texts: LC ringing on synchronous buck converter

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I am working on a board that uses LTC3891 as a buck converter to step down 24V to 12V. There is quite a significant oscillation at the switching node, upstream to the inductor which I am curious about. The inductor does a great job of cleaning up the ringing and the output 12V rail is very clean and steady. But still I'd like to understand if this ringing is normal at the switching node or not.

I've at least rooted the oscillation down to the output capacitances of each FET forming a tank circuit with the inductor. The calculated resonant frequency matches the frequency in the scope capture. I've tried adding a 1k resistor in parallel with the inductor to dampen the ringing and this does help but not a whole lot.

Attached is a snapshot of the schematic and a scope shot of the switching node, upstream to the inductor.

For a little more info, I've changed the high side FET gate resistor to 20 ohms which cleans up the ringing on the rise time, so I am not concerned with that.


texts: Circuit to enable (inverted) clock glitch free

texts:
This is a follow-up question to https://electronics.stackexchange.com/a/95195/13354, in which I was asking about a specific solution to the more general problem described here.

I'd like to create a logic function that toggles with the (inverted) clock when enabled and stays low when disabled, like so:

clk ena out
 0   0   0
 1   0   0
 0   1   1
 1   1   0

In addition to that, I'd like the out signal to be glitch-free, as shown in the following example waveform:

As shown in this image, potential glitches of the ena input can happen shortly after the clk edges; nevertheless, the out waveform should be glitch free.

According to this answer to aforementioned question, the circuit should be a clock gate rather than a self-resetting flip-flop. This is the proposed schematic:

simulate this circuit – Schematic created using CircuitLab

Unfortunately, this still causes glitches when ena goes low, because the Q output of the flip-flop is delayed with respect to clk (note that I ignored the common delay between clk and its inversion, which I think doesn't contribute to the issue):

Now my question: What circuit should I choose to have the out signal glitch-free?


texts: Understanding relation between energy use, watts and amps

texts:
I'm looking into air conditioners and I've been unable to fully understand the relation between watts, amps and the energy ratings (in this case, the one used in the United States, the yellow Energy Guide label).

Both are 115 V.

Air conditioner 1: 8000 BTU, it is listed as 660 W cooling power, 6.2 A cooling current. The yellow label Energy Guide lists yearly costs at $65. The energy efficiency ratio is 12.

Air conditioner 2: 9500 BTU, it is listed as 920 W cooling power, 11.5 A cooling current. The yellow label Energy Guide lists yearly costs at $50. The energy efficiency ratio is 13.8.

Questions:

Why in both air conditioners the amps is not equal to watts divided by 115 volts? 660 / 115 = 5.74 A and 920 / 115 = 8 A.
The air conditioner 1 clearly uses less energy than air conditioner 2. However air conditioner 2 is listed as cheaper in yearly costs. Maybe it has to do with the way it cools the room, using less energy over time? But then why watts are higher, if the energy consumption is lower?

Thanks for helping me understanding this!


texts: in saturation of BJT, the current gain is reduced

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I studied in sedra and smith 'microelectronic circuits' that in saturation, beta gets changed and becomes less than the original beta (which is constant for a transistor).
How is it possible?
Because in saturation the drop at collector base junction is approx 0.2V which is larger than that in active mode, and applying KVL in the outer circuit (let's say in common emitter amplifier) gives more value of Ic in active mode. So what is this contradication?
I also want to know whether kvl rule is applicable for active region or not?


texts: Questions Regarding Metal Detector Tx Coil Circuit

texts:
The following circuit is the transmit coil of an IB metal detector.  I recognize most of this: an op amp astable with a CE push-pull output stage driving a resonant circuit.  But, I have questions.

The frequency of the tank is about 27KHz, which I'm guessing is the fundamental frequency of the astable.  I understand the general astable frequency formula, but I'm finding it difficult to calculate the positive feedback fraction in this instance. How to calculate the feedback fraction?

My other question relates to capacitors C1 and C2.  They seem to act like a charge pump, pumping the centre-biased input signal up (and down) to either rail.  My feeling is that it makes the push-pull pair more efficient by turning off one or other of the transistors, but I'm not sure.  Can anyone shed any light?

Incidentally, here's the original project document (for context) Buccaneer Metal Detector.


texts: Why do some diodes have a glass package?

texts:
Put simply, why do some diodes such as most Zeners and Schottky diodes have a glass package as opposed to the more traditional plastic package?

Is it ease of manufacturing, thermal properties, or some other electrical phenomenon?


texts: How can i drive this 5v Relay board with RPi?

texts:
Beginner here, so this problem came up:

I got a 250vac 30A relay board which seems to require 5v to be driven.
It has 4 input pins: GND, IN-, IN+, VCC
What are the IN- and IN +?

My rpi output pin does not seem to be able to triger the relay when connected in the IN+ (although the board's led does turn on and off)
Here is a pic of the 4 pins:

Here is the ebay link: Ebay Item Link
The manufacturer page: chinalctech Link

Please note that my relay (pic #1) has 4 connection pins while the other two (pic #2 and #3) have 3 pins.

update:
Thanks for the plenty of answers, I went through all of them, then went back and tested the things you guys suggested.
The GND and IN- pins are indeed connected through the jumper present in just behind them. I think it's in place in case you want to power the 5v input from another source on VCC and GND, then fire the relay with the IN+ and IN- connected to the GPIO and GND respectively.

That said, it seems like although i am powering the board with 5v on its VCC and GND, the switch wont fire unless it has 5v on IN+. I tried connecting the board to a usb 5v source like this (jumper shorting GND:IN-):

5v+ : VCC
GND : GND

Then got a wire of the same 5v+ and touched the IN+ pin. The switch fired whenever the pin touched 5v.

Update 2:
I tried to replicate the same connection on the RPi 5v rail, (5v:VCC, GND:GND, test 5v: IN+) the relay does not fire. (jumper shorting GND:IN-)

I guess i reached the bounds of my E.E. knowledge, please advise, what am I missing?
Is it an Amperage issue?


texts: Connect Esp32 and a w5500 to a blue pill stm, doable?

texts:
I am looking for a way to give my project both wlan and lan but because I need all the io pins on a esp32 ( who may also be a bit to slow for my application) I can't just use a lan module on the esp.
My thought was to use the esp as wlan receiver and a w5500 as lan receiver and connect them both over spi to a blue pill stm or some other mcu that is a bit stronger.
Now I would like to know if that is practical and doable or if you guys may have any other ideas!
Thanks and greetings


texts: Accumulation of batteries' energy to rise electrical power capability

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I am looking for a method to drive/pulse (ocasionally) an inductive load from a battery. The problem is, that the battery does not deliver enough power the load needs. But, energy is not a problem. I thought about boosting the voltage and charging a capacitor, then almost instantaneously releasing that energy to the load.
These are the batteries' specs:

I_max = 200 mA
U_bat = 3 V

Regarding the load:

L = 500 mH
I = 0,5 A
P = 6 W
t_drive = 30 ms

Of course, if something is missing, please point out and I will be glad to supply that information.

What I'd like to ask is if you see any pitfalls or would propose another approach?

@Neil_UK: The load is a selenoid. Which specs are missing you think?

@Transistor: 3 V is the battery voltage. The capacitor's voltage I want to boost up to maybe 16 V

@Joribama: hence I'd like to boost up the voltage since:
$$E=\frac{1}{2}C U^2$$

@pipe: I do not have the datasheet yet :/, just those numbers posted above.

@pjc50: Yes, boosting up the voltage is what I was thinkgin of, too.


texts:
I have a generic question about Graphic LCDs with built-in controllers and RAM. I observe that whenever I change a large portion of the screen with say a new image or a object (or just clear the whole screen with a new color), there is a noticeable flicker. Is there any way to avoid this? I am using the 8080 mode to update the display controller's RAM. The problem occurs because the refresh rate of the LCD is faster than the speed that I am writing into the diaplay's RAM.

I imagine that it should be easy to do if there were an option to update only the RAM of the controller (while the LCD panel retains the old display) until I set a bit to tell the controller that RAM update is complete. Once that's set the controller should output the contents of the RAM on the physical LCD. Is there any way to achieve something like this? The controllers I am referring to are of the class of HIMAX 8232 that come built-in to LCDs.


texts: What microprocessor for experimentation?

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I harbor a secret fantasy (oops, not so secret anymore) to build a simple computer from scratch. I'm looking for an easy-to-use microprocessor to start with. I know about the usual suspects such as the 6502, 68000, 8086, Z80, etc. But I'm wondering if something better is out there. Here's my wish list:

Must have:

Low clock rate (4-25 MHz)
No more than 40-60 pins, preferably in DIP configuration
Ability to address around 64KB of memory, but up to 1MB or so would be good
Stored-program architecture (not read-only instruction space) (Edit: this rules out most low-end microcontrollers, like the PIC and AVR)
Flat memory model, not banked or segmented like the 8086

Would like, but not necessary to have:

RISCy instruction set (load-store)
General-purpose registers
Assortment of TTL I/O pins
Built-in flash ROM

What microprocessor or microcontroller would you suggest that's relatively easy to wire up and get the first ROM routines written for?

My goal is to get a simple Forth (or similar) system going. Just to say I did it.

Edit: After doing a bit of research, I think something like the ARM7 would suit me. It comes with a non-trivial amount of flash and SRAM to play with -- sometimes as much as 256K flash and 64K SRAM -- along with digital I/O, ADC, serial I/O, and more.

Here's one: the STR711 ARM development board.


texts: PIC18F4550 microcontroller pin pulled high on PC wakeup

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I got a PIC18F4550 microcontroller connected to the PC via USB. All is working fine except for one thing. If the PC wakes up from sleep, I notice that certain pins are pulled high (LEDs connected to them light up). I'm pretty sure there's nothing in the MCU code that sets those pins high when the MCU is powered on or something. By the way, if I remove the USB cable and put it back, those pins are not pulled high. Is there any explanation for the PC wakeup mystery? Thanks a lot.
Here is the schematic I'm using:


texts: How does this circuit control motor speed?

texts:
I was curious to see how the foot pedal of a sewing machine drives the universal (?) motor inside the appliance. I had expected a simple variable resistor like the ones in vintage machines but that's not what I found. My experience is limited to digital circuits, so I would appreciate any explanations you can offer.

From a mechanical point of view, the R4 variable resistor is the main control input, and the switch S1 is linked so that it opens as R4 is pushed to one of its endpoints thereby breaking the circuit and resetting the triac.

There is one unknown component on the PCB- it looks like the other 0.5W resistors, but only has a single black band going down the middle.

