly switch between two control signals?

texts:
I have a Labview program which sends 4-20ma current signal through a ni usb device to control the speed of a motor by controlling a sew eurodrive MOVIDRIVE ® MDX60B / 61B. Here is the data sheet of MOVIDRIVE:https://download.sew-eurodrive.com/download/pdf/16837614.pdf. PAGE 60 shows the layout of signal terminals. On the actual device, the input terminals are just two normal terminals,nothing special.

Originally, this motor is controlled by manually pushing some physical buttons on a device. The device is just some kind of signal generator that generats 4-20ma current signal.

The MOVIDRIVE ® MDX60B / 61B is set to accept 4-20ma current signal as control input.

So how can I switch between the two control signals (1.from labview, 2. from the device) so that there won't be any gap between the switch? I want to accomplish this because if the control signal drops to 0 at some point, the driver may get damaged. Since these equipment (both the movidrive and the motor) is really expensive and important, I can't risk damaging them by placing a switch in the circuit and just switch between the signals. Any advice is much appreciated!


texts:
can i use lc filter on three phase stepper motor (variable reluctance motor) to get sinewave current ?
We know that if we put sinewave voltage on ststor windings, the stator current will not be sinewave shape due to variable reluctance of the stepper motor.

Lets assume the input voltage is :

1 PWM pulses voltage.
2 Normal 50/60 Hz sinewave voltage.

Thanks.


texts: Piggy-backing off power amplifier outputs

texts:
My motor-scooter has a built in radio, with a small speak either side of the front panel, below the handlebars.  It's a JonWay, i.e. cheap Chinese, so I suspect the radio is more suited to developing countries where helmets are not yet mandatory.

For me to listen while wearing a helmet, I need zero traffic, or a headphone jack, and I'd like to do the jack myself.  I may not find the radio board without too much dismantling, but the speakers are very accessible, so I may have to grab my input signal directly from them.

My electronics knowledge has all but evaporated after 15 years of non-use, so all I can start with is that I'll need a high impedance input, to make the increased load on the amp negligible, and my own power amp stage.  Where do I go from here?  I would like to do a rough design myself, maybe make the amp component a kit, but nothing ready made.


texts: Simple, passive way to remove high frequency interference from low power audio

texts:
I have used the innards of a Korg Mini-KAOSS Pad to add some amusing effects to one of my electric guitars, but in order to do this I had to remove the original input connectors and wire my pickups directly to the input circuitry.

The input voltage is fine, however I do now have a problem with a high pitched digital sounding whine when using effects. My assumption is that the input connectors probably had some type of rolloff circuitry (almost certainly passive) and in removing these I am getting interference from the high frequency oscillators in the DSP circuitry.

As part of my remediation I am increasing shielding, but realise I probably need to add a filter to remove higher frequencies.

tl;dr - is there a simple circuit (ie probably just an R/C) that I can pop in to roll-off rapidly above the usual frequencies I would get from my guitar strings?


texts: How to connect/terminate differential CML logic outputs to single ended ECL logic input?

texts:
If I want to use a CML differential gate's (Ex: SY58051AU) output as the enable ECL input for an ECL counter(EX: MC100EP016A), whats the best way to connect the output to input? I think I need to use a Line Driver, since it's differential to single ended, but don't think CML to ECL line drivers exist? I thought about just connecting the positive differential output of the gate to the single ended input of the counter and grounding the negative differential output(assuming the counter and gates are close to each other), but the voltage swing is 400 mV with a Voh=3.28. Therefore, Vol=2.88 and the counters Vil=1.675 and 2.88 is not less than 1.675 V. How would this connection be made?

Update: Pic of output and input levels.


texts:
In this wiki page:http://en.wikipedia.org/wiki/Framebuffer

There is something called "SMART" protection capability to avoid monitor to driven
it's hardware capabilities.

  An unfortunate side-effect of this method was that the display device could be driven beyond its capabilities. In some cases this resulted in hardware damage to the display.[6] More commonly, it simply produced garbled and unusable output. Modern CRT monitors fix this problem through the introduction of "smart" protection circuitry. When the display mode is changed, the monitor attempts to obtain a signal lock on the new refresh frequency. If the monitor is unable to obtain a signal lock, or if the signal is outside the range of its design limitations, the monitor will ignore the framebuffer signal and possibly present the user with an error message.

How this works? Can anybody give me the mechanism behind this.
I need to study a schematic which does implement this "SMART" protection capability.
I have searched for the specification on google, but I didn't found it.
How could I one implement this feature on a industrial CRT?


texts: What tool is used to cut back the outer jacket and dielectric of a coaxial cable?

texts:
I would like to assemble a few SMA connectors on 0.086" semirigid coaxial cable.
Here is an image of the assembly instructions on one such part (Amphenol 901-9723).

As you can see, the outer jacket of the cable and dielectric must be cut back by dimenion a.
What tool is suitable for cutting/scoring a controlled length the outer jacket and dielectric of the cable without damaging the inner conductor?

I'm willing to spend up to around $1,000 on a tool set.


texts:
I have a motor which runs in only one direction when excited by a square PWM at 500kHz with a voltage of 5.6V across the two pins of the motor. Consumption is around 100mA.

I have a 1.8V square 500kHz PWM and a steady 2.8V VCC supply.

How can I build a h-bridgbe (or something else) to action the motor?


texts:
I'd like to create the classic game of Simon Says utilising nothing but logic circuits, LEDs and ICs, no Microcontrollers like the Arduino.

I would like to use 4 LEDs and 4 Tactile Switches for this circuit.

I'm doing this as an educational exercise for myself, I'm not studying electronics however I am studying Computer Science.

I understand that I will need several components including decade counters and 555 timers.

However my question is, how am I able to decide which LEDs to display in a random sequence? I understand I can decade counters/Flip Flops to store the sequence in memory.


texts: Measuring capacitance of Metal-Insulator-Semiconductor (MIS) structure with LCR meter

texts: I can not get my head around what a LCR meter measures. My LCR meter measures my device (MIS) which is displayed as C_p and G_p (other components can be neglected). My LCR meter displays C_p, G_p, the applied voltage and frequency. I guess the capacitance of my MIS structure is C_p, but I do not understand why it also displays G_p, why should this be relevant to me if I only want to measure the capacitance?


texts: What is the proper procedure to charge a lead acid battery?

texts:
and thanks in advance for your answers.

