texts: What is the current when there are no resistors?

texts:
How come I always see videos with what seems like a random amount of mA flowing from a battery with a certain amount of voltage?

For example, what if a wire had 0.13 ohms resistance and a battery had 5V electrical difference. That would mean that 38 Amps should be the current (right?).

I=V/R
I=5V/0.13ohms
I=38A (about)

Okay, so I'm editing this now using internal resistance, of about 1ohm.

This gives about 4.5A, so is this correct?

Why are common schematics showing some amount of mA shouldn't it be something like what I've shown, or do they have hidden resistors?


texts: DC Chopper Drive for Brushed DC Separately Excited Motor

texts:
I have a 6 pulse SCR drive, driving a large (1000KW, 750VDC) DC Separately excited DC Motor. In a typical SCR drive, the power factor improves with speed, and if the drive is to be run at 50% speed for a long time, then this reduced power factor puts a strain on the AC Generators.

I can replace the SCR drive, with a DC Fed Chopper Drive, such that incoming AC is fully rectified by a 6 pulse Diode Bridge and appropriate capacitor(s) is used to form the DC link. Then this is connected to the DC motor, via an IGBT switch, which chops the DC at either positive or negative or both ends.
The same logic that determined, phase control angle for SCR shall now decide the Duty Cycle for the IGBT switch.

Will the above arrangement improve power factor? If Yes, what specific requirements need to be fulfilled in the control circuit, if any. If NO, why not.

My assumption here is that since the DC rectification is full wave, there is a higher chance that current drawn can be made sinusoidal. However, once the DC link capacitor charges up to the full DC voltage, any current draw will depend on the duty cycle of the PWM. I am trying to find out if there is any special consideration for this PWM, such that as far as possible, the current drawn from AC source remains in phase with the AC voltage. That would improve power factor, right?

Thanks and Best Regards,
Vishal Sapre


texts: Why doesn't current increases when the voltage is increased

texts:
When connecting two batteries in series the voltage is increased.
For example: Connecting two 5V batteries in series will produce 10V voltage but the current will be the same.

According to Ohm's Law V = IR the voltage is directly proportional to the current. Then why is the current not increases when voltage is increased?


texts: If a transistor only gives you a maximum current flow, what's the maximum voltage?

texts: In some data sheets of NPN transistors it only says "maximum collector - emitter current." But my question at what voltage is this current value given, because 1 ampere at 1 volt is somehow less energy than 1 ampere at 100 volts.


texts: What are the differences between function generator and oscillator? (Specific design)

texts:
I design the attached circuit:
75 MHz Sine wave that connected to R and C in parallel:

In the output, the amplitude of the sine wave is changing according to the C, more capacitance smaller amplitude of the sine wave.

When I tried that in the lab I got 2 results:
1. When I connected the function generator as the source I got the same results - higher C lower amplitude (of the sine wave in the output)
2. When I connected it to oscillator (http://www.farnell.com/datasheets/75480.pdf) I'm getting different results: the output is a sine wave, but if I make C higher the amplitude becomes lower until the sine wave (in the output) is "flipping" (kind of changing phase) and, if I keep raising the C higher, the sine wave in the output starts getting higher.

What are the differences between the two?
How can I make the oscillator work like the function generator in this case?


texts: Why should I have the wrong voltage value when I use another way to calculate it?

texts:
The question wants to know \$V_{XY}=V_{X}-V_{Y}=X-Y\$

simulate this circuit – Schematic created using CircuitLab

The solution said \$I=\frac{10}{15\text{k}\Omega+10\text{k}\Omega+5\text{k}\Omega+20\text{k}\Omega}=0.2\text{mA}\$,and \$V_{XY}=V_{X}-V_{Y}=(-0.2\text{mA} \times 20\text{k}\Omega)-(0.2\text{mA} \times 15\text{k}\Omega)=-7\text{V}\$,I understand its solution,but I have other thinking,and U think it should be right, but the answers are different.

My thinking:

\$I1=I2\$,that is,\$\frac{10-Y}{10\text{k}\Omega}=\frac{Y-0}{15\text{k}\Omega}\$,and we can know \$Y=6\$

\$I3=I4\$,that is,\$\frac{0-X}{20\text{k}\Omega}=\frac{X-(-10)}{5\text{k}\Omega}\$,and we can know \$X=-8\$

so \$V_{XY}=V_{X}-V_{Y}=X-Y=-8-6=-14\text{V}\$

Does anyone know where am I wrong?My answer is -14V,but the answer from the book is -7V.


texts: What is the gain of this capacitance measurement circuit?

texts:
To sense the capacitance value of a sensor, I found the following circuit.

My knowledge on analogue electronics isn't that great, so I'm not sure how I'd determine the gain of this circuit.

Vo is the output voltage I need, the peak value detector and Vdc can be ignored.

So what is the gain, Vo/Vs, in this circuit?


texts: Connection between PID, Pole placement and LQR

texts:
I am trying to control a wheeled inverted pendulum with a PID controller. I already designed a linear quadratic regulator (LQR) and a pole placement regulator (PPR). I would like to design a PID controller, but it seems almost impossible to tune the PID gains. I wanted to check if I could stabilize the system by using the solution that I obtained from the LQR/PPR.

Is there any method or reference that is linking the design of a PID controller to the solution obtained by a LQR or pole placement regulator?


texts:
I'm a new hardware design engineer. I have a few questions about high speed pcb design.

1) when I search high speed pcb design, I saw pcb routing like snake. What is this ?

2) When I draw a high speed way (like can-bus line), I used differential pair. Can ı use with only differential pair at all high speed line ? Or Should I do different things ? Like lenght matching.

3) How many MHZ after a line being high speed line?


texts:
Computer science & math major here.

I'm designing a linear power supply to introduce myself to electronics. To keep things cool and cheap, I am trying to limit the amount of power dissipated in the LDOs when delivering high currents (1 amp) at low voltage.

My plan is to use a relay (or maybe a pair of traics) to switch which tap of my center tapped transformer feeds my rectifier and filtering caps to reduce the voltage drop across my LDOs.

Is this a totally misguided idea and need I be concerned about transients caused by the change in current of the secondary coil of my transformer when I switch from the center tap (12 VAC) to the outer tap (24 VAC)?

I've read some articles and done some modeling of the behavior of a transformer feeding into a full-wave bridge rectifier and then into filtering cap as a pre regulator for my LDO (image not mine).

Because, as I understand it, kickback transients are proportional to the current flowing across the inductor; I've started to design an "interrupter" using an opto (to detect 0 points of the AC wave) and a couple of logic gates to force the transition to happen when the capacitors are supplying current. Is this enough precaution to protect my puny circuit from high voltage transformer transients?

Imgur link to pdf output from kicad for those interested of schematic without "interrupter".

Wolfram alpha output of "interrupter" logic also for those interested.
Where U is high when user needs to use the outer tap, O is the opto (high when AC is near 0v), and C is high when the outer tap is in use.

[edit 1] changed a word.


texts: Problems with input leakage current in a microcontroller

texts:
I'm trying to build a system in which a microcontroller receives (through one of its input pins) a logic 1 if a switch is pressed and a logic 0 if it's not. For that purpose, I want to implement a circuit like the following:

I understand that the 10k resistor is necessary for avoiding a short-circuit between the 3.3V and ground, what I haven't completely clear is why it must be 10k.

According the explanation I'm reading, that value is chosen doe to the microcontroller IIL and IIH (Input Leakage Current, right?) is 0.2 micro amps, and this is what I don't truly understand.

In the text I'm reading it's called the input current of the microcontroller input pin, and I'm assuming that it is something like a residual current that the microcontroller is delivering out (thorugh the input pint). Am I right?

If so, how is possible that that current exists if the circuit is openned? How can an INPUT pin deliver current to the outside?

Finally, if my assumptions are more or less correct, that means that what I need is to achieve a voltage between 0 and 0.8 V (considered logic 0 by the microcontroller according its datasheet).

So, since V = I * R, if I put a R of 10k, that means V = 2 microAmps * 10K ohms = 20 millivolts, which is between 0 and 0.8 so I will obtain a logic 0. Is this correct?

If so, as far as I understand, we could achieve the same goal with many different resistors, always if the generate a voltage between the input pin and the resistor which is between 0 and 0.8, right?


texts: Driving multiple loads with a single TRIAC and multiple optoisolators

texts:
I simulated this circuit in multisim.

It is working fine.
However, I am just curious to know if it is possible to drive multiple loads with multiple opto-isolators with single TRIAC? Something like this:

Sorry for the rough drawing. Is it understandable?
All loads are parallel to the TRIAC.

I am going to put arduino instead of that +3V.

Thanx.


texts:
I would like to hook up a piezoelectric sensor to my ATmega8 microcontroller via its ADC.

The reason being is that I would like to use the sensor as a force sensor. I noticed that the harder I press it, the higher a voltage it delivers (but for a very short time). This is expected behavior, of course.

What I am wondering is how I would connect it to the ADC. I mean, when I press it really hard, the piezo registers upward of 10 V. When I press it softly, it usually gives me around 1.3 V.

As I understand it, the micrcontroller cannot take anything more than 5V, or else I run the risk of damaging it. Is this correct? I mean, I am guessing the current coming out from the piezo is extremely small, though I don't know if that changes the situation.

Essentially, I would like to know if it is possible to hook up this piezoelectric sensor to my AVR microcontroller to take analog readings.


texts: Renewable based Electric vehicle charging station

texts: I have a solar plant generating 100kw, connected to a boost converter whose output is 500V,what should be my battery nominal voltage and Capacity(Ah) and what can be the maximum current the battery can allow?


texts:
I'm looking for a power supply filter for this mcu. In page 1789 and 1790 referred that lots of the power supply pins needs decoupling capacitor filtering. Some of those pins need an additional inductor for LC filtering.
The question is:

Why Cut-Off Frequency starts from few KHz (e.g. 10kHz) and not with value closest to Zero (0Hz)?
Why Frequency ends at few MHz (e.g. 10MHz) and not continues beyond of that boundary?


texts:
I would like to use more than one VL53L0X, laser distance sensor that works in the same time, next to another, and they have to measure slightly different distances.

Q: Is it possible to use an array of VL53L0X laser distance sensors without them interfering with one another?

VL53L0X datasheet


texts: Reducing the number of pins needed to read a 12-key keypad where the buttons are grounded?

texts:
Unfortunately, I'm not sure what the right question is; I'have a 12-key keypad. I wanted to utilise a matrix based approach, except that they all seem to be connected in such a way, that they're floating when not pressed; when you press one, it connects to ground. This seems to me as if it's prepared for a set-up with a pull-up resistor on the wire over to the MCU, and not a matrix-style reading, where I (if I understand correctly) sequentially pulse on the rows, and sequentially read the voltage on columns.

However, I don't have 12 spare pins on my MCU, so I'm wondering how to minimize the number of pins needed to read this 12-key keypad.

Are there any ICs that I might use? Any approaches?

If I recall correctly, the board it used to be connected to had several (de)multiplexers connected in cascade, but I couldn't figure out the way it worked. However, I'm pretty sure the keypad itself is wired like this (it has its own connector as it's on a separate board which I'd like to keep), and that makes me confused.


texts: Cannot program ATTiny85 fused for 32 kHz

texts:
Now, I know what you're thinking. I've been thinking it all night too.