My (naive) assumption would be that C3 or C1-R1 provide a low impedance path for the AC, so how can the rest of the circuit affect the motor speed? Also, is L1 part of an LC circuit or does it serve a different purpose? The appliance is rated at 0.9A @ 110V, how can they get away with only 0.5W resistors in that case?


texts: How can I attach the same footprint to subparts of the same IC in Altium?

texts:
I have two sub parts of the same IC (STM32L476RG).

I have added these sub parts as two components in the same schematic library and have attached the same footprints for both of them. But when I make the layout, I get two separate footprints for them. How do I make sure that both these subparts are recognised as parts of the same IC? I am using Altium designer tool.


texts: Photo-diode for a high-frequency tachometer

texts:
I intend to build a tachometer, which is capable of detecting rotations up to 1kHz (60 000 RPM).  From the Internet I know that this is possible to do with a magnet and a Hall detector.  However, I would prefer a non-invasive solution with a light and a photo-detector, but from Internet it seems that ordinary low-cost photo-diodes are just too slow for such a task (700 RPM in this video https://www.youtube.com/watch?v=WG_4iChrvR4).

I assume that I would need a photo detecting device, which response time is at least an order of magnitude lower than the period of the oscillation, that is less than 100 micro-s.  Are there any photo-detectors (photo-diodes) capable of that?  If possible, please suggest a product.


texts: why is the current of a aluminum-hydrogen galvanic cell low

texts:
I am having a galvanic cell with the following half cell equations:

Anode--> 2Al(s) + 6OH --> 2Al(OH)3 + 6e-

Cathode--> 6H+ + 6e- --> 3H2(g)

I connected my cell to a 47 ohm resistor and measured the voltage across the load, which was 0.07V. I used ohms law to calculate current:

$$\frac{0.07V}{47Ω}$$ = 1.5mA. I wanted to know why my current is so low even though i am producing 6 electrons.

My anode electrolyte is 0.02 Molar aluminum sulfate and cathode electrolyte is 0.00026 Molar acetic acid

The open-circuit voltage is 1.34 volts


texts: LDO ground with Diode for temperature Drfit compensation

texts:
I work the below circuit.

LDO is 3.2V fixed , Two diode is connected one at output and one at ground for compensate the temperature drift occur.

Op is connected to a micro controller VDD-BUS which takes generally 10mA current.

D1(SD103ATW-7-F) top diode which i mention in datasheet ( 0.32 at 5mA If),

So the output voltage (OP) should be
a) 3.2V with respect to ground ( since both diode cancel each drop)

b) 3.4V with respect to ground ( since diode at ground will have very low current Iq of LDO)

Any adivse.


texts: Would the static charge from a silicone work mat be dissipated by an ESD mat if placed on top of it?

texts:
I know the proper rubber mats that are both ESD safe and heat resistant are quite expensive, and definitely out of the price range of a beginner hobbyist like me.  I have also read that the silicone work mats, while they are highly heat resistant, are insulators and can build up a static charge.

My idea is to buy a basic 2 layer ESD mat and a silicone mat to put on top of it, the theory being that any static charge built up in the silicone would be dissipated by the mat in same way any other static from the part being worked on or my hands etc. would be.  This would give me both ESD protection, and heat resistance.

Would this work?  I could get a silicone mat that is smaller than the ESD mat so that my hands are still brushing and being grounded by the ESD mat while I work.


texts:
I'm trying to make a shield for Arduino in Eagle.
I connected a floating NET from my shield pin and labeled it as for example PIN5 and marked it as XRef
But on ERC I'm getting Only INPUT pins on net PIN5 and Only one pin on net PIN5
Here is and image of it:

What is the correct way to fix this?


texts: Power Arduino Pro Micro from MCP2025 Vreg

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I'd like to power Arduino Pro Micro (5v) from MCP2025-500 LIN BUS transceiver.

Can I connect MCP2025-500 Vreg pin directly to Arduino Pro Micro (5v) RAW pin?


texts: Why inductive and capacitive reactances have opposite signs and why they cancel out eachother?

texts: For example in a series RLC circuit with ac source why total reactance is inductive reactance  minus capacitive reactances ? I dont need any mathematical proof. Can anyone provide me a a logical answer for that please?


texts:
I transmit a signal using LVDS over a CAT6 ethernet cable. However, instead of coming through clean, it always 'bounces' back to the high state: (Pink is the input and yellow is the output)

(Sorry for the glare and angle, there is a window behind me so it's impossible to take good photos)

When the input is turned high, pretty much the same thing happens to the output.

The setup is as follows:

The SN65 chip takes the sync signal (left, 6) and puts a differential output on any channel that is enabled (left, 9..16). Then the differential signal is routed to the RJ45 port (right).

Then there is 5 meter of CAT6 cable.

On the other side there's another RJ45 port that is hooked up quite the same.

The differential signal leads to this DS90 chip which outputs the sync signal again.

Note that there isn't termination. The designer of this circuit assured me that it's not (or at least shouldn't be) necessary. However, when I manually press a 100 Ohms resistor to the contacts, then the signal is better, but not fixed.

Can you spot a mistake that would cause this signal going back to high to happen?
Do you have tips on how to improve this situation?

The sync signal is not a clock or anything. It will just be occasionally toggled (once every minute maybe or only at bootup. Depends on what the system will need in the end).


texts: How to boost (double voltage) a sawtooth generator

texts:
I have a circuit to drive, using a sawtooth generator, four varactor diodes (FC54).
These varactor diodes has the following specs:
from 2.5pF (at 15V) to 30pF (at 0V), but my sawtooth generator, based on an NE555 (feed at 12V) is only able to give a max Vout of 8V.

I was thinking to implement, to the sawtooth output, some "voltage doubler" (which should be adjustable, to not exceed a max Vout of 15V), or maybe a transistor.
The idea of using a voltage doubler circuit is valid or there is another better way to achieve the improvement? Some hints how to implement this improvement?

Thank you very much.

Current schematic:


texts: Why is the load output voltage from my relay so low?

texts:
I’m trying to build a simple circuit with a relay controlled by an Arduino that will turn on/off a little LED light string I have that was previously powered by two AA batteries (that would be 3V, according to the diagram on the battery case). I have the circuit wired and the Arduino programmed so that it triggers the relay on every .5 seconds and off every .5 seconds. I would expect the lights to blink with this configuration, but they do nothing.

I have tested quite a few different configurations, I have tested the lights (they work perfectly fine with power directly from my breadboard power supply), and I have tested other known-working devices on the circuit and I have not been able to get anything to work on it. The relay does function as expected — the LED on the PCB blinks on when it is triggered and it does make the clicking noise from the circuit closing — so I figured that it had to be an issue with the load power.

As I mentioned, I’ve got a breadboard power supply attached that should be providing enough power to the circuit to light the lights, and I have tested the lights directly on the power supply and they work. This lead me to think that there must be something wrong with the relay. I tested the output voltage from the relay with a multimeter and I had to turn it all the way to the most sensitive setting to get any sort of reading at all, which turns out to be something in the range of .3 millivolts. Obviously much lower than the expected 5V that should be coming out of there. I checked the resistance through there and it was within expected values.

So my question is, what’s happening here? Why am I not getting power from the relay?


texts:
Please help me identify a component on a PSU I saw on EEVblog.

What's the name of this component and what does it do? Thank you.

Source: EEVblog #1036 - PSU Fire PCB Repair

Edit: The component in question is circled in red


texts: A (touch) screen technology to identify several input devices

texts:
This may sound vague, since I am not sure if what I am looking for even exists, but please bear with me.

I am interested in a technology that would allow me to not only locate, but also identify items placed on a screen. Imagine, for example, a large screen with chess pieces on top of it. I would want to know where each piece is. Specifically, I would want to be able to identify each piece, and match that unique ID with its current location. Note that the pieces should not be the limiting factor - I'm fine with adding sensors/actuators/etc. to them as long as that actually helps the screen identify them.

My hope is that there exists an obvious technology that I just haven't thought of. In a perfect case scenario, that would be a capacitive touch screen with the identification bit done in software rather than hardware. In the worst case scenario, you'd point me to a research paper and wish me good luck in building the screen myself†.

EDIT: to clarify certain things that came up in the comments, I am indeed talking about a screen that can display images in addition to sensing objects placed on top of it. @gbulmer suggested Reactable, and that's very close to what I need (at least when it comes to its operation, the technical part of the solution of course can be very different). The screen should probably not be larger than 30 cm * 30 cm, and I'd expect up to 10 objects being on the screen at the same time.

† I've found papers on building touch screens with fingerprinting capabilities, but somehow that sounds like an overkill.


texts:
I'm developing a magnetic field sensing kit for a project. The kit contains sensors (specifically an accelerometer, a gyroscope, and a magnetometer) that will detect and measure magnetic fields, and my team plans for this kit to be placed in a location with high amounts of radiation, specifically neutron, alpha, and gamma radiation.

I'm really new to radiation effects, so I was wondering how does radiation cause strange behavior to occur in electronics, and which components are the most likely to be affected by radiation? Right now, I'm looking for sensors for the kit, and it's near impossible to find radiation-hardened sensors. Given my unfamiliarity with radiation, I'm trying to understand how it affects electronics so I can see if we need to purchase specialty components or if we can make do with just regular components.

EDIT: After speaking with my team, to be honest, we don't have a specific value on the intensity of the radiation to be expected. All I was told that the source will emit neutrons. Looking at what's available in terms of components, rad-hard components tend to be quite expensive and big, not in a small IC form factor, so I think I'll just have to go with a different solution.


texts: Radiation Source placement and waveguide parameters for Horn Antenna

texts:
I am designing ("arranging", actually) a horn antenna for a 77-81 GHz Radar. My module has a patch antenna which can't be placed inside the waveguide for some reasons. After the patch antenna, we have a radome to protect the patch antenna. Then, the waveguide starts which then flares into the horn antenna.

In all the literature, all discussion was on the horn design (i.e. getting optimal horn parameters D and L for given λ), and waveguide minimum diameter (d) for given λ. Now, after getting the optimum horn, I have a few doubts about waveguide and radiation source placement:

Where should ideally be the source placed inside the waveguide?
If it can't be placed inside the waveguide (like in my case), how far can it be?

2.1. Also, in this case, if we use the minimum-diameter waveguide, would it provide a sudden change in impedance for the radiation coming from patch antenna into free-air and then into radome and then into the waveguide? So, should we make the waveguide with a larger diameter?

2.2. Is the waveguide even required in this case?
Does the thickness of the waveguide surface or horn surface have any affect?

UPDATE-1:

Conventionally, horn waveguides are fed with pins. I found that what I am trying to do is to feed the horn with patch antenna, and the technical term for this is : "patch excited horn antenna", as discussed here. However, patch antenna is always put inside the waveguide/horn entrance in most designs. In my design, it is put outside the horn. So, the design is tricky.


texts: Isolation transformer and scope when troubleshooting SMPS

texts:
I have a simple question, when troubleshooting a SMPS is highly adviced to use an Isolation transformer. But my question is this, if im using a scope to troubleshoot the "hot" side of my SMPS, both the SMPS AND scope AC power should come from the isolation transformer ?

