texts: The concept of protection diodes across a fan/motor?

texts:
I'm designing a circuit which includes a fan being controlled and I've seen on a few websites that I should include a protection diode across the fan (as shown in the diagram below).

However, after searching and trying to think about it, I can't see what the purpose of the diode is? If it's in that direction it's not allowing any current to travel down that branch of the circuit anyway as it will always be reverse biased?

Does anybody know/can explain if this is necessary/correct to use a diode in this way for a fan/motor circuit?

simulate this circuit – Schematic created using CircuitLab


texts: Buck Converter Error Amplifier Input Polarity Confusion (TL598)

texts:
I'm trying to design a buck converter using TL598. I'm studying the technical article Designing Switch Mode Power Supplies With the TL598 - Application Report for this purpose. This article references the paper The K Factor - A new mathematical tool for stability analysis and synthesis (Dean Venable) for designing the error amplifier compensation circuit and does the all calculations according to it.

The application report gives the polarity like this:

(Page 29)

(Page 32)

However, Dean's paper gives it like this:

TI Article:

Inverting Input     : Fixed Reference Voltage over the Compensation Network
Non-Inverting Input : Buck Converter Output Voltage

Dean's Document:

Inverting Input     : Buck Converter Output Voltage over the Compensation Network
Non-Inverting Input : Fixed Reference Voltage

What is the reason for this contradiction? Texas Instruments clearly states that their calculations are based on the Dean Venable's article. They are completely consistent with each other except for this input polarity detail. Which polarity is the correct one? And what is the cause for this ambiguity?


texts: Capacitor current leakage measurement using transimpedance amplifier

texts:
I was reading a text about measuring capacitor's current leakage using a transimpedance amplifier circuit as the author says this is a rather cheap and reliable to measure currnt leakage, I was wondering if it can be a true statement, since we have a current leakage test setup in our university and it consist of very very expensive measurement devices like as agilent E4890A LCR meter as well as SMU unit, picoammeter and some swith matirxes. So I am wondering if such a soloution can compete with that expensive and complex setup that we have already. (I am planning to give it a try, but I would like to hear some comments before I get involved).

The steps for measuring current leakage with this setup is rather easy. First (SMD) capacitors are soldered on a cartridge, then theire value will be measured. Next step they will be charged with a voltage using a SMU (not more than 30V because of switch matrix limit of relays maximum voltage) and finally after charging is done the picoammeter measures the current leakage.

So, back to the Transimpedance Amplifier. Author explains that following circuit can measure current leakage quite good.

  Since high value resistors can be (very) expensive it is worth
  considering an alternative approach which eliminates this component.
  If RF is removed and CF increased then the input current will charge
  CF and for a fixed i the output v(out) will be a ramp. CF must be a
  good quality capacitor with low leakage. If Q is the charge on CF and
  t is time, then:

  CF = Q / v(out) and since Q = i . t
  = (i . t) / v(out)

  or v(out) = (i . t)/CF and hence dv(out)/dt = i / CF or i = CF.
  dv(out) / dt

Here is link to the orginal text

So I would really appricite if more experienced people here tell theire opinion, and if sucha a circuit has any chance to do better than the current setup taht I showed you. Or is it practical at all?


texts: What determins the available amps in an AC to DC converters (wall wart)?

texts:
Concerning the older, simple transformer, rectifier, capacitor AC to DC converters, what determines available amps (amp output)? Is it simply the thickness of the transformer wires?
What about the lighter, smaller, more complex, more modern converters. What factor/component determines available amps (amp output) for them?


texts: How should I use a multimeter to determine which AA batteries to keep and which to toss?

texts:
I have a bag of about 50 non-rechargeable AA batteries (1.5 V) that I have collected over the years.  I bought a multimeter recently and would like to know the best way to test these batteries to determine which ones I should keep and which I should toss.

