texts: Options for custom connecting a temperature sensor with a USB 2.0

texts:
I'm exploring a little project that would involve creating a custom USB device by connecting a temperature sensor to a USB device. There seems to be a dearth of information online about how to do this. Originally I found a pretty good sensor that uses the 1-wire protocol, and someone outlined how they were able to connect this with USB in this tutorial. However, they still ended up having to use a proprietary library from 1-wire's manufacturer to read data from the sensor. Ideally, I would avoid this, and could write my own device driver in C if necessary.

I'm inexperienced with embedded and hardware, so just trying to explore options and find good resources for this project. Is something like this even possible without using a proprietary SDK?  What would be a good standard to work with (1-wire, I2C, etc.)?


texts: How do you monitor communications on a positive-grounded device from a negative-grounded desktop?

texts:
I have a need to read the signals being sent between two boards in a lighting fixture.

In preparing to do this I have read much about the chips, RS485, and analysers/decoders that are out there. I am getting close to purchasing a USB to RS485 adapter and software to use it with - but have been unable to find critical information specific to my situation:

My desktop computer is negative grounded and the device is positive grounded.

I don't have a laptop that can be used for this purpose (which I have read could be used if it wasn't plugged into mains when connected to the fixture.)

Stuck with just the desktop to use, it seems to mean I'll just short it all out if I connect the grounds - possibly damaging the fixture, my desktop, the adapter, or any combo of these.

How do you properly set up for reading the signals with a -GND desktop and the +GND device?


texts:
The value of C1 is 680pF and C2 is 220pF.

I think this is a series resonant circuit with a parallel capacitor C2 to the inductor.

My question is how can I calculate the resonant frequency from this circuit? And what is the effect of the capacitor C2 to the circuit? Is C2 increases the inductance?

It would be appreciated if any one can help.


texts: What should the voltage of a fully charged lead acid battery be?

texts:
I don't have a proper lead acid battery charger...  But I own a small Yuasa 7Ah battery.  I am using a 13volt 1.5A wall wart to charge it.  And I have a volt-meter to check the voltage.

At what voltage should I take the battery off the charger?


texts:
I am building a solar powered lego catapult for my science fair project. I am trying to build a simple and efficient DC motor circuit that maximizes the power of solar panels to the DC motor (the catapult should be able to lift and throw something like a football). Here's my schematic below, I'm not sure whether if a capacitor (C1) is used correctly, I'm using them to make the current flow fast. (Also is this capacitor (C1) is necessary for this circuit?) I don't know if a flyback diode will have any effect on the lego motor when turned off since it contains a mini startup capacitor. Any ideas? Can you guys please give me tips and suggestions on how to improve my circuit design? My physics knowledge are limited to high school level.

simulate this circuit – Schematic created using CircuitLab

Note that the boost converter above steps 3V up to 6V. This is my first time using circuitlab sorry if it looks confusing to you.


texts: Is the voltage across a diode always 0.7 volt?

texts:
The question comes because I read that "for actual practical diode, when Id = 0 A, Vd = 0v". Fine, that's because no current flows through it. But shouldn't at that instant the circuit be open? Since no current flows through the diode?

A picture would make things clearer:

Why won't VD1 be a open circuit? Since we need at least 0.7 V of flowing current? Why would VD1 be 0?


texts: How to plot voltage vs current in HSPICE/MacSPICE?

texts:
I have a transient simulation for a simple voltage divider for MacSPICE shown below. I'm able to plot certain variables under test vs. time. How can I do a current vs. voltage plot for the transient data?

Voltage Divider - Sine

vin 1 0 sin (0.0V 1.0V 50) ac 1.0 dc 0.0
r1 1 2 1.0K
r2 2 0 1.0k

.control
* dispose of any 'save' statements from previous runs
delete all
tran 0.1ms 20ms
plot v(1) v(2)
plot -i(vin)
.endc

.end


texts:
So I haven't soldered in years and only have experience with through hole soldering and large components. Today I attempted a repair with a HTC Vive controller. I know where to solder and managed to do one side but the others points where I had to solder I think I've screwed up. So my question is how do I fix this? (If it's even possible) And was it the result of too much heat?

I know how to repair trace points and pads that lead to obvious places but these pads I think which are test pads I don't have a schematic, any ideas?
EDIT
For reference this is what I intended to do to fix my broken power cable. https://www.ifixit.com/Guide/How+to+fix+broken+power+button+ribbon/119514?permalink=1#comment-694934
I know they are test points. I need to solder to them because the ribbon cable connection on the main board on the other side was damaged, this bypasses that. If I have lifted the pads is it possible to fix ?


texts: For this diagram reduction question, I thought pushing the summing junction to the left past the G1(s) is can be a solution but is it correct that pushing to number 2 then we can collapse the summing junctions?


texts: Audio soft mute using optically isolated MOSFET

texts:
I have an audio signal running through a device that switches it over using a mechanical relay, as a result of the DC offsets and the parasitic capacitance on the output (which also connects to a high Z input) I can hear a 'pop'.

My original plan was to use a device called TLP222G which I had around to shunt the signal to ground quickly (before the relay action starts) and release it after a few ms, after the relay was set.

I had to use the same signal that feeds the relay's coil when that triggers I'm creating a pulse which should open the MOSFET, short the path to ground and keep it that was for about 0.2ms which is enough time for the relay to switch over.

The problem is that I can hear noise when the MOSFET opens or closes. Is there something else I should add to the circuit in order to keep the switching action completely silent?

Below you can see the simple circuit. The 360 Ohm resistor is fed from the 5V pulse that also activates the mechanical relay.

The LED inside the photocoupler has a max forward voltage of 1.3V so with the resistor it gets about 10mA.

This is a typical output stage of a device that is connected to the input of a high Z amplifier. The relay in the system shorts the input to the output so the entire device is bypassed. This creates a noise.


texts:
We are working on a project that requires us to use a high-valued inductor, with at least 10mH and ideally 40mH inductance.

There's nowhere in our area that sells inductors with these values, so we concluded that we should make one ourselves, but all attempts we've made using small ferrites lead us to a max value of 0.5mH, which is way off.

So, how can I make an inductance value this large without having to wire 10000 turns of coil?

EDIT: It's for a theremin project, frequency is around 200-300kHz


texts:
I succeeded entering ASPM L1.1 and L1.2 for my device. After entering ASPM L1.1 or L1.2 and trying to initiate to exit from Host side, I saw some hosts that are:
• Able to initiate an exit from ASPM L1.1 and L1.2 using CLKREQ# (Host side is pulling it down) • Unable to initiate an exit from ASPM L1.1 and L1.2 using CLKREQ# (Host side is NOT pulling it down) As measured in the lab by scoping the CLKREQ# pin.
When comparing the Config Spaces, Form Factors and BIOS settings of the Hosts, I don’t find a relevant diff in their configuration. When looking at the Linux kernel code, I don’t see any relevant reference.
It is strange that the Host advertises itself as L1.1/2 capable, sets L1.1/2 as enabled, however it does NOT tug on CLKREQ# in order to exit.
My device supports CLKREQ# and ASPM L1 substates.
Maybe it's the driver responsibility to disable L1.1/2 when the host doens't support CLKREQ#, but how does the platform indicates whether it supports CLKREQ# or not?


texts:
I'm using an Endevco Model 2220D Accelerometer with an Endevco Model 2721B Charge Amplifier to get vibration readings from a motor. I was asked to get a reading in IPS (Inches per second) but the Charge Amplifier gives a normalized output in mV/g. How do I convert that to IPS? I've not been lucky finding any math on the google... And this stuff is pretty new to me. Thanks all!

Maybe the better way to ask is this: I see a dampened sine wave on my scope as the output of the charge amplifier. The datasheet for the amplifier says it's normalized to mV/g. I need my output converted to Inches pre Second (IPS). How do I go about that?

Update: The dampened sine wave, for clarification, was due to me pinging the motor with a hammer to get a test reading prior to running the system.


texts: Role of the neutral conductor in three phase systems

texts:
In a symmetrical and balanced three phase system no current flows on the neutral conductor.

Obviously the real electric power distribution systems are not perfectly balanced, so there is a current on it. But it seems to me like a parasitic effect, which is due to the fact that I connect devices which are different from those of other people etc.

But, at least in Italy where I live, we receive from the electric power distributors two wires which are the phase and the neutral (and this one is about at the earth potential). So, the neutral is designed to let the current flow on it (and so it is not a parasitic effect due to the fact that the load is not balanced). So, which is the role of the neutral conductor?


texts: How to stabilize and add additional power to an existent line?

texts:
My first question on this Exchange so I hope this is the right place for it.
Currently, I have a quite unstable power supply in my workshop, coming from a very old electrical installation. It is a 220V installation.
When I weld, besides experiencing fluctuations, my welder is unable to reach its power rating as it is unable to draw the required amps from this old line.
I was wondering, would it be possible to stabilize the line and provide the additional peak power say, by placing an accumulator (battery + electronics) in the middle/in parallel? How would I go about it?


texts: Output impedance in a circuit with Operational Amplifier

texts: How I can obtain output impedance of this circuit? I would like to know in the ideal case and the LM741 case.


texts:
In reference to this question

Is it possible to program the LEDs each to flash on consecutively each with its own activation speed in the sequence chase then add some sort of a randomizer programming to choose to speed up the chase by 1 second or slow down by 1 second at random intervals which is also shown by a LED as a visual notification. Can this be done through the Atmel AT89C2051 microcontroller?


texts: Transforming logical circuit in NANDs and ORs

texts:
I can't transform this circuit in an exclusively NOR and another NAND circuit.
Everytime I tryed to simulate both circuits, neither of them gave me the correct result.

F=(notB)+AC

English is not my native language and I couldn't put it in better words, sorry.

Thank you.


texts: How is this design for a basic PCB pick and place?

texts:
I have zero experience with any serious mechanical design, but out of necessity and curiosity, I'm attempting to build a pick and place machine (for my hobby projects as well as low-volume PCB production) -- but a very basic version of it, customized to my own typical applications.

Specs: I'm trying to build the system with:

Cost < US $100 (excluding the vacuum pickup, microscope, etc.)
Board/panel area: Approx. one square foot (not important)
Speed of about 1 part picked and placed within 5 seconds (not important).
The "probe" (see figure below) is intended to be a vacuum pickup (as well as a miniature USB digital microscope attached)
Resolution/step-size of 0.3 mm or less (my smallest part footprints are 1206 resistors and 3 mm QFNs).
Accuracy and repeatability not too important since I have visual/magnified supervision of the process via the USB microscope.