OR

Should i connect the SMPS to the isolation transformer, and my scope to the house (non-isolated) outlets?


texts: What kind of effects does a relay have on signals?

texts:
Currently I'm working on a DDS based function generator. The idea is to use an AD9834 chip that will generate a triangle/sine or square wave. With some amplification electronics I want a configurable frequency, offset and amplitude. I have no set frequency I want to achieve, but getting more than 10MHz would be nice. I'm trying to get things to work out for the best result.

I've been looking into ways to switch between several ranges of amplitude resolution. For example, I wish to get 10V amplitude as a maximum but with 1mV step size on the lower amplitudes (<2V). To avoid using a 16-bit DAC I was thinking of using relays to switch between two feedback resistors or two amplification circuits (two different ranges on closed and open contact). The relays would be switched by a microcontroller of somesort that would determine which settings all DAC's and relays should be in for the desired waveform.

My main concern is that relays may add additional noise. I think mechanical relays might be OK (is this true?). I was also looking at solid state relays because of their size.

However, I've read on wikipedia that solid state relays have a higher resistance when they are closed and 'increased electrical noise'. How big are the issues with solid-state relays on low-amplitude (100mVpp for example) or high frequency signals (>5MHz). Is it even worth using SSR or use several MOSFETs instead?

Should I avoid solid-state relays and focus on mechanical switching instead (because I expect they pass through a signal much cleaner)?


texts: Why does parasitic capacitance influence high frequency Dc-Dc switching?

texts:
From my understanding, Dc-Dc switching means turning something between 0 and some Dc voltage value. In doing that fast enough we obtain an equivalent Dc voltage value (pwm principle).

When talking about capacitor impedance, the relations is:

In example in the image below, if we imagine that the voltage source is switching DC power source, instead of a sinus, that gives a signal as one on the image below:

In that scenario, a current would never flow.

Doesn't that imply that the impedance of the capacitor is always infinite regardless of the frequency of switching?

If that is true, what does the suggestions not to do Buck-Boost circuits on breadboards?


texts: Type of diodes for a particular application

texts:
Read some of the other answers, some of them are not easy to read (I'm not a specialist), some others do not fit my application.

A pretty simple system

two brushed motors, each takes between 12V to 20V
each consumes 5A at 12V
both are driven by the same "smart" controller

However, the load (attached to the motors) may have at times (especially when a motor power gets down) a reverse move that induces a reverse current back to the controller. This disturbs the behavior of the system, and I'd live to prevent such a reverse current to flow back to the controller.

My idea is to serial branch (after checking polarity) a diode between one of the two motor legs and the controller (for each motor).

However

the power (voltage) drop should be as minimum as possible
the two diodes should bear the 12-20V (5A) as described above

What kind of diode would you advise for such system?


texts: Does Interrupt interrupt a blocked read call

texts: If you were to read() incoming socket data in an infinite while loop, would an interrupt with top priority still run its ISR if the read() call is blocked (i.e. no data in the buffer)?


texts: How to drive electric power steering motor

texts:
I want to drive an electric power steering motor from an European Opel Corsa C in a way that I can control the steering of the car programmatically. I have a steering angle sensor which I will to use as rotary encoder for feedback to be able to set a desired steering angle. Unfortunately I do not know what kind of electric motor it is but I suspect a common DC brushed. Can anyone judge from the part number or use scenario on the motor type or do I have to open it to see the internals?

The whole power steering set includes the motor, ECU and torque sensor. In its normal operation, the torque sensor "reads" the torque (on the steering column) that the human driver's hands apply to the steering wheel and the ECU computes how much additional "assistance" will be applied from the power steering. The operation of the set can be seen on this video (Corsa B has identical parts).

A problem with steering is that the torque applied by motor depends not only on the human input but also on vehicle speed - more torque will be needed when vehicle stands still and less when it is moving fast... The ECU probably has a speed/torque map that it uses. I am trying to figure out how to deal with this - I guess the rotary encoder may solve the issue by giving feedback - in case the steering angle would change too slowly, more torque would be needed.

The motor may likely be driven in following two ways:

Reverse engineer the torque sensor. Input "fake" torque readings to the original ECU and let it drive the motor. This method may be easier but may not give precise control of the motor since the ECU will still behave like a black box and will try to map torque via vehicle speed - this may likely be prevented by not inputting speed to the ECU (by disconnecting it from CAN bus) - the ECU would behave consistently then thinking the speed is 0 (or whatever constant).
Directly control the motor with a custom driver. This may be harder but will give full control over the motor. Rotary encoder may be used to deal with the speed/torque dependency.

The motor looks like this (part number - GM/NSK 1407140):

This is the whole power steering set (motor, ECU and torque sensor):

My ECU part number is 13136672:


texts:
I have a question about power sequencing requested by FPGA/MCU datasheets. I always see in datasheets that a particular power supply input must reach a voltage level before another power supply input (for example Vcore before Vio). But every time I look at evaluation boards I can't find anything that does that (e.g. power sequencer ICs). My question is related to FPGAs and MCUs, and not to particular ICs that maybe must have a described power seq. to correctly work.

Since my evaluation boards never fault as power up, is this power sequencing really necessary? Or is it perhaps accomplished in some way by the decoupling capacitors?


texts:
I need to power a string of 12v RGB LEDs, but they're controlled by a 3.3v micro controller (Wemos D1 mini)

As it's wearable (inside a hat) I need to minimize weight so don't want to need separate batteries to get the two voltages.

If I have a 12v Li-ion battery can I use a voltage divider to get 3.3v for the micro controller? Or is there a better solution?


texts: Is there an LED constant current driver that works like the UNL2003?

texts:
I need a constant current driver that works like the UNL2003. Most of the LED constant currents drivers use serial communication with an MCU. Are there any ICs that might works like a ULN2003? (input wise)
edit - Well, there are actually some ICs that works like ULN2003 heck. Even better than that, it won't cost as many I/O pins as thevULN2003. They are generally called I/O expanders, a good example would be a TCA6408APWR. It can drive LEDs upto 25mA and uses I2C communication.


texts: 2 full bridge with 2 secondary winding in series... is it possible?

texts:
simulate this circuit – Schematic created using CircuitLab

Is this possible? Think of the center tap transformer as a 2 winding connected in series


texts: Gain of filter high-pass and gain of filter Sallen-Key

texts:
I can not calculate the gain of these two filters separately. I know the first filter is high pass and the second filter is a Sallen-Key, which is low pass. Could you give me a hand, please?

For the first filter (high pass):

For the second filter (low-pass):


texts:
I don't mind if it's a band-pass or low pass filter (although I think low-pass will give a better result). Input operating frequency range is 100Hz to 1kHz. Input amplitude will be about 1Vp-p and although it will be a bit noisy and not very square-wave-ish it'll be good enough to feed into a comparator to get a decent square-wave should that be required.

Basically I need a design that will take a noisy square-wave output from a strain gauge amplifier, determine the frequency of said square-wave and filter out the high frequency noise and harmonics leaving a sinewave.

EDIT - the end game is to measure the amplitude of the squarewave accurately - by filtering-in the fundamental frequency it becomes easier to measure because the squarewave amplitude is very accurately linked to the sine amplitude (4/Pi from memory)

This is for a test box where the strain gauge (connected to the amplifier) is supplemented with a FET switching a large value resistor connected across the strain gauge - this simulates a small but predictable amount of strain. The output from the amplifier needs to be converted to a sinewave for measurement purposes. I'm aware that this signal could be taken into a PC running a Fourier analysis on it but it's not always convenient to have a PC handy.

I suspect, for this tracking filter a switched-cap filter like the MF10 (or based on similar) will be required and a phase-locked-loop to track the actual input frequency to generate a clock at a much higher rate.

Currently, I have a 12th order low-pass filter that is good for a small range of frequencies around 600Hz (with minor adjustments) but this is no good for lower or higher frequencies.

Please let me know if there is information missing that would help answers. I am looking for quite high precision and if it needs a select-on-test components that's not a problem.


texts: Benchtop Frequency Counter - what does the AC specification mean?

texts:
Newb here. A friend and I are working on a small hobby project, trying to learn and mess around with some old electronics stuff he has. We have a need to accurately (+-0.1Hz) measure frequency of an AC square wave from the 1Hz to 5.5kHz range, 2-60v peak to peak.

When looking at something like the Victor Precision Frequency Counter 0.01Hz to 2.4GHz Digital RF Meter it lists the following specs:

  Freq range: DC couple 0.01-100Hz ; AC couple 100Hz-50MHz
  Sensitivity: "DC" 0.01-1Hz = 500m Vp-p, 1-100Hz = 80m Vrms, "AC" 100Hz - 50mHz = 80m Vrms
  Input impedance: 1 M?  Channel B (50MHz - 2.4GHz)
  Freq: 50MHz - 2.4GHz
  Sensitivity: 50MHz-1.2GHz = 80m Vrms, 1.2-2.4GHz > 80m Vrms
  Coupling: AC only

Being a newb, I really don't know how to make sense of that.

My question is: Given my previously stated requirement:

  need to accurately measure frequency of an AC square wave from the 1Hz
  to 5.5kHz range, 2-60v peak to peak.

What specs should I be concerned with?


texts:
I'm trying to set up an analogue to digital converter to read electrical noise.  The noise is kinda Gaussian with a very very very rough amplitude of the order of 2Vp-p.  I'm using a 10 bit range ADC that spans 2.5V, and have the opportunity to alter the amplitude of the signal up or down.

My problem is the Gaussian bit.  This means that there is no limit to the range of the signal, just that signals spanning much more than 2V become increasingly rarer.  Some times they might span 3Vp-p on rare occasion.  More on even rarer occasions.

How do I set the input amplitude?  Do I go low and only use 5 bits most of the time ensuring that I will never miss an out lying reading until the Universe cools?  Or do I go high, use 9 bits then often miss higher amplitude signals?  Err...

I'm not sure if this is actually an electrical or statistics question.  However, this must be a common situation in signal acquisition so I'm hoping for some best practice advice.  How would a commercial industrial acquisition device be configured specifically for this use case?  I can only think of stupid analogies such as an accurate scientific beaver weighing device.  How would I get the best use from my 10 bits to ensure that I can weigh all beavers with a good resolution?  Please try to see this from a commercial perspective so that you're actually trying to design and sell these devices.