Yes, I know that with the tiny fused for a 32 kHz crystal that I'll need the SPI clock to be 8 kHz or less. Even that, however, seems to not be working.

I started with a working board that had a 4 MHz crystal and divide-by-8 fusing. I first used a USBTiny to reset the fuses to the default using avrdude (62 DF FF). I then removed the crystal and its loading capacitors and tacked in a 32 kHz 12.5 pF crystal in its place. I then used the same USBTiny to set the fuses to E6 DF FF. And that's all she wrote.

With a scope, I can peek at the xtal pins and I can see 32 kHz. So I suspect the clock is running.

I knew that I'd be adding -B to the avrdude command line. Before I started all this, I experimented with various values of -B and a flash read. Sure enough, altering -B made the flash read happen faster or slower.

But I've tried adding -B values up to 250 (which I read on this page should result in a 4 kHz SPI clock). Nothing. I've tried using at least 6 different versions of the AVR-as-ISP-but-slowed-down concept with an Arduino Uno. None of them work. All of them work with an unmodified version of the device I started with (with its 4 MHz crystal and original fusing), so I'm confident the wiring is correct.

What else could it be?


texts: Designing an PCIe ethernet NIC with built in ethernet switch

texts:
I am trying to design a ethernet network card that will plug into a PCIe slot and have 2 etherenet ports visible to the user that are connected by a unmanaged layer 2 switch.

My architecture thought is to get a PCIe ethernet controller and connect that to a switch, and connect 2 ports of the switch to the output of the card.

Is there a better way to do this that would not involve having both the controller and switch IC?  I know I could have a 2 port controller and have a software ethernet bridge, but I don't want to put the load of that on the OS.

Additional Info:
I need gigabit speeds, but I don't think that should not have an effect on the architecture.


texts: Does short circuit always (in every electronic circuit) shunt the resistor that has both sides connected to the short circuit branch?

texts: I wanted to know if short link always (in every electronic circuit) shunt the resistor that has both sides connected to the short link branch


texts:
I am trying to set PLL as my system clock source upon startup of my microcontroller, STM32f103

I have commented all the defines in my system_stm32f10x.c

/* #define SYSCLK_FREQ_HSE    HSE_VALUE */
/* #define SYSCLK_FREQ_24MHz  24000000 */
/* #define SYSCLK_FREQ_36MHz  36000000 */
/* #define SYSCLK_FREQ_48MHz  48000000 */
/* #define SYSCLK_FREQ_56MHz  56000000 */
/*#define SYSCLK_FREQ_72MHz     72000000*/

So my system starts with hsi(8Mhz) as the clock source. This I have verified to be working just fine. However when I try to initialize pll to set it as the clock source, the PLL Ready flag never sets.

//on boot the system core clock is set
//HSI @ 8Mhz. Set this to PLL with PLL source HSI
//to get the max sysclock of 64mhz

//ensure hsi is ready
while(RCC_GetFlagStatus(RCC_FLAG_HSIRDY)!=SET);

RCC_PLLCmd(DISABLE);
RCC_PLLConfig(RCC_PLLSource_HSI_Div2, RCC_PLLMul_16);
RCC_PLLCmd(ENABLE);

printf("1");
//wait till pll ready
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY)!=SET);
printf("1");

//configure sysclk to use pll
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);

//after changing clocks ALWAYS call this function to update
//the system clock variables
SystemCoreClockUpdate();

When I debug my code, I only get '1' in my debug output window which means the pll ready flag never sets.I have tried with lower pll multiplication factor with same result.

Any idea what could be going wrong here?


texts: Communication between a USB/serial device and an AVR (atmega/Arduino) microcontroller

texts:
I have a device which provides a USB port. If I attach it to a Windows PC it is recognized as a "CP2103 USB to UART Bridge Controller". According to the device documentation, it should communicate in serial format at 38400bps.

I have to talk to this device with a atmega microcontroller.

Since the USB pinout is different from the serial UART of the uC, firstly I thought I would need a circuit to convert the signals.
I found the AVR-CDC project and put on a CDC-232 in order to convert USB (GND, D+, D-, VCC) to RS232 (TX, RX, GND):

To make it I used another atmega328 as uC, flashed with the specific hex, with a 16Mhz crystal instead of the 12Mhz one specified into the diagram.

Then I built another piece of circuit to convert the RS232 signal to TTL:

So the signal conversion should be USB -> RS232 -> TTL.

I programmed my uC to send some data to the device and I can follow the signal with the oscilloscope until it enter into the CDC-232, then I lose it. I have no output on pins 4 and 5 of the CDC-232 uC, where I should have a USB signal.

Is my overall approach right? Sould I go on debugging the CDC-232 part or there is something wrong elsewhere?


texts: Will copper pour help on my single-layer PCB?

texts:
I have a PCB which contains one 20x4 LCD, eighteen 12x12  mm push buttons, and three LEDs. This board is connected to an Arduino Mega through a 30 cm long ribbon cable. Now during testing, I found that sometimes the LCD goes blank. In my previous PCB I was not using a ground pour, but if I use a ground pour, will my system be more resilient to EMI noise?

I am working on other aspects as well, but I just want an expert opinion on this to use a ground pour or not on a single-layer PCB.

I am attaching both PCB pictures for clarification: one with, and one without a copper pour:

After reading through all suggestion I have following understanding in my head
1. Transfer VCC and ground lines near LCD interface line i.e. on right side

Remove jumper connections on each button lower two pins as they are trans versing copper pour making it less effective.

3.Increase distance between R1,R2 and R3

4.Increase space between LCD control lines and button lines at down right corner.

Add more ground lines( I am not sure about that but experts have suggested this)
Place connector on top instead of bottom as it will reduce track distance for lcd control and data lines which in turn will make it more immune to noise?

Please comment whether I am in right direction.  Two layer is not an option as here in my area they only make two sided pcb in big quantity otherwise its too expensive. Same is the case of china manufacturing


texts:
I'm planning to use an MCP4011-xxx/MC (DFN version).

This package has an exposed PAD. But nowhere in the datasheet, I can find the information if this exposed PAD should remain NC or tied to GND/VSS.

I used for other components DFN packages before and it was always mentioned, how the exposed PAD should be connected.

How the pad should be connected and where do I find this information?
Can I assume that when it's not mentioned the default is connected to GND?

Datasheet

Microchip website


texts: How can I solve this PCB problem in Altium?

texts:
I tried to change width size and also design rules wizard, but it didn't work. Can anyone help me?

The problem is small circles. They shouldn't be on the components and I tried to fix with design rules.


texts: Gain of an active filter without calculating the transfer function with two OP-AMP's

texts: I need to calculate the gain of the filter without explicitly calculating the transfer function, ie I have to replace the capacitors with an open circuit. The problem is that I've been trying to solve the problem but I do not know how to start. Thanks.


texts: Fan-In/Fan-Out - Circuit - Explain why this circuit does not work

texts:
Problem: Explain why this circuit does not work for Fan-In=1 and Fan-Out=3 for all logic gates(including the complex logic gate).

Firstly, I would say the Inverter Gate is fine because it does not violate the Fan-Out=3.
But I don't know what the problem is in the case of Fan-In=1.

Secondly, I would say that because x is routed to the 3 inputs of the complex logic that the Fan-In=3 thus it would overload the inverter thus making the gate not work properly.

Am I right?
Hope somebody can give me a lead and or help me.


texts:
I am making half adder circuit for my school project but I saw their datasheet and it says maximum supply volate is 5.25v and I have 9v battery, How do I use it if I want to test my circuit without burning ICS?
I watched this video to complete my project but he didn't specify the battery he used. Pls help
Video link -: https://youtu.be/rNG_KD1hfpc. Thank you
IC I used : Ic 7408(SN74LS08N) , IC 7432 (SN74LS32N), IC 7404 (SN74LS04N) . thank you


texts:
I am designing a PID regulator but experience difficulties in simulation. My design is:

I have chosen the value of the elements for:
Ki = 12ms, Kp = 5, Kd = 1.5ms

Here is the result I get:

What am I doing wrong?


texts: Constructing a transformer: how to limit the primary side current?

texts:
I am confused on how a transformer works. I know it uses a changing magnetic field to induce current into another coil that has a set turn ratio to achieve a specific voltage.

My question involves the current draw of a transformer. I understand that a wires resistance is very small and coiling it does not change its resistance. So how does the transformer not trip the fuse every time it's plugged in.

I have tried creating a primary coil before and have only had two results: I trip the fuse, or my coil starts on fire...

Could someone explain to me how I am able to make a coil not draw too much current?


texts: Why wifi can not act like a server and client at the same time?

texts:
According to my experiments, any wifi card can (naturally) connect to a access point as a client and act as a server (most of them in ad-hoc mode).

Why can not a wifi card behave as both a client and a server at the same time?

Is there a hardware restriction that can not be worked around by a software? Can't switching between the modes be an option if we accept performance impact?


texts: Do I have to use EXACTLY the same power cable

texts:
I've purchased some surround sound speakers but the jack plug is L shaped and won't fit through my speaker stand.
The power supply states it's a 18V 1.3a but I can't seem to find a power supply like that. Is there an alternative I can use??
Many thanks


texts: How can I tell if a MOSFET is enhancement-mode or depletion-mode?

texts:
Today, from ignorance I have fallen head-first into the world of MOSFET transistors. In my scramble to find some information on the MOSFET I will be using as a switch (HEXFET actually), I learned that MOSFETs in general come in two modes, enhancement mode, or depletion mode.

When I tried to find out which mode the IRF3710 was, from the datasheet, I found that it does not say (or maybe I need glasses). At this point I started searching to find how to tell the difference between the two modes. After some time I gathered that the schematic symbols differ:

Enhancement-mode MOSFET:

Depletion-mode MOSFET:

The difference being the highlighted part below.

Three separate lines means enhancement-mode (left) and one solid line means depletion mode (right).

So, my question: Is this the only way to tell which is which, or is there a quicker way to tell (by markings on the device maybe?). Also, are there symbols out there which use a different method to differentiate between them?

I am asking here for my own learning, but also for other people who might have the same experience as me. I did not find that much helpful info in my searching.


texts: Can I turn a 12V 5A (60W) supply into a 5V ~10A (50W)?

texts:
I am debating whether to get a cheap high current 12V power supply together with a voltage regulator or an expensive high current 5V power supply for my project. I need about 50W total at 5 volts, which I can do in the two ways listed.

I can get a 5V 10A power supply for about $24. I can get a 12V 5A power supply for about $10. None of them include shipping, they both have 5.5x2.1mm plugs, and are both from UK Amazon.