Sometimes a battery will be useless for certain high-power devices (e.g. children's toys) but are still perfectly suitable for low-power devices such as TV remote controls.  Ideally, I'd like to divide the batteries into several arbitrary categories:

As-new condition (suitable for most devices)
Suitable for low-powered devices such as remote controls
Not worth keeping

Should I be measuring voltage, current, power or a combination of several of these?  Is there a simple metric I can use to determine what to keep and what to toss?


texts:
First of a disclaimer - I'm a hobbyist and quite the beginner at that, so bear with me.
What I'm trying to build is a metronome with an astable 555 oscillator that is driving an 8 Ohm loudspeaker. I have gathered some experience with 555's now and have already completed this project with a piezo.
In that case I used two 555 oscillators, one that produces the square wave and one that uses a transistor to turn the first one on and off at the desired beats per minute.
Now I've looked into how to do it with a loudspeaker and have found these guides:
https://www.555-timer-circuits.com/metronome.html
https://www.instructables.com/How-to-Make-a-Metronome/
https://www.instructables.com/How-to-Make-an-Electronic-Metronome/
Safe to say I'm quite confused, baffled even. They all just use one astable 555 that represents the bpm. Don't loudspeakers need an AC signal? My piezo does.
How do they turn on the loudspeaker with just the "on period" of the duty cycle?
I suspect it has something to do with the capacitor in series with the loudspeaker but it would be nice if someone took the time and explained it to me.
PS: My confusion in a simple picture:

EDIT: As requested, I added a schematic of the mentioned piezo circuit below.


texts: ADC with I2C interface with multiple addresses

texts:
I want to connect 31 ADC slaves to a master. The ADCs simply should measure voltage and response its values to the master after request. I thought about using I2C as bus system. The problem is that most ADC ICs with I2C interface only offer 2 or 3 bits for address (4 or 8 addresses possible) I need 5 bits for my 31 addresses. What can I do to use 31 I2C ADC slaves in one bus system? Are there such devices like address mappers, expanders, switches, multiplexers? What is common and good practice for my requirements?
The reason I would like to use a bus system is to keep wiring and pin usage of the master low.

To be more specific I need to measure voltage from multiple in series connected sources:

simulate this circuit – Schematic created using CircuitLab

I am aware of that I need to provide a galvanic isolation between I2C master and slaves. I am afraid that I cannot use multichannel ADCs in this case am I right?


texts: A situation regarding AVR and bad power grid voltage

texts:
I have a question regarding the following situation:

Some poultry farm has taken some serious losses when their diesel generator died, only being able to provide backup for 45 minutes and killing several ten of thousand of chickens. The reason they had to switch to the generator was because the power grid voltage was oscilating wildly (even managing to activate the generator transfer switch several times previously). A technical lab has pinpointed the AVR card as the root of the malfunction. Here comes the trouble:
After an technical examination, the damage was traced to a malfunction of the AVR card of said generator. Here comes my trouble:

-Insurer A has refused payment because the damage was "caused by the electro-mechanical effort of the repeated activation and deactivation via transfer switch, forced by the oscilating voltage in the power grid". Thus the fault falls solely on the power grid operator.

-Insurer B is questioning this refusal as "the AVR card only regulates the output voltage of the generator, having no connection to the power grid. The damage caused is more probably due to insufficient maintenance or card age, as the repeated deactivation and activation would not be enough to put such stress on the card." Insurer B wants to cover the payment but demands the farm to install power line monitors and additional surge protection devices, perform maintance with more frequency .

-After the incident, the Insured has purchased a replacement AVR and 1 additional diesel generator.

Questions:

-Who is right: Insured A or B?
-Taking into account the poor performance of the power grid voltage, would the measures taken by the insured be enough to prevent or lower the chance of a repeat of thie incident? Is insurer B's advice regarding this matter sound? Would you suggest any other measures?

Thank you very much for your advice, as this area is not one of our expertise.


texts: Confused on Lithium-Ion Batteries to Output 5V 4.4A for a Project

texts:
I have been looking into Lithium Ion batteries, things such as the 18650 lithium ion battery; however, the details are confusing me.

I am attempting to extract 5V 4.4 Amps (Peltier element powered runs at 5V4A, Fan at 5V .4 Amps) from the smallest Lithium-Ion battery (or batteries) possible.

Before I go into Parallel, I was wondering if someone could help me out on how to find a battery with these specifications, either a single battery, or putting 2 smaller batteries in Parallel.

What I know:

Parallel is less than desireable
You can discharge batteries at whatever rate you want, but it becomes more efficient to draw 4A from different batteries, say, not 18650s.
Different temperatures affect discharge.
Nominal voltages don't come at 5V, so getting to 5V is a challenge.