P.S.  Having written the title lastly, my problem seems to boil down to "How to measure the amplitude of noise?"


texts:
My project is finished and Xilinx gives lots of statistics in the summary like :

How shall I evaluate these values, what can I say about them? What means what? Is this report good or bad? With what can I compare my results with?

Also timing constraints failed with below stats:

Is there a way I can fix this and what can I say about it? What would be the source of the problem?
I would be glad if you can give me a hand!


texts: Music distortion from a Bluetooth board at high volume levels

texts: I have a Drok Bluetooth audio amplifier board that comprised of a TPA3116 audio amplifier, a JL Bluetooth receiver and processing IC and a couple of RLC circuits. I've noticed that when I turn up the volume all the way the music gets distorted, so I connected the audio out to an oscilloscope to see if it could give me some insight on the problem. The audio signal seems to get cut off when the amplitude of the audio signal surpasses the supply voltage. I have tried increasing the supply voltage to see if that would change the output, but it did not. Why does this distortion happen?


texts: What is the function of AVDD,AVSS and Vref of ADC in Microcontoller?

texts: I want to know the function of AVDD,AVSS and Vref in Analog to Digital converter in a Microcontroller. If AVDD and AVSS represents the range of input voltage ,what is the function of Vref?


texts: How inductance of a coil changes when there is a metal object nearby?

texts: I am not sure if it is increasing or decreasing as some sources say it is increasing whereas some say it is not. What actually happens when a metallic object is put under a coil that is meant to be used as a detection coil for metal detector?


texts: What prevents abrupt voltage change in a circuit with a capacitor?

texts:
Let's say we have a simple circuit consisting of a power supply and a resistor, and currently the input voltage is 0V. We now apply a voltage of 5V to the circuit (like a step increase - instantaneously). The voltage across the resistor changes instantaneously to 5V.

If a capacitor is introduced into this circuit, it will gradually charge until the the voltage across it is also approximately 5V, and the current in this circuit will become zero.

My question:
What is now preventing us from suddenly changing the voltage from 5V to let's say 10V (again like a step increase - instantaneously)? We could do it before the capacitor was introduced, but why not now?

The answer I have thus far always gotten is that for that to happen, according to i=C*(dv/dt), the current flowing in the circuit must be infinite, and since that cannot happen, the voltage cannot be changed instantaneously.

The problem is that we ARE changing the voltage of the power source instantaneously, just like before the capacitor was introduced. The introduction of the capacitor has not somehow taken away our ability to change the voltage of the power source (instantaneously), has it???

So, in this circuit with the capacitor included:

Can we change the input voltage instantaneously or not? (theoretically)
If we can, what will happen to the current? Will it try to become infinity as i=C*(dv/dt) states? Or is there something else that I'm missing?
If we can't, is the capacitor somehow magically preventing this change? How can any component actually affect the input voltage of the circuit?


texts: Can I use blue-green LEDs as MCU state indicators on 3.3 V power?

texts:
Modern electronics industry has developed very efficient LEDs with nice and fancy colors (“true green” , “cyan”, and “blue”) based in InGaN technology, or similar. Some of these LEDs are specified as having forward voltages of 3.2 to 4.2 V. Here are examples of such LEDs, Kingbright WP7104PR51C/A, or surface-mount APT3216VBC.

But the usual MCUs are powered from 3.3 V supply, and the GPIO output is usually at 3.1-3.2 V, which seems to be barely enough to drive these LEDs . How can I use these LEDs as indicators of some signal statuses, or power rail status? Do I need a series resistor R1 here?

If yes, how do I choose its value?

DISCLAIMER: This "question-answer" comes as elaboration of the original question "Is there a point in adding a 1 Ohm resistor to this LED circuit?", to address the particular use case of LEDs as logic state indicators.


texts: I know MOSFETs are much more efficient than BJTs in that they don't consume as much power when on whereas a BJT consumes base current the whole time it is on. I also know that MOSFETs tend to fail shorted. I can't find any information on BJT failure modes though/do they usually fail open or closed. Does anyone know about this?


texts:
I am trying to synthesize a combinational logic block in verilog using Xilinx Vivado. I am trying to reduce the number of luts and still try to find the critical path of the circuit.

Many solutions tell that the timing analysis is done from register to register. However if the output are made as registers the area of my design increases.

Is there a way to find the critical path  of the behavioural design without using output registers?


texts: Electric-grade gel / silicone to provide physical protection for circuit boards from damage

texts:
Not looking for a brand or product (unless allowed to ask) just the generic name for electric-grade gel / silicone that can be poured on the circuit board or embed the circuit-board in it.  It would serve as a cushion to provide physical protection for circuit boards if dropped (2 meters) and/or the case moderately banged so they won't get damaged.
The circuit-board is inside an airtight metal case and may be left out on the sun for prolonged periods.    It would also be a plus if the gel / silicone would act as a heat sink of sort to, although the circuit itself does not generate heat only from being baked in the sun inside a metal case.
Obviously, it has to be non-conductive.  It's ok if entombed for good, but would be great something that could be peeled off later.
Also, welcoming any other suggestions for PCB mounting to the metal case.
Thank you.


texts:
For an application I need to generate a 10 MHz sine wave signal that is modulated with 20 KHz triangle signal. This is going to be frequency modulated.

This goes into another circuit which require a low phase noise. What is my best option to generate this signal effectively with low noise and reasonable cost. So far I have seen DSS solutions from ADI.


texts: Anyone know the exact setup needed to send KiCad files to OSH Park? Specifically how to set the trace widths correctly?


texts:
Using KVL, KCL and circuit analysis, Can you explain why is there zero voltage at the source of a differiential MOSFET amplifier?
In the textbook, they just state that because it's balanced the source is zero.


texts: Homework - Find where the components belong

texts:
A black box has three electrical connections labelled A, B, and C, arranged
  in a triangle as shown below.

  The box contains three components: a resistor, a small capacitor and a
  diode. You know that one component is connected between each pair of
  terminals, but you cannot see exactly how they are arranged. You make
  the following observations with a 9 V battery connected in series with an
  ammeter:

  When the battery is connected with + to A and − to B a current of
  3 mA ﬂows
  When the battery is connected with + to B and − to C a very large
  current ﬂows
  When the battery is connected with + to C and − to A no current is
  measured
  When the battery is connected with − to B and + to C no current is
  measured

  On the diagram sketch the arrangement of the three components in
  the box indicating the terminals clearly.

I have had a lot of trouble with this particular problem. The only thing I can confidently say is that the diode is blocking the current in the 2 cases, but what bothers me is that in those 2 cases the currents flow in opposite directions  (counter-clockwise in the third, clockwise in the fourth), which confuses me.

The first 2 cases probably mean that the diode blocks current in the clockwise direction, because otherwise you wouldn't have a current at all, but that still leaves me with the issue of the third case, where the current flows in the counter-clockwise direction, but apparently still gets blocked.

Can anyone help me with this problem?


texts: Find datasheet for an industrial radio remote control

texts:
At work, we have what seems like radio-based remote controls to control the window stores, the light and the temperature.  We'd like to find out what the commands are that are sent by the remote control.

I've been able to open it and take a picture of the circuitry and was looking for any tell-tale signs as to what components are.  But I'm not expert enough to recognize anything ... :-(

The company name is YRIS TECHNOLOGIE (a French company apparently bought up by Schneider Electric).

How can I find out more about this remote control? Thank you for your help in advance!


texts: how do i select a battery for a circuit which has multiple ICs?

texts: I am using INA125 amplifier, a PIC controller, a load cell and a ESP 8266 wifi module. how can I calculate the power consumption to select a battery?Do I just add up the currents of my 4 devices or is there something I am overlooking?


texts: STM32 USB CDC - VCP TX data wrong, RX works fine

texts:
I have some trouble with the USB CDC on a STM32F7 uC. The whole project was generated with CubeMX and runs on a custom hardware.
When I plug in the USB controller into my computer, the device gets directly connected and the virtual COM port appears, which I can use with a normal serial terminal. When I send some string from my PC, I receive it correctly on my uC in the function static int8_t CDC_Receive_FS(uint8_t* Buf, uint32_t Len). When I send data to the PC by using uint8_t CDC_Transmit_FS(uint8_t Buf, uint16_t Len), there appears some data in the serial terminal, but it seems to be totally wrong.

As you can see, the data repeats, so it must somehow be the same everytime it is sent, but I don't get it what kind of data that actually is. CDC_Transmit_FS looks likes this:
uint8_t CDC_Transmit_FS(uint8_t* Buf, uint16_t Len)
{
  uint8_t result = USBD_OK;
  /* USER CODE BEGIN 7 */
  USBD_CDC_HandleTypeDef *hcdc = (USBD_CDC_HandleTypeDef*)hUsbDeviceFS.pClassData;
  if (hcdc->TxState != 0){
    return USBD_BUSY;
  }
  USBD_CDC_SetTxBuffer(&hUsbDeviceFS, Buf, Len);
  result = USBD_CDC_TransmitPacket(&hUsbDeviceFS);
  /* USER CODE END 7 */
  return result;
}

So this seems to be fine and when I debug down into the register layer, the right data seems to be added to the send register.
Anyone an idea, what I need to do to receive the correct data?


texts: 1.8 V to 5.0 V level shifter with low delay and low rise time

texts:
i have a problem with finding the right components and circuit for the following problem.

I have a device that is producing trigger signals with a length of 100 ns at a amplitude of 1.8 V (left part of the picture). To trigger a RF-Switch it is necassary to shift the 1.8 V to a 5 V signal (TTL). The circuit have to operate only in one direction but really fast. The delay between the trigger signal and the amplified signal should be less than 5 ns (if possible!).

I am not sure which option is the best solution for this problem. Should i use a CMOS or a set of bipolar junction transistor. Do you know components that have a low raise and delay time for this application?
Thank you in advance


texts: Simple circuit with dependent source interpretation

texts: For the following circuit, taken from the book "Circuit analysis for dummies" what would its BJT transistor counterpart look like (I mean the most basic circuit with the BJT transistor instead of the dependent source)? I'm especially interested in figuring out how the R2 resistor is connected in the circuit with the BJT transistor.


texts: Why doesn't my operational integrator work?

texts:
Here is the schematic I'm following, to build an operational integrator.

(Image source - Electronics Tutorials)

I'm using a LM358N IC which has 2 op amps. Below is a crude drawing of my connections.

I don't seem to get what I want, when I feed a square wave signal 0 to 5 V with a 20 ms period. I expect a negative sloped signal, but just get 0 V output.