However, I already have a good 12V 6A (6A not 5A) power supply laying around, which I can use no problem. Can I turn one of these basically into a 5V 10A supply? It can be higher than 10A, but my concern is how much current I would lose in heat and conversion. How much would one of those regulators cost?


texts: Unclocked, edge-triggered version of RS flip-flop?

texts: Is there such a thing as an edge-triggered RS flip-flop? That is, one input would, on rising edge, set the output to 1, and the other input would, on rising edge, set the output to 0. Falling edges would be ignored. I feel like this must exist, but I don't know what it would be called.


texts:
I'm using an ICM7555 chip for a monostable/one-shot circuit.
https://www.renesas.com/sg/ja/document/dst/icm7555-icm7556-datasheet
In the figures, it shows a capacitor on pin 5 (control voltage). But it is listed as "optional". Does anyone know why this is optional? Does that mean we should include that cap as long as we're not applying a different (meaning, anything other than 2/3*VDD) voltage at that input?


texts: Can I swap a MLCC for a tantalum capacitor?

texts:
Can anyone tell me if this (RadioShack)
10uF 16V 20% Dipped Tantalum Capacitor

is a suitable replacement for (Mouser)
Multilayer Ceramic Capacitors MLCC - Leaded 10uF 6.3volts X5R 10% 5.0mm L/S ?


texts:
A motion sensor and a relay should be connected with an atmega328p. I soldered my circuit on a perfboard and have 5V power and ground rails on it.

Can I use the rail for the COM port of the ULN2803a or do I need to remove the VCC, jdVCC jumper on my relay and connect a separate power supply to it? And take connect the COM port to  that VCC?

It strikes me as a bit strange that  I would need that many power sources for such a simple project, including the socket for the lamp that should be controlled with the relay, I'd need 3 sockets for this project.

Also, am I under the correct impression, that the use of the ULN2803a inverts my logic? Without I switched the relay ON with LOW, now HIGH provides the ON state.

And on a side note, any suggestions on how to improve my schematics are welcome. I'm just starting out and I would image that my schematic probably isn't that well to read.

Regarding the diodes:

On the product pictures on my 8CH relay these are labeled D1-D8.


texts: Should internal signal layers of a PCB have a ground pour?

texts:
I see a lot of discussion about using copper pours on the outer layers of a multi-layer PCB, as well as a single continuous ground plane on a multi-layer board, but there isn't a lot of information out there about ground pours on the internal signal layers.

For example, take a standard 6-layer PCB stackup:

Signal
Prepreg
Ground Plane
Core
Signal
Prepreg
Signal
Core
Power Plane
Signal

Where the top internal signal layer looks like this:

This signal layer contains the high-speed signals (SQI, USB, and Ethernet), as well as some other low-speed digital traces (GPIO). Should this layer also have a ground pour? Would this help isolate the digital traces, or would it cause more interference/coupling?


texts: How to create pulses which are 10ns long and 15kV/ 80A amplitude?

texts:
I'm looking for an easy way to create short high voltage pulses.  These would be 10-100 ns in duration, 10-30 kV in amplitude (the load is complex but roughly similar to a 200 ohm resistive load).  The source can look like either a current source or voltage source during the pulse.  The load should (ideally) be shorted outside of the pulse.

It is easy to find adjustable high voltage generators to (for example) 30-50 kV DC, so the high voltage side of that is relatively easy.  But I have no idea how to switch 30 kV on (and especially off) in nanoseconds.  Triggered spark gap?

EDIT I'm surprised nobody has mentioned stacked MOSFETs (or IGBTs?) as a possible solution.  After doing a search I found a few references like this: Stacking power MOSFETs for use in high speed instrumentation.  I don't have any experience with this approach but solid state seems way more controllable.


texts: Why is a Zener diode in a crowbar configuration dropping the input voltage?

texts:
simulate this circuit – Schematic created using CircuitLab

I'm trying to hook up a Zener diode in order to add some measure of protection (fused "crowbar") to a circuit that includes a loop powered oxygen sensor with output read by a GHI Cobra ADC/Analog In. The idea is that if there was a short in the sensor that caused 12V on its output, the Zener with 4.7 V breakdown between the sensor output (and the ADC input) and ground would keep the 12V current away from the ADC long enough for the fuse to blow as the limit on the Cobra pin is 5V.

However, I find that when I put in the Zener diode it drops the voltage being read by the ADC (volt meter right now), e.g., from 4.38 volts to 3.98 volts. When I replace the Zener with a regular diode just to test, the voltage does not drop. What gives? Can a Zener be used for a "crowbar" so it doesn't change the voltage on the sensor output side? The Zener is installed with the ring towards the ADC side.  The electronics store said it has a 4.7V breakdown, but I'm not sure how to test that.


texts: Create a circuit with 3 identical light bulbs that all have different brightnesses

texts:
I'm learning about circuits in my physics class, and we've been given an assignment to create a circuit that can only use 3 identical light bulbs that should all have a different brightness. I've tried for hours to get this to work, but I've so far only found several ways to make it where one lightbulb has a different brightness but the other two are the same. I've tried many different combinations of parallel and series branches and haven't gotten anything to work so far. Any suggestions? Thank you! EDIT: Not glowing at all DOES count as a different brightness, but only as long as the current is still going through the bulb, i.e. it is not just a broken circuit.

simulate this circuit – Schematic created using CircuitLab

simulate this circuit

These are just a few of the things I've tried, I can't remember the other ones right now but they were basically variations of these.


texts: What is the impact of a lower TG for an RF Board?

texts:
I have a board that contains a WiFi module (2.4GHz). Does Tg have an effect on RF performance in any way ?
If the material can satisfy the other constraints, such as Dk, Df etc.. would the Tg be a factor in material selection for RF ?
I should note that this is a relatively high volume unit so it's extremely cost-sensitive.


texts: Cable Position Sensing for a winch motor

texts:
I have been asked to help with the design of a small (tiny) winch system intended for use in very harsh automotive road conditions.

This system is required to raise or lower an assembly with a total travel of about 18 inches.  My task is to come up with a method of setting the upper and lower limits.

One of the options that we have come up with is purely mechanical: the winch motor turns a threaded rod (all-thread) which has a traveler nut.  The nut hits a micro-switch at each end of the travel.  Upper and lower limits are set by sliding the micro-switches to the appropriate position at each end of the threaded rod.

Although this system should be reliable, it is both large (long) and hard to seal.  I'm trying to come up with something better.

Counting motor rotation is dead easy.  This gives me a way to control the total distance that the winch cable travels.  What I need is some method of coming up with an index point.

Suggestions gratefully accepted.


texts: How to prevent buck regulator chip from blowing up when using near maximum input voltage?

texts:
I need to step down 24V to 5V in one of my projects, so I used TPS54302DDCR (has a maximum input voltage of 28V) by TI and designed the circuit according to its datasheet and example schematic. However when it has been powered up, it will either work, or it will burst into flame. However I tried powering at 12V and it had no problem at all. So I wonder if it is because the input voltage rippled when powering up and exceeds the maximum input of the buck converter, resulting in an internal breakdown that created a short, so it burns? Does a big capacitor on the input side solve this problem? Is there a recommended value? Or I need to add some more components? Here is the circuit I am using:

EDIT: Here is the image of the board layout (I already added a 470uF cap on the input side), I tried my best to stick to the layout recommendation from the datasheet.


texts: What happens to Filtered High Frequency Noise?

texts:
How to filter out high frequency noise from power supplies has been covered ad nauseum, but no one ever discusses what actually happens to the noise itself.  Surely it doesn't just disappear? My understanding is that it is just bypassed around your load but is still present on the return line.  But this got me thinking about the nature of the noise itself.

Take the simple RC Low Pass Filter circuit where high frequency signals travel through the capacitor back to the source instead of into your load.  Is the noise still present on your return path to a power supply or is it dissipated somehow?

simulate this circuit – Schematic created using CircuitLab

Is this a fundamental property of Power Supplies themselves? Is the ripple just an effect of the return line being slightly out of phase from the supply line? It's all relative, so if you measure Supply output to an isolated earth ground reference instead of the supply return, will you still see the output ripple? Is the high frequency noise still present if you probe just to the right of R1 with reference to return, but gone (since it flows through the cap) if you probe to the right of the cap intersection on the same wire with respect to return?  If so, how, if these are technically the same voltage node?!

I really can't seem to grasp how high frequency filtering techniques are actually working.  I understand that the HF parts will flow through the virtual shorts instead of your load, but I don't understand how the noise is actually dissipated.


texts: Why separate AVDD and DVDD if the datasheet recommends powering them from the same supply?

texts:
I am working on a bio-impedance analysis project and am using the Analog AD5933 IC, since it seems like a capable impedance analyzer. Pins 9, 10, and 11 on the IC are DVDD, AVDD1, and AVDD2, respectively.
I understand that it is usually desirable to separate analog and digital power sources to mitigate issues stemming from noise but I don't understand why the datasheet then recommends tying "all supply connections and running from a single supply between 2.7V and 5.5V." Doesn't that defeat the purpose of separating the pins/supplies?


texts: Periodic Steady State analysis for class C amplifier

texts:
I am working on a simple Class C amplifier which is non-linear, therefore conventional AC analysis could not be used. Instead, Periodic Steady State analysis has to be used.

The context of this question is understanding PSS analysis throughoutly before applying it to analyse my class C amplifier.

For page 2 in Computer-Aided Circuit Analysis Tools for RFIC Simulation: Algorithms, Features, and Limitations , could anyone further explain the following statement ?

  consider the simulation of high-Q oscillators. These also require very long transient simulations; a Q of 10 000 suggests that the turn-on transient time starting from a zero initial state will be of the order of 10 000 cycles of the oscillation period

Edit: For clarification purpose.

The second screenshot below shows that the turn-on transient time is about two microseconds.

Using the equation (8.56) given in the third screenshot below gives Qtot = 628.318530718

However from the paper discussed above, the author claimed that the turn-on transient time will be of the order of 'Qtot' cycles of the oscillation period (in this case, period is 1/15.9154943092Meg)

What I have from calculation is 31.8309886184 cycles (2us divided by 1/15.9154943092Meg).

Could anyone suggest why I am getting two different 'Qtot' values using different calculation methodology ?