I have a 12v 6Ah lead acid battery, and have been instructed to charge it using a configurable power source.

They told me I should use a float charge, setting the voltage at a fixed level according to the battery datasheet, and end the charge when the charging current is lower than about 5% C (5% of 6A in this case).

Doing this, I have barely gotten about 80% of the rated capacity. Now, doing some research on my own I've found that what I should really do is a cycle charge, which as I understand it is a constant current charge until voltage reaches a higher level than with the float charge (also specified in the datasheet).

Long story short is, what is the proper way I should charge this kinds of batteries? Should I do constant voltage then constant current, just constant current, whatever? What I really wanna do is understand how to evaluate a given battery.


texts:
I'm working on something at the moment that uses an ESP32. I would like to have simple strings that I can specify within the ESP32 code to automatically "type" on the screen. For example, if I did keyboardWrite("Hello World") and I had a blank notepad open on the PC/Mac, it would automatically write Hello World.

I realise the ESP32 does not have a USB interface, so I decided on using an MCP2210(SPI->USB bridge) to take information (simple strings) from the ESP32 via SPI and then transfer them to the PC. Microchip claims that it is a plug n' play device however they supply a .dll to develop applications for it.

My question is - is there any way to carry this out without having to develop/install any custom software or drivers or any .dll and it would simply be a plug n' play device for PC/Mac. For example, is there any way to embed the functionality of sending keyboard strokes from the MCP2210 itself, rather than through an application on the PC/Mac.

In short, how can I interface an ESP32 to USB to emulate a USB keyboard without any extra software.


texts: I'm new to this field hence this weird question. Why would we need to ground an AC source? Why wouldn't it be enough to have just one pole to get an AC current going? I understand why it wouldn't work in DC case where current is flowing in one direction. However, in case of AC source where the current is not flowing anywhere but rather just oscillating back and forth it's not that clear to me why connecting load to only one pole wouldn't work?


texts:
I am trying to use current sensing functionality of Arduino Motor Shield R3, the shield is based on L289.
The values that I read seem to be very noisy. I am using Arduino UNO A0 analogRead() function to sense current. To fix this I have tried to use low pass filter between the motor shield and arduino uno.

simulate this circuit – Schematic created using CircuitLab

This helped to fix measurement noise however I have several questions about it:

Is the noise in the sensing signal caused more by the motor it self of the fact that the motor is driven by PWM? (Note I have already increased PWM frequency of Arduino Uno to to 32kHz.)
If I would add a low pass filter to the input PWM signal would the current sensing still be noisy?  I have tried adding low pass filter to PWM but it did not seem to change current sensing. The low pass filter however affected the motor, it started to run as usual and slowed down almost to stop over time. Maybe I connected the low pass filter for PWM incorrectly.
Is there actually any advantage of adding a low pass filter for an input PWM signal or is 32kHz PWM fast enough and I should just go with the low pass filter for current sensing?


texts: I need to be sure that these are right values for MOSFET 2N7000

texts:
I made A circuit for test mosfet in proteus But according to datashet the values are incorrects. I need your help : Is it normal these values ?

For example : V(gs) in my circuit is 4 volts and amperage is 0.40 amps. But in datasheet for v(gs)=4 volts amperage is from 0.5 to 0.75 amps. look:

So whats the problem. Best regards.


texts: Simulation LTSpice a two stages Operational Amplifier with CMOS

texts:
I need to simulate this circuit on LTspice. In the exercise I have to balance the parameter to makes it work and estimate the gain in the center of the band. The inputs are v+ and v- (differential stage) and the output is Vout. So I need to estimate the gain on Vout.

The model of the circuit is this one:

On LTspice I have made this one:

With this one the simulation failed saying: "Matrix is singular".
I do not understand where I am wrong. How can I fix this and estimate the center band gain?

Thank you so much!!


texts: How well do microcontrollers deal with unstable power supplies?

texts: Assuming the VCC voltage never goes below the minimum of the specific chip (1.8v for the ATmega48PV) or above the maximum, how well do microcontrollers deal with noise? Are they guaranteed not to malfunction? Does anything happen, apart from I guess ADC readings might get a bit funny and inputs and outputs fluctuate?


texts: How to find the values of capacitors required for Power Supply circuit

texts: In the below circuit, capacitors with several values are utilized (Eg: why 1000μF and 100μF capacitors are chosen). Could you please let me know how to identify the required values of the capacitors and the reason to have a electrolytic capacitor and a normal capacitor in parallel.


texts:
I am looking for IGBT module for motor drive..
Approx. 50A, 1200V rating.
7 Pack module, Including Inverter + Brake circuit + Built-in drivers

For this I have found a module and it's datasheet mention that its 'Intelligent Power Module' but there is no detail about it that how it is intelligent..

I mean does it possess any machine learning features in it or in what sense it is an intelligent power module compared to other non-intelligent ones.

If anyone has any know-how about this please share your thoughts.

I am not writing the name of the company because it will violate the forum rules.

Here is the link to datasheet: https://pdf.direnc.net/upload/7mbp50rj120-datasheet.pdf

IPM = Intelligent Power Module


texts: Why the point of a ramp function where its derivative doesn't exist is not taken into account?

texts:
In a caltech course on physics by prof. Goldstein it was mentioned that in the apex point of a triangular-shaped (2D pyramid-shaped) function its derivative doesn't exist as there are no points in the vicinity of this point to take approximation from for a tangent. I was curious about how this applies to a triangular-shaped electronic ramp (capacitor) function. I learned tutorials by Neso Academy and others on differentiation of unit ramp and step functions and found out that while differentiating the ramp function through its apex point this discontinuity point where its derivative doesn't exist seems to not be taken into account and it is assumed that a unit ramp function has a continuous derivative. Whereas while differentiating a unit step function,
it is at least mentioned that there are 2 discontinuity points in this function.