My 1st draft of a very barebones structure, so far including 3 steppers, 3 rods threaded, a USB microscope, and a vacuum pickup:

Operation:

On my PC, for each part to be placed, I store (X, Y) coordinates for its corresponding tape reel as well as coordinates for target position on the PCB.
Y-axis motor/rod/pickup moves to tape reel and picks up part, then moves along Y-axis to target position's Y-coordinate on PCB.
X-axis motor/rod/PCB moves along X-axis so as to allow X-coordinate alignment too.
Z-axis motor/rod/part descends to PCB to place part, then rises.
Repeat until completion.
I supervise any mis-alignments or part misses, etc. via the digital microscope viewed on my PC monitor.
If any adjustments need to be made during any of this, I can just manually pause and adjust the position/action using the computer.

Here are my questions:

Is the mechanical setup drawn above too simple to accomplish the movement? Based on my reading of some literature and watching some videos of pick and places, the systems look much more intricate in build form, and also only either the PCB or the vacuum pickup moves, not both -- whereas in mine, I have one moving along the X-axis and the other along Y-axis (so as to simplify the stage/build).
What will be some key determinants you can think of that will make possible the resolution of 0.25 mm or better? I presume a good choice of stepper/motor (e.g., steps/revolution) is a start.
I see there is one laughably major flaw: Rotation of any of the three rods will cause the PCB or the vacuum pickup, or the picked-up part, respectively, to be rotated along with the rod! Any simple modification to solve this?


texts: How to interpret a negative primary leakage inductance in a three winding transformer?

texts:
i would like to compare the leakage inductance on the primary side of different transformer geometries.
I simulated a three winding transformer with an UI Core.
On one leg i have the splitted primary winding and on top one secondary winding and the same on the other leg of the core.

The result of the simulation was the inductance matrix. When I try to calculate the leakage inductance as described in "Induktivitäten in der
Leistungselektronik" (Albach) I will get an negative primary leakage inductance.

As described in "Avoiding the Use of Negative Inductances and Resistances in Modeling ThreeWinding Transformers for Computer Simulations " this can be right, but I don't know how to interprete the negative inductance because I want to compare it with the other transformers.
Thanks for your help.


texts:
Last week I successfully could connect my STM32F103C8T6 (aka Blue Pill) with Virtual Com Port. My OS is Windows 10, 64 bit.

In the Ports (COM & LPT) section of Device Drivers, COM8 was shown and I could see my print statements (sent over USB) while running the program (after uploading, disconnecting + reconnecting the USB cable and start putty).

Today I wanted to try it with my (also) STM32F103C8T6, but this is a minimal eval board.

When I plugged it in, I get in the device drivers/Universal Serial Bus Controlelrs:

Unknown USB Device (Device Descriptor Request Failed),

And when clicking on details:

Windows has stopped this device becaue it has reported problems (Code 43)

A request for the USB device descriptor failed.

Than I check on google and found some (very few resources) to reinstall the Virtual Com Port driver (from ST Electronics).

I did that, but since now on both my STM32s (also the blue pill) I get an Unknown USB Device and the COM8 is not showing up anymore.

I use (USB stick like) ST-Link V2 (not V2.1).

Does anybody know how to see my STM32s in the device manager again (also as COM port)?

Side question (but maybe I should post it as separate question): Is it possible to use two STLinks (to two different STM32 devices) at the same time? (preferably with Virtual Com ports)


texts: Amplify a signal having a DC component without using an opamp

texts:
I am building a simple modular synthesizer. I would like to keep everything simple and prefer to use discrete components over integrated circuits. My goal is to improve my knowledge about electronics.

How can I amplify a signal which has a DC component (e.g. 1V DC + a sine wave which is 1V peak to peak) without using an opamp?

It is easy to amplify a pure AC signal with a transistor, some resistors, and 2 capacitors (to decouple DC at input and output). However, now I want to also amplify the DC component, so the decoupling with the capacitors is not possible.

I am looking for a solution that doesn't have DC drift with temperature change, but it doesn't need to be perfectly linear.


texts: How does phone charger output current relate to input current?

texts:
Typically 1 charger takes a 120V input, and produces an output of 5V and 2A, so its power consumption is 10W. Theoretically a single power outlet (20A limit on breaker) can supply 120V * 20A = 2400W, which is 240 chargers connected to a single power outlet to overload it.

But one single charger can already deliver 2A, and each power outlet can deliver at most 20A... I am confused how these add up, because it seems like >10 chargers can already deliver more current than a single power outlet.


texts:
I'm trying to send CW (like hello world) with the SX1278 on ttgo t-beam. I've read the datasheet and some examples and come to this code:

  sx1278my.writeRegister(REG_OP_MODE, FSK_SLEEP_MODE);
  sx1278my.writeRegister(REG_OP_MODE, FSK_STANDBY_MODE);
  //433500000MHz
  sx1278my.writeRegister(REG_FRF_MSB, 0x6c);
  sx1278my.writeRegister(REG_FRF_MID, 0x60);
  sx1278my.writeRegister(REG_FRF_LSB, 0x00);
  delay(10);

  sx1278my.writeRegister(REG_DIOMAPPING1, 0x00 );
  sx1278my.writeRegister(REG_FDEVMSB, 0x00);
  sx1278my.writeRegister(REG_FDEVLSB, 0x00);
  sx1278my.writeRegister(REG_BITRATEMSB, 0x00);
  sx1278my.writeRegister(REG_BITRATELSB, 0x00);

  sx1278my.writeRegister(REG_PACKETCONFIG1, 0x80); //variable length
  sx1278my.writeRegister(REG_PACKETCONFIG2, 0x00);

  // Disable radio interrupts
  sx1278my.writeRegister(REG_DIO_MAPPING1, 0x00);
  delay(10);
  //sx1278my.writeRegister(REG_OP_MODE, 0x00100011); //continuous mode, TX
  sx1278my.writeRegister(REG_OP_MODE, 0b00100011);

AFAIK it shall transmit now, however it does not.
The Serial.print("REG_OP_MODE:"); Serial.println(sx1278my.readRegister(REG_OP_MODE), HEX); gives 0x01 which is stadby mode. gives 0x23 but no carrier is to be seen with rtl_sdr&gqrx. Any tips?


texts: BLDC Motor running fine for 1 minute, then stuttering

texts:
I am trying to run a BLDC motor made for model airplanes by locking it to a 3-phase rotational field.
Setup:

motor spec'd as 10V, 1700 V/RPM, max current 9.5A, without a significant load attached,
screwed down to a piece of hard wood
driver IC PCB widely available on ebay, using the ST L298N variant, i.e. 2 H-bridges supporting permanent 2A per bridge - since
you can control the halves of the bridges, I actually (ab)use the PCB
as 3 half-bridges, keeping the 4th part unused. What is peculiar is
that it has 2 electrolytics, but not the 100nF decoupling on the Vs
and Vss pins as prescribed by the datasheet.
microcontroller PCB with 3 PWM outputs of 1 timer peripheral. Currently using a 20 kHz PWM - to avoid the hellish noise of the apparently more standard 3 kHz used among RC plane enthusiasts. It may have more losses, but as I do not intend to use this for model vehicles, but rather stationary, reducing acoustical noise is more important.

the modulation of the pulse width is done using s sine table, with PWM channel0 having 0, ch1 120, and ch2 240 degree phase offset.
the frequency of table sweeps is adjustable (roughly) from 0.1 Hz to 200 Hz, by using a potentiometer attached to the MCU PCB for experimenting
the maximum PWM value is determined by a sedond potentiometer, to hand-adjust / determine the power needed at a certain rotation frequency

The funny thing now is:
This runs as expacted at e.g. 1 Hz rotation frequency, 10V, adjusted PWm to drawing 700..900mA for that frequency, for maybe a minute or two, then the previously smoothly running motor begins to "stutter" every couple seconds to every other second.
If I switch everything off and try again 20 minutes later, the same thing happens.

I wondered whether heat could be a problem, either directly, so I blew air on the heatsink that's mounted to the IC, or indirectly - raising the logical level that I maybe was operating at the edge with my 3V MCU, so I built 3 discrete NPN inverters to bridge my 3V MCU and the 5V logic, but that didn't help.

Resetting just the MCU does not help, and I don't see any difference at the beginning vs. when the malfunctioning starts in the PWM signals on the oscilloscope.

When the maltunction starts, the lab PSU does show current spikes which appear to be in sync with the metallic sounding stuttering noises of the motor, I detect no mechanical problem per se in that motor, though.
The heatsink does get warmer than I'd like to touch for longer than the blink of an eye.

I don't have thermal imaging equipment, but get my lips down to ~ 5mm distance to the motor coils, and as far as I can tell, they don't get particularly warm.

Any ideas what may be the cause?


texts: Draining a car battery down to a specific voltage

texts:
I would like to be able to drain a car battery down from fully charged at 12.6v down to between 10.5 to 11.9 volts without having to manually check it with a multimeter periodically, yet have some obviously visible sign that the discharge process has finished.  Anywhere in that voltage range is acceptable, although closer to the higher end of the range is preferable.

The car batteries typically have capacities between 50 to 100 amp hours.
I was planning to use one or two 12v 60watt ( 5amp ) car headlights as the load, such that the discharge time would be both reasonable, but not so fast as to damage the battery.

Is there some circuit design / device which could meet that goal and be implemented by someone with a basic knowledge of electronics?

EDIT

OK, this ICStation Battery Low/Under Voltage Protection Kit is basically exactly what I'm looking for:

Obviously the easiest thing would simply be to mail order an item like this, however I'm not sure I could get it shipped to the country I live in.  Would it be horribly difficult to build something like this?

EDIT

OK, so here's a project suggestion for building something like this.


texts:
I'm trying to simulate the following chopper controlled dc motor in MATLAB Simulink using a PI controller.
Now without the freewheeling/flyback diode across the motor terminals I can simulate the model to get the desired speed output. But with the diode the motor seems to run at full speed and is uncontrollabe.
Is it a glitch in the software? or is there anything I can do about it in the software?


texts: Continuously on power strip with short cycle ON/OFF switch?

texts:
I'm trying to build a mobile device testing rig to hold 10 tablets.

The tablets should be constantly charging via USB cables plugged into a power strip, but when I publish new content to the devices (via a specialized wifi app) I want to walk over to the rig, flip a switch and begin a continuous power cycle (off/on every 10 seconds) that will wake the devices and keep them awake while I'm standing there. When finished I want to flip the switch off to end the power cycle and continue normal power to the devices.

I've seen short-cycle timers like this (http://www.amazon.com/Digital-734170-Short-Cycle-Timer/dp/B00AKEOQWE/ref=sr_1_1?s=hi&ie=UTF8&qid=1439664239&sr=1-1&keywords=short+cycle+timer) that could potentially do the trick, but it's not quite there.

Any suggestions appreciated!


texts:
After reading a lot of posts (here and on the web), I am a bit confused.
All I want to do is to get the best practice of push button connection to AVR.

I have 2 "sections" to my question. the first one is the HIGH or LOW connection, and the 2nd one is the resistor issue. I will start with the HIGH/LOW options:

+5V --\ ----AVR : The AVR pin is set to LOW by default and checked if the pin is HIGH (so the switch is on).
GND --\ ----AVR : The AVR pin is set to HIGH (Pull-up?), checking it for LOW to see click.