Please correct me if I have mistake in any of the calculation steps.


texts: Problem using UART0 in TM4C123 Tiva C Launch Pad

texts:
I'm trying to interface UART0 with the my laptop using the ICDI
the code I used is from Mazidi's book :
#include <stdint.h>
#include "tm4c123gh6pm.h"
void UART0Tx(char c);
void delayMs(int n);
int main(void)
{
    SYSCTL->RCGCUART |= 1; /* provide clock to UART0 */
    SYSCTL->RCGCGPIO |= 1; /* enable clock to PORTA */
    delayMs(20); /* wait for output line to stabilize */
    /* UART0 initialization */
    UART0->CTL = 0; /* disable UART0 */
    UART0->IBRD =  104; /* 16MHz/16=1MHz, 1MHz/104=9600 baud rate */
    UART0->FBRD =  11; /* fraction part, see Example 4-4 */
    UART0->CC = 0; /* use system clock */
    UART0->LCRH = 0x60; /* 8-bit, no parity, 1-stop bit, no FIFO */
    UART0->CTL = 0x301; /* enable UART0, TXE, RXE */
    /* UART0 TX0 and RX0 use PA0 and PA1. Set them up. */
    GPIOA->DEN = 0x03; /* Make PA0 and PA1 as digital */
    GPIOA->AFSEL = 0x03; /* Use PA0,PA1 alternate function */
    GPIOA->PCTL = 0x11; /* configure PA0 and PA1 for UART */
    delayMs(1); /* wait for output line to stabilize */
    for(;;)
    {
        UART0Tx('M');
        delayMs(1000) ;

    }
}
/* UART0 Transmit */
/* This function waits until the transmit buffer is available then */
/* writes the character in the transmit buffer. It does not wait */
/* for transmission to complete. */
void UART0Tx(char c)
{
    while((UART0->FR & 0x20) != 0); /* wait until Tx buffer not full */
    UART0->DR = c; /* before giving it another byte */
}
void delayMs(int n)
{
    int i = 0 , j = 0 ;
    for(i = 0 ; i < n ; i++)
    {
        for(j = 0 ; j < 3180 ; j++)
        {

        }
    }
}

and there are no problems with the COM port I've set it up in a correct way and I made sure to modify options for target to get 16Mhz clock frequency and to debug using ICDI ( I'm using keil uvision IDE)
and All I get is this symbol
What should I do ?


texts: Differential Amplifier small signal analysis

texts:
I am having trouble doing the analysis the small signal model of this circuit:

So far, I have come up with this this circuit for the small signal analysis:

However, I can't come up with a formula for the circuit gain. I tried to split the circuit in half by removing the wire between the source of the transistors (Assuming the transistors are the same, the circuit is symmetric), but I ended up with a gain of 0. I am wondering if this methodology is good.


texts: Composite video from rear car camera - bad signal (wrong levels?)

texts:
I have bought a car radio (AMPrime 4022D) that has ability to connect rear camera to it, so you can see the image on its screen. The problem is that radio doesn't detect the signal (blue screen).
But on an old portable TV, video is shown normally. Camera, that I use, was bought separately.
I have tried to connect different resistors (later on trimmer) on signal line of coax cable, and figured out that around 700-800ohm the radio detects video signal but the image is black. Maybe there is slight presence of otherwise bright spots. Every time I wanted to reduce resistance, the screen became blue again - no signal. Then I tried to do the following: when image was black (signal present) I would shortcut resistor with a screw driver and the true image from the camera would momentarily appear on the screen! Then soon after image from camera appeared, the blue screen came back again...
I don't know exactly what is going on, but I connected oscilloscope on an open connector and measured voltages that appear 1V higher than on specification of composite video. Could that be the reason, the signal couldn't be detected. I have also tested this camera on another more "modern" car lcd screen and the symptoms are similar... no video detected, except momentarily when camera is powered on.
What is the cause that this is happening and what could be a solution?
Sync level measured at 1.11V:

Voltage at color burst is 1.7V:

Another level measured at 2.3V:

Video on an old portable TV:


texts: Is voltage same till end , using dc battery ?

texts:
I want to find the remaining charge of  12v dc  battery . I am confused in voltage and current , either voltage remains same till battery power get finish ? ( I mean if a battery is 12 volt and is fully charge , will the power be same 12 volt after using the battery ? Or it get decrease with use ?)
Anoter , what is the mechanism beyond the remaining power show in cell phones . '?


texts: Implementing a function using a mux and no gates at all

texts:
Given the function \$f(w,x,y,z)=x'y'z'+w'xy' \$, where \$ '\$ means negation.
I was given this function from a mux \$2^3*3\$ - 8 inputs and 3 control lines.
In the original implementation \$y'\$ was connected to inputs 0,2,3,4, and the control lines were \$w,x,z\$ where w is the MSB, the rest are zeros.
I want to implement the same function using the same MUX, but without Not gates.
After trying everything I cant really point the problem here.


texts: Need a little help with a Chinese tesla coil

texts:
I bought a little tesla coil kit that can play music. I soldered it all up, and a friend of mine distracted me at the last second when I was hooking it up...
I blew the original "BD243" transistor up on accident, at this point, by mixing up positive and negative leads while using a laptop power supply (rated at 19v by 3.8Amps).
I replaced it with a tip31ag transistor.  It has 30% less gain, and I assumed that it would just throw slightly weaker sparks; it however barely mak3s a spark more than a few millimeters when fully amplified by my sound equipment.
I am just looking for some advice to amplify it more. The schematic says that the primary is 1 wrap, and the secondary  is 350. I would like to make it better. Any help would be great. I can take extra pictures if needed.
I have so many extra components. I can make do; if I have to desolder some old stuff lying around, then so be it.
       Any help is appreciated.


texts: Do I need to connect capacitor across MOV?

texts:
I was designing some circuit for powering my module, where I need to provide protection against high voltage AC.

I found one reference from Microchip MCP39F511 where they have used MOV which is accompanied by a capacitor of high voltage rating connected in parallel to this.

I don't understand this concept. MOV used for protection against high voltage protection where it gets shorted when it finds high voltage across this. If I if connect a capacitor across this then it will hold this voltage for awhile.

I know this time is very small but this it may damage my circuit.

So can anyone help me with this to figure out that's the matter behind this.


texts:
In the schematic taken from a device's service manual, if I want to bypass this volume knob and make it 100% all the time, which pins should I connect and how?

I have read online, prior to seeing the schematic that I should jump 1-2 and 5-6 and was told 3 and 4 "weren't even connected".

I do not know the relevance of the 10ka indicator and wonder if I need to use a resistor to jump the pins or if a straight wire would be proper.

Thank you in advance for your help!


texts:
I am looking at a schematic that has a very similar form to a emitter follower but in the mosfet world. It's intended to keep the brightness relatively constant  as the battery battery voltage depletes

I am trying to figure out what the current in this device would be and if the components are rated appropriately. Unfortunately, my mosfet knowledge beyond a switch is not sufficient.

How can I go about figuring out the current through the resistor?

simulate this circuit – Schematic created using CircuitLab


texts: Need help understanding LCD Power Enable circuit

texts:
Here you will see a schematic for an LCD panel. Header on the right, panel on the left, backlight power circuit on the bottom left and enable circuits in the middle. I am having difficult understanding some of the logic behind the enable circuits.

The LCD_PWRE signal. When it goes high, T3 (npn transistor) activates creating a path from the power pins to ground, but I don't know what this accomplishes. How does it affect FET1 and FET2 (p-channel mosfets)? What purpose does the two channel diode D1 serve?
The backlight enable circuit, I understand that when the base goes low on T1 (PNP transistor) that the backlight will turn on. What I don't understand is the signal connected the base of T1. What is happening with T2 (NPN transistor)? It would appear that the base of T2 is always high, causing the base of T1 to be equal to the LCD_BKL signal. I assume this is not the case as then why bother having T2 at all? Why not connect LCD_BKL directly to the base of T1 with a pulldown resistor?


texts:
I am using the following simple program to blink 5 pairs of LEDs using my Digispark ATTiny85. The circuit is very simple, not even have the necessary resistors to limit current. I was just trying for the first time with Digispark ATTiny85 board. But, when I run it by plugging in 5V power supply to the Micro USB  Port on the board, I see the P5 LEDs glow dim and the P4 LEDs glow bright continuously. No blinking effect. Neither does the other LEDs glow at all. Just these 2 pairs glowing continuously. Am I doing something really wrong? I know the HIGH on P5 is 3V and current limiting resistors are missing. But that should not prevent the microcontroller to blink the remaining LEDs.

void setup() {
    pinMode(0,OUTPUT);
    pinMode(1,OUTPUT);
    pinMode(2,OUTPUT);
    pinMode(4,OUTPUT);
    pinMode(5,OUTPUT);
    digitalWrite(0,LOW);
    digitalWrite(1,LOW);
    digitalWrite(2,LOW);
    digitalWrite(4,LOW);
    digitalWrite(5,LOW);
}

void loop() {
    digitalWrite(0,HIGH);
    delay(500);
    digitalWrite(0,LOW);
    digitalWrite(1,HIGH);
    delay(500);
    digitalWrite(1,LOW);
    digitalWrite(2,HIGH);
    delay(500);
    digitalWrite(2,LOW);
    digitalWrite(4,HIGH);
    delay(500);
    digitalWrite(4,LOW);
    digitalWrite(5,HIGH);
    delay(500);
    digitalWrite(5,LOW);
}

And following is the schematic.

simulate this circuit – Schematic created using CircuitLab


texts: USB to Serial cable and VCC current output

texts:
I have question about generic USB TTL Serial cables,  FTDI FT232R-based. The cables differ in voltage, 5V, 3.3V and output current.

USB TTL Serial Cables

I need a cable for a USB to serial converter, for a modem with 3.3V voltage. Only 3 wires are required: Tx, Rx, GND (VCC not used). There are two models:

TTL-232RG-VSW3V3-WE: +3.3V / 50mA output.
TTL-232RG-VREG3V3-WE: +3.3V / 250mA output.

In my particular case the power output rate doesn't matter, as VCC is not used. But I may need this cable in the future for other electronic devices, like modems and routers, which may need VCC. Which from these two models is better for use with CPE devices (routers, modems, set-top boxes), the one rated at 50mA or 250mA?


texts: Is it possible to add resistance using a push button?

texts:
Does anyone know if this is possible to add resistance using a momentary switch/push button?
Meaning that I just want to push down on a button and go from 2 Volts down to 1 Volt.  Any help is greatly appreciated.  Thank you.


texts: Difference between load resistance and Thevenin/Norton resistance?

texts:
In the Norton/Thevenin theorem, what is the definite difference between the load resistance and Thevenin/Norton resistance?

I cannot find any sources defining the difference, all of the sources use them as if I already were to know the difference.

Take this example.

Here I know the load resistance is the 40 ohm resistor. But not really why. Is it because of the direct connection to ground? If the circuit was more complex, I might not have been able to see it as clear as in this picture, because I don't really know what qualifies 'the load resistor' to differ from the rest of the circuit.


texts: What is this add-on to my 1980s AC magnetic contactor?

texts:
I'm renovating a Shizuoka ST-N CNC knee mill with a Bandit 3 controller from ~1980 in it. The spindle drive is a Todai Electric Co DC Motor Control Pack model number MOP-1500 which has absolutely no documentation online.

There are two Fuji Electric SRC3631-5-1 magnetic contactors in it, one for each spindle direction. However, one of them has this strange add-on component on the bottom of it.

The picture below is from an ebay listing with an identical add-on, except theirs has a knob with labels 4, 6, 8, ARC, while mine just has a large plastic phillips screw in the same position.

The small white rectangle next to the knob is a piece of loose plastic in a slot, and below it there's a button which it can press. In the configuration I received this part in, that button is held down by some sort of internal toggle mechanism, so pushing or pulling the white plastic does nothing. However, if I turn the knob a quarter turn clockwise, the toggle releases and the button becomes a normally open momentary switch which I can close by pushing on the white plastic. If I turn the knob back, the switch stays open until I press it again, and then the toggle engages to keep the circuit closed.

What is this add-on called? What's its point?

My best guess is that it's some sort of safety feature, where if something passes a threshold (adjustable with the knob) the switch will momentarily open. But, I need to know what it is because perhaps the toggle is the safety feature, and the operational state is un-toggled, with the circuit open.

Thanks!


texts: How to recognise I2c patterns from the scope

texts:
The scope photos shown below are from I2c communication with Si7021 sensor shown below.
From the reference manual page 482 of EFR32FG14 the start and stop are as shown below.
I am sending measure command with slave address as shown in the code below.
In the end I am supposed to recieve LS MS and checksum bytes.
I can't see those parts.
Could you please draw on my scope photo the START, the ACK, and the recieved data and stop parts?