What am I doing wrong?


texts: I am currently working on making a two sequence Moore machine detector. I am having trouble as to how to have the machine detect my second sequence and how to make a state table with T flipflops from this. I am working with 1011 and 1110. Thank you for any help or advice!


texts: Challenges to DIY a USB QC 3.0 charger for a DJI Mavic Pro @ 13V?

texts:
One of the big pain points with all of the DJI Mavic Pro drones is that they do not charge via USB. In order to charge the batteries you have to buy an AC-DC adapter which adds a good amount of extra weight and bulk to something that could just otherwise be a single USB-C cable.

https://store.dji.com/product/mavic-50w-battery-charger-without-ac-cable

The charger outputs 13.05 V at 3.83 A. Since QC 3.0 can go up to 20V and 18W, it could output 13.00V at 1.4A, slower than the stock charger but vastly simplifying the charging hardware.

How difficult would it be to hack together the DJI battery's charging plug into a USB-C cable that somehow directs the QC 3.0 power adapter to only provide 13V?

I'm assuming that the current will actually be controlled by the DJI battery, right?  So if the DJI battery tries to pull 3.83A it would fry the QC 3.0 charger?


texts: Is a bootstrap capacitors always required for mosfet drivers?

texts:
I am designing a H-bridge to drive a motor that is running at 12V / 3A.

To prevent shoot-through I decided to select a IC with integrated dead time - IR2111.

What I got so far is the following circuit (showing just one half of the full bridge to conserve space):

What I am curious about is the need for the bootstrap capacitor between \$V_B\$ and \$V_S\$ and the diode as shown in the datasheet:

My understanding is that usually the drain of the high-side MOSFET is connected to a much higher voltage as the supply voltage for the IR2111. To switch the MOSFET a higher voltage has to be generated, therefore the bootstrap capacitor.

But in my case the voltages (drain of the hide-side mosfet and supply voltage of the IR2111) are all 12V. So the voltage is high enough to switch the high-side MOSFET and I do not need the bootstrap capcitor. Am I right?


texts: Which electronic device is this one below?

texts: I found this thing in a piece of a very old circuit board. The shaft turns, inserting the black rods inside the metal cylinders. Inside each of the shiny cylinders there is a coil. It has 6 black rods in total. I have no idea what use this is intended for.


texts: 74141 BCD-to-decimal converter not working?

texts:
I set port D are output and have hex value 0xca at BCD format. But LED is all HIGH.
I wonder why this converter not do its function??


texts: Powering 600 WS2811 5V LEDs by using larger voltage power supply and DC:DC convertors close to the LEDs

texts:
I am working on designing a device that will have about 600 WS2811 5V LEDs on it. I am trying to figure out a way to power all these LEDs. At about 60mA max per led this is about 36 amps of power required.
This is for a piece of art that hangs on the wall, so I really don't want to have to run a bunch of +5V power supplies and multiple wires up to the artwork.
I am considering running a higher voltage power supply (maybe 36V) to the artwork and then using some type of DC-DC module to power smaller segments of the LEDs (to be mounted behind the artwork). This will enable to me to use smaller gauge wire to the artwork itself and just sprinkle around these modules to power maybe 75 LEDS 4.5Amps?
Is my thought on this realistic? Any brand/types of modules I should be looking for?


texts:
Background:

I am not providing diodes for free wheeling of motor as:
- I have one big capacitor, 100uF
- CW and CCW will be switched with dead band delay of 1.5 to 2.5 seconds

can there be a Hbridge without freewheeling diodes


texts: Wiring DPDT (ON-OFF-ON) toggle switch to Two-Speed DC motor - Hours spent on interesting study - Still a fail :-)

texts:
Can someone show me, completely even, (cringe) on what wires go where.
Here's a picture of the 3 parts. BIG DC BATTERY - TWO SPEED MOTOR - DPDT (ON-OFF-ON) SWITCH

https://imgur.com/a/i35QbmC

When the switch is in the off position, center of course, the motor is off, then in one direction it goes on, low speed, on the other direction is goes to high speed.

When manually connecting the wires it works.

TOPLINE: 2-speed motor - not trying to reverse motor just change between two speeds.

it's a chunky 20amp stock acting toggle DPDT ON-OFF-ON - I don't care which direction is high speed or low speed. (when thrown full one way, or,  fully the other way)

I need (already have) a wire from every marked point on The battery, AND the 2-speed motor. shown in IMGUR link diagram (above) link work i hope.

Just need to figure out the clever bits for getting the DPDT wired up.

I have done tons of study and have down-graded my opinion of my confidence/IQ at figuring stuff out, a lot. heh-heh

--> Could anyone make a point-form list or other, as to exactly how I'd wire-up my current DPDT switch?  (BIG-cringe for asking)


texts: Why is Q1 taken as 'on' and Q2 as 'off' in the differential amplifier?

texts: The book tells that we can arrive at the conclusion by reasoning. Why can the voltage at the emitter not be -0.7 V so that both the transistors would be on?


texts: I find an adjustable current source circuit with UC3842, but without description. The main difference with a voltage regulator is the error amplifier's negative input comes from the current sensing resistor. But I can't find any detailed docs about this kind of usage. What's the main difference to the conventional output voltage regulator? Can anyone can give some clues or links about this kind of usage?


texts: Positioning of the stabilizing capacitor for the ESP 12

texts:
I have been researching the ESP 12, and I am ready to hook it up. Because the Wi-Fi uses high current, it has been advised to add a stabilizing capacitor across the Vcc and ground terminals of the ESP 12. These are on opposite sides of the ESP 12.

I am wondering whether the capacitor should be right beside the Vcc, or right beside the ground.


texts:
I recently purchased a YIHUA 995D SMD Rework Station and me being the geek that I am wanted to see if I could perhaps control it (via USB/ATMEGA) by using my PC and touch screen instead of physically doing so with my hands. Being able to control it via PC would allow me to mount the 995D under my desk and out of sight so that I have more room to work with on the top of my desk.
However, I have limited knowledge on "snooping" or "Reverse Engineering" and that is why I am posting my project ideas here in hopes that someone more knowledgeable will be able to let me know what all I need to do in order to accomplish my task.
I started out thinking I would just simply hook up the ATMEGA and just control the buttons/knobs and leave everything else as-is and just use a webcam focus only on the LCD to view what was on. Although that would work, its not ideal nor is it geeky enough  ;D .
The LCD screen seems to be controlled by the chip Holtek ht1621b. The website for it defines it as a "RAM Mapping 32x4 LCD Controller for I/O MCU". Here is the datasheet for it.

There also seems to be another chip which seems to be the main MCU? It's called the S3 Microcontrollers u820 s3f8s19xzz-qr89 and it's datasheet.

I've noticed that the IC above has a TX/RX UART line(s) looking at the diagram on page 9 of the datasheet.

9.7 Port 4
Port 4 is an 8-bit I/O port with individually configurable pins. Port 4 pins are accessed directly by writing or reading the port
4 data register, P4 at location F5H in set 1, bank 1. P4.0–P4.7 can
serve as inputs (with or without pullups) and outputs (push pull or
open-drain). P4.7–P4.0 can serve as segment pins for LCD or you can
configure the alternative functions:
Low-byte pins (P4.0-P4.3):
T0OUT, TBOUT, TACLK, TACAP, TAOUT
High-byte pins (P4.4-P4.7): TxD1,
RxD1, TxD0, RxD0

Would this be something I could use to read and write the needed info/data to/from the micro controller chip? Would simply getting a USB to UART cable and hooking it up to those 2 pins work like it would when reading RS232 data on an Arduino?
I have high resolution images of the 995D here so that you can see the main board and all it has to offer for this to potentially happen.
So I am looking forward in learning from others on here as to what I could do for this to happen - or laugh at me and tell me its not possible at which will only get me more interested in doing it  :).
Disclaimer: Also posted on these sites:
electronics.stackexchange.com
Electronicspoint.com
electro-tech-online.com
electronics-lab.com
EEVBlog.com
forum.allaboutcircuits.com
AVRFreaks.net


texts: Alternative for arduino for simple requirements

texts: I want to capture new email in inbox. I want something very tiny to accomplish this task. Arduino is quite big in size. Is anything available out there which I don't know by name. Please help.


texts: What effect does selecting the wrong load capacitance for a crystal have?

texts:
I've seen questions such as this one and this one that talk about selecting capacitors that, in series, match up as closely as possible to the load capacitance of the crystal.

What effect does selecting the wrong capacitance have? Does it skew the frequency, alter the shape of the waveform produced, or something entirely different? Is there an obvious correlation between too low and too high capacitance? Is it a case of slight errors, or orders of magnitude?


texts: So I was playing around with my amica nodemcu. So here’s the story. I first powered up my nodemcu with a power bank which outputs max of 5v 1A so then after that I was playing around with the pins of the nodemcu. I saw a pin named ‘VIN’. I thought it outputs 5v of power and then I took a 9v battery and connected the live terminal to the vin and neutral to Ground and immediately the nodemcu built in led was so brightly lit up. I figured out what was happening and checked whether my nodemcu was working. It worked fine. Should I worry about damage to my board. I do not see any visible damage.


texts:
I am taking an analogue electronics course and have been given an assignment to create/develop a 64.5kHz Hartley oscillator using any 5V rail-to-rail operational amplifier. I am trying to design the circuit in simulation first before I build.
I will be using this circuit:

simulate this circuit – Schematic created using CircuitLab
The design equations we have been given for the Hartley oscillator are:
\$\omega_0 = \frac{1}{\sqrt{C_3(L1+L2)}}\$
\$K(\omega_0) = -\frac{L1}{L2}\$
\$A = \frac{L2}{L1} = \frac{R2}{R1}\$
I began by choosing \$L_1 = L_2 = 10\mu H\$ and then solving for \$C_3\$ with \$\omega_0 = 129000 \pi\$ to obtain \$C_3 = 3.04\times10^-7 F\$
then \$A = \frac{10\mu H}{10\mu H} = \frac{100k\Omega}{100k\Omega}\$
I've simulated in LTspice using the circuit below giving it a quick pulse to get the oscillation going:

The results:

From this I observe that the oscillation frequency is very close (64.3kHz) but the response dies out very quickly and does not sustain. My understanding of oscillators is that I want the negative feedback to be equal to positive feedback to fulfill Barkhausens criteria in which the magnitude of the total feedback should be 1 and the phase shift 0. I am obviously missing something important. Any advice on getting this circuit to have a sustained oscillation would be greatly appreciated.
edit:
Based on the suggestions below I added an extra resistor between the output and resonant circuit and adjusted my gain. Re-simulating gave these results in LTspice. I've added three screenshots below from the simulation. The first is over 10ms, the second I have zoomed in when the oscillation stabilizes and the third is a frequency domain plot showing an impulse at 64.5kHz:


texts: AtmelStudio 6.2 changes the ISP clock when I try to run a program

texts:
I'm having a strange problem with AtmelStudio. I took a few screenshots:

Here, atmel studio is open and I check the project settings. ISP Clock is set to 125kHz. This is good.