The 2nd section of the question is about the resistor, and if I need to use it.

If I am using the pin with HIGH value and by pushing the button it connected to groud,
I saw some of the blogers put resistor before the button and connecting it to VCC:

Do I need it? if so, what should be R1 value?
If I am setting the pin to LOW as default, should I use resistor as well, but connect it to GND?

Thanks guys..


texts: Motor calculations for go-cart / go-kart

texts:
I built a basic wooden go-cart and I want to convert it to electric power, and my question is how to calculate the motor. I searched here and apart from this 24V 250W motors I can't see any similar questions. The go-cart is not intended to be high performance. Details are:

It has 4 wheels which rotate independently on two axles, the front axle is for steering and rear axle fixed.
It's intended for paved or mostly-smooth and mostly-level surfaces
For simplicity I planned one motor driving one rear wheel, or two identical motors driving two wheels.
The wheels are 23cm diameter (0.72m circumference) and I realize gearing is needed between the wheels and the motor.
Total mass of go-cart, passenger and motor <= 50 kg
Maximum speed of say 4 m/s, go-cart doesn't need to accelerate faster than 2 m/s/s
The max speed and acceleration are very approximate and I don't mind if they are greatly different from the above. I based the max speed on the speed of a running person
Powered by 12v or 24v lead-acid batteries
Motor to be controlled by controller or even a large rheostat https://surplussales.com/Potentiometers/Rheostats/PotsRheost-1.html

So my approach is to calculate the kinetic energy (KE = 1/2 M V^2) at different speeds to see what power is needed:

Speed of 1 m/s = 2.2 mph (equivalent to walking). KE = 25 x 1^2 = 25 Joules
Speed of 2 m/s = 4.5 mph (fast walk). KE = 25 x 2^2 = 100 Joules
Speed of 3 m/s = 6.7 mph (jogging?). KE = 25 x 3^2 = 225 Joules
Speed of 4 m/s = 9 mph (running). KE = 25 x 4^2 = 400 Joules
To acquire a velocity of 2 m/s in 1 second = 100 Joules in 1 second (requires 100 watts)
To acquire a velocity of 4 m/s in 2 second = 400 Joules in 2 second (requires 200 watts)
Power = V x A, so assuming a 200 watt motor, this needs 200/12 = 17A from the battery.
This website https://www.powerstream.com/battery-capacity-calculations.htm says (step 3) if we drain a lead-acid battery in 1 hour we get about half of the rated capacity. So to get 17A for 1 hour would need a 12 volt 35 A/hr battery
When we know the required current (eg 17A above) this would be the minimum current handling capacity of the motor controller or variable resistor

I realize this method is very approximate, the KE isn't dissipated in 1 second, and the calculations don't allow for friction, gearing, motor or other losses. So my question is: how easiest to calculate the required motor for the go-cart as described?


texts:
I designed this circuit to switch on my P channel mosfet because the Vgs will be more than -20 V (maximum Vgs) if I put the traditional design .

Is this circuit correct or can you help me to improve it more?

thank you .


texts: ATmega32u2 fuse bits - can destroy using FLIP?

texts:
I want to build some simple application using ATmega32u2, and have it programmed strictly only via USB, by using the factory-builtin USB bootloader on µC, together with the "FLIP" program running on Windows computer.

I've read, that in ATmega32u2 there are so-called "fuse bits", which control some internal configuration. Also, on many forums I've seen calls for help from people who have accidentally reset/changed those bits (in various AVR chips), and now have problems programming their microcontroller.

Thus my question is: can fuse bits be set/destroyed via the FLIP program, over USB? If yes, then what should I "not touch", or what I must verify is set properly (and to what exact value?), to be safe against such problems?

Thanks.


texts: Momentary to Latching Circuit with Zero Off Current

texts:
I have a project with several physical constraints so that I want to use:
 1. A sealed very thin momentary switch as main on/off switch
 2. 2 x AAA battery supply = 3V or less
 3. Load is a small DC motor pulling max 0.3 amp
 4. Momentary to Latching circuit to be as small as possible and with zero current drain in the off state

I have looked a various momentary to latching circuits using transistors, MOSFETS, and Flip Flops but as best I can tell they all have a very small drain current of approximately 10uAmp or more in the off state.

I am correct about the off drain current for these circuits?

If I am not correct can you suggest a circuit that would work for my project?

If I am correct does anyone have a circuit design that would meet true zero drain current for the requirements above?

Many thanks.


texts: Can Solar Panels Be Made From Other Semiconductors?

texts: I have heard that most solar panels use polycrystalline silicon. It seems like a very expensive material. Are there any other materials we can potentially use to capture photons in solar panels?


texts: Trimmer Capacitor for TX Crystal Oscillator / RF

texts:
I'm building a 433.92MHz transmitter.

I have gone through some revisions, and have been hand tuning the transmitters.

I settled on two 1pF caps, and that has been working for sample units.

I got our pre-production batch of 10 boards, and we noticed a few of the transmitters are not well tuned.  Typically a modification of +/- 0.5pF to the tuning caps, get the oscillator back to the center frequency.

The crystal being used is ostensibly 10PPM, and honestly theoretically should work up to 100PPM if you do the math based on the stated permitted frequency deviation of the receiver.  I however, do not have the luxury of math -- because the 10PPM crystals I have, are not performing like they should when you start mass producing boards.

I'm thinking of adding a trimmer cap, but I'm not familiar with the underlying oscillation circuit being used in our transmitter IC.  I think it's a parallel resonant circuit, as the caps are parallel to the trimmer cap.

If the two caps are in parallel, the total capacitance to the crystal is one half of each?

Based on the schematic below, I'm thinking I could get rid of the two load caps, and just add one trimmer in place of the cap?.

I need in a range of 0.5pF to 4pF, in the trimmer cap so that is why I am thinking of getting rid of the other 1pF cap.  Maybe I replace the 1pF with a 0.5pF?  Does it really matter?


texts: How an electrical component behave after being exposed to excessive current/voltage?

texts:
I wan't to know more about how to recognize a damaged component due to excessive impulse or constant current exposure. Particularly resistors, ceramic/electrolyte capacitors, protective diodes, transistors, voltage regulators. Which of them will behave like an open circuit and which of them like a short circuit? Also where I can find literature about that topic, and how is that usually described in the datasheets?

Thanks!


texts: Gamepad changes descriptors if it's connected to an OTG port vs normal USB host port, but how does it know?

texts:
I have an MSI Force GC20 gamepad. It has several different "modes" which can be selected which basically allow it to reset and offer different USB descriptors. For example, it can be several variations of HID or an XInput (literally using the XBox controller descriptor verbatim).
When I plug the controller into my desktop PC, it always enumerates with the Xbox descriptors. I also have an embedded target, an STM32F767, which is running the ST USB host stack. I wrote a device class driver which works great with an XInput XBox controller, but the trouble is that this controller refuses to enumerate with these descriptors when connected to the Stm32F7, and instead will only use it's HID descriptors.
Using wireshark to probe the USB interactions on my desktop, the very first thing that occurs is the descriptors request, which is satisfied with the XBox descriptors. There's nothing too interesting going on before then.
I thought this could be the case that the controller was somehow determining some difference in ports because on the Stm32F7 VBus is switched off when the port is inactive. So, I changed the code such that VBus is always on. No change. I am using an off the shelf USB OTG host adapter. This should ground the ID pin and make no further changes to anything electrically (AFAIK). So I'm at a loss for how the controller is figuring out there is a difference.
My question is, what part of the USB OTG or host spec could the controller be using to make this early determination what descriptors to return? Potentially some configuration of pullup/down res on the USB 2.0 pair?
This is the Wireshark capture from my desktop:


texts:
If a transformer draws more current than the voltage source can supply, what happens to the voltage across the primary? It should be the same as the source but it has been reduced from load current canceling original flux and the source is unable to supply more current.

eg. http://inverter-circuit.com/12vdc-to-220vac-inverter-with-555-timer.html#jp-carousel-127


texts: Fixing or finding a replacement for a Potentiometer

texts:
I am trying to do a little home repair on an older set of CH Pro Rudder Pedals. These are a 3-axis USB game controller, and I have isolated the problem to one of the potentiometers in the right break axis.

The signal from the pot initially had a large amount of hysteresis when read by the controller card. It took about 70 seconds from the reading to fall from 255 to 6 when the access was moved from one extreme to the other. I could prove it was not the card or software by switching the left and right axis pots an observing that the problem migrated from one side to the other.

The potentiometers in question are a bit interesting. They all run 120KΩ, but while the armature rotates the typical 270° the active range is only over the middle 90° of movement; beyond that the pot reads full deflection.  The malfunctioning pot reads open circuit on the center tap and the expected 120KΩ from end to end on a multimeter. It has a 1/4" shaft with a 3/8" deep half cut on the shaft. The two good ones are marked HP-100A 0004 ROC the bad one is stamped 900-604B 0105.

My preference would be to simply purchase a replacement potentiometer but I've never had to find one this specific. The narrow active band seems particularly unusual. Some CH Products forums suggested that this is a custom made part and that they cannot be purchased new any longer.

If I cannot get my hands on a replacement, I wonder if I can fix the old one.  If I remember pots are among the more straightforward devices.  Can I open this thing up and fix what ever is wrong with it?


texts:
I finally got my first PCB through in the post today. Very happy with it, but I made a very amateur mistake in my excitement and eagerness to have it ordered. I seem to have used a 2N2222 part with the wrong pin out.

R5 should be to the base of T1, however all the 2N2222s I have seem to have the base on pin 2, not pin 3 as shown here.

Does anyone know how I could track down a version of this transistor that has the pin out of 1 - emitter, 2 - collector, 3 - base? The datasheets I've trawled through so far seem to indicate I might be out of luck.

Lesson I've learnt here, don't autoroute without checking very carefully.


texts:
let's consider a certain finite state machine, for instance a Mealy Machine:

I was told that it cannot work properly in absence of a reset signal (for the State Register), since we would not know the initial state of the device at the moment in which it is switched on.

But I do not understand clearly this concept. In fact, a Mealy machine may be described by an ASM diagram, for instance this one:

Let's consider the instant in which it is switched on: why cannot it work properly without a reset button?

If it is not present, I think that the machine will follow anyway the related ASM diagram correctly, and the difference is simply that it may start from another state (for instance from s1 instead of s0).


texts:
Got one for you guys. Is there any reason why I should argue against putting ESD flooring inside an electrical room with 480/277V and 208/120V panels present?

I would gladly accept any NEC references and/or safety regulations to support the argument.

Reason why I am asking: Boss of cleanroom design firm is amazing at cleanroom design but is not well versed at basebuild and other engineering disciplines. I am the sole electrical person with two years experience so I want to find out if my reservations are right before arguing my position.