#include "stddef.h"

#include "em_system.h"

#include "em_device.h"

#include "em_chip.h"

#include "em_cmu.h"

#include "em_emu.h"

#include "em_gpio.h"

#include "i2cspm.h"

#include "si7013.h"

#include "sl_sleeptimer.h"

#include "graphics.h"

#include "em_adc.h"

#include "bspconfig.h"

uint8_t com1[1] = {0xE3};

uint8_t i2c_rxBuffer[3];

int main(void)

{

I2C_TransferSeq_TypeDef i2cTransfer;

I2C_TransferReturn_TypeDef result;

I2CSPM_Init_TypeDef i2cInit = I2CSPM_INIT_DEFAULT;

/* Chip errata */

CHIP_Init();

// Enabling clock to the I2C, GPIO, LE

CMU_ClockEnable(cmuClock_I2C0, true);

CMU_ClockEnable(cmuClock_GPIO, true);

CMU_ClockEnable(cmuClock_HFLE, true);

// Starting LFXO and waiting until it is stable

CMU_OscillatorEnable(cmuOsc_LFXO, true, true);

I2CSPM_Init(&i2cInit);

// In order to enable the I2C0_SCL function in PC10 you need to use ROUTE 14

// In order to enable the I2C0_SDA function in PC11 you need to use ROUTE 16

//Also note that there's a GPIO pin PD15 that need to be set to high in order to route the signals to the sensor,

// Using PC10 (SCL) and PC11 (SDA)

  GPIO_PinModeSet(gpioPortC, 10, gpioModeWiredAndPullUp, 1);

  GPIO_PinModeSet(gpioPortC, 11, gpioModeWiredAndPullUp, 1);

  //Si7021 switch on

  GPIO_PinModeSet(gpioPortD, 15, gpioModePushPull, 1);

  // Enable pins at location 15 as specified in datasheet

  I2C0->ROUTEPEN = I2C_ROUTEPEN_SDAPEN | I2C_ROUTEPEN_SCLPEN;

  I2C0->ROUTELOC0 = (I2C0->ROUTELOC0 & (~_I2C_ROUTELOC0_SDALOC_MASK)) | I2C_ROUTELOC0_SDALOC_LOC16;

  I2C0->ROUTELOC0 = (I2C0->ROUTELOC0 & (~_I2C_ROUTELOC0_SCLLOC_MASK)) | I2C_ROUTELOC0_SCLLOC_LOC14;

  i2cTransfer.flags=I2C_FLAG_WRITE_READ;

  i2cTransfer.addr=0x80;//address with write

  i2cTransfer.buf[0].data=com1[0];  // Measure Temperature, Hold Master Mode

  i2cTransfer.buf[0].len=2;    //2 bytes length

  i2cTransfer.buf[1].data=i2c_rxBuffer;

  i2cTransfer.buf[1].len=3;    //LS MS checksum

while(1)

{

  result=I2C_TransferInit(I2C0,&i2cTransfer);

  // Sending data

   while (result == i2cTransferInProgress)

   {

    result = I2C_Transfer(I2C0);

   }

}

}


texts: How to read configuration bit register from PIC?

texts:
I'm debugging and want to inspect

  CONFIG1H (CONFIGURATION REGISTER 1 HIGH)

of a PIC18F.  CONFIG1H does seem to be recongized as an SFR when I enter it into the Watch window.

After stopping at a breakpoint, you can open the configuration bits window:

  Window >> PIC Memory Views >> Configuration bits

but it's unclear whether those are cached in MPLABX or newly read from the MCU.


texts: Is 'IF' statement necessary for the clock process?

texts:
I'm used to writing the following process that will react on the rising edge of the CLK (script 1):

X: PROCESS(CLK)
BEGIN
    IF RISING_EDGE(CLK) THEN OUTPUT <= CLK AND VAR;
    ELSE NULL;
    END IF;
END PROCESS X;

Now I need the process to react on both rising and falling edges of CLK, so according to the device datasheet I wrote this (script 2):

X: PROCESS(CLK)
   BEGIN
        IF (CLK'EVENT) THEN OUTPUT <= CLK AND VAR;
        ELSE NULL;
        END IF;
END PROCESS X;

Both cases fit and can be programmed on the device. But it seems like the second case does not really work: the OUTPUT does not change.

I need the OUTPUT to be updated on both edges of the CLK. Would it be functionally equivalent to script 2 if I rewrite the process as the following (script 3)? In other words, do I have to put IF condition, or the process reacts on the rising/falling edge of the CLK regardless?

X: PROCESS(CLK)
   BEGIN
      OUTPUT <= CLK AND VAR;
END PROCESS X;

EDIT:
With script 2 I get the warning that the signal VAR is missing from the sensitivity list. However, I need the OUTPUT to change only with CLK, but be dependent on VAR value.

With Script 4 (below), which I would expect to be equivalent to script 2, the warning is different: WARNING:Xst:2110 - Clock of register OUTPUT seems to be also used in the data or control logic of that element.

X: PROCESS(CLK)
   BEGIN
       IF (CLK'EVENT) THEN
           IF CLK = '1' THEN OUTPUT <= ('1' AND VAR);
           ELSE OUTPUT <= '0';
           END IF;
       ELSE NULL;
       END IF;
END PROCESS X;

Here's the fitter report with relevant vars(NICLK is for OUTPUT and SampEn is for VAR):


texts: How to determine if an edge-triggered flip-flop is positive going or negative going?

texts:
I have an SR flip-flop such as above, and I'm to determine whether it's positive-going or negative-going. How can I do that?
I understand that edge-triggered flip-flops' output only change upon edges of clock. But I don't know how to determine which one.


texts:
Hi I'm driving some leds using bs170 mosfet. The led's are lighting up however I would like to be able to turn it off after 30 seconds say.  I tried using the following code but it didn't work. I think it's turning off and on faster than I notice. I seem to be getting a square wave on the scope on the pin that the fet is connected to.

/*
 * AVRGCC1.c
 *
 * Created: 21/04/2011 21:38:56
 *  Author: steven
 */

#define F_CPU 20000000UL  // 1 MHz

#include <util/delay.h>
#include <avr/io.h>

int main(void)
{
        //TODO:: Please write your application code
        DDRA=0b00000001; //Make PDA0 as output
        PORTA =0b00000001; // turn on fet
        _delay_ms(30000);
        DDRA=0b00000000;
}


texts: Zener diode behaviour at operating limit

texts:
I am looking to select an appropriate Zener diode from the ZMM range for MCU input pin protection.

They are specified at a Zener current I_ZT = 5 mA having a maximum impedance of Z_ZT = 90 ohm.

They also specify a maximum impedance (at working current threshold?) Z_ZK = 600 ohm @ I_ZK = 1 mA.

I am assuming absolute maximum input pin voltage of 5V.

My analysis is as follows:

The Zener diode requires at least 1mA to break down: 5V / 1mA = 5kOhm current limiting resistor. Below 1mA the Zener is not guaranteed to break down and my input pin could see the full voltage.
At 1mA the Zener impedance is 600 Ohm leading to a voltage drop of 0.6V.
5V permissible input voltage - 0.6V zener voltage drop: --> require zener diode with a maximum zener voltage of 4.4V.
From the ZMM range, the next best part would be the ZMM3V9 with a V_Z(max) = 4.1V @ I_ZT = 5mA.

My issue is, that steps 1-3 of my analysis were based on I_Z = 1mA but the Zener voltages are specified at 5mA.

Assuming we calculate an 'junction voltage' without the resistance voltage drop:

V_j = V_Z - 90ohm * 5mA

Does V_j vary with respect to the current I_Z?

Is it acceptable to calculate a Zener voltage at lower current as follows?

V_Z @ 1mA = V_j + 600 ohm * 1 mA

I started my analysis at the working threshold current, because a selection at 5mA gives insufficient over-voltage protection:

Assuming 0.25 W current limiting resistors:

V_input_max = 35V with 5kOhm (1mA analysis)

V_input_max = 15V with 1kOhm (equivalent 5mA analysis)

I am looking for protection from sustained voltages of 30V and an expected normal operating voltage of 15V.


texts:
I'm working on a project that will be using RS485 to communicate between a bunch of modules and a master controller. Low baud rate, 9600, but a decent distance, like a couple of hundred feet. I'm wondering if I can get away with reliably using Cat5e for this, and whether or not I need it to be shielded and connected to ground?

If that is the case, would I be able to use the remaining 3 pairs as the ground instead of getting cable with actual shielding?


texts: Why averaging in Spectral magnitude domain not in complex domain to estimate spectrum of a process

texts:
Consider we need the magnitude spectrum of the signal. Signal is recorded in \$N\$ trials to a certain stimuli. Signal varies from each trial because of noise. So, to estimate the actual magnitude spectrum, there are two approaches:

Avg. in temporal domain: Average out trials in temporal domain to obtain signal of less noise and then take its fourier transform to obtain signal's complex frequency content. Visualize magnitude spectrum. The output would be the same, even if we average the fourier transforms(complex), as it is a linear operator.
Avg. in magnitude spectrum domain: Compute fourier transforms of each trial, get magnitude spectrum and average this across trials.

According to me, approach (1) is correct as we are not neglecting any of it. Averaging has to be done in linear domain, which is real and imaginary parts of the complex output (Fourier transform). Whereas the second approach neglects phase spectrum of each trial, i.e. averaging in Polar representation of complex number individually. Many of my friends, even a professor approve the second approach (2). Their argument is that, because the requirement is the magnitude spectrum which is random, because of noise in each trial, so averaging the required output (Fourier transform) over many trials to obtain its estimate is a reasonable step. I am not convinced with it, as spectrum consists of both phase and magnitude and just neglecting one of it to get an estimate individually, by linear approaches, (here Arithmetic mean) is not proper, as the true underlying magnitude spectrum, getting modulated by noise, may be some form of non-linearity (function mapping temporal signal to magnitude spectrum). Thus, averaging magnitude spectrum out won't null out the noise. So, please help by providing opinions of what may be correct and why ?


texts:
i am reading computer networks and i am trying to solve  an excercise.
the excercise is

  What is the theoretically the maximum rate at which data can be transmitted to a 4000Hz bandwidth communication channel having a noise of 30dB if the number of discrete signal states is 6?

I thougth that i must use the sannon hartley because the channel having noise.
The the formula is =log2(S/N+1). Then from the type =10log10(/) i calculate the /. But i cant understand

  if the number of discrete signal states is 6

i must modify the formula or something else?
What should i do?


texts:
I have a project where I am using an STM32 to pretend to be the SIM card of an LTE module. The actual SIM card is located elsewhere and the SMT32 acts a middle man between the LTE module and another device with the physcial SIM.
At first I had a level-shifter to go from 1.8 to 3.3V of the STM32. But for some reason when I used the level shifter the STM32 could never send the answer to reset correctly because the level shifter would not drive down to 0V on the 1.8v side. Now I have the LTE sim bus connected directly to the STM32, the STM32 is configured to respond when the LTE module tries with 3.3V logic levels.
My SIMs ATR is :3B 9F 96 80 3F C7 82 80 31 E0 73 F6 21 13 67 56 05 30 E0 09 02 01 FB
The problem is that after the LTE module receives the ATR from the STM32, it seems to see some information in there which makes it think the SIM can operate at 1.8V, does anybody know exactly which byte is responsible for this?
If I can find that I can fake it and the checksum of the ATR to make the LTE module really believe its a 3.3v SIM


texts: How can I calculate voltage drop on non resistors?

texts:
I understand that calculating voltage drop with two or more resistors in series is easy because we can apply ohms law and divide up the supply voltage relative to the resistance of each individual resistor.