I also check the setting in device programming (Tools -> Device Programming). 250kHz is fine. Reading out the signature is no problem and I can even program the device here under Production File.

So all looks good, I hit F5 to compile and run the program, and this happens. Ouch, unexpected device signature 0x00000000.

At this stage I'm confused. Communication with the device worked perfectly just before. Going into Tools -> Device Programming reveals what happened. The ISP clock is set to 1MHz! Too high for the chip. Obviously reading the signature here fails.

What exactly is happening? Why is AtmelStudio changing the ISP Clock of the programmer? Or where is the 1MHz coming from, is there some config I've overlooked?


texts: Simple PC fan controller PWM discrete components

texts:
Recently I switched some case fans in my pc to find the horror that the new ones were even louder than the old ones. After some quick checks just by eyeing and monitoring on my pc I can confirm the new fans like to spin with the pc reporting about 1000 RPM whilst the old fans at best ran at around 600 RPM. These fans only have three pins so I though I could make some PWM controllers as a fun project, calculating the power drawn from the new fans would be in the range of about 2-2.5 watts per fan. So I'm thinking of using 5 watt components to drive it. However I came across no clear way to actually do this, for the tachometers to work I need straight DC into the fan.

I came across this circuit:

So would something like this work given I invert the signal just before sending it to the a power stage like the one shown in the upper quarter image? I think I remember PC fan PWM signals saying the fans should be off when the duty-cycle approaches 0 (until the built in shmitt trigger activates).

Would this work?


texts: What is Analog and Digital supply voltage

texts: Currently I have start working on MSP430 Controller and found that there are 4 pins for the supply voltage viz. AVcc, DVcc, AVss, DVss. These are used as analog supply voltage and Digital supply voltage. What are the purpose of providing these twins pins? How can I use these pins during designing of supply section.


texts:
Possible Duplicate:
  Best edge connector for my pcb?

I want to find a mini jtag connector (about 1.00mm pitch, 6~10 positions) to connect to the edge of my pcb.
Something like these but with opening on the side so the PCB does not need to extend:
http://www.digikey.com/product-detail/en/91930-21109LF/609-1588-ND/1001902

or

I spent lots of time searching, but still cannot find anything suitable.
All suggestions for how to solve the problem are appreciated.
Thanks in advance!


texts:
In the data sheets for 8284a, the said The crystal frequency should be selected at three times the required CPU clock.
why they use crystal frequency three times the required CPU clock?


texts:
I have a K-30 CO2 sensor connected to a Raspberry Pi 3 model B. When I connect the sensor to the Pi via serial and power the sensor with the Pi, my program works fine: the CO2 concentrations are displayed on the screen.

On the other hand, when I try to power the sensor with a portable battery, the program does not work: the Pi recognizes that the sensor is connected, but it doesn't read any values from the sensor.

I know the sensor is receiving power from the battery because there is a light blinking on the sensor and the Pi recognizes that the sensor is there. Also when I measured the voltage running through the wires from the battery, it says 5.3 V, which is sufficient for the sensor according to the data sheet.

I have the sensor ground and power ports connected to the ground and power wires of a USB cable, which then plugs into the battery.

Any ideas as to why this isn't working?

K-30 CO2 sensor

Battery


texts:
I am trying to generate a 1 s delay using Timer0 of PIC18F2520. I am using the internal 8 MHz oscillator. The timer works with FOSC/4 so I have :

8 Mhz/4 = 2 Mhz
T = 1/2 MHz = 0.5 µs

Now the number of counts for rollover is 0xFFFF (65536) so according to the delay I want I need to set the values of TMR0L and TMR0H. Now let's say I want a delay of 1000 ms, so:

65536 - 64536 = 1000 ms
64536 (0xFC18) is the value which I need to put in TMR0L and TMR0H.

If the above calculations are correct then the following code should work properly (using the C18 compiler):

#include <p18F2520>

#pragma config WDT = OFF       //Disable watchdog timer
#pragma config OSC = INTIO67   //Internal oscillator
#pragma config LVP = OFF

void main()
{

 //8Mhz oscillator
 OSCCONbits.IRCF0 = 1;
 OSCCONbits.IRCF1 = 1;
 OSCCONbits.IRCF2 = 1;
 OSCCONbits.SCS = 1;

 TRISCbits.TRISC2 = 0;    //output led

 while(1)
 {
    LATCbits.LATC2 = 1;
    DelayMs();
    LATCbits.LATC2 = 0;
    DelayMs();
 }
}

void DelayMs()
{
  T0CONbits.PSA = 0;         //Prescaler assignment bits
  T0CONbits.T0CS=0;          //clock source select bit
  T0CONbits.T0PS = 0x01;     //1:4 prescaler

  TMR0H= 0xFC;
  TMR0L=0x18;
  T0CONbits.TMR0ON = 1;       //enable timer1
  while(INTCONbits.TMR0IF==0);
  T0CONbits.TMR0ON = 0;
  INTCONbits.TMR0IF=0;

}

When I programmed the device with the code above, the LED was on. It didn't turn off even after 4-5 minutes.


texts:
Can someone tell me what is the meaning of "Maximum forward voltage drop per bridge element at 4.0A dc is 1.1v" in 4 diode bridge rectifier?

Does it mean that there is a voltage drop of 1.1v per diode or total 1.1v voltage drop for all the 4 diodes together?

Please refer this link to page 1

I wanted to know what will be the total voltage drop with this above-mentioned bridge rectifier? I am specifically talking about model number "FL401" in the datasheet.

Also, can someone suggest me right ratings for bridge rectifier?
My requirement is as below.

Vin 7~40v AC or DC to bridge rectifier.
And for my application, I need 3A current

I have chosen the following ratings. Please correct me whether that is right or wrong.

No. of Phases: Single
Repetitive Reverse Voltage Vrrm Max: 100V
Forward Current If(AV): 4A
Bridge Rectifier Case Style: SIP
Forward Voltage VF Max: 1.1V
No. of Pins: 4Pins
Operating Temperature Max: 125°C

Also, Please tell me with the above ratings what will be the total voltage drop in the bridge rectifier when I give input as 9v and what will be the output current.

P.S I am not an electrical engineer. Please apologize me if I used any wrong electrical terms or asked any silly questions.

Thanks in advance.


texts: 24V Circuit Protection - Fuse, TVS Diode, RC Snubber

texts:
I have pored over data sheets and read numerous articles on circuit protection.  I understand conceptually, but I don’t trust my level of knowledge to implement it optimally.  I want to be as specific as possible to meet forum guidelines so I’m asking for critical analysis of the circuit protection in particular, both for the LM2931 and the relays.  Specific components selected below with rationale for selection.  Data sheet links included.  The circuit provides intermittent operation of a wiper motor.

Power Supply.  LM2931 accepts up to 40V (suitable for both 12V and 24V systems), is “designed primarily to survive in the harsh automotive environment,” and the TO-220 package generates much less heat than a TO-92.  Per the data sheet, C1 is a ceramic 10µF cap and C2 is a low-ESR 47µF aluminum cap.  Providing some protection is D1 for reverse-polarity, the P6KE TVS diode – P6KE20 (17V standoff) for the 12V and a P6KE39 (33V standoff) for the 24V system – and a PTC 100mA fuse.  Load on the 2931 is an ATtiny85 and two 2N2222 NPNs; around 10-15mA.

Relays.  Switching is through two 20A Panasonic automotive relays: CP1-12V or CP1-24V as appropriate.  Relays have a diode across the coil and a snubber across the C and NO contacts.  The snubber is a 0.1µF metallized film cap and 100Ω carbon 1/2Watt resistor.  Relays are controlled by a 2N2222 NPN with 1kΩ on the emitter reducing current to ground and 1kΩ between the base and the ATtiny.  [D6 ensures K1 is energized if K2 is energized.  This prevents both M_LO and M_HI grounded simultaneously.]  Power to the motor enters the board from either M_LO or M_HI and exits through a 6.3A PCB fuse to M_GND.   The PCB traces for the motor current are 200mil (100mil on top and 100mil on bottom with a via mid-length.) capable of carrying over 8A.  The longest motor trace is 17mm.

I have operated the circuit with a different TO-92 regulator and without the TVS, fuses, and snubbers and it works correctly.  Before I build another, I would appreciate some critical scrutiny and constructive criticism on the incorporated protection.

Is the 100mA PTC fuse appropriate for the circuit?
Is the TVS a good idea or unnecessary with the LM2931 already having 60V load dump protection, -50V reverse transient protection, internal current limiting, and temporary mirror-image protection?
Is the 6.3A fuse appropriate?  (The motor power from M_LO and M_HI are on a 20A fuse, much too high for the PCB).  The motor can pull over 2A at start and about 1A while in operation.
Are the emitter resistors (R4 and R8) appropriate?  I did not have them in the original circuit but believe there should be some value there to limit emitter current to ground.
Are the snubbers necessary for a 28V/2A motor relay?  Selection of snubber components acceptable?
Would any components apart from the TVS diode and relays need to be substituted when building for 12V (~14V) use rather than 24V (~28V) use?

LM2931

P6KE TVS

CP1-12V relay


texts: "Unable to open parallel port I/O driver" when trying to connect "RS232 to USB" cable on Linux

texts:
I have a JDM programmer for pic micro-controllers, but it came with RS232 port. I have bought a "RS232 to USB" cable with its driver for Windows only and I use Xubuntu 14.04 LTS.

I have tried dmesg and lsusb, it shows that the cable is connected. But when I try to burn hex file to the programmer, it gives me this output:

PICPgm Development Programmer Version 2.8.1.0
http://picpgm.picprojects.net
Copyright 2002-2014 Christian Stadler (picpgm@gmx.at)
(built on Dec 29 2014 at 22:32:45)
==================================================================

Autodetecting Programmer ...

Warning: Unable to open parallel port I/O driver!
         Installing driver requires admin/root rights!

Error! PIC Programmer not found! Check connection!


texts:
Over the last few days I've been working on an anode RGB LED in Arduino, I've tried getting it to do an RGB spectrum but all I would get is just the colors from red to green, then it would get stuck on white and cyan, I believe that the red LED in the RGB Anode turns on and off, as the combination of green and blue is cyan and the three of them result white if they're equal which in this case I guess they are (not entirely sure).