I'm a beginner in electrical engineering and my main interest in this question is to track how an electronic ramp function (what is displayed on an oscilloscope from charging and discharging a capacitor, probably) is generated both mathematically and by electronics components. Can it be that these discontinuity points (and possible other math) in electronic functions be sort of irrelevant when applying an overall (intended) function of an electronic component or circuit?


texts: How to prevent internal MOSFET from being precgharged?

texts:
For MOSFET circuits:

simulate this circuit – Schematic created using CircuitLab

Say, how do we make sure that the gates M3, M4 are never pre-charged, so that they will always produce the right result at boot-up?

Though I realize this is a poor example as this one will still settle quickly to produce proper results.


texts: Op-Amp Input Bias Compensation for Multiple Feedback Filter

texts:
I'm adding an input bias current compensation network to the positive op-amp input of my band-pass multiple-feedback filter.

I'm setting the source impedance for the positive input pin equal to that of the negative pin.

Should I be matching the impedance at DC or at the frequency of interest?


texts: ORing, cascading and reverse polarity protection for power inputs

texts:
I'm trying to design a circuit that could be powered by an USB host OR by a wide voltage range power input. These are my requirements:

the USB rail (VUSB) should be obviously protected from the auxiliary power input (VIN)
VIN should have priority over VUSB
THRU could be used to power a sibling device by connecting THRU(unit1)->VIN(unit2)
voltage drops should be negligible (in particular when using VUSB)
VIN should offer polarity inversion protection
downstream voltage: 5VDC

I'm currently using two ideal diode controllers LM74700 (D1, D2) and a DC/DC stepdown converter LMZM23601V5SILR (U1), the circuit above synthesizes the power input stage. D3 is a clamp contained in a ST USB6B1.

So far, all the requirements are satisfied, with the exception of (5): by applying a reverse voltage to VIN/GND, I end up with a short.

This happens no matter whether I use the LM74700 or a diode, so I suspect I'm missing something really basic here. I added D3 because so far it's the only potential shunt on the upstream side of the circuit but I can't explain why is being engaged.

Does anybody have an explanation and a solution to fulfill all the reqs?

Any help is wildly appreciated!


texts:
I'm interested in building a really, really simple computer I've been designing using resistor transistor logic gates like these:

(when I can get away with it)

(when all else fails!)

I'll be using 2n3904 transistors since I have quite a few on hand. I'm having trouble deciding on the resistors I'll be using though. I want to use a 5V power supply and I've decided I would like to limit the current draw of my gates to about 1mA. So, I've chosen 5.1k ohm resistors for my collector resistors. But, I'm not quite sure what value I should use for my base resistors. My primary problem is that I really don't know how to estimate the fan-out I'll get with whatever choice of resistors I make.

So what value would be best for my base resistors, and how do I at least estimate the fan-out of these types of gates?


texts: SPI Flash memory programming with small buffer(uC memory)

texts:
I have AVR(or any, doesn't matter) microcontroller and 1 Megabyte SPI flash IC that I want to write to, I can do it already, have no problems with communication between these two.
But so far I write to chip directly from microcontroller, basically I write data to the uC and then I write it to the flash with uC. Microcontrollers do not have big memory inside them, so this method is only good for very small data.
What should I do if I want for example write 1 Mb of data(from PC)?
I mean I have ideas how to do it with some kind of USART or with FTDI chip, but I wonder what is the right/efficient way of doing it?


texts: How much time does it take for a switch to go from on to off?

texts: The equation for the voltage across an inductor is  v = L di/dt. When a switch changes the circuit from closed to open, it changes the current very quickly. My question is how would one know exactly how much time this takes, since you need an accurate answer to calculate the voltage that will be induced.


texts: Cable Splitter Loss and Impedance Matching

texts:
From my memory, cable splitters (such as for splitting a cable tv coax cable into two televisions) provide impedance matching to prevent signal reflections, etc.

If one 50 Ohm line is split into two 50 Ohm lines, the two will appear as a single 25 Ohm line (two 50 Ohm lines in parallel).  The splitter, therefor, will include 25 Ohm impedance in series with the incoming line.  Half the incoming power is dissapated in this impedance and the other half is split between the two cables, so there is -6dB loss on each line.

Yet... recently looking at splitters I've noticed some for sale advertising -3.5 dB attenuation on each line.

How is this possible without impedance matching issues?


texts:
Is it possible to use AVR PWM outputs and ISR interrupts at the same time?
I've got a project I'm trying to do on an ATMega328P and I need 3 PWM outputs but ALSO need to be able to use ISR interrupts from two different timers to do some other multiplexing and button handling (oh yeah, also need to use INT0 and INT1 external interrupts).

Is there a way to do both?

Update for clarification: Here's the full setup. I have 3 RGB LEDs for which I need PWM for each of their channels. This PWM can run at the same frequency but needs independent duty cycles for each channel so that I can create any color I need. Since the ATMega328P doesn't have 9 independent PWMs I need to fake it. So my plan was to use multiplex the PWM. Basically, set PWM for RGB1, switch to RGB2, and then RGB3 all at > 400 Hz. That way I only need 3 PWM channels on the chip and can just toggle which LED is being grounded (they are common cathode).
So, I need an ISR interrupt to handle the multiplexing itself and then I usually use a lower frequency (~ 100 Hz) ISR interrupt to handle button presses (basically my way of doing debouncing, I find it quite effective). So, as you can see, I need 3 PWM channels and 2 ISRs.


texts: A very basic question about PLC field input switches

texts:
Below shows two simple ladder logic examples written for a PLC:

As far as I understand, the -| |- and -|/|- above are the symbols we write for the PLC not the actual input switches.