I also understand that if we only have one component in a circuit, the voltage drop must be equal to the supply voltage.

What I find difficult to understand is what happens when we have a resistor and some other component (maybe an LED, or a motor , or something else).

How do we know what the voltage drop on each component will be, when there is usually not a resistance value specified for the component?


texts: Coherent FSK Modulation correlation coefficient derivation

texts:
FSK has a large bandwidth requirement and its minimum bandwidth is around \$4 B_T\$, where \$ B_T \$ is the bit rate.

In a coherent FSK system the signals \$s_1(t)\$ and \$s_2(t)\$ representing bit 1 and bit 0 respectively are given by:

\$ s_1(t) = A_C . \cos(2\pi (f_c + \frac{\Delta f}{2})t) \$

\$ s_1(t) = A_C . \cos(2\pi (f_c - \frac{\Delta f}{2})t) \$

Assuming \$f_c > \Delta f \$

Show that the correlation coefficient between \$s_1(t)\$ and \$s_2(t)\$ is given by:

\$ \rho = \frac{\int_0^{T_B}{s_1(t)s_2(t)dt}}{\int_0^{T_B}{s_1^2(t)dt}} \$

is approximately given by:

\$ \rho \approx sinc(2\Delta fT_B) \$

How do I approach this question? I can do the integral but I don't know how the integral is derived, the squared looks like a matched filter or power calculation \$(V^2/R)\$?


texts:
I am using LM350 for regulating 12V for 1.7A load. As per datasheet it can drive max 3A load.

But in my case, it's stops regulating after keeping this circuit for burn test for 3-4 days of testing. During burn test,randomly it stops regulating even though current is well below 3A.

I have stepped down output from bridge rectifier by using resistor (0.5Ohm,2W) and voltage I have marked below.

Any suggestion without much modification in existing hardware.

Thanks in advance.


texts:
I am trying to use TIP120 for my inverted switch where I wish to have my DC water pump(rated at 5v, 3W, 600mA) running when switch is open (in actual these will probes that will complete path when there is ample water in between them) and when switch is closed the transistor should shut off.

I have calculated the (base current - Ib) for the above load at 0.6mA (600mA/1000) and base resistor Rb at 4.1 kohms.

I am using circuit wizard for simulation, which is showing explosion on the transistor when the state of switch is changed. Can someone tell me what is wrong with the below mentioned circuit

I tried this sample circuit at

https://cdn.sparkfun.com/assets/learn_tutorials/1/9/3/switch-animated-600h.gif

but had similar prediction of transistor exploding. Can I get some information on why the simulation is predicting exploded transistor. I have also tried placing diode after the Emitter but no luck in simulation

thanks
Imran


texts:
I have an Outlet Tester like this:

It is used to see the mains electric connection, it has the next states:

I opened it and then I reversed engineer it. The diagram I obtained is this:

I would like to make the circuit analysis (Kirchoff's Laws) but I don't know how to apply them in this case, I don't see a well defined voltage source, like in other cases:

I mean, yes, there is a Hot (+) and a Neutral (-), but, what about ground? .. Let's suppose that Hot is 127 Vrms and 60 Hz, How do I apply KVL and KCL here?


texts: Rauch filter (or) MFB filter - Input interfacing

texts:
How to interface single ended input signal to inputs of the MFB filter or Rauch filter?

Is it okay to grounding the reference of the input signal rather connecting it to 2nd input terminal?

Note: I got this circuit from Anadigm's FPAA Quad board manual


texts:
How do you know what R1 should be to completely turn on the transistor?

simulate this circuit – Schematic created using CircuitLab


texts: I have a small pump rating at 96 Watt, and the input is 12V DC, max current 8A. The product also comes with a 250V 8A glass fuse. Because the pump is 8A and the fuse is also 8A, does that mean the device will draw 8A current flowing through fuse when working on full loading. Will the fuse be always hot and can easily blow when the device is continuously working for a long time?


texts: How is the signal Multiplied with the Carrier in AM

texts:
In wireless transmission, via Amplitude modulation, we multiply the message signal by a carrier wave to get the modulated signal
$$x(t) = m(t) \times cos(\omega t)$$
Where \$m(t)\$ is the original message, \$\omega\$ is the frequency of the carrier wave and \$x(t)\$ is the modulated signal.

My question is, how does this multiplication take place in Hardware?

I am aware of chips like the MPY 634 which use a Gilbert Cell-based Architecture to achieve Multiplication and have a transfer function of the form
$$x_{out}=A\Big[\frac{(X_1-X_2)(Y_1-Y_2)}{SF}-(Z_1-Z_2)\Big]$$
Where the capitalised letters represent signals at 4 different terminals.

But this seems like an awfully complex, expensive and bulky solution for something that needs to be done often


texts:
What is the pin-to-pin pitch of the KRC-86B Bluetooth module?  All I know is it is smaller than the standard 2.54mm pitch.

I am trying to find a JST connector that will fit properly.

Thanks in advance.


texts: LED Driver IC off a single-cell Li-ion battery (Too large of a voltage difference?)

texts:
So I'm an idiot and I need help interpreting a basic datasheet. This is for a Boost-mode LED Backlight Driver IC. https://media.digikey.com/pdf/Data%20Sheets/Diodes%20PDFs/AP3031.pdf
I need to drive an LED that draws 700mA with a typical forward voltage of 7V, and I want to drive it from a 3.6V Li-ion battery (worst case scenario, 3V when flat).
That's a voltage difference of 4V, so at 700mA, the heat dissipation would be 4V * 0.7A = 2.8W, not too bad. But that's only on the high side... Given that the LED draws 4.9W (7V * 0.7A), the current draw on the low side is actually 1.6A (4.9W / 3V battery voltage, and that's assuming 100% efficiency). 1.6A is above the max switching current, plus it would create a whole 6.4W of heat dissipation with the 4V voltage difference.
So from my understanding the chip wouldn't be able to handle that? Or am I doing something dumb with the math?


texts: This L293D just blew up. Can someone pease help me figure out why?

texts:
I was using a motor driver breakout board with a L293D IC on it, along with a 7805 voltage regulator and a couple of capacitors.

I have een using it for 4-5 months and the wire connections stayed the same. Everything was well connected. Last night it suddenly stopped working and there was huge amount of smoke out of the board. Upon inspection I figured out that the IC was burnt.

But I'm unable to figure out why. Maybe I'm missing some huge part in my knowledge. Any help in figuring out what went wrong would be really helpful.
Also, would it be safe to use the same board after replacing the wasted IC?


texts: Solving this circuit using node analysis

texts:
Hi I'm having a really bad time in analyzing this

I can't seem to establish the node equations, I've been reading on articles on how to solve it but the majority use current sources and the methods differ quite a bit, any help is really appreciated.

I know that I have to use KCL on each node, for example for node B I said:

\$ I_{1}+ I_{2} - I_{3} = 0 \$

\$ I_{1} = \dfrac{A-B}{220} \$
\$ I_{2} = \dfrac{C-B}{100} \$
\$ I_{3} = \dfrac{B}{330}  \$

Given that and solving for B

A = 12 v
C = 4.5 v

\$ \dfrac{A-B}{220} + \dfrac{C-B}{100} - \dfrac{B}{330} = 0  \$

\$ \dfrac{A}{220} - \dfrac{B}{220} + \dfrac{C}{100} - \dfrac{B}{100} - \dfrac{B}{330}  = 0
\$

\$ \dfrac{A}{220} + \dfrac{C}{100} - B ( \dfrac{1}{220} + \dfrac{1}{100} + \dfrac{1}{330}) = 0  \$

\$ \dfrac{A}{220} + \dfrac{C}{100} = \dfrac{B}{\dfrac{1}{220} + \dfrac{1}{100} + \dfrac{1}{330}} \$

B = 650( A/220 + C/100 )

Substituting A=12, C=4.5

\$ B =
  \dfrac{
   \dfrac{A}{220} + \dfrac{C}{100
  }
  }{
   \left( \dfrac{1}{200} + \dfrac{1}{330} + \dfrac{1}{100} \right)
  } \$

B = 5.66 v

because of independent voltage sources.

I know my problem is on establishing the equations as I don't fully grasp how the analysis is made.


texts:
I want to implement a momentary power backup in my circuit using a supercapacitor. I have come up with the following circuit. Am I right in implementing the super capacitor like this? Also, the input voltage is 5V. Should I have a capacitor rated above the input 5V?

Increased the resistor value to 100R and added a Schottky diode parallel to the resistor. Supercapacitor rated at 10V.


texts: Bipolar transistor as a switch. Cut off mode?

texts:
I have a question regarding bipolar transistor and it's operation as a switch.

I know that, in order to make transistor work as a switch, we need to avoid active region, meaning, we need to make transistor to work only in saturation and cut-off region.

This basically, cannot be implemented perfectly, but we can make transition period from saturation to cut off region as fast as possible, but I am not quite sure how to make transistor to work in cut off region, meaning, I want to know how to turn the transistor off correctly.

Let's take NPN transistor as an example:

The transistor is off if it's base-emitter and base-collector PN junctions are reverse-biased, however, that means that we would need significant negative voltage on base in order to do so, but I am wondering, how would this affect the circuit and transistor?

Another approach I've heard of is that we only need to make base-collector reverse biased and then we need to add a resistor between base and emitter, how is this any better? Do I need a resistor with huge resistance or with low resistance or it actually doesn't matter, and why?

Any help appreciated!


texts: How does this construct drive the RESET pin low?

texts:
I've seen this in a bunch of ATMega / Arduino reference designs:

The RESET pin is pulled up high with R10, pulled low with a switch (S1), but then tied to the DTR line from a UART breakout via C27 - a small capacitor. This last bit is how the Arduino bootloader triggers the reset, but what's actually happening here? How does DTR going low translate to the pin triggering?


texts: How can I prevent HDMI 5V (55mA) from entering a circuit?

texts:
I have a circuit which uses a camera with HDMI out and a HDMI to AV converter, as well as some other 5V components.

The issue I have is that when the main 5V power source is off, but the camera is on, the 5V (55mA) used for device ID on the HDMI cable enters the circuit via the HDMI to AV converter power supply, and causes issues since all the 5V components are now underpowered.

Is there a way to prevent the 5V backfeeding to the main circuit in this situation? Is that what a Schottky diode is for? Any advice on specs required would be much appreciated. Other relavant info, given that only 5.1V is supplied from tha main power source (so voltage drop may be a consideration). All the components are "off the shelf" so not readily modified, but parts/components can be added into the circuit at any of the power/cable junctions.