* Thank you everyone for your responses. Boss heard what I had to say and decided to stick with a sealed concrete slab in the electrical room.*


texts:
I think I understand how to answer this question but am missing how to do a certain part which stops me from getting their.

For this question this is all I know how to do.

cos-1(0.31) = 71.94°

sin(71.94°) × ? = kVAr

I dont know how I am supposed to calculate this missing value "?". Am i on the correct track?
The answer to the question is 27.12 to verify your own working.


texts: Motor controller - transistor taking up 3/4th of the voltage

texts:
I am trying to make a motor controller for a DC brushed motor. The design is fairly simple, see below - motor represented by inductor

The problem I am having is that if we imagine A to be HIGH and B to be LOW, the motor is not dropping 12V (or close to). If I use a multimeter to measure voltage between drain-source on Q5 I get about 8.4V, on Q8 I get close to 0V. The voltage drop across the motor I measured to be the remaining 3.6V.

Would anyone have an idea why my circuit is not operating as I had imagined, and if so, what improvements could I make?


texts:
I'm trying to interface a SparkFun Serial Enabled 16x2 LCD (3.3V) to a Beaglebone Black. Since the beagleboard has on-board 3.3v and ground, I used that for the power to the LCD. For the 3.3v TTL serial, I used Pin 21 on the P9 header (aka SPIO_D0). I've encountered an odd issue with this setup, and I need help with a possible solution, as I'm still trying to learn electronics.

The issue is that if the LCD is plugged into pin 21 during boot up, Linux starts running really slow. I found out that if I plug the pin in after (1) linux has booted, and (2) I've initialized that pin to serial mode from the software, then Linux runs fine. So it seems that pin being initialized to serial mode is a must for the OS to not crawl to a halt. And that seems that it's not the default setting during boot up - which causes any operations in a terminal (such as dmesg) take an excessively long time to complete until that pin has been initialized properly. I have no idea why that would happen, and I haven't been able to find a way around it.

So, as one possible solution, I figured I'd use one of the other GPIO pins and a transistor to turn on the LCD after I've initialized pin 21. The problem here is that the LCD really wants 3.3v, and I'm getting an 0.5v drop across the transistor, which drops the voltage too low to power the LCD. I suppose I could use the 5v line, a transistor, and a 3.3 voltage regulator, though that seems like it's probably not the best solution, since the board already has on-board 3.3v power. I suppose I don't know if this approach would actually fix my problem...

Does anybody have any suggestions on how to fix this issue?

Thanks!


texts: How to stabilize a control loop for an opamp-based linear regulator?

texts:
I'm trying to build a digitally controlled linear bench power supply. The idea is to have a DAC that will output a low voltage (in my case it's 0-2.5V) and then scale it (let's say 0-25V for simplicity). And of course, buffer it with a big transistor.

In the first iteration I used simply a 10x gain opamp and then just used it to drive a darlington pair. This works, except it's limited by the opamp's supply. In my case I'm just using a TL072. Absolute maximum for this this is 36V, with max differential input voltage <30V. Which effectively limits my power supply's voltage to, realistically, less than 25V (since it needs -V lower than -3V to reach zero. TL072 is not rail to rail). TL072 is easy to find and I'd like to avoid the need for "fancier" high voltage opamps

Now, for the second iteration someone suggested I simply use something like the following:

In this case, the feedback is passed through R9/R3, scaling it 1/10. When the opamp has 2.5V at its inverting input, it compensates to make the noninverting input 2.5V as well. To do this, it needs to make the output 25V. This works. Until I alter the output.

If I add any sort of capacitance at the output, the whole circuit starts oscillating.

How can I compensate this? Or in any case, is this the right topology to use?

UPDATE

I have figured out a different topology, using a PNP transistor instead of NPN to supply voltage to the output darlington. Here's the schematics:

In this case I have also added current limiting to the circuit. I'll try to explain the idea. First of all, the load is simulated by R15 in the diagram. V2 is a voltage source, in my case a DAC controlled by a microcontroller. This sets the voltage reference for U1, through the noninverting input. The output of the opamp is connected via R2 to Q4 which "modulates" the base for Q3, which finally sets the voltage for the Q2/Q1 pair. This allows me to output a larger voltage than supported by the opamp. In this case, V+/V- is +/-10V while the collector voltage is 40V. Using R9/R2 I get feedback from the output, which is scaled 1/10. C1 slows down the response to keep the whole circuit from oscillating when there's a capacitive load at the output. Now when there's a capacitance at the output my circuit doesn't oscillate anymore.

Now on to the second part: a programmable current limiter. R6 is a shunt resistor, 0.1 ohms. This is the input for U2 inverting input. The noninverting input is another voltage source. In this case, 0.1 ohms provide 100mv/A. If I want to have a fixed 2A output current, I'll set the reference input to 200mV. When the noninverting input reaches  the set voltage, Q5 will "rob" current from V2 (voltage setting), thus making the output voltage drop enough to keep the current at the set value. C3 slows down the circuit to make it respond smoothly instead of clipping.

The problem is, again, a capacitance at the output. This makes my circuit oscillate again.


texts:
I'm trying to find a way to translate small angle rotation into some form of digital signal. 1 degree resolution would be excellent, but something like 5 degrees would be ok.

I need something like a rotary encoder, but with much higher resolution, similar to what we see inside old rubber ball mouses, which have an encoding disk and IR leds/sensors to detect when the disk spins.

Is there any commercial component that would do that? Or I will need to build it myself?

Thanks in advance!


texts: How viable is it to just use 1% resistors and calibrate out the error?

texts: At the moment, I use 0.1% resistors to get accurate voltage measurement through a voltage divider. However, the cost is high, so I was thinking of using 0.5% or 1% resistors and calibrating out the error in software by using a precision voltage reference during production. Has anyone done this successfully? What pitfalls might I encounter?


texts: Can I use MOSFET as replacement for the SSR or EM relay?

texts:
I am trying to look for a solution that can help me in turning ON/OFF my 24VDC, 2A LED load. So as per the application needs I may have to turn ON/OFF this load 30 times max per day. So it is a DC operation.
Below sketch shows a quick pictorial representation of what I am trying to do. Not a final layout yet.

I am looking if I can use a MOSFET rather electro mechanical relay. I am referring to the ROHM RQ7L050AT
datasheet. This is a 60V, 5A Mosfet.
But by looking at the SOA curve as below, I am not sure if this MOSFET approach is advisable for continuous DC loads.
As per the graph, I guess at the desired 24VDC VDS the maximum allowed Id current is less than 0.07A before I hit the thermal runaway situation? (whereas my actual requirement is for 2A Id).
Let me know if I am getting if right. Can anyone help me understanding the MOSFETs for DC load operations?
Will it help if I choose higher VDS and Id rated MOSFETs?

Thanks in advance!
-Yugandhar


texts: Cut-Off Sinusoid or Sinuosoid?? - Standing Voltage Waves on Transmission Lines

texts:
My textbook shows two diagrams that appear to contradict each other to me. Each depict the magnitude of the standing voltage waves on a transmission line. The first, fig 2-14, shows a sinusoid bounded by Vmin and Vmax. The second, fig 2-15, shows general patterns that are clearly the result of cutting the sinusoid in half at the minimums. The second makes sense to me, and the first seems incorrect.

I have two questions:

Have I actually found some contradiction here, or am I incorrectly relating these scenarios together?
If this is a contradiction which depiction is correct?


texts: Voltage Comparator IC's Output (LM339) Never Goes To VCC (But Can Go To Ground)

texts:
I'm trying to set up the most basic form of voltage comparator using LM339 (http://rohmfs.rohm.com/en/products/databook/datasheet/ic/amp_linear/comparator/ba10393f-e.pdf).

I'm giving it 12V supply (from an ATX PSU).
On input 1 I give again +12 and GND. Output 1 goes to ground, but when I switch the inputs it does not go to VCC, instead it gets floating.

When it goes to ground, I can measure the voltage between output and VCC and it is 12V.
But when I switch the inputs, I measure voltage between both output and ground and output and VCC and it is always 0, which leads me to thinking it's floating.

What could I be doing wrong?
The fact that it gets to ground leads me to thinking the IC does something  and if I remove its power, the output pin no longer goes to ground.
But I cannot understand why the output never goes high.

I tried with 3 ICs (same model) to eliminate the possibility of a buggy chip, also triple checked wiring - same thing.

Any help will be greatly appreciated!


texts: How to view a detailed resource utilization report on an FPGA design when implementation fails in Xilinx Vivado?

texts:
I'm using Xilinx Vivado 2020.2 on Windows 10.
When I attempt to generate a bitstream, it fails at implementation with this error:

So I need to reduce the number of FDCE cells I'm using. That's doable, but I need to know where they are. The synthesis report only tells me the total number of FDCE cells used across the design, not a per-module breakdown.
I can usually use the utilization reports produced in the implementation stage to see where resources are consumed, but since implementation failed, the "Report Utilization" option is greyed out.
Implementation got far enough to know I'm using too many FDCE cells for my target device, so how can I see where they're being used?


texts:
I'm using an STM32L053 MCU to interface to a poorly-documented PCB module (DRA818V).  There are a couple of GPIO driven signals as well as a UART involved, and I want to make sure I'm doing things safely.  It seems that I can connect the UARTs directly (RXD to TXD) and nothing else is needed there.  For the GPIOs, I'm not so sure.  I believe, in the module, the GPIOs just go directly to the MCU inside it.  I'm concerned that, when I pull the lines low in the STM32, the other module might source too much current (though, configured as input, I would hope not).  Should I have a current-limiting resistor in line on the GPIOs?  Would there be any harm in putting a 1k?  (i.e., preventing the input from seeing "low")

Additionally, I'd like to drive an LED from one of these lines.  I'd just planned to connect the base of a PNP in addition to the connection to the module (the other MCU) -- do I need to do anything special here, beyond the normal base resistor?  Specifically, I would branch the GPIO to drive the transistor base and also signal the other MCU.


texts: voltage regulators: How does Ohm's law apply here (and how not to fry an ams1117)

texts:
Very basic noob question here, asking for an analogy rather than a 'it's law xy':
I used an ams1117, 2.5V, sot223. To test it, I used an usb cable 5V and plugged it into my phone charger (rated 2A) and measured the output of the IC: it quickly overheated (no measurement taken). I should mention the connectors got so hot it even desoldered one of the cables: the green one, connected to the ams1117 (this is how I inferred it overheated).  Basically the question is, why is testing your IC this way silly or suboptimal.
It was my understanding that when you regulate / fix the voltage in a circuit (i.e. the output of a voltage regulator, set to 2.5V, such as this ams1117), the current will be basically 'regulated by the resistance'. Here, I guess the resistance would be only the wires and the IC, as nothing else besides the multimeter was attached.
Did this overheat because the resistance was low, and due to the inverse relationship between current and resistance? If no, please point out my misconceptions.
Edit: sorry for the horrific picture below (I didn't know how to do this best). Legend: Ams is ams1117 2.5V out, usb is a usb cable with ground and 5v separated (power supply quick charge, up to 2A). MM is multimeter in voltage mode, auto, dc. Red is Vin, Green Vout, black ground.


texts:
Apologies if this is the wrong exchange.