But we also need to wire actual switches to inputs as field inputs. Is there any convention or good practice to wire NO switch in case (a) and NC switch for case (b)?


texts: Very long distance analog audio transmission over cable

texts:
Summary: I want to transmit an audio signal (300Hz-3kHz) without modulation over a 10 km cable.
I don't know how to.
I have looked for a similar post and couldn't find any I hope I am not creating a duplicate post.
I am an electronics and communications student and also a caver.
This summer in a cave I went, the communication system didn't work properly.  I said to myself maybe I can make one that works better. The current system was a commercial intercom board fitted into a waterproof box. I suspect it performed poorly because it was designed for much shorter distances (and due to budget limitations it is very likely to be a cheap one.)
This particular cave is 1200m deep and the cable length is probably 6-7 km.
I want to design an intercom that could work reliably for 10 km.
I am having difficulties in analog audio transmission. I haven't taken analog electronics class yet. I could wait until I take it next semester but I am trying to make at least a version1 by the summer (in summer there is an expedition to the aforementioned cave.) I have kind of figured out the ringing circuitry etc. I need to figure out audio transmission circuitry.
My budget is limited, that is why I want to avoid modulating the signal which (might) increase the overall cost.
The cabling in the cave has approximately 100ohm/km and 120nF/km. The cables have no shielding, but there isn't much electromagnetic noise in caves.
So far I am thinking of driving the speaker using an IC like the LM386. I was thinking of amplifying the microphone output to around 5-6V and then reducing it to smaller than 0.4V (LM386 max input 0.4V) at the receiver side, nd use a some sort of common emitter or common collector amplifier (though there isn't much reasoning behind this.)
I haven't made much progress. My questions are:

If you were to do it how would you do it ?
What are the things I should consider regarding the 10 km cable ?
Is there a particular type of amplifier circuit for this type of application (perhaps an amplifier which doesn't get affected by the output impedance very much?)
Does it make sense to amplify the microphone output to 5-6V then reduce it at the receiver side? If it does or doesn't what are the reasons behind it?
How should I pick parts for amplifier (transistors, etc,) what should I consider for device specifications?

If you can guide me by recommending sources or giving keywords so I can research I would be very happy.
Edit: I forget to mention that there will be multiple nodes in parallel. Transmitter will work in push-to-talk fashion and all nodes can listen to it simultaneously given they are in receive mode not standby mode. Privacy is not needed.


texts:
I need to buffer an audio signal (feeding into a variable input impedance), and make it mutable with a digital control.  The best thing I can think of is an op-amp (maybe TS971? 3×2 mm SOT23) feeding into an analog switch, like NLAS4599 (3×3 mm TSOP-6), but this requires several external components (example circuits).

Anyone know of anything better?  A tiny IC that acts as both a unity-gain buffer and a digitally-controlled mute?  Supplies are 4.5 V and ground, signal is biased to half that, and the mute and unmute transitions should be pop-free.


texts: What is the purpose of the following configuration of diodes on an RF line?

texts:
I've been told that these are disconnect diodes. However, I am unsure as to what purpose they serve. They are used on the line that sends a signal to a piezoelectric, the return signal from the piezoelectric returns on the same path but has a RX/TX switch that doesn't allow the initial signal in.

simulate this circuit – Schematic created using CircuitLab


texts: How does a motor perform when it is given a load greater than its rated ability?

texts:
I have a 24V motor which is rated output of 250W at 2750 rpm (I calculated torque to be .87 Nm).
If I have a wheel which needs 1 Nm of torque to retain a speed of 2750 rpm, I assume that the motor will have a lower rpm. However, will the motor voltage also be lower?

In the case of my wheel, will the power output be greater or less than 250W (how so)? I am new to motors and am trying to figure out their behaviors for a project.
Any help would be appreciated. Thank you.


texts:
What is the official name again for the small black trimming 'border'/'mask' around the four edges of a display?

I just forgot the official name.. and google turns up results about a wrong display ratio or to small display setting, which is not what I'm after.

As one can see on the following picture the image (desktop) is to big and gets 'cropped' by this 'border', before reaching the edge of the display's case.

Here is another image, where I put a circle around a piece of this 'border':

and another (burned in, over 3 years, cool right?) bare tube:

Update 1:
Thanks to DeanB's answer, a close-up picture showing that this 'border' is part of a shadow mask:

Update 2:
Upon further research on DeanB's answer, the term 'shadow mask skirt' seems most appropriate (according to a multitude of patents, if I interpret their accompanying texts correct, but please don't hesitate to comment/answer/correct this if I should be wrong).

Update 3:
I have added 2 extra images.
According to Richman's answer, this border is a separate border, called 'oversan skirt' and not related to the shadow-mask.
I might have been been to hasty to accept an answer (because the shadow-mask detail image made sense), but Richman seems to have a point to, since different types (crt/trinitron/diamondtron) of tubes have this edge/border, so I'm un-accepting DeanB's answer for now.

For extra clarification, I'll reformulate my question to: Complete the following sentence:
"adjust the width/height/over-scan until the image touches the edge of the ????"


texts: Help confirming probable dead flyback diode

texts:
I'm a beginner in electronics and not really my field, but I have a dead network switch (Unifi US-24-250W) which, from what I found, tends to have defective PSUs.
The PSU on mine seems to be working though, the led on it is on and all the rails (24v and 48v for POE on secondary board, and main board connector) are bringing the right voltage. Everything else, from the status led, to all the port leds, which are supposed to do a pattern when turning on, are dead.

No obvious signs of what could be the culprit, no burn markings or blown caps. The only thing I found is an inductor, near the main processor, that gets hot enough to be uncomfortable to touch rather quickly. Looking on the internet I found about flyback diodes and it seems that a diode is shorted near it. I can't identify the diode but I think is probably something like this: https://www.diodes.com/assets/Datasheets/ds13004.pdf

The markings on it are:

LT7A30
B260A

and I wasn't able to find the exact specs online. Here is a picture, sorry if it's not very readable

It's just under the middle of the picture, what's on the left is the main processor with its heatsink. I have not desoldered it yet because I don't have a replacement on hand, but in the upper section of the board you can see an identical inductor that doesn't get nearly as hot, and a resistor that doesn't look shorted both ways with the multimeter.