Any help much appreciated.

Thanks!


texts: In Razavi's textbook, the following contour plots for the transfer function \$H(s)=A_0\frac{1+s/ \omega_z}{1+s/\omega_p}\$ are given. It's stated that \$H(\sigma_N) > H(\sigma_M)\$. How is this possible when the input moves further away from the pole and closer to the zero?


texts:
So, please forgive me for the naiveté I'm most certainly going to exhibit here. I'm mostly a software guy, so this project is a little out of my comfort zone. Nevertheless:
Project
I have been given a Python script that sends commands to an Arduino board, which in turn runs a servo motor, turning a plate to which it is attached.
When I run this script, the plate is supposed to do 1 full rotation.
Problem
The motor doesn't turn. The script works, and the Arduino does get the proper commands, but the plate just sits. Here's the expected workflow:

Run script
Motor turns
Plate rotates 360 degrees

Here's the only workflow I can get to work:

Run script
Give plate a push
Motor turns
Plate rotates 360 degress

Background
There is nothing obstructing the motor or the plate. This exact setup has allegedly worked in the past. Because I've not had much experience with Arduinos and servos, I'm having a hard time pinpointing where to begin debugging this problem. Any help or suggestions would be most appreciated.
Hardware

Power Adapter: CUI INC EPS060100 Output: 6V, 1A
Servo: Hobbico CS-80 Speed: 0.14 sec/60, Torque: 24.7 kg-cm

Further Testing
About once out of every 5 times (20%), it will just work. No pushing or prodding; it just zips up to speed and rotates.
About once every 50 times (2%), it won't move at all, even with pushing. This, however, might be an issue with the script/Arduino communication.


texts:
How do you measure quiescent current?
(For instance, a Battery connected device)


texts: What exactly would be the problem with a small amount of ferrous material inside a QFH GPS antenna?

texts:
This video describes the construction of a home-made QuadriFilar Helical (QFH) antenna for a GPS receiver module. A few seconds after 04:00 the narration says:

  Being a loop antenna I’d imagine it unadvisable to use any ferrous material at all, including the braid of the coax which is running straight through the whole antenna.

With large diameter conductors, no tuning instructions, and no ultra-critical dimensions in the fabrication, I'd imagine this is not a terribly high-Q antenna. Early in the video the design wavelength is listed as 190mm - the 1575 MHz L1 band of GPS.

What would be the primary problem (if any) caused by a small amount of ferrous material inside this particular antenna design? A shift in resonance frequency, or unwanted nulls in certain directions of the radiation pattern, or just an overall loss of gain?


texts:
I have a board with a device that outputs data over SPI (as slave device) and a microcontroller.  The device signals that data is available (24 bits) by setting a certain pin low, around 8000 times per second.  If the data is not read before the next data is available it is lost.  Unfortunately the microcontroller may sometimes be busy with another task, for as much as 1-2 milliseconds.

I would like some way to read the data from the device whenever it is available into a FIFO or buffer of some kind.  The microcontroller can retrieve that data later when not busy.  I also want to be able to do SPI read/write directly to the device when the buffer is empty.  What is the best way to set that up?


texts: Can anyone make the transfer function and magnitude of the transfer function more intuitive for me? I understand using them but I feel like there is still a gap in my understanding. I would like to get a more intuitive understanding of the transfer function. I have Googled and asked and it's still not that easy to grasp.


texts:
I want to use lm336z-5.0 as a reference voltage for Arduino Uno. In the data sheet I see an example of the chip being connected to a 10V source via a 5k resistor. In Absolute Maximum Ratings section I only see that the max reverse current is 15 mA.

What is the lowest and highest possible voltage at the input (I assume I will adjust the resistor to keep the current well below 15 mA)?


texts:
I have been using a Tiva C microcontroller (TM4C1294NCPDT) as master to communicate with 6 SPI devices (slaves). The SPI clock is 8 MHz with 1.5 ns rise time. My idea is depicted bellow.

My design do not allow chaining devices, thus, I need to attach a separated CS line to each slave. The PCB I have designed is depicted bellow

This is a 2-layer board with signal and power at the top and a solid ground plane at the bottom. The bus lines is 8 mil wide and there are no relevant stubs (pass beneath the pads). This board with the slave devices is connected to MCU evaluation board through 2.54 mm headers.

My worry is related to length of the SPI bus tracks on the PCB, which we can see, is > 55 mm long, and because the same SPI bus is attached to multiple devices, which can cause reflections due to impedance mismatch. I never connected multiple SPI devices to a single SPI bus before, just one-to-one, and I have no much knowledge about transmission line techniques. My question is: Should I have to consider some termination scheme at the bus ? I read that the series termination should be used when just one slave is attached to the bus (one-to-one). For one-to-many (master and slaves) either parallel or AC can be used at the end of the SPI lines to do the trick, but I'm not confident about the need to use termination in my case and if necessary, which is the proper scheme to use and in which lines.


texts: The LDO on my STM32 circuit heats too much after long hours of operation

texts:
I have an STM32F0 based circuit to control two AC loads (a compressor unit and an MD40 pump). A 12V supply feeds the circuit. On the PCB there is an LM2576T to step the voltage down to 5V. This is further regulated to 3.3V (for powering the STM32) using an LM3940.

My modules seems to be working fine. But once in a while (for two days it was working fine), when the loads are operating on the relays, the LM3940 heats up to 80 degree Celsius and my circuit temporarily turns off (as indicated by the 7 segments dimming and turning off eventually). The design of the circuits looks okay to me and the 12V power supply has been tested with other circuits and can provide a current of up to 5A. This was not a one time issue. This problem was recurring. At one point, the main circuit stopped working because the LDO got burned.

I've attached the power supply circuit diagrams. Also attached is the circuit for the relay boards which control the loads. There is a Darlington pair of BC847s on the board for driving the relay. The relay circuit is not optocoupled. The relays are powered by the main 12V supply.

C18 - 10uF Tantalam

I've been unable to figure this out so far, so any help is appreciated.

Other components on my circuit:

4 seven segments
An MAX485 on UART for MODBUS communication
Some tactile switches
Some NTC thermistors read by the STM ADC


texts: what is the best way to solder wires onto 3d print beds

texts:
My 3d printer has a heated bed similar to the one in this picture.

https://ae01.alicdn.com/kf/HTB1.7gFKVXXXXbMapXXq6xXFXXXa/HICTOP-3MM-MK3-Aluminum-Heated-Bed-Hot-Bed-PCB-Heatbed-Platform-for-Reprap-3D-Printer-200W.jpg

It has some nice molex connectors but sadly the wires are too thin. With my multimeter I measured around 2v of drop caused by the wires they've used.

As soon as I soldered on supplmentary 10awg cable that droppped significantly but since the bed can get very hot depending on what filament am using, am worried the wires will eventually come loose  and cause a short.

Am assuming the manufacture has already thought of this. what kind of solder would they have likely used before I contaminated it?


texts: Which products should have FCC certification and about how much does that cost?

texts: I'm aware that nobody actually does this at the hobbyist level, that successful commercial products have been launched without certification, and it's probably something I can't afford if I have to ask. However, I've always wondered about the ballpark cost. About how much does it cost to receive FCC certification?


texts:
How can I use MOSI and MISO at 89S52 ? can I use serial port from computer, directly connected to these pins ?
Any example codes for this function ?

Thanks a bunch

Anyone has a code example, from the pictures above ?


texts: Grounding between enclosures in a closed system

texts: Currently we are developing enclosures in an isolated "system of systems". Our overall system is fed AC power and converted to 28V with an off-the-shelf converter. Currently the enclosures we are designing each have a PCB internally and currently these PCB's power supplies are tied to the same ground (dashed red lines shown in the below diagram). My project manager is worried that this connection will cause problems when we go to test these items for EMI and he wants to remove these connections and have isolated lower voltages. I'm contending that the grounds should be connected because there won't be any common reference for the single ended connections between each enclosure. Also, some of these circuits use the 28V input as a reference as some of the signals are 28V. Do these lower voltages need to be isolated from the 28V?


texts: LTSpice: How to save output from multiple .op runs

texts:
So this is a somewhat complicated question... I am trying to run a .op simulation (DC operating point), using the .step command to iterate through a bunch of component values. I would like to save the output as a series of text files. Information that must be saved for each run:

the component values in each .step instance
the corresponding voltage at a specific node

Each run can be output in a separate text file, that's fine, but if it's possible I would like to just have 1 text file with the key info from each run separated by a few lines.

Is this possible?

=====

So I've been trying to use the .meas command to print data to the error log, but it doesn't seem to work as advertised and I don't understand why. Here's an example of a resistor divider where I step one of the resistors and want to print the divider voltage values. For some reason .meas doesn't output the requested data?

R1 Vout 0 {rVariable}
R2 N001 Vout 1k
V1 N001 0 1
.step param rVariable list 1k 3k 9k 12k
.meas V(Vout)
.op
.backanno
.end

=====

OK, I have just now figured this out. Here's what I did:

I ran the stepped simulation for the operating point.
I then selected the graph drawn by the .meas command.
Going to the File menu, I selected "export" and then V(Vout)
This generated a txt file with the data points I wanted.

Unfortunately this doesn't seem to actually output the variable selected by .meas yet, but I'm confident that that can be solved soon.

=====

Well, I've did some more reading and found people claiming that the .meas command doesn't work with the .op command, it has a bug and will only print the last value from a .step sequence. Is this true? Does anyone know of a workaround for this problem?


texts: On/off circuit using photo-resistor (LDR)

texts:
I am not afraid of the work but do not know how to do the math to calculate what I need for components.

I am trying to create a photo resistor circuit to control some LED model street lights. I have cobbled together a diagram of what I think it needs to look like but am not sure if I made any errors and I am not sure as to what some of the values would need to be for parts.

Input power will be 15 V AC.

The LEDs are 3 V - 20 mA white and led.com said R1 will be 150 ohm, 1/8 W. 16 LEDs are set up in four series strings of four LEDs and one resistor.

The diagram bellow is pieced together from 2 pics. R3, from what I understand, is not critical other than low resistance in light and high when dark (it is in the basement). My biggest questions are what would be the value of R2 and is a 2N3904 still OK for T1?

Any help would be wonderful. As I said I do not know what I am doing but am willing to do it with the supplied knowledge of those smarter.


texts: Calculating Impedance for capacitor in AC circuit with some undefined waveform

texts:
I need to set up equations for some simple AC circuit. The problem is that I dont know the formula, definition for the resistance.

I know for the 1/2*PI()*f*C, but I think this is only valid for the sin, cos, waveforms.

My question: is the formel 1/2*PI*f*C valid for other waveforms, and if not, what is the most basic formel.

Thank you


texts: Round LEDs are often indicated by "T-1" for 3mm LEDs or "T-1 3/4" for 5mm LEDs. What does the "T" mean, and how should I read other indications like this when I encounter them? "T" doesn't seem to fit neither mm nor inches.


texts:
I've been eyeing using an Ultrasonic distance sensor for an upcoming project; either the Parallax Ping or the OSEPP Ultrasonic sensor (I think they are identical other than branding).

Ex: https://www.parallax.com/product/28015

My concern is, this will be used at home where I have pets. I don't wish to injure nor annoy my pets.