I would like to start a home project, in which screw-in bulbs are left mostly exposed, and connected to semi-flexible wire. Something similar to this:

A closer shot, from a different peice shows the concept a little more clearly:

I'm very new to electronics, and intend to invest plenty of time into learning before I begin the project properly, but I'd like to know whether making the bulb-wire connection safe (as I assume/hope it is in the links provided) for others to be around/touch (interested kids, pets, etc) is beyond the reach of an amateur like me. Surely this is beyond simple grounding? If so, and if anyone knows what direction I should be going, I'd be very appreciative for any input.

Cheers!


texts: How do you solder a metallised film capacitor?

texts: I have recently bought some MKP film capacitors to make a capacitor bank in parallel. While viewing their datasheet, it was mentioned that the soldering temperature should not be over 600 degrees Fahrenheit. Is it recommended to fix them on a soldering board or am I better off designing a PCB and fixing them?


texts:
Ok, this is my very first question here so please forgive me if I'm asking a too broad question or if my problem description is too imprecise.

I have a 13.56 MHz (RFID) pierce-type quartz oscillator from which I have to derive a burst packet of exactly 136 periods (~10us burst length). There is a trigger signal (TRIG) available to trigger this 10us burst. [Edit1: TRIG is fed to a 74LVC1G126 buffer driver which enables/disables the burst]

The problem: I need to do it cheap (<10 cents @ 10kpcs) and space constrained (somewhere below 40mm^2). So a microcontroller is not an option. RC timing is also not an option considering the required temperature range from -20°C to +70°C.

I think I need some type of discrete, synchronous counting circuit.

My first idea was to use a SN74LV161ADGVR type counter which is available in a 6.4x3.6(TVSOP16) housing, but it has only 4 bits and 6.4x3.6mm already scratches at my space constraints.

Do you have any idea how to achieve such a tiny,cheap burst controller/counter fed by a crystal oscillator?


texts:
I am learning VHDL and I am using the Lattice boards. I want to know how to declare a GPIO. I found the following block of code in the diamond software folder example. It is ".lpf" file and I guess it is the place where the pin are declare. Can anyone explain simply what the lines mean:

BLOCK RESETPATHS ;
BLOCK ASYNCPATHS ;
BLOCK JTAGPATHS ;
IOBUF ALLPORTS IO_TYPE=LVCMOS33 ;
LOCATE COMP "seg_1" SITE "V6" ;
LOCATE COMP "seg_2" SITE "U7" ;
LOCATE COMP "seg_3" SITE "Y6" ;
LOCATE COMP "seg_4" SITE "AA6" ;
LOCATE COMP "seg_5" SITE "U8" ;
LOCATE COMP "seg_6" SITE "T8" ;
LOCATE COMP "seg_7" SITE "AA5" ;
LOCATE COMP "seg_8" SITE "AB4" ;
LOCATE COMP "clk" SITE "L5" ;
IOBUF PORT "seg_1" IO_TYPE=LVCMOS33 TERMINATEVTT=OFF ;
LOCATE COMP "reset" SITE "J7" ;
IOBUF PORT "reset" IO_TYPE=LVCMOS33 ;
LOCATE COMP "direction" SITE "J6" ;
LOCATE COMP "LOCK" SITE "W5" ;
LOCATE COMP "seg_9" SITE "Y20" ;
LOCATE COMP "seg_10" SITE "AA21" ;
LOCATE COMP "seg_11" SITE "U18" ;
LOCATE COMP "seg_12" SITE "U19" ;
LOCATE COMP "seg_13" SITE "W19" ;
LOCATE COMP "seg_14" SITE "V19" ;
LOCATE COMP "seg_15" SITE "AB20" ;
LOCATE COMP "seg_16" SITE "AA20" ;

Correct me if I am wrong, so
The first 3 lines block the user to use Pins that are used in JTAG & Reset?

A line like this:

LOCATE COMP "seg_16" SITE "AA20" ;

mean to the synthetizer that the variable seg_16 from the VHDL files is linked to the "real" pin of the board.

Finaly, I got no idea what the IOBUF keyword mean. So Did I get something right or I am plain wrong?


texts: Biasing an NMOS to get rid of \$V_{th}\$

texts:
So here's a common way of cancelling out the \$V_{th}\$ in an NMOS. Am I better of use a good quality zener (in series with a resistor) or stick with voltage divider R1 and R2 below.

Assuming we can have very low tolerances for R1 and R2 and we can choose the value of a zener continuously (rather than the preferred values). Which is still better?


texts: Optoisolated MOSFET to control a load - should I take in consideration MOSFET typical use?

texts:
I've already asked a specific question, but I'd like to evolve it in a more general question.

In a typical optoisolated IC like this:

Should I or not interconnect control (-) and DC (-) or will I lose my optoisolated considerations?

Since there's a MOSFET N inside this IC schematics, should I take in consideration MOSFET typical use with load on drain side? To avoid MOSFET high side configurations.


texts:
Static RAM requires, as I understand it, six transistors per bit.

How many transistors per bit are required for a shift register, of the simple serial in serial out variety? Is it likewise six transistors per bit, or can it be simpler because of the lack of requirement for random access?


texts: Need to divide variable DC signal voltage

texts:
I have a CNC controller that outputs 0-10v PWM signal voltage for the purpose of controlling cutting spindle RPM (or in this case, laser power output). This is not the actual driving voltage, this is a signal voltage (I hope that makes sense).
My laser engraver requires 0-5v PWM signal, so I essentially need to cut the controller's output voltage by 50%.

I am not an electronics expert by any means, but I can successfully put a circuit together. I have op amps, resistors, capacitors, and diodes at my disposal, so hopefully it can be done with what I have on-hand.

Thank you very much for any help.


texts: I am developing application for Time Proportional Control of thermostat. I know that the output for heater is proportional to an error. For example, if SetPoint is 20 and proportional band is 2, in case if actual temperature (AT) is 19, then Output would be 50%. However, I can not figure out what happens if AT is higher than 20? For example if AT is 21, then output would be again 50%, that does not make any sense.


texts:
Im having trouble trying to understqnd this circuit , as you can see from http://www.instructables.com/id/Arduino-Audio-Input/?ALLSTEPS its a circuit that will amplify a signal from 200mV to 2.5V and then apply  an offset to it in order for it to be centered in 2.5v this way the entire signal can be read by the arduinos ADC

however, as you can see from my picture i dont understand the porpuse of the 10uF cap, and even worse i dont understand how the arduino its feeding itself with 5vDC when im actually aplying a voltage divider to an AC signal

This Voltage divider only makes sense when using 10v DC (which is actually the dc current used in the proyect) where

Vout = (10v * 100k)/(100k+100k) = 5v

However according to the schemmatic we are not using DC we are using a 2.5v AC signal


texts: I encountered the word bus isolation resistors in my datasheet for a processor. I have not heard of it before and I cannot find anything on Google. Is there anyone who can explain it to a beginner what it is and what purpose it serves?


texts: Parallel connection between distinct DC Bench Power Supplies

texts:
I'm using a 30V DC power supply which is said to be 30V/3A with a switch between series/indep/parallel mode. Connecting the supplies in parallel, we have a maximum of 6A. However, in order to execute my current project, I´ll need over 10A. When we parallel connect the outputs, even if there is a small voltage difference, the internal control ends up managing to balance this difference so the output is the same in both channels.

My DC Supply is meant to be a linear ICEL PS-5001.0014 30V/3A.

Looking at the datasheet of an Agilent DC power supply, I read that I can actually connect two independent linear supplies in parallel. So, I could buy two distinct DC supplies and connect their channels such as I have them in parallel. I was wondering if I could also do it with my DC power supply.

I have this question because, even though I've purchased the supply as a genuine ICEL DC Power supply, I found many other ones from china (this means mine is just a copied version sold as genuine) which may be manufactured with low quality components. My question is, can I purchase another similar linear DC Power Supply, connect its channels in parallel and finally connect the two DC supplies in parallel again (in order to have 30V/12A)? Can I trust in the internal control so it will manage to balance all voltage differences (let's say one channel has V=29.99[V] and other has V=30.01[V])?

I'm attatching a picture of my DC power supply and two others I've found on internet that actually are the same as mine.


texts: How to optimise Boolean functions in very many variables?

texts: Given a black box with N binary inputs and specification of the output for every one of the 2**N possible input states (but no pre-knowledge of the logic in the box) I need software tools to design the minimal gate logic in the box. What method or software can anyone suggest, and can it handle problems with N=256 ?


texts: board to board soldering without castellated vias, how?

texts:
I want to produce (small scale) a simple device  (0.5A stepper motor controlled by atmega and a498 with a potentiometer to regulate speed).
To simplify the whole process I'm using as many ready made modules as possible. A498 and Arduinos are simple - can be connected with "mother" pcb by headers, but I'm not sure about buck converters.
The ones I'm interested in do not have castellated vias, they have regular pads with vias (do they have a proper name?) at each corner of the module. How to connect them properly to other pcb? Can one just solder those IN, OUT pads to "mother" board?


texts: Will a capacitor of 10uf 250v work as good as a cap 10uf 50v?

texts:
what is the difference between  electrolytic capacitors 10uf 250v and 10uf 50v?

if i connect it to my circuit  with a 9v battery?

will the 250v cap work?  or which is the most preferred for a 9v circuit  xuf 250v or xuf 50v or with voltage <250v?

Does A 250v capacitor has high resistance as compared to a 50v or < 250v cap?


texts: Does my total power supply voltage need to equal the sum of the voltages in my circuit in series?

texts:
If I have let’s say, 4 bulbs, each rated at 1.5 volts and they’re all connected in series.
Would my battery need to be rated 6 volts? My logic is that each bulb would have a voltage drop of 1.5 volts across them, but I’m not sure.
Like wise, if I put all the 1.5 volt bulbs in parallel with each other, is using a 1.5 volt battery okay as they would all share the same voltage?


texts: What is the way to detect sd card insertion/removal?

texts:
I am interfacing 32GB Micro SD card with PIC32MX795F512L. I am following the examples provided in Lucio de Jasio book. In one of their example, they are using while( !getCD()); to check if the card is present or not. But this seems not working in my case because when I remove the card, it doesn't give any error and moves forward. Below is its code:

// SD card connector presence detection switch
int getCD( void)
// returns TRUE card present
// FALSE card not present
{
 return !SDCD;
}

In the hardware, SD-CD pin is connected to RA15. So what is the way of detecting the card presence?