Could this be the cause of the issue? There is a slight coil whine from another part of the board which I wasn't really able to identify but nothing hot nor blown there. Can add pictures if required, the board is the same as in https://youtu.be/0_t1-uP4Q8Y?t=56 but in the video the PSU was at fault

EDIT:

U103, the IC near the probably-dead diode is an AEOSMD with markings:

Z1212AI
ZA7S18

Here is the datasheet


texts: High voltage AC-AC or DC-DC buck conversion

texts:
I have a schematic for an amplifier which if supplied a lower voltage will still work as a low-wattage amplifier. In the original circuit this is achieved using a 3-tap transformer:

I would like to "emulate" that 15W/7W switch using some buck conversion circuit.

The high tap giving 238VAC and the lower 173VAC. I have a transformer which gives me 238VAC, and I want to optionally "regulate" that voltage into 173VAC.

I tried searching for buck-converters but there seem to be none in this voltage category.
I thought about using a resistor network as efficiency is not a concern, but as the amplifier can't be treated as resistive that doesn't seem right.

How could I convert 238VAC to 173VAC or DC equivalent 314VDC to 229VDC?

If possible I'd prefer a cheap and simple solution over an efficient one.


texts: Can I use a supercapacitor (like Maxwell boostCAP 3000F) on a coilgun?

texts:
Can someone tell me if I can use a supercapacitor (like Maxwell boostCAP 3000F) on a coilgun?
I want to obtain a very intense magnetic field for a project, and I'm not sure what capacitors should I use


texts: possible CMOS techniques for altering the pulsewidth and phase shifting of a pair of complementary squarewave signals

texts:
My question is very simple in terms of input and output required. Following illustrations are for input and output:

input signals are a pair of complementary signals operating under 1MHz of speed. The way I though I could implement this was to reduce the pulse width of both signals, then shift them in time to produce the output as illustrated. What are the possible ways of implementing such CMOS block to produce that pair of output required, given the pair of input given as illustrated above? What essentially I need is that to not to let both inputs be ON at the same time. Any guidance is appreciated.


texts: What is the impedance of this unusual (magnetically coupled) circuit?

texts:
Inductors X1 and X2 are magnetically coupled

M = 20 [Ohm]
X1 = 20 [Ohm]
X2 = 30 [Ohm]

I am not sure how to interpret short circuit. Is the circuit impedance given by the equation:

_Z = R1 + jX1 + j2X4 + _Z1 ?


texts: Active region in BJT in a Common emitter configuration

texts:
In BJT for working in active region  for a common emitter configuration emitter and base should be in forward bias and base and collector should be in reverse bias. But in case of voltage we say that base-collector voltage should be less than 0.4V.

But if V(base)-V(collector)=0.1 (suppose) then base-collector junction will be in forward bias that means it will enter into saturation mode. But book says it will remain in active mode. How is it possible?


texts:
This lecture (page 59) shows how chooper amplifier works.

What I am confused is about the signal m2(t). It is delayed a time Δt. What is the purpose of this delay and how it effects the output Vout?

Thank you.


texts: How do I run two Arduino sketches at once?

texts:
I have got two stepper motors that I want to drive at the same time using an Arduino. They both work with 2 separate DRV8825 stepper drivers that are connected to the Arduino. I can get them both to work at different times with the code but want to merge the code so that they both do different things at the same time?

Is this possible to do?


texts: Can the following conditional assignment be done on a verilog localparam

texts:
parameter enum_e TYPE = VAL_0;
localparam type INTERNAL_TYPE = (TYPE==VAL0) ? struct_a : struct_b;

Thanks


texts: I have the MAX II EPM240 CPLD Minimal Development Board which has an on-board 50 MHz oscillator. According to the "EPM240MAINBOARD Schematic Diagram" file, the output of the oscillator goes to PIN 63, but there is no PIN 63 on the board. How do I use it? What modifications should I make to my VHDL file to enable it? Thanks.


texts: Role of input resistance in LM384 Audio Power Amplifier

texts:
let's consider the LM384 Audio Power Amplifier (here the datasheet)

Can you explain me why is there the 150k resistance? It lowers the device input impedance, which is not good for a voltage amplifier.


texts: Is it possible to attach extra text labels to components in Altium PCB?

texts:
I recently migrated from old Orcad to Altium, and so I often run into things that work differently.
One of these things is adding extra text labels to a component in the pcb editor.
A good example is a board with multiple onboard switches. You'd want a label indicating what each switch is for and also labels for each position of the switch. In orcad this was easy. When attached, the labels would move along with the component when that was repositioned accross the pcb.
Is this possbile in Altium? I could think of using the comment property, but then that would mess up the bomdoc.


texts: How adding a capacitor reduces the signal gain to 1 in an op-amp?

texts: Here I can't understand how adding a capacitor reduces the signal gain to 1?


texts:
Bit of a noob question but i'm having trouble understanding rs-232.

I'm sending data out over serial on an Atmel XMEGAA1U chip located on an Atmel XMEGA Xplained pro broad.

If i send binary 0000 0001, what is received at the other end (seen through a protocol analyzer) is 1111 1110.

From what i understand (google) this is normal as rs-232 inverts the logic.

What i don't know is whether I have to accommodate this inversion and flip the logic so the receiving end can just read it raw or if its normally the job of the receiving party to do the inversion.

What the "Standard" case of sending rs-232?

My requirements are just to send data over rs-232 with no mention of doing any logic conversion.

Thanks


texts: Charging a lithium-ion battery with 5V but stopping at 4.2V

texts:
I just want to charge one lithium ion cell, but don't have the right equipment. I only hear it's possible to charge one if you use 4.2V, but that's only, because a higher voltage means higher current and therefor it could overheat and of course if you charge it for too long it will break it, because you are stressing the capacity.

But if I just make sure that it doesn't overheat and doesn't exceed it's rated capacity, what is the problem? Just limit the current with a resistor and wait till it reaches 4.2V?


texts: What does the CT (center tap) value mean in a transformer datasheet?

texts:
I came across this datasheet, and I am unsure what the CT portion means.