Will the ultrasonic sensor cause problems for the pets? Should I instead use something different such as an infrared sensor?

(I'm mainly concerned about cats and dogs, although would be curious about other types of pets such as birds, etc...)


texts: VHDL IF statement not behaving as expected

texts:
The code is implementing an ALU. I've tested individual bits, but as I try to do the if-statement at the end, which is implementing a specific conditional function, it does not work. I'm using xilinx vivado, the most recent version.

library ieee;
use IEEE.STD_LOGIC_1164.ALL;
use ieee.std_logic_signed.all;
use ieee.std_logic_arith.all;

architecture part of project is

    signal bit6 : std_logic_vector(5 downto 0);

begin

with S select -- S is a control value of 4 bits
    sum <=   <expression 1> when "0000",
                   <expression 2> when "0001",
                   -- more code here --
                   -- it's not important --
                   -- it works fine --
                   <expression n> when others;

-- X is a 5 bit input below --
if (S = "1100") and (X(4) = '1') then
    sum <= <expression alpha>;
else
    sum <= <expression beta>;
end if;

Bracing the if-condition does not help. I.e., neither:

if ( (S = "1100") and (X(4) = '1') ) then

Similarly, another if-statement, using elements of a input also throws an error:

if  ( X(4) xor Y(4) xor (Z(4) ) then

I don't know if I've misunderstood the allowed syntax here, or if there's something else going on that isn't proper.


texts: Measure resistance accurately with an arduino?

texts:
I'm looking at performing accurate temperature measurements with a three wire RTD, and I'd like to be able to measure the resistance and thus the temperature using an arduino. The accuracy I'm looking for is better than 0.1Ω @ 100Ω.

I was told that to get good accuracy, I would first need a stable accurate low current source and very accurate low temperature coefficient resistors in a wheatstone bridge.

I was wondering if there was to better utilize the arduino's capabilities to perform this measurement, or is the external current source + wheatstone bridge the way to go?


texts: Confusion with flux and Lenz's law in an LC tank circuit

texts:
Below is an LC tank circuit and its V I plots:

I marked the points in red on the plots.

As far as I understand, at point a the capacitor is fully charged and the current is zero. At point b the current reaches to maximum and the voltage goes to zero(point y).

1-) Can we say that at point b, the net magnetic flux through the inductor is maximum?

2-) Here is my real confusion: According to Lenz's law the inductor should create a magnetic field which opposes the magnetic field rate through it. But in this case the magnetic field already is created by the coil it is not external. So does the Lenz law apply here? What can we say about the flux created by the current and the opposing magnetic flux?

Between the point a and b the current increases. Does that mean the net flux increases? What about the opposing flux? Is that in opposite direction?


texts: Headphone amplifier: negative charge pump vs. phantom ground

texts:
I want to use a "capacitor-less" headphone amplifier that doesn't require DC blocking capacitors at the output.

I found a headphone amplifier that has a negative charge pump that generates an internal negative supply voltage, which removes the need for output caps. However, I found these parts are more expensive. As an alternative, I found a lower cost headphone amp that has a "phantom ground" configuration to eliminate the need for output coupling caps, as shown below:

Is there any potential issue with directly connecting the phantom ground (Vout3 in the diagram) to the headphone's ground? What's the disadvantage of this method over the negative charge pump method?


texts:
Does increasing PCB copper thickness have any benefit for improving its heatsinking ability?

I am looking at mounting some SMD Op Amps (OPA552) which will need to dissipate up to 2W each. I will probably have to add heatsinks, but I am wondering whether increasing the copper thickness will also help. I have bare copper (well HASL plated but without solder resist) fill areas around the op amps.

Obviously copper thickness helps when it comes to current carrying capacity, but this is not my case


texts: Is there anything that can be done about this U5215 universal motor?

texts:
Recently my hairdryer stopped working properly. While drying my hair, the fan would suddenly turn off after a minute or two (it seems as if a thermal switch in series with the motor cut the current to it). It looked as if the heating coils were still powered, they heated up quickly with no more airflow and started to glow red, before also being cut by there own thermal switch. After that it would take about half an hour before I could use the hairdryer again. However, the behavior was the same again, with the fan turning off after short use.

I disassembled the hairdryer and found that it contained the motor shown below. It turns out that this is a fairly common motor for haidryers, a U5215 universal commutator motor. When disassembling the hairdryer, the motor was still warm (about half an hour after I was using it and it shut down). It tried to remove any dust that had accumulated (assuming that it was causing additional friction or blocking cool air), but unfortunately that did not help and the motor is still overheating after a minute of use.

Is there anything I can do to make this motor work properly again? Should I replace the motor (motors of this type seem to be available online)? Or should I simply buy a new hairdryer?


texts:
I have a DC power cable that ends in a 5.5 x 2.5 mm plug. I purchased a panel mount jack for it, and yes, the plug fits. However, the barrel is much longer than the jack, so the barrel does not fit flush, which seems like a bad idea.

The barrel length is about 12 mm.

The panel mount jacks I see online seem similar to the one I have. How do I find one (a spec or search term) that will have the right depth?


texts: What technique is used for thermistors embedded in an IC, and what should I think about when measuring them?

texts:
I would like to measure the resistance of a thermistor integrated in an older CPU, the Motorola Freescale NXP 68060, but the documentation is limited. This is all it has to say on the subject:

  THERM1 and THERM0 are connected to an internal thermal resistor and provide information about the average temperature of the die. The resistance across these two pins is proportional to the average temperature of the die. The temperature coefficient of the resistor is approximately 1.2 2.8 Ω/°C with a nominal resistance of 400Ω 780Ω at 25°C.

The corrected numbers comes from an errata.

What I can't figure out is what technique has been used to manufacture this, and how that affects the design of a circuit that can measure its resistance. Every other on-chip sensor I've seen has been of a diode type, and when reading about PTCs, they all seem to be made with a different process than what a common CPU is made with.

Is there a name for this type of thermistor?, and related, is there a "standard" method used to convert this resistance into a voltage that I can then sample with an A/D-converter? It's difficult to find reference designs since I don't know what to search for. Presumably, one constraint is that I can't let either end of the thermistor go outside the CPU's GND or VCC, but maybe there are other constraints I am not aware of.


texts: Horizontal offset with generic SSD1306 OLED display

texts:
I bought a generic OLED 128x64 display on ebay and had some success in getting it running with the Adafruit SSD1306 library.
I ported the initialization function to C and am driving the LCD using the SPI interface. However, when the splash screen appears, there is a horizontal offset.

I think should be possible to patch this by modifying the display function. However, my question is, is there a cleaner way to do this in the configuration settings for the OLED display. The relevant initialization settings that I am using are given below:

void ssd1306_init(uint8_t vccstate) {

    // Init sequence
    ssd1306_command(SSD1306_DISPLAYOFF);                    // 0xAE
    ssd1306_command(SSD1306_SETDISPLAYCLOCKDIV);            // 0xD5
    ssd1306_command(0x80);                                  // the suggested ratio 0x80

    ssd1306_command(SSD1306_SETMULTIPLEX);                  // 0xA8
    ssd1306_command(SSD1306_LCDHEIGHT - 1);

    ssd1306_command(SSD1306_SETDISPLAYOFFSET);              // 0xD3
    ssd1306_command(0x0);                                   // just changes the horizontal offset
    ssd1306_command(SSD1306_SETSTARTLINE | 0x0);            // line #0
    ssd1306_command(SSD1306_CHARGEPUMP);                    // 0x8D
    if (vccstate == SSD1306_EXTERNALVCC)
    {
        ssd1306_command(0x10);
    }
    else
    {
        ssd1306_command(0x14);
    }
    ssd1306_command(SSD1306_MEMORYMODE);                    // 0x20
    ssd1306_command(0x00);                                  // 0x0 act like ks0108
    ssd1306_command(SSD1306_SEGREMAP | 0x1);
    ssd1306_command(SSD1306_COMSCANDEC);

    if( SSD1306_LCDWIDTH == 128 && SSD1306_LCDHEIGHT == 32) {
        ssd1306_command(SSD1306_SETCOMPINS);                    // 0xDA
        ssd1306_command(0x02);
        ssd1306_command(SSD1306_SETCONTRAST);                   // 0x81
        ssd1306_command(0x8F);
    }
    else if (SSD1306_LCDWIDTH == 128 && SSD1306_LCDHEIGHT == 64) {
        ssd1306_command(SSD1306_SETCOMPINS);                    // 0xDA
        ssd1306_command(0x12);
        ssd1306_command(SSD1306_SETCONTRAST);                   // 0x81
        if (vccstate == SSD1306_EXTERNALVCC)
        {
            ssd1306_command(0x9F);
        }
        else
        {
            ssd1306_command(0xCF);
        }
    }
    else if (SSD1306_LCDWIDTH == 96 && SSD1306_LCDHEIGHT == 16) {
        ssd1306_command(SSD1306_SETCOMPINS);                    // 0xDA
        ssd1306_command(0x2);   //ada x12
        ssd1306_command(SSD1306_SETCONTRAST);                   // 0x81
        if (vccstate == SSD1306_EXTERNALVCC)
        {
            ssd1306_command(0x10);
        }
        else
        {
            ssd1306_command(0xAF);
        }
    }

    ssd1306_command(SSD1306_SETPRECHARGE);                  // 0xd9
    if (vccstate == SSD1306_EXTERNALVCC)
    {
        ssd1306_command(0x22);
    }
    else
    {
        ssd1306_command(0xF1);
    }

    ssd1306_command(SSD1306_SETVCOMDETECT);                 // 0xDB
    ssd1306_command(0x40);
    ssd1306_command(SSD1306_DISPLAYALLON_RESUME);           // 0xA4
    ssd1306_command(SSD1306_NORMALDISPLAY);                 // 0xA6

    ssd1306_command(SSD1306_DEACTIVATE_SCROLL);

    //Debug
    //ssd1306_command( 0x22 ); // Set page start and end addresses
    //ssd1306_command( 0x00 ); // start at zero
    //ssd1306_command (0x07) ; // end at seven.
    //DEBUG

    ssd1306_command(SSD1306_DISPLAYON); //--turn on oled panel
}


texts: Can’t reproduce oscillations using a simple inductor capacitor circuit?

texts:
I’m trying to reproduce a simple oscillator conductor / inductor circuit as shown here.

I replicated exactly the same scheme on a breadboard and check all the connections using a led

However when I try to get a measure of voltage it seems to stay constant even though according to the simulation on here (with exactly the same parameters) I’m supposed to have an oscillation.

Link to simulation

Here’s my wiring where I connected my osciometer

What am I doing wrong and how can I have voltage oscillations back and forth like in the simulation?


texts:
Looking for an HX711 ADC alternative.  Sparkfun sells a pricey breakout board with the chip, but I cannot source the IC anywhere online for some reason ♂. Are there any ADCs out there that have a built-in instrumentation op-amp?
My current plan is to hook-up my load cell to a stand-alone instrumentation op-amp and funnel that into the ADC of my MCU. However, since my design requires 4x of this circuit, I would much rather free up some MCU cycles and off-load these duties to a dedicated IC. Any ideas?