EDIT:

Above is the schematic for SD card connections. SD-CD# pin is the pin for card detect. I am checking the voltage change on R34 but there is no change. When the card is removed, it shows 3.5v and when card is inserted, it again shows 3.5v. Am I doing something wrong or hardware has got some problem.


texts:
simulate this circuit – Schematic created using CircuitLab

How would the feedback resistance be found in this setup? I am used to seeing the negative-feedback resistance as a single resistor between the inverting input of the op amp and the output of the op amp. I am not sure how to calculate this resistance with the resistor going to ground in the mix.


texts: Three phase systems - are there any single phase devices that are connected between two phases instead of between one phase and neutral?

texts: In star system, single phase consumers are connected between a line and neutral but are there any single phase devices connected between two phases (would that even be considered a single phase device?)?


texts: How to create this opamp circuit for mind machine

texts:
I'm trying to create a circuit to blink lights at the precise frequency for a mind machine. The lights need to be in sync with audio.

Audio channel 1 300 hz
Audio channel 2 310 hz

The led needs to blink at 310-300 = 10 hz
And it should be in sync with the audio I.e. It should peak when both audio channels peak

I tried using a computer to generate the frequencies and a lm358 opamp . I am getting confused whether this is the right opamp I should use and what kind of external circuitry I should use.

The audio frequencies may be changed to 300 to 350 hz to get desired effect.

Edit : more details:
The input frequencies are generated by a computer or an MP3 player. I don't know what voltages they are.

The brightness of the led can be changed.. I think this is easily controllable by using a potentiometer. I want to experiment with different LEDs of different power and brightness (upto 1w). But for now I'm testing normal 5mm red LEDs .

The whole thing needs to be powered by a 5v battery ( so no negative voltages available)Switching between different output waves is desirable, if it's easy to achieve, or only sine wave is fine.

I have an Arduino uno and pro mini if that's useful.
I do not have an oscilloscope, so using an Arduino to count output frequency.

heres a video of what I achieved so far. It's a lm358 with almost no external circuitry. Showing result for sin and square wave.
http://youtu.be/Aj5mE7mWrZA

In future I also need frequency filters to filter out interesting frequencies from audio. E.g. When nature sounds are mixed with the 300 and 305 hz audio channels to give relaxing effect, 300 and 305 hz signal needs to be filtered and fed to this opamp circuit. Frequencies of interest lie between 300 and 360 hz.

Thanks


texts:
I have connected a NXP NFC Module (pn7120) over I2C to i.MX6 Board.

I tried to check whether the device is detected in the i2c probe command. It didn't detect in the first call, but got detected in the second, third time failed and fourth time success. What does this mean.. How to solve this.


texts: Is the output of this LC circuit a DC current?

texts:
On the left of the circuit shown below is a 120V AC current. I know that the diode (D1) rectifies the signal so that only the positive half of the AC signal goes through.

I have seen circuits with a Diode, L1 and EC2, but with EC1 left out that acts as an half-wave rectifier.

So my question is as follows:

Is the output at node 2 a perfect DC signal?
What is the voltage of the DC signal if the original AC signal has a voltage of 120V?
Am I correct that EC2 keeps the voltage supply to node 2 constant and that L1 keeps the current supply to node constant?
What is the purpose of EC1? If it is the same as EC2, why is it not in parallel with EC2 after the inductor?

Note: This is not a homework question. I am brushing up on my knowledge about circuits and came across this as part of a design of a power PCB.


texts: How can I test battery for true mAh rating?

texts:
Is there a way I can test the capacity of a 3.7v rechargable lion battery like this at home? All I really have is a multimeter.

(Image source)


texts:
I have some questions about the accuracy of some electric components, especially for SMD components.
We can reveal that each SMD resistor has 1% or 5% or 0.5% of accuracy.
I wonder if the accuracy means 'just the absolute accuracy of the resistance', which means the temperature will not affect to accuracy, or not.


texts:
I am planning to design a wind turbine that is has rotor blade radius of 0.915m and is connected to a generator. The generators specifications are, it is an ac generator with 5000 coil turnings and a 0.050 tesla magnet with area being \$1 m^2\$. The generator rotating at 135rpm producers 3534.29 V. The fan has 6 blades and when the wind velocity is 10m/s, the rotor will be going at 36.53 rpm (counting the efficiency of 35%). So, to get to the 135 rpm, gears will be used.

My question is, will the wind velocity be able to move the fan to 36 rpm when the gears will be attached to turn the generator at speed of 135 rpm?

Also, how can you figure out the theoretical yield of current that can be produced by the generated or is the current only found experimentally by attaching a load?


texts: How does non-ideal charging affect the life of a Li-Ion/Li-Po battery?

texts:
For lithium ion batteries, the standard way of charging them is CC - CV - cutoff. My question is, what are the effects of not following this pattern?

For example, what if you charge with just a constant voltage source and a resistor (assuming the max current is below the max charging current of the batter)? Or what happens if you charge in bursts (again, keeping the current below the max)?

How much do these affect the energy stored in the battery, and how do they affect its overall internal resistance and life? Does it have any effect, or is it just that its slower than CC/CV?


texts: What is this NOR feedback loop in the AGC Cross Point Generator II?

texts:
This feedback loop looks similar to a LFSR, however there are no registers present. It looks to be some kind of oscillator.

There seem to be three inputs to this component, IXP10 (pin 111), STBE (pin 237) and STBF (pin 239). There is also a tap, CGMC (pin 240).


texts: What is the pin state during microcontroller flashing?

texts: I know that upon reset most micros put pins into high-z state. Is this state preserved during microcontroller flashing? What precautions need to be taken if you are going to reprogram microcontroller on your board with external devices powered and connected? Particularly I'm interested in STM32F4XX micros. Thanks


texts: What are some good resources for graphing diode characteristics?

texts: A big part of my next exam will feature questions about graphing diode characteristics. Questions like the image below or questions where I am given an input signal and have to graph Vout over time type of thing. My question is are there any resources out there to practice these kinds of problems. I know how to use LT spice but I was looking for more of an explanation as well. Thanks.


texts:
I'm trying to build a Linear bench PSU, Here's what I did so far:

simulate this circuit – Schematic created using CircuitLab
So I'm converting the PWM to voltage using a low pass filter and opamp, but the mosfet gate threshold is 1V that means I can't have precise control over the output voltage. I did tried to increase the opamp gain but again it's not accurate at all.
How can I control the output voltage only with Arduino PWM (digitally)?
Without using a potentiometer to change opamp gain.
This question is not a duplicate, because in other questions they didn't specify that their output is controlled digitally.


texts: Do lead and lag filters have the behavior of high and low pass filters even if the zero and pole used are complex?

texts:
Consider the compensation transfer function \$\frac{s+z}{s+p}\$ so that the inequalities \$0<z<p\$ and \$0<p<z\$ correspond to lead and lag compensation respectively.
At very low frequencies of input signals \$|s|\approx0\$, and at higher frequencies of the input signal \$|s|\approx+\infty\$. Therefore, the gain due the lead compensation at very low frequencies is \$\approx \frac{|z|}{|p|}<1\$ and at very high frequencies is \$\approx 1\$, while the gain due the lead compensation at very low frequencies is \$\approx \frac{|z|}{|p|}>1\$ and at very high frequencies is \$\approx 1\$.
This indicates that lead compensation attenuates lower frequency signals while lag compensation amplifies high frequency signals. In fact, the classical high pass filter (\$\frac{s}{s+p}\$) is recovered from the lead compensator in the limit \$|z|\rightarrow 0\$, while the classical low pass filter is mathematically identical to the the lag compensator for high values of \$|z|\rightarrow +\infty\$.

In general, lead and lag filters have the behavior of high and low pass filters. Is it accurate to say that this similarity with respect to the objective of filters holds true even if (either or both of) the zero and pole used are complex?


texts: simple six-position voting machine into a 7 position voting machine

texts:
I'm new to learning about full and half adders and what not. but I am struggling to understand this question out of my study manual.

The pictures shows a simple six-position voting machine module using CMOS logic. what change could you make to the module to allow a seventh position? (hint: no ICs are needed.)

If I could ask for some assistance on figuring this out, that would be flat out awesome!

Thanks in advance


texts: Can I replace a PLL Charge Pump with an Active LPF?

texts:
Background

I am using a MAX9382 phase frequency detector in a project. The application notes recommend using a charge pump on the output of the IC. In PLL applications there is an up and down line that causes the voltage of the charge pump to go up or down. Wikipedia says:

  The use of a charge pump naturally
  adds a pole at the origin in the loop
  transfer function of the PLL . . . The
  additional pole at the origin is
  desirable because when considering the
  closed-loop transfer function of the
  PLL, this pole at the origin
  integrates the error signal and causes
  the system to track the input with one
  more order.

However, for my project I am not using the IC in a PLL, rather I will be using an ADC to measure an average voltage proportional to a phase and/or frequency difference.

Question

Do I need to use a charge pump similar to what would be used in a PLL? I was thinking I could just use an active low pass filter to produce the average(UP-DN). Am I forgetting about something?

Some Details

I will be feeding the PFD with signals that are in the 400-450MHz range and then will use an ADC to measure the average voltage at about a 1 Hz sampling rate.

In some circumstances I will be looking for a phase difference while in other cases I will be looking for a frequency differences.


texts: "Simple" thermal analysis of component on PCB over time

texts:
I'm trying to be pragmatic about designing a PCB and circuit that will have to dissipate heat. It's pretty simple: a surface-mount power transistor charges up a 4F 5v supercapacitor with a roughly constant current of 2A. It will not do this repeatedly - so it only needs to dissipate about 20 joules over 10 seconds, once, from room temperature.

I like the idea of killing two birds with one stone: keep calculations simple by building in safety margins and taking worst-case simplifications. But calculations or thermal dissipation over time, especially combined with electrical dynamics is not simple, mainly since the PCB's copper tracks and their layout have such a significant effect, but also since the transistor is not ideal.

So I imagine the only two practical ways of designing this are one or both of: with specialist CAD software, or testing of a physical prototype,  simply measuring the temperature parts of the PCB and its components reach.

Realistically, what would be the simplest, effective way of doing the electrical and thermal calculations/assessments necessary?


texts:
On page 11 of this ESD Book:

  ESD  sensitive  device  can  experience  a
  damaging discharge if touched by a person,
  even if that person is properly grounded.
  Increasing  the  electrical  path's  contact
  resistance is one way to control the speed of
  the discharge.
  A good way to accomplish this is by wearing
  static dissipative cots and gloves.

I thought antistatic gloves are not being used to avoid ESD, but to avoid fingerprints on electronics and whenever you want to wear gloves for that purpose, these gloves should be antistatic. Otherwise they can cause ESD.

Yes, ESD is a point-of-contact thing, but can antistatic gloves reduce ESD?


texts: What does it mean when components in schematics do not connect?

texts:
I'm fairly new to the whole Arduino world, and I'm just really curious about this schematic that I came across... I can read the basics of a schematic, but this one has me puzzled. What are the integrated circuits down at the bottom that aren't connected to anything?