The datasheet does say that CT means center tap, but specifically in the image below what does the "10k CT" betweeen primary and secondary mean ?


texts:
I have read a lot about off grid solar systems. Most of the reasons I have seen to not directly attach PV panels to an inverter without a battery are:

Under voltage when not enough sunlight.
Pulling to much current due to the power curve from pv panels (Ohm's law) resulting in under voltage.
Over voltage from PV panels exceeding the maximum voltage for an inverter.
Under voltage from burst when starting an appliance

My use case: I want a long shelf life solar generator to use for camping or in case of a grid failure. Where I live, the majority of the time it is sunny. So if there were a storm that knocked out the grid, its more likely to be sunny faster than the grid to be repaired. I want to use it to run charge power tool batteries, run laptops, etc.

So here is what I have done

This takes 2 12V 100W PV panels. They go through a voltage regulator which regulates the voltage to 12V or less. A 1000V 10A diode on the positive output to prevent current from heading back into the regulator if one of the panels  were blocked.

The outputs are wired together in parallel. It goes through a 2 farad capacitor.

and into an inverter.

The inverter has low voltage protection built in.

Questions

Anything wrong with this setup?
Anything I am not protecting against?


texts: Altium Designer update nets in SchDoc from PcbDoc

texts: I have an Altium Designer project with a PcbDoc and a SchDoc file. For some reason a few nets (connections) in PcbDoc are not present in SchDoc. Can I update SchDoc from PcbDoc so that schematic connections (wires) would be added automatically?


texts:
Designing a PCB in Eagle, and I have mysterious areas that throw 'clearance' and 'width' errors. I don't know where they come from, and I have been unable to move, or click on them to see why they are present.
Has anybody seen this problem before, or know what may be causing it?

The image shows an example area that is throwing an error. The areas are in the 'top layer', but are shown as red hashed surfaces, as opposed to solid.


texts:
I have a GFI circuit that's part of an EVSE (electric car charger) that is known to work.

What I need to do is be able to support testing for residual current on two pairs of conductors simultaneously.

I could run all four conductors through the coil, but they don't fit (for the purpose of this question, please do not simply suggest using a larger coil. That's not the point).

I could duplicate the circuit completely and use two coils, but that seems wasteful.

What I'd like to propose for discussion is wiring two GFI coils either in series or parallel, with the idea that a residual current in either coil would be fed into the amplifier and the rest of the GFI coil (see this application note for the schematic of the GFI in question).


texts: High voltage voltage controlled linear variable resistor

texts:
I have some high voltage (300v+) analog circuits that I want to control digitally which requires the use of a voltage controlled linear resistor that can withstand the high voltages. I don't expect the current levels to be that high.
I originally settled on LDR optocouplers but it turns out they can't handle big voltages so that leaves me with transistor or diode optocouplers.
As far as I understand it, photodiodes are light controlled zeners and phototransistors are light controlled transistors.
Which one should I choose for a high voltage linear variable resistor meant for a voltage divider?
Here is an example of how I would use the variable resistor


texts: Can we connect a DAQ to a micro-controller via a CAN bus?

texts:
I want to establish communication between an Arduino to a DAQ that I am using from DEWESOFT called the Dewe 43-A. The DAQ has 2 CAN bus ports according to its specs, and I was wondering if I can connect it to an Arduino using them via a CAN bus, or is there another way I can do so?

DAQ user manual: https://d36j349d8rqm96.cloudfront.net/3/6/DEWE-43_user%20manual.pdf


texts: How was ceiling fan speed controlled before the invention (or availability) of Triac?

texts:
I am interested to know about the circuit diagram of the ceiling fan regulators of the old days (when Triacs were not available). I have searched on google but all of the results were related to SCR. I heard that they used resistors but never got the circuit diagram.

I also need to know how much power was saved if the speed was reduced in those old regulators.


texts: Finding \$\small K\$ for a given \$\small\zeta\$ value when \$\omega_n\$ (frequency) is not given

texts:
Here \$\omega_n\$ (frequency) is not given.
Then upon plotting the Root Locus, how will we find \$\small K\$ at  \$\small\zeta = 0.5\$ if we're not using a graph sheet and want to find everything mathematically?


texts: I bought the Raspberry Pi cobbler kit a while ago, and I needed to solder a part together. The local hardware store (Useless ACE) only has a specific solder, which has just Sn, a diameter of 1.0mm and 2.0% Flux. I'm unsure if this is suited for the job; since the wiki page for solder says that Sn only solder is used in food processing equipment.


texts:
I would like to add an offset to a signal to send it on a differential ADC. But i want to be able to control the value of this offset with a PWM.
My sensor has a bandwidth of [1-100Hz] and i only have a 0-5V supply.

It works well with offset of 2.5V / 2V / 1V but for 0.512V i have an offset of 4V instead at output. And i don't understand why.

The OP-Amp use is a TL072, maybe it's a limit of that Op-Amp?

If you guys have an idea about how i can fix that or which Op-Amp should i use or an another way to doing that i'll like to hear that !

Thank you

File:

https://www.catupload.com/download/c5e9aaaa13797a98368cb01dce96e3f5.html

Schematic V2 :


texts: Memory timing values for microprocessor (8086)

texts:
There is something vague with the memory timing operation of 8086 microprocessor as I read from many sources. There is a TAVDV which is the time from when a valid address goes on the bus until a valid data appears on the bus (in the read cycle). Have a look at this book (page 58).

To calculate that (the figure on page 59), it assumes 3 clock cycles as a whole and then subtract two redundant terms. One is the TCLAV which means the time from clock to when valid address is on the bus and the other term is TDVCL which means the time when valid data is on the bus until the edge of the clock.

The idea is pretty simple if you look at those pages. The problem is that the calculation of TDVCL seems to be wrong. Why??

The clock period of 8086 (5 MHz) is 200ns. Since the duty cycle is 30%, that means 133ns for low and 66ns for high is assumed. Therefore,

TCLAV = ONE_PERIOD - Tsetup - T_ONE

I don't know the Tsetup but 200-66=133 and assuming an arbitrary value for Tsetup, we reach 110ns for TAVCL (as stated in the book).

Now, the book says TDVCL is 30ns. How that is calculated? Data lines must hold valid values according to the Tsetup. Therefore, in my opinion, TDVCL is absolutely greater than 66ns (which is the time for the clock to be high).

Can someone explain how that is calculated?