Thing is the RGB Anode doesn't display all colors, I made it so the level of voltage given to the RGB anode is increased with a loop function and decreased once reached 255 with a decreasing function, here's the code:

    int redPin = 11;
int greenPin = 10;
int bluePin = 9;

void setup() {
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);
}
void loop() {

redFuncInc(1);
delay(100);
greenFuncInc(1);
delay(150);
blueFuncInc(1);
delay(200);

// calling decreasing methods

redFuncDec(255);
delay(10);
greenFuncDec(255);
delay(15);
blueFuncDec(255);
delay(20);

}

// Increasing from rainbow spectrum

void redFuncInc(int red){
  for (int i = 1; i<=255; i +=1){

  analogWrite(redPin, i);
  delay(10);
}
}
void greenFuncInc(int green){
  for (int z = 1; z<=255; z +=1){

  analogWrite(greenPin, z);
  delay(20);
}
}
void blueFuncInc(int blue){
  for (int u = 1; u<=255; u +=1){

  analogWrite(bluePin, u);
  delay(30);
}
}
// Decreasing from rainbow spectrum

void redFuncDec(int red){
  for (int y = 255;  y <=255;  y -=1){

    analogWrite(redPin, y);
    delay(10);
  }
}
void greenFuncDec(int green){
  for (int x = 255;  x <=255;  x -=1){

    analogWrite(greenPin, x);
    delay(10);
  }
}
void blueFuncDec(int blue){
  for (int g = 255;  g <=255;  g -=1){

    analogWrite(bluePin, g);
    delay(10);
  }
}

Thanks for your help, please don't mind my English...


texts:
I was wondering if someone could explain what a totem-pole output driver is?

I have seen the term mentioned in connection to the inner circuitry of an AND gate (consisting of transistors) and in terms such as "Standard Totem Pole Output." However, nowhere is it actually explained what it is and what function it serves...

thanks!


texts:
I'm on the hunt for a circuit which is simply to dump 3A (+/- 0.5A) cc to ground if it receives a signal from an Arduino or if the voltage exceeds 5.5 V on the load it should clamp it for up to 5A (+/- 0.5A) to prevent capacitor breakdown at 7V. The powersourse the charger uses is a high precision bench powersupply whith cc set to 3.7V 3.3A. It's to be used to discharge a 500mF 5V super capacitor for safety reasons (I can't allow a charged cap to leave the production test) and prevent over charging if malfunction of charger. It's part of a production test and this part is for the capacitor.

My current plan is to use an NPN BJT to dump the charge and use a resistor in series with the Arduino input signal to set the voltage. But I can't figure out how to use a Zener diode or similar to automatically trigger the constant current circuit without the need of many components.


texts: what's the difference between these two low pass filter types

texts: Is there any difference between these two types of lowpass filters?  I see the equation is the same, I assume they're both first order then.  Just curious if there's any practical difference.  Maybe one allows me to set gain and the other doesn't?


texts:
I'm reading a paper by Guillermo Serrano and Paul Hasler, A Precision Low-TC Wide-range CMOS Current Reference, IEEE JSSC Vol 43, no 2, Feb 2008. Link to paper - requires subscription to IEEE Xplore to acces

In  this paper they use the temperature coefficient of a MOSFET to cancel out the temperature coefficient of a resistor.

I understand the temperature coefficient of a poly resistor: As temperature goes up, the amount of electrons in the conduction band increases as the bandgap decreases. Hence there are more charge carriers, causing more current to flow at lower voltages. (so a higher conductivity or lower resistance).

What I'm confused about is the temperature coefficient of a MOSFET. From what I know, the mosfet actually has a shift in temperature coefficient - at high gate-source voltages it has a positive temperature coeficient, at low gate-source voltages it has a negative temperature coefficient. This negative tempco is what causes thermal runaway to occur. Plotted on a graph, this looks something like this (from an ON Semi appnote - AND8199

But what physical properties underly this temperature coefficient? What I have been able to come up with is that as temperature rises, the valance band will go up. As a result, more potential is needed to enter inversion. As less electrons are formed in the inversion later (or holes, depending on the substrate doping) there is less to conduct, and thus the current decreases. Is this correct? What about the negative tempco at low Vgs? Can anyone explain?


texts:
Edit: After extensive discussion with HikeOnPast (thank you) and then a brief hiatus, I am back with more specific questions. The edited question follows...

Let me start by saying this is my first Arduino project, and I'm a little confused with some of the hardware.

I am attempting for my first project to make a fingerprint door lock, and the only thing that's stopping me from purchasing the components is knowing if my setup is going to work or not.

The basic schematics of the idea are below:

Old image: http://i.stack.imgur.com/3dT8v.jpg

Is this an acceptable setup? For the actual fingerprint reader, I was going to use this one, https://www.adafruit.com/products/751, which upon receiving the correct fingerprint, tell the Arduino to send power to the lock to unlock it for a certain amount of seconds.

The coding I can handle.

The strike that I will be using is similar to the "Electric Door Strike for Schlage Locks," and the power supply will be similar to the "Linear Corporation AAE00381 12-Volt DC 2000ma Power Supply."

Specific questions:

Do these schematics make sense? After discussing this with HikeOnPast below, I believe I copied his schematics correctly. I'm not sure what he meant by "12V Return" from the strike but I assumed it is the same as sending it back to the power.
Is there a better, more efficient, or simpler wiring setup?
Would the above work with an electromagnet substituted for the strike (I'm assuming yes, I would just need to find parts that are compatible with the magnet)?


texts: What does the collector resistor on this LED driver circuit do?

texts:
The resistor in question is R2.
The below circuit provides roughly constant current above a certain Vcc.
For R2, I arrived at the value by trial and error by checking simulation outputs.
I would like to make a more precise decision on the value of this resistor. How can I start to to think about doing this?

Here is the current through the LED:


texts: Crossing ground planes with low current low frequency signals

texts:
I have a board which has two ground planes, analog and digital, that on this board are completely separate. The grounds connect on another board, which is connected via a flat cable.

All signals on top of the two powerplanes are independent (i.e. they interact on the other board only), except for four "jack detect" signals, which detect when a plug is inserted into a jack on the analog side. These need to cross to the digital side. The jack detect signals are DC except when a plug is inserted or removed. The voltages involved are \$0\$ or \$3.3\mathrm{V}\$, depending on jack state, and read via an I2C expander on this board. The following is a schematic for one of four jack detects, others are identical.

simulate this circuit – Schematic created using CircuitLab

When nothing is connected to the jack, the switch is closed, and R3, which is connected to the virtual ground of the opamp (powered from analog \$3.3V\$ and connected to analog ground) pulls the input low enough to read a logic zero at the I2C expander. So in this case the current comes from the opamp and goes to the digital \$3.3V\$ and the I2C expander. When a plug is inserted, the switch opens and R1 pulls the input up to (digital) \$3.3V\$. In this case the current travels entirely in the digital side, and there's no problem.

The digital side and the jack detect signals obviously only need to be clean enough to always read the correct logic state. However, the analog side contains somewhat sensitive signals, which we need to read to about 12-bit accuracy.

My question: this requires crossing the ground plane split from the analog to the digital side. How should I do it? Some options with justification:

Sure, there's a loop that travels to via the flat cable to the other board, where the grounds meet. However, the current involved is minuscule, the \$100\mathrm{k\Omega}\$ resistors alone limit it to \$16.5\mathrm{\mu A}\$ (and in reality much less than this), so I just jump over the split with R2.
I connect the powerplanes under R2. Now there's no large loop for the jack detect current. However, other ground loops become possible in principle, and I need to make sure that this connection is not the preferred return path for any other signal. I should be fine with high frequency signals, since those want to travel under their respective tracks, right? However, depending on resistances in the flat cable, connectors and the other PCB, some DC signals might want to take a shortcut here, causing ground offsets (biggest currents traveling between the boards are some tens of \$\mathrm{mA}\$, so at 12 bits, 1 LSB error corresponds to about \$0.1\Omega\$ resistance).
Connect the power planes next to R2 with a capacitor. However, this doesn't seem to make sense since there shouldn't be any problems at high frequencies anyway.
Bring the jack detects all the way to the other PCB and cross them where the power planes do connect. This cannot be done, as there's not enough conductors in the flat cable, currently the only digital signal between the boards is the I2C bus.

Currently I have a prototype using option 1., which works perfectly fine. So perhaps none of this matters at all, for DC and such low currents?


texts: Why does my solid state relay not properly power a DC load?

texts:
I'm using a T108S02 to try to use a logical signal to turn on or off a small 3V DC toy. I'm not sure of the load current of the toy since my ammeter is not working.
When I activate the relay, my toy turns on, but appears to be running with limited load as the motor runs at about half speed.
I am expecting this SSR to be either all on or all off. What would make it act like a resistance?


texts: Reversing the Direction of An Induction Motor?

texts:
I have this motor I salvaged from a dryer, and I'm interested in reversing the direction of spin because it spins in the direction opposite of typical machine threads.

The Capacitor is shown at the bottom of this picture(relative to the picture, just above the white letters):

The cyan and white-red wires are AC lines. I can't figure out what the purple wire is, and the dryer wiring diagram says nothing about the motor aside from how it is wired in the dryer. Additionally, the connector that connects to the terminal block does not have a wire for the purple pin, leading me to believe that it is used in starting the motor. Using an ohmmeter, the purple wire is connected to all of the ac lines.


texts: Read variables from Arduino code into PureData?

texts:
I've been trying to find ways to pass a variable from my Arduino code into PureData in real-time. I've explored PDuino and the Firmata library, but the tools seemed a bit more for reading and controlling pins. Maybe I glanced over how do get variable data.

If you have done something like this, could you briefly explain the process being utilized here? I don't fully understand the connections being made or how Firmata is mediating things. If you have a suggestion for a library or simple code, please let me know.


texts: Is it likely that one I2C device is interfering with communication to other devices?

texts:
I have two I2C devices on a single bus, with different addresses.  Let's call them device A and B.  Device A always works, no problem.  Device B only works (means responds to I2C messages) either if device A is disconnected, or if I initialise (means setting calibration coefficients - hard to know why this would make a difference)  device A before trying to communicate with device B.
Weirder still, device B is less accurate when device A is plugged in.  It still works, but I have more dropouts (device unable to get a measurement).
Does anyone have experience of anything similar happening?  Devices are of a similar type and form factor - I don't expect adding device B is changing capacitance of I2C lines or anything like that.
I have measured current draw with and without device A and it doesn't make a big enough difference to suspect a problem with power.
It seems incredible but I am out of ideas, other than redesigning my board to use an I2C multiplexer..
All devices use the same 2.8V supply.
Below is diagram showing how microcontroller is connected to scl/sda lines:

And here is how device A is connected.  Device A is connected in the same way.


texts: How do these current pull-up sources work?

texts:
I'm looking at the data sheet for the TPS54160 (https://www.ti.com/lit/ds/symlink/tps54160.pdf). The UVLO feature mentions the use of current pull-up sources l1 and lhys.

The EN pin has an internal pull-up current source, I1, of
0.9μA that provides the default condition of the TPS54160A operating when the EN pin floats. Once the EN pin
voltage exceeds 1.25V, an additional 2.9 μA of hysteresis, Ihys, is added. This additional current facilitates input
voltage hysteresis.