How do you know where they go in the circuit?


texts: STM32L4 SystemCoreClock access crashes the program during HAL initialization

texts:
I'm trying to blink an LED on a Nucleo-L476 with CubeMX and ST's HAL. It worked perfectly on Windows (System Workbench). Now, I'm trying to do the same on Linux with CubeMX and Qt Creator (my favorite IDE) and OpenOCD. I am now able to compile and debug the target.

However, the program crashes during HAL initialization. More precisely, when it tries to access the SystemCoreClock variable. The following code is called from HAL_Init(); in main():

__weak HAL_StatusTypeDef HAL_InitTick(uint32_t TickPriority)
{
  uint32_t tickNum=123, *ptr1=NULL, *ptr2=NULL; // Added by me to debug
  ptr1 = &tickNum;                              // Added by me to debug
  ptr2 = &SystemCoreClock;                      // Added by me to debug
  tickNum = SystemCoreClock;                    // Added by me to debug *** crash here ***

  /* Configure the SysTick to have interrupt in 1 ms time basis */
  HAL_SYSTICK_Config(SystemCoreClock/1000);   // *** Crash here ***

  /* Configure the SysTick IRQ priority */
  HAL_NVIC_SetPriority(SysTick_IRQn, TickPriority ,0);

  /* Return function status */
  return HAL_OK;
}

I could replace SystemCoreClock by a constant, but the variable needs to be modified further down the line anyway. SystemCoreClock is declared in system_stm32l4xx.h and defined in system_stm32l4xx.c. Both files are part of the project.

** extern variable SystemCoreClock seems to have two different addresses.

Normal stuff (ptr1 == &ticknum and *ptr1 == ticknum):

(gdb) p &tickNum
$3 = (uint32_t *) 0x20017fdc
(gdb) p ptr1
$4 = (uint32_t *) 0x20017fdc
(gdb) p *ptr1
$5 = 123

Strange stuff (ptr2 != &SystemCoreClock and *ptr2 != SystemCoreClock):

(gdb) p &SystemCoreClock
$6 = (uint32_t *) 0x20000004 <SystemCoreClock>
(gdb) p ptr2
$7 = (uint32_t *) 0x681b4b20
(gdb) p *ptr2
$8 = 0

When I say 'crash', I mean the program falls in an infinite loop in startup_stm32l476xx.s:

/**
 * @brief  This is the code that gets called when the processor receives an
 *         unexpected interrupt.  This simply enters an infinite loop, preserving
 *         the system state for examination by a debugger.
 *
 * @param  None
 * @retval : None
*/
    .section    .text.Default_Handler,"ax",%progbits
Default_Handler:
Infinite_Loop:
    b    Infinite_Loop

Trying to narrow down the search, I noticed that a variable declared outside a function is not properly accessed from within the function:

uint32_t dummyVar = 123;

void dummyFunc()
{
    uint32_t loc = 123;
    uint32_t *p = &loc;
    p = &dummyVar;            // Debugger says &dummyVar = 0x20000004 and p = 0x011a3b01
    __asm("nop");
    __asm("nop");
    __asm("nop");
    loc = dummyVar;           // *** Crash here
}

The variable p here points outside the RAM, which starts at 0x20000000. The nop instructions make sure p = &dummyVar; is really executed and the debugger doesn't fool me.

Any idea?


texts: PIC16F877A not working with 4MHz oscillator

texts:
I was trying to do a LED flashing program, but the LED didn't turned on. I tried also with a program to just light the LED, but it didn't work either. I searched and one solution says to change the config bits, but also tried it and didn't work.
This is the XC8 code of the LED on program:
#include <xc.h>
void main(void) {
  TRISA = 0;
  while(true) {
    RA0 = 1;
  }
}

Config bits are:
WDT FALSE
PWRT TRUE
BOR FALSE
LVP FALSE
CPD TRUE
WRT FALSE
CP TRUE

I'm runnng it without capacitors on the oscillator, but it also didn't work with 47pF capacitors.
The source of voltage is an Arduino Mega, with the 5V and GND pins.
MCLR is connected to 5V with a 10k resistor


texts: How do we decide which circuit is a latch?

texts:
Will A and B always be the complement of one another regardless of
what logic gates we use in the latch-like circuit? For instance (the
two circuits shown as examples):
How do we decide whether A and B will be the complement of one
another or not?
How to find the invalid states?
Are these two latches?

simulate this circuit – Schematic created using CircuitLab

OR

simulate this circuit

I have tried following a few videos for instance this. But the presenter says that a certain state is invalid because Q and Q' should be the complement of each other. But how do we decide/prove that Q and Q' are the complement of one another?

UPDATE:

Truth Table of First Circuit:

How do I derive answers to the above questions from here.


texts: Some battery-operated devices switch off when plugging in powerless cable or during insertion?

texts:
One example is a CD boombox.
Battery-powered.

During operation, if I pull or insert a cable, it restarts, if the cable is connected to the wall power supply.

If I pull/insert fast enough, it even stays on, but the screen backlight of the JVC RC-EX30 goes dark for the fraction of a second.

If I insert a cable which is not connected to the wall on the other side, the device refuses to run from batteries, unlike smartphones, that also run while the USB cable is connected but not powered by any power source or by an empty powerbank.

What is the technical explaination behind this?.


texts: 280LM Led Headlamp needs FCC certificate?

texts:
Do I need FCC certification for my 280LM Led Headlamp with 1800MAH Lithium battery which is rechargeable only via USB?

More details:
Watts out: 3W
Lithium-ion Cells: 103450
Energy Content:1800Mah
Battery Voltage:3.7V
Battery Weight:32g

It already has CE and ROHS certifications, would that make any help for getting FCC?

Thank you in advance


texts: What will be the initial voltages in this circuit?

texts: What will be v1(0) and vo(0)? As the voltage across the capacitor cannot change abruptly im sure that v(0) will be 0 as v(t) for t<0 is 0. But im confused about v1(0) and vo(0). Will they be 0 as well?


texts:
I was reading hackaday review about Orange PI (small single board linux computer.

And in the comments they were talking about mis-aligned ICs. Some claimed it is bad, some claimed it is optimized.  Most just say it looks weird and drives them crazy.

I have no experience in electrics design, but this is my first time to see such strangely oriented components!

Is this rotation good or bad?  Does it matter?  Why would the PCB designer orient some of the chips like this?


texts: Is it necessary to separate ground planes in a PCB if there are different voltages?

texts:
I'm designing my first PCB and probably the circuit is a bit complex for my electronics knowledge. So a doubt arised while drawing the layout.

The board has got a Microchip MCP73871, an integrated circuit that manages the charge of lithium batteries with solar power. If there is a load while the battery is charging, the MCP73871 sends the power needed to a step-up/step down voltage regulator IC Texas Instruments TPS63060 to regulate the voltage to 5V in order to power an AtMega328P.

So speaking with voltages, we have:

MCP73871 powered with 6V (from solar panel)
TPS63060 may receive 3.3-6V and outputs 5V
Arduino works with 5V

The question is, should I separate grounds and ground planes?


texts: LTC3525 datasheet states that capacitors must be X5R or X7R, not Y5V. Why?

texts:
I'm selecting parts to build a 3 to 5V boost DC-DC converter using the LTC3525-5. The board I'm planing to build is based on the typical application shown in page 11 of the aforementioned datasheet, which schematic I reproduce below:

At the end of page 10, the datasheet says:

  The input and output capacitors should be X5R or X7R types, not Y5V.

I'm not familiar to the various types of SMD ceramic capacitors, so my main questions are: Why exactly makes Y5V capacitors not suitable for this application? And why X5R or X7R are suitable?

I've tried to search for the answer elsewhere, but nothing stood out on the sea of numbers and parameters on various datasheets out there. The best hits I got were the following documents:

WikiPedia article on ceramic capacitors
Basics of Ceramic Chip Capacitors

I suspect that the answer has something to do with ESR and maybe the capacitance varying with voltage on switching applications, but I can't tell exactly what's at play in this particular circuit.

And, the really silly question is: can I use a through-hole aluminum bipolar capacitors instead? If not, why not?


texts:
I created my first circuit with a microcontroller, an stm32f446 in lqfp64 package. However I have soldered such tiny parts and I'm struggling a bit and already destroyed one of three chips I bought.
Is there any kind of training kit? I do not want to spend each time 10 bucks for training purposes.


texts: Capacitor rated for 100vdc on 5vdc board

texts:
As the title says, I have capacitors rated 100VDC 18pF. Can I use these on a board that uses 5V Max ?

I can't really find any direct answer to that question.

What I want to do is to put a crystal to a chip and hopefully use these caps on the crystal.


texts:
I am making a Playstation Raspberry Pi project and I am using a new PSU inside the PS1 case to power the Pi. See link to PSU below:

https://www.amazon.co.uk/dp/B01DDTYMAS/ref=twister_B01DDTYM9E?_encoding=UTF8&psc=1

I want to use the original power socket at the rear of the PS1 which is a generic 2 pin (figure of 8) input. I will then solder some wires to the new PSU and then take the 5V output back to the Pi.

My questions are as follows:

1) Is there an issue with the AC+/- inputs on the PSU and the fact that this will change depending on how someone inserts the power cord in the rear 2 pin socket?

2) when the Pi is powered down and the unit is not in use, Should I be worried about heat or general waste of electricity in the PSU whilst it's sitting there connected to the mains?

Many thanks for any help.


texts: Powering small DC load ( 1W ) using 220V AC supply

texts:
I am trying to design a small control circuit for controlling large currents (not too large, around 200W, AC 50Hz). I have kept in the AC circuit isolated from the DC control circuit. But the problem arises when it comes powering the control circuit. My control circuit will take maximum of 1W of power at any time during its operation. Also I am bound to not use any battery for this purpose and the size of this circuit has to very small (smaller than a typical mobile phone charger).

Since the load is very small I was wondering if can use AC supply from mains to power it by converting the supply voltage to DC using a rectifier and then using a potential divider to lower the voltage to usable form (Note: Since the space available to me is very small, I cant use a transformer to step down the voltage).

So my question is that can I use this configuration to power the small load (1W). The schematic is attached. I know that voltage regulation will be affected but I have no idea "How much".


texts: Shorting of VCC & GND for short duration of time

texts:
I have used ULN2003A for my custom board. While checking "continuity" between VCC and GND there is a continuity for a short duration of time(less than a second), it comes at a random time.

I have powered ON a fully assembled board and tested. Everything is working as expected.

In the datasheet, it is mentioned that there are freewheeling diodes for protection. Do these diodes cause that short duration continuity?

Edit:-
I have followed EVM for designing schematic:-


texts: I'm switching a 1mA load current that has 24V load voltage. The Control voltage is 5V and is driven from a microcontroller that can also source 24mA. Is it better to use an N Channel MOSFET or a NPN BJT Transistor?


texts: Purpose of metal sheath in display cable?

texts:
I want to repair a display cable which I suspect has some broken wires. The cable seems to be wrapped in a metallized fibre cloth. (I don't know the correct name for it).