I paste the text and figure here


texts: Is it ok to put GND and VDD pours below IC (AS7265x)

texts:
I am designing a PCB to use with the AS7265x sensors. The datasheet states, on page 51:

  In order to prevent interference, avoid trace routing
  feedthroughs with exposure directly under the AS7265x
  devices.

Would it be fine to use a 4-layer PCB with a middle layer for a GND pour and another with VDD?
I would expect the pours to shield the ICs from any routes traced on the bottom layer (ICs on top).

Datasheet: https://ams.com/documents/20143/36005/AS7265x_DS000612_1-00.pdf/08051c8a-a7f6-6231-7993-2d3fe0bf38b8


texts:
Sorry if this question may be stupid but what's the difference between ideal and non ideal diodes? When the question says "Assume ideal diode with VD = 0.7 V" and when another says "Assume non-ideal diode with VD = 0.7 V" how will the solution differ?

(New to electronics....)


texts: Is it bad practice to place a bypass capacitor under its respective component?

texts:
I am designing a double layer board and in my layout I am running into problems.
I want to keep the board as small as possible, but I should also be able to assemble it per hand. I made all my resistors and ceramic capacitors of 0805 of size.
My problem is that I am running out of space with these dimensions for possible routing on the top layer.
Since the bypass capacitors need to have a low impedance path to the component I was thinking of placing these bypass capacitors directly under an IC to save space. Wouldn't that potentially introduce a parasitic element and disrupt the working of the chip? I have no idea. Any share of expertise on the matter would be appreciated.


texts: SPICE how to assign a variable voltage generator for receiving antenna

texts:
I would like to do an AC analysis, noise analysis and signal to noise simulations using TINA TI - LT spice is OK

How do I assign a variable voltage with parameters to an AC voltage source in SPICE? If the voltage output of an receiving antenna increases with frequency that is

~ V = 2*piNA*f. Parameters are:

N - number of turns

A - area of the loop

f - frequency

Thanks.


texts: How do I add support for PIC12LF1822 to gputils

texts:
I've used the PIC assembler and tool kit from gputils with success before, but I noticed that they're lacking support for my new pic12lf1822 chips. How do I go about getting it supported?

After checking out their source code I couldn't find any useful information other than lots of existing .inc and .lkr files which seems to be taken from MPASM. As I don't have a Windows box I can't download MPASM and use their files.


texts:
I am using the L293D to run two motors, and am controlling it via an ATmega328.

I am a bit confused about how grounding works. I was following this tutorial, and searched this question a lot, but am not satisfied. Essentially, notice how pins 4, 5, 12, and 13 are all connected to ground? And the two enable pins must be connected to +5V. Well, what if my micrcontroller is being powered by a completely separate power source from the motors, yet I am drawing +5V from the MCU for the pins which require +5V on the L293. Which ground do I use for pins 4, 5, 12, and 13? If I use the MCU's ground, then what would complete the circuit for the motors? And if I use the motor's power supply ground for those four pins, then what what complete the circuit for the enable pins?

Basically, I am confused about how to ground the L293 chip, since I require input from both the MCU's power source, as well as from the motor driver's power source (at 12V), yet the datasheet does not seem to indicate separate grounds.


texts: Circuit diagram of the Full Order Observer

texts:
I am a novice in the field of control system and electronics per se.

I am trying to implement the Full-order observer in an electrical circuit made of R, C and Op-amps.

I understand the block diagram, but I am unsure of how the circuit will look like.

The block diagram is as follows:

r is a voltage signal.

Any kind of help will be useful.

N.B. As I am at the early phase of learning, providing links to resources while you answer the question will be a big help.

Thank you.


texts:
A simple question about ClassAB common source amplifier. There are two circuits which I have attached with this question, the one on the left is a standard cross coupled circuit which I have taken from CMOS Analog Circuit design by Allen & Holberg.

On the picture to the right I replaced transistors M4 and M3 with the opposite counterpart. Vb1 and Vb2 are bias voltages.
My analysis:
For the circuit on the left: As Vin increases, M1 will try to push more current,hence source voltage of M1 will rise (or fall?). I am considering that it will rise since the drain voltage of M6 must rise to accomodate more current. This will in turn increase the |Vgs| of M3 and hence the overdrive. The Vds of M3 should remain constant hence the drain voltage (Vgs) of M6 should rise which will cause M7 to sink current. The same analysis for M5, M4, M8 and M2 when Vin decreases.
For the circuit on the right: As Vin increases, M1 will try to push more current,hence source voltage of M1 will rise. Since Vb2 is constant, and increase in Vds or Vgs of M6 will cause M3 to go into cutoff. Hence it wouldnt work.
Now as for my questions:

For the circuit to the left or right, why should the source voltage of M1 rise when Vin increases? Shouldnt it decrease for M1 to push more current? Since the drain of M1 is constant, the only voltage that has to change is the source voltage of M1 such that the Vgs of M1 increases. If it increases then why does it increase?

Circuit to the right: Is my analysis of the fact that M3 will go into cut-off and that is why it wont work, correct?

Any help will be appreciated, thank you!


texts:
I am trying to measure the magnetic field strength of a pancake (flat) coil. I know the turns, inner radius, current, and frequency from an AC input and am trying to measure the magnetic flux so I can use faraday's law to measure EMF output in a different coil. What equation/formula would I use to measure flux/field strength.

Thanks.


texts:
I have an entry gate pilot operating on 12v. I would like to connect it to my esp8266 (3.3v) to control it over the WiFi. I would like to use 12v power line which I already have.
The components which I have at home are couple of 2N2222 transistors and some relay modules (5v).

I have a two problems here:
1. How to power esp chip? Buy some 12v to 3.3v step down converter or I could use 2N2222 somehow?
2. How to switch 12v using 3.3v logic? I know that I could use a relay, but they are operating on 5v logic and I would like to avoid 3 different voltage levels in this circuit.

Of course I could buy some extra components but using what I already have would be nice.


texts: Modeling inductance in series with drain of source follower

texts:
How can I model the effect of an (on the order of 1 µH) inductance on the drain of a source follower?