How are these current sources created within the circuit?
What happens to the current source l1 if I open circuit VIN to EN? There would be no path for the current to flow.
The lhys current source cannot form a complete loop since its top port is disconnected. What is the meaning of this?
How does this weird mechanism implement "input voltage hysteresis" as the data sheet mentions?


texts: Why ship a low power charger with an overkill thick cable?

texts:
Today I saw a Sony camera charger that claimed to provide 8.4V/1.7A output but had a cable going to the device being powered with 18AWG (0.824mm2) cross-section and insulation rated at 300V (yeap, three hundred volts). It was composed of two single-wire components each insulated separately and being about 3 millimeters thick (measured over the insulation). Components were aligned in parallel and welded together which resulted in about 3 by 6 millimeters cross-section.

AFAIK such beefy cable could be used to power a several hundred watts desk lamp anywhere in the world (even in Europe where mains is 230V) and having such bulky (and not very cheap) cable looks quite unreasonable unless it is necessary.

Why would a tiny low-power charger be shipped with such beefy cable?


texts:
I am trying to find Vout in the following image

What I have found from searching a bit is that the op-amps v- and v+ are supposed to be equal to each other.

$$ V^- =   V^+ $$

In the case above I run in to the issue that what ever the op-amps range(-15v to 15v) is equal to Vout. This means that the statement above is not true.

If someone could give a break down of this circuit, it would be much appreciated.


texts:
So I know that you need a certain current flowing through you to die,  I've heard from some people "its the amps that kills you",  and from others "Its the volts that drive the amps" and I realize that these are true according to ohms law v=ir or i=v/r.

But I was watching this video:
https://www.youtube.com/watch?v=ubZuSZYVBng

A guy touches a constant 200kv and i've seen a similar experiment in real life,  assuming that his body has 100Kohm of resistance which is generous,  thats 2 amps flowing through his body if you use ohms law,  and realistically way more as there would be less resistance and it would decrease after it makes a circuit.  How is this possible without him dying?


texts: How connections in a multilayered PCB used to be done?

texts:
how each layer works do each of them has an individual task or functioning or all are interconnected to each other beacuse i am confused as when they get fabricated how assembly of components on each layer takes place.As now there is no space for components placement.Can any one explain me with a simple example.

Thanks in advance :)


texts: GPIO state of MCU (AVR) with no supply voltage

texts:
In general:
what state do the GPIOs of a MCU (an AVR in my case) have when there is no supply voltage and the MCU is "off". Am I right that the pins are floating as there isn't any "reference" for the logic level at all.

In special:
I have a bilateral switch (BS) shifting a variable voltage (provided by a DAC) for an analog device (AD). Both the BS and the DAC are controlled by a MCU. As the BS's output will be floating when its input is not set high by the MCU, I need a pulldown at the output to define the low-state. I've attached a simplified circuitry illustrating the scenario.

If the MCU is running, everything is clear: the BS will supply the AD with an analog signal as long as gpio1 is high.

But if (for a reason) the 3.3V power supply is not there, I still need to have a defined voltage at the AD's Ain pin. So if my supposition, that the gpios of an inactive MCU are floating, is correct, the following circuitry should meet my requirements:

MCU active: gpio2 is configured as low output -> strong pulldown (1k & 10k in parallel equals 0k9) outweighs 100k which leads to a negligible voltage divider. Ain is pulled to low voltage (not ground exactly, but close to it - 0.2V)
MCU inactive: gpio2 is floating -> weaker pulldown (10k) and not negligible voltage divider (100:10) leading to a defined voltage of 0.9*24V = 2.2V.

I'm quite sure that the circuitry as such makes sense, but if it works or not  completely depends on the behaviour of gpios when there is no supply voltage for the MCU.
Can this damage the MCU? (I guess not,  as long as R1 is high enough)


texts: Does biphasic wave mean current is bidirectional?

texts: Does biphasic wave mean current is going bidirectional in a circuit?


texts: Dual power supply circuit dropping voltage on applying load

texts:
I'm not an Electonics professional, and hope someone can explain why the circuit below, I've used to build a dual rail +15v,0v, -15v Power Supply drops voltage down to about -7.7 volts when connecting -15v and 0v across a 4.7k resistor; the voltage should remain stable.

What I would say is that on removing C5, C9 and C10 out of the circuit it then stablises as would be expected. This circuit, with the capacitors is quite common; could anyone tell me what's happening in this case?

If a load is places across -15V and 0v, and more current is drawn, does this decrease the voltage drop across C9 and therefore adjust the output voltage?

Thanks in advance.


texts: RF PCB Design Inductor length conciderations

texts:
I am making a RF amplifier for my Communications Electronics course. I am looking at creating a PCB for it and figuring out how to get the desired reflection coefficient which I will most likely use a matching networks technique for.
I have not seen anything talking about taking into account the total length of an inductor for the electrical length L (such as seen below). Is there any kind of factor that should be considered for this and/or the gap in a capacitor?


texts:
Hello I am looking for the S/N formula that incorporates the probability of catching the signal, and setting an arbitrary treshold level above which we detect the signal.

I can't figure out the formula but I have this nomograph where it is represented:

http://www.rfcafe.com/references/electrical/ew-radar-handbook/receiver-sensitivity-noise.htm

For example for a 98% probability detection with a false alarm rate of 10-3 we get a S/N or 12 dB.

I would like to know the formula being used there.


texts:
For the sake of simplicity, the voltage drop across a diode, \$V_d\$ made of silicon is assumed to be \$0.7\mathrm{V}\$ after the input voltage exceeds this voltage; and \$V_d\$ is assumed to stay constant regardless how large the input voltage, \$V_i\$ is after the input voltage exceeds the threshold. In practical, there will be an increase in \$V_d\$, albeit a very small one, as compared to the large increase in \$V_i\$. There is an ideal diode equation:
$$I=I_s\left(e^\frac{qV_i}{kT}-1\right)$$
which relates the current flowing through diode \$I\$ with the input voltage \$V_i\$. So a little increase in \$V_i\$ will result in a large increase in \$I\$, as \$I\$ is an exponential function of \$V_i\$.

I didn't express my question clearly in my previous attempt. Here is my question:

We consider a circuit consists of a diode is connected to a DC power supply. If we were to connect a voltmeter parallel to the diode, and plot the reading of voltmeter(voltage drop across the diode) against the value of the DC input, how will the graph look like? Is there any equation to describe the graph(like the ideal diode equation relating \$I\$ with \$V_i\$)?

Should the equation look something like this? $$V=IR_1+V_t\ln{\left(1+\frac{I}{I_s}\right)}$$ based on an article in Wikipedia under the title Shockley diode equation.


texts:
This is a basic multivibrator circuit that I am testing. The problem is that I can only get about 160kHz with the left circuit; using smaller capacitor or larger resistor will give me 0Hz. Second problem is the lack of power output under higher frequency, ie. powering a simple boost converter circuit with a MOSFET with VCC=5V, when the frequency is 20kHz, output is 8.5V and 160kHz => 6V; I have tested with different inductor values with similar result. Last problem would be the duty cycle, both transistors have 40% duty cycle instead of 50%;
My questions are:

Is there a maximum frequency for this simple multivibrator circuit? If not, why I can only got 160kHz maximum?
Does a higher frequency affect the power output of a MOSFET?
Why is the duty cycle  only 40%/40% instead of 50%/50%? The output is measured at the collector of the NPN transistor.


texts: Raspberry PI, PCF8574AT, MPU6050, BMP180 i2c voltage difference?

texts:
I'm building a rpi 3 b+ based robot which collects data from a MPU6050 (Gy-521 breakout board, I power it with 5V), a BMP180 (3V input) and displays some data on a LCD via a PCF8574AT i2c converter (which I want to power with 5V, because on 3V the LCD loses contrast). Currently it is utilizing an Arduino connected with a usb cable to collect the data and print to the LCD (so all the devices are connected to the Arduino, not the rpi, but I want to get rid of the Arduino completely and control everything from the rpi directly). The problem is that rpi supports max 3V on the GPIO. Information about these modules' i2c voltage are hard to find, although I read in the datasheet of the PCF8574AT converter that it has a 'non-overvoltage i/o' - but i'm still unsure if it really means that it can be safely connected to the rpi? And won't the mpu6050 and bmp180 also fry the rpi? Will I need a voltage level converter or are these devices compatible with the rpi's 3V GPIO i2c?
Links to docs: pcf8574at: https://abc-rc.pl/templates/images/files/995/1426613116-konwertertwi.pdf
Mpu6050: https://abc-rc.pl/templates/images/files/995/1443347244-dokumentacja.pdf


texts:
I am sorry but I have no idea on how to rephrase my question, this is the best I could come up with.

But as they say, a picture is worth a thousand words.

As you can see, the 2K resistor is "enclosed between the same node" for the lack of a better expression on my behalf, namely node (b). How would I treat this resistor?

To give some background information, this is for my Principles of Electrical Engineering course, all my previous knowledge of circuitry is from my Physics II course, and I must add that my professor did NOT do a good job in explaining basic circuit analysis.

Now back to the subject at hand, we are being asked to find the equivalent resistor and I could do that just fine. The thing is when I looked up the solution manual that the professor handed us, she had bypassed the 2K resistor but offered no explanation as to why she did that and I am assuming it is because the resistor is situated between node (b) on either ends.

Could someone be kind enough and explain to me what is happening and how should I treat such situation in the future?

Thank you in advance.

EDIT: Thanks to everyone who took their time to explain the concept to me. You guys are great. I get it now.


texts: Two limit switch signals affecting each other

texts:
I'm trying to make circuit which will allow me to sense some platform presence at the ends of some rail.

I'm using the limit switches, here is schematic:

SENS-* signals connected to MCU pins, that is configured to trigger an interrupt on a rising edge of a signal. When I trigger manually only one of the switches - then both interrupts are triggered - right one first and wrong one second. It seems like signal from switches interfere each other through GND line, but I cant figure how exactly.

How to prevent triggering of a second interrupt? I feel, that there is some well known solution, but I could not find it.


texts:
I want to build a circuit for my home. The setup is as follows: I've got a circuit in my house, I can turn my lights on and off with switches from different positions. I'd like to have them switched off automatically after, say, five minutes, in case I forget them on, just like it works with staircase lamps.

It seems quite challenging to me, especially if I only limit myself to mechanical spring switches, step by step relays and timers (delay relays). Could such a circuit be possible to realize only with analogic components? Am I forced to use digital electronics?

Thanks!

Edit: clarification: at any given time, I want to be able to switch the lights on and off arbitrarily, just as I would do with my living room lights, except that I want them to turn off automatically after a given interval of time.