What purpose, apart from holding the individual wires together, does the sheath serve? Does the metal (assuming it's metal) have something to do with RF noise?

If I was to replace the entire jacket/sheath with heatshrink, is there any functionality I risk losing?


texts: DC transient behavior of precision rectifier circuit

texts:
I am working on a homework problem that I do not understand the solution to.

From my understanding the inverting input of the opamp is at 0.

So when the input is positive, the output swings negative, thus the bottom diode is turned on and we see a -0.7 voltage drop at the output.

What I'm not understanding is when the input goes negative. Shouldnt the voltage drop at the output be the diode voltage drop plus the current across R?

My issue here is I dont fully understand the effect of the reference voltage (V1 in the schematic)

note: When the reference voltage is high enough, the output is -0.7 with a small ripple.


texts: How do we know that voltmeters are accurate?

texts:
Something that has always puzzled me is how we know the accuracy of voltmeters. From googling around, it seems that today's digital voltmeters use an ADC. An ADC works by comparing the voltage that is to be measured against a highly precise known voltage reference. However, how is the voltage of that highly precise voltage reference known? It seems to be like a chicken vs. egg kind of problem - knowing the accuracy of the voltmeter ADC reference voltage relies on the accuracy of another voltmeter using another reference voltage which relies on the accuracy of another voltmeter using another reference voltage and so on and it continues infinitely.
From looking at the Wikipedia page for a voltmeter, it seems like something such as a Weston cell, which uses a reproducible and stable chemical reaction, is used as the ultimate reference voltage for calibration. But still, that falls prey to the chicken vs. egg dilemma - how do we know the voltage of the Weston cell without again using a voltmeter?


texts: How to make a 12V DC variable voltage supply with more than 30A output?

texts:
I have a SMPS capable of outputting 33A at 12V and I would like to make it have a variable output with full current potential, or close to it.

Now,

Is it possible to do it with a PWM-controlled MOSFET with a filter at the output?
Is Arduino with its 490Hz/980Hz enough, or would higher PWM frequency values (either through changing Arduino timers prescale factor or with 555 timer) be necessary in order to simplify the output filter?
Could the output be made stable enough to power microcontrollers at 5V without a linear voltage stabilizer in between?

If the above solution is impractical, what else is an option except a buck or buck-boost converter?

Edit: added the link.


texts: Help to understand incremental rotary encoders

texts:
I have this encoder.
But I'm having extreme difficulty understand how these encoders work.

I tried to google but still cannot picture in my mind how they really work. I spend two days for research but no luck.

Here are my questions:

1-) What I read is that when we rotate the knob the output A and B should output pulses with 90 degree phase difference and this phase difference is only to determine the rotation direction:

But how does output from A produce this shifted wave form? I mean what happens internally/mechanically so that even we switch one click there becomes these waveform. This is very confusing to grasp. Btw when I wired up in scope I dont see 90 degree phase differences between A and B when rotating. Sometimes it is very very little phase difference. Do all mechanical rotary encoders supposed to work same way?

2-) Is only one of A or B used to measure the rotation angle? How is this waveform interpreted so that we can measure the angle rotated. Again I cannot picture the relation between pulse per revolution (ppr), and angle here.

3-) I'm also confused with term gray code. Is that something unrelated to these type of encoders?


texts: Why do cascading D-Flip Flops prevent metastability?

texts:
I understand what metastability is but don't understand how linking together flip flops reduces this?

If the output of the first flipflop is metastable, this gets used as input for the second one. But I don't see how the 2nd flip flop will be able to do anything with this input and make it stable.

Thanks in advance!


texts: 3 wire load sensor connection to INA125P

texts:
I am trying to use a 3 wire load sensor, connect it to INA125 for voltage amplification and then use the amplified output to be fed to ADC of Arduino.

I had used below configuration with INA125.

Where S+ and S- are Sense + and Sense -. I tried all the configuration i.e single load cell, half wheat-stone bridge, full weat-stone bridge but nothing worked. I only keep on getting some random ADC value 14-16 and even on pressing the load sensor upside down, nothing changed. Basically i followed the below configuration while trying with single load cell.

And a simple arduino code, just to read ADC value in order to check , whether i am getting things right. As per code, the ADC value must change, but they didn't. Below is the sample code.

#include<stdio.h>
#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

int sensorValue = 0;
int sensorPin = A0;

void setup()
{

  Serial.begin(9600);
  Serial.println("Weight sensor reading");
  lcd.begin(16, 2);

}

void loop()
{
  lcd.begin(16, 2);
  lcd.setCursor(0,0);
  lcd.print("Weight measurement");
  sensorValue = analogRead(sensorPin);
  Serial.print(sensorValue);
  lcd.setCursor(0,1);
  lcd.print(sensorValue);
  delay(200);
}

Now with respect to the single load cell, i connected black to GND, white to +5V and Red to S+ at pin 6 of INA125 and i connected PIN7 that is S- to GND. But this didn't worked.

When i used 2 load sensors, i connected the white wires of both load sensors to +5V, Black wire to GND, RED wire of 1st load sensor to S+ and RED wire of other load sensor to S-. But even that didn't work and readings remain same  i.e. 14-16 volts and didn't change even on applying sufficient amount of pressure.

Now with respect to the full wheat-stone bridge configuration, i used this pic based configuration given on this link.But even it didn't worked.

I am not able to understand what i am doing wrong.Can any one suggest me

Important : I am using 10k resistance between PIN8 an PIN9, which provide me a gain of 10. Is that sufficient for arduino to read ? Or i must use some other resistance which must provide me a higher gain. But i think even with 10k resistance i must see some change in the value of the ADC, but i am not even getting that. In my earlier question also, i asked a similar type of question, but at that time i wasn't having INA125 with me.

Below is the pic for the configuration which i am using.


texts: Can I generate frequencies faster than 32 MHz with ATTINY85?

texts:
I believe I can use the 64 MHz PLL clock with PWM to toggle every cycle
and thereby generate a 32 MHz square wave output on an IO pin, right?

Is there a trick to generate an even higher frequency (with at least 1V
of swing) without needing external components?  For example, can I get
the 64 MHz PLL output itself off the chip?


texts: How to calculate for how long an LED emits light when in series with a capacitor?

texts:
Given the following DC circuit with a fully discharged capacitor (\$V_c(0) = 0 V\$):

How can I calculate for how long the LED emits light until it "turns off"?
The LED is a red one with a forward voltage of 2.0 V and a forward current of 20 mA. It stops emitting light at 1.6 V. (When powered with my lab power supply directly, the LED conducts a current of 7.5 uA at 1.6 V)
The question leading to an answer might be: How long does it take until the voltage of \$V_c = 7.4 V\$ is dropped by the capacitor (KVL: 9 V - 1.6 V = 7.4 V).
$$
t = -RC \ln(1 - V_c/V)
$$
...but R depends also on the resistance of the LED which depends on the changing voltage of the capacitor while that one charges...
Is a (first-order nonlinear?) differential equation needed to calculate this and which equation is it? (As a plus, a derivation of that equation would be very appreciated to be able to understand how to solve these kinds of questions.)

edit -- Here are measurements I have taken to create an I-V curve of the LED if that helps:
V_led   I_led (A)   R_led
1.480   0.0000007   2,114,285.7142857
1.560   0.0000031   503,225.8064516
1.600   0.0000076   210,526.3157895
1.700   0.0000372   45,698.9247312
1.790   0.0010000   1,790.0000000
1.830   0.0020000   915.0000000
1.850   0.0030000   616.6666667
1.870   0.0040000   467.5000000
1.880   0.0050000   376.0000000
1.890   0.0060000   315.0000000
1.895   0.0070000   270.7142857
1.900   0.0080000   237.5000000
1.910   0.0090000   212.2222222
1.920   0.0100000   192.0000000
1.930   0.0110000   175.4545455
1.940   0.0120000   161.6666667
1.945   0.0130000   149.6153846
1.950   0.0140000   139.2857143
1.955   0.0150000   130.3333333
1.960   0.0160000   122.5000000
1.965   0.0170000   115.5882353
1.970   0.0180000   109.4444444
1.980   0.0190000   104.2105263
1.990   0.0200000   99.5000000

edit 2 -- Answers/comments below; answer accepted
I want to thank everyone very much for his/her contribution(s) and invested time! There are very help- and useful, practical, and excellent answers and comments below, especially those by @Transistor, @mkeith, and @rainer-p.
Together, you all have filled up a treasure chest of knowledge here. So my recommendation is that you (who is seeking an answer) take a look at all given answers and comments, read through them, and - if you lack knowledge like me - learn from it!
I was fortunate to be spoilt for choice... As only one answer can be accepted, I have selected @jonk's as it solves my question for equations the most.


texts: Same thermistor model (103) with varying response

texts:
I was using thermistor model 103 to measure temperature of surroundings. To my surprise, when I checked different thermistors of the same model (103) bought from the same shop by changing them in the circuit, each had their own resistive response to the surrounding temperature. Like the first thermistor gave an error of 1.5 degrees celcius and other 2.5, due to varied resistive response.

My question is:

How can these thermistors of same model differ in the way they measure temperature and what can be a universal solution to all thermistors of this model to be accurate?


texts: 555 timer won't trigger monostable mode unless I add a switch between R12 and ground?

texts:
I have this setup which is a part of a bigger circuit to control motors.
This is supposed to be a timer in monostable mode with about a minute of hi output when triggered.
The lines going down are to give the Q2 base high and Q4 to turn the timer off when the downward lines are high but when they are low the timer should trigger and start giving out high.
I tried randomly to put a switch between R12 and ground and that helped trigger the device. So I would in theory turn the device on and then turn on the button to trigger this timer.
I don't quite understand why it won't trigger when this bottom common line is low.
Should it be dragging the base of Q2PNP down to open it which would then add voltage to the base of Q3 NPN which would drag the trigger of the timer down?
The setup of the C2 and R2 is so that the output time won't be affected by the input staying low so the output time is always the same as this capacitor and resistor pulls it up.
I want it to just

Device ON
Trigger low
Output Hi
until trigger is reset by Q4 or time is up.

Am I missing something here?
---------EDIT----------
Uploading the full schematic just for a better understanding.
Currently, the rest of the schematic works fine in simulation except the part I posted originally.
I have a counter to count button clicks.
Once a button clicks a 555 timer for backwards goes high, and once it drops from high to low it triggers the 555 timer for turning.
Both backwards and turning timers give out high into the forward 555 timer to make sure that one isnt giving out high.
I just need the forward timer to start off as high and get deactivated by the other timers but once they go back to low that forward will be activated once again.
Using a PNP transistor as a switch is a mess and a half.
I just realized that the whole point of C2 and R2 was for the trigger event to only trigger once so it wouldn't affect the output time, but on this specific timer the output is allowed to be high as long as it can.