The circuit in question is an electronic load, conceptually this (compensation, gate drive, etc. not shown for clarity):

Motivation

I'm refining the design described in this earlier question of mine. It turns out the stability of the op amp circuit is very sensitive to inductance between the power source under test and the load, typically introduced by the leads used to connect the two.

Based on what adding \$L_{src}\$ to the LTspice simulation does to the loop gain, it looks like the inductance interacts with the net MOSFET drain-to-source capacitance to form an LRC circuit that adds a pair of poles at around 1-2 MHz. The position of the double pole moves depending on the MOSFET and L value used, but their position also depends on the operating conditions because the capacitance of the MOSFET changes significantly with \$V_{DS}\$ (lower \$V_{DS}\$ => higher capacitance).

In any case, I'd like to derive a symbolic expression that characterizes this vertical branch of the circuit from Load_IN+ through the MOSFET to ground, in such a way as to also have symbolic expressions for the poles (and perhaps any zeroes) in terms of L, C, and R. So maybe something of the form:

$$ A \frac{\tau_z s + 1}{s^2 + 2\zeta s + \omega_0^2} $$

What I'm thinking so far

I'm thinking the first step is choosing the right equivalent circuit, which is where I encounter the first conundrum.

The small signal models I've encountered use a voltage controlled current source; this is the simplest form, neglecting all capacitances and a few other details. The one I would end up using would include at least the parasitic MOSFET capacitances:

My conundrum is a reluctance to place an inductor in series with an ideal current source, which in the ideal case causes an infinite voltage to appear across the inductor on a step current change.

So I'm thinking there are two possible ways to go:

Replace the voltage-controlled current source (VCCS) with a voltage-controlled resistor.
Leave it the way it is, the current source will draw current from the MOSFET capacitances during current transitions, softening the \$di/dt\$ waveform. Also, as long as the transitions are not super fast, the \$di/dt\$ induced voltage across the inductor will remain low enough to keep the MOSFET in its saturation region, and the current source will be an faithful model.

Just doing some thumbnail calculations, the e-load needs to provide a zero-overshoot (say \$\zeta=0.5\$) 0 - 5 A current step down to at least 3 V source (to test 3.3 V supplies) and 1.5 would be better. And, I was thinking a fixed rise time of about 1 µs (i.e. not building in adjustable slew rate). For a series inductance of 1 µH, that seems like it would mean a \$di/dt\$ of 5 A/µs, producing 5 V across \$L_{src}\$ which would be greater than the DUT supply voltage. So that leads me to the next option:
I need two analyses, one for the usual case of say \$V_{supply} > 10V\$ and another for low voltages.

Can someone with more experience with this sort of thing help me get to the next step?


texts:
I've Googled this very hard, and I'm not coming up with any good answers. This question seems very simple: Are there ceiling lights/lamps in the market that have a 14-gauge wire for the black/white/ground wires that supply it?
I find the frayed, cheap 18-gauge wires that seem to dominate the market to be difficult to work with. They fall out of the nuts when you try to jam them into the electrical boxes. I would gladly pay more money for a fixture that has 14-gauge wires.
If not, is there an adapter that I can put the 18-gauge black/white/ground into, and then shove in the 14- or 12-gauge supply/return wires?
This may seem like a noob question, but Google isn't giving me any quality hits (I'm just getting stuff like "What Gauge Wire Should I Use for Lights and Outlets?").


texts: How to wire up optocoupler for digitally controlled UV (under voltage) input protection?

texts:
What I am trying to build is an under voltage input protection.
It will always limit the voltage flowing into the output end to the microcontroller to be 3.3V, but when the input goes below 380V, it will give value less than 3.3V to the microcontroller, telling it there's something wrong.

In my optocoupler, I don't know why, the output only follows the activation voltage, and doesn't behave as I would like it to be. Please help!

Well, i have a voltage divider there that gives 4.67V, so, any input V DC that gives above 3.3, will output 3.3, and anything lower than 3.3 (after voltage divider), it will reflect it, wouldn't it ? according to the simulation, it does do so.. the huge question, or rather, the question is the optocoupler wiring.. whatever the voltage goes into the LED side, it always gives the activation voltage (the one goes to the collector) :(


texts: I'm working on a project where I need to drive 20 motors with no speed control just running the motors. But I don't have 20 available pins to connect to all the drivers directly. Is it okay to multiplex these drivers with pulling all the GNDs HIGH and all the input pins LOW and then reversing the pins of the needed motor eg. I have to run the row 3 column 4 motor I put the row 3 LOW and column 4 HIGH. Is it a preferred method of doing it or should I choose another method? Sorry for the bad diagram.


texts: Can I use a voltage divider circuit instead of a level shifter here?

texts:
I am trying to hook up an LCD module to my microcontroller, and was following this tutorial.

Notice that the three signal wires all go through a level shifter, which drops the voltage from 5V to the required 3.3V. I don't have a level shifter on hand, so I can't implement what the tutorial shows exactly. However, I do have a pile of resistors, and could easily make three separate voltage dividers for each signal wire. Would that work equally well, or are there scenarios where voltage dividers are not preferred (i.e. this one)?


texts: lowering current of a constant current driver

texts:
I have a constant current led driver which gives 180ma @24volts. But I need 120ma to drive a led strip at same volatge. Is there any way to lower the current from this driver? I tried shunting led driver with a 500ohm 1w resistor and managed to get 130ma but the resistor gets little hot. Is there any other solution?
Any help is appreciated.

Thanks
David


texts:
I am making a frequencygenerator, that will have sine, triangular and square output (choosen with a rotary switch) but first, I'm having a problem with setting the right frequency with components. I've came to this schematics, where:

-SIN ADJ is from datasheets
-DC freq ADJ has connection, that will have a selection switch as duty cycle = 0.5 or adjustable with double switch

What I don't understand here is, what should I connect to Tcap or what capacitors should I select to cover the whole range (0.1 to 300 kHz) and how should be FM bias and SWEEP connected?

The datasheet of ICL8038 is HERE

Thanks for all the help in advance!

EDIT:

How to use the SWEEP and FM Bias pins? What exactly does these pins do?