Follow Up:

Is it better to try to find a battery whose nominal voltage is at 12V, so that I can discharge at a lower amperage? Where would I find a 12v/7.6V battery that's small as a 18650 but can kick out the power needed?
Thank you

Time to Run:
I would hope that the setup lasts for around 1.5 hours of run time, and 1 hour is fine but no less. I am willing to run the batteries in parallel, but i'm trying to keep costs down and size small.

If the 18650 battery a must? Are there other batteries that may be better suited?


texts: Adding a bike generator to a solar panel system

texts: I have a 12V solar panel setup currently and would like to add a bike generator to it. I've created the bike generator and have it also producing 12V direct current. I've seen some other post where a separate charge controller is suggested, but if it's all 12V, can't I just add it to the series? I've tried hooking the bike and the panels into the same charge controller and with a diode on the positive wire I was still pulling power from the panels to the generator. (though I may have put it on the wrong direction, I've been tinkering on it for a while now)


texts: What protection circuits do laptop batteries come with?

texts:
I am currently using an old lithium-ion laptop battery pack for my portable sound system. The battery seems to work pretty well for its age. I simply hooked up a cable to the positive and negative pins (which I needed to guess) which directly leads into the amplifier. For charging I simply put the battery back into the laptop.

However, is there anything I have to care about? What would happen if the battery pack is empty? Is there an integrated underdischarge protection? And does the voltage output fall over time or is it regulated internally (I don't own a multimeter to test that)?

The pack is rated at 14.8V and the capacity is about 5000mAh.


texts: Do I need ground for RS-485 if it is galvanically isolated?

texts:
I am designing an RS-485 communication.

The communication interface is isolated. So, only the noninverting and inverting line will be connected outside to the cable.

I know that I have to include the signal ground for the RS-485 interface to be perfect. However, I am short on the number of terminals I can use.

Will it be OK if the interface is isolated and the noninverting and inverting line is pulled up and down with 47k Ohm resistor?

Will 47K Ohm pull-down resistor some how work level the ground level of the system to same level of the network even if the signal ground is not connected?


texts: DIY: What is required in order to save a picture captured from a CMOS image sensor to a digital format?

texts:
I have a need to programmatically capture HD pictures (2 MP or better) under predictable lighting from at least 8 locations. Buying multiple cameras is not only expensive, but does not allow me to automate taking pictures and collate/label them.

Buying multiple CMOS image sensors and stitching things together seems to be what I require. However, extensive Google searching continues to leave me at a loss of what steps I need to take outside of buying an image sensor in order to get to my goal.

I am new to diving into hardware at this level so any help regarding ways to centralize and read image sensor output would be great.


texts: GPS current consumption is not reducing Why?

texts:
I have interfaced l80 gps module to my pic24f microcontroller . This controller works under 3.3v and gps at 3.3v . The total current consumption is 27 to 28 mA it takes . After sending the command as per datasheet suggested for stand-by mode it should take 1mA only but it is consuming 13.35mA,totally after making my controller to sleep mode and disable the  interrupt ,adc and timer.
My schematic for gps is

Schematic supplied by datasheet

And in datasheet it is suggested that

They have mentioned in the above diagram if vcc and battery  backup tied to vcc the backup and standby modes are not supported.Totally it should take less than or equal to 2mA.  What is the problem between the quectel schematic and my schematic design ? How can i solve this issue?.
Power supply schematic


texts: RMS phase currents based on motor driver rating

texts:
This is probably a bit of a dumb question, but is it reasonable to assume that the max continuous/RMS phase currents for a motor is equal to the motor driver continuous current rating/# of phases?

Ex: 3 phase BLDC, motor driver has a continuous rating of 21A, so the max continuous current for each phase is 7A?

I am looking to select a connector for motor phase lines and want to ensure it can handle the max possible current from a specific motor driver.


texts:
I have a flashlight that malfuntions. I opened it up and traced the circuit, came up with this schematic

Power input 3V, LED bulb dia. 9mm

I checked the transistor with a multimeter. One side has reading, the other side none. So, I know there's something wrong with it. I want to replace it with a good one. I searched the web with the number on the housing which is 0118, and found nothing. Does anyone know what kind of transistor(part #) I can use to replace that defective one?


texts: Linear voltage regulator output capacitance limit

texts: I am in doubt about selecting the value of bulk capacitors for my system. I am going to use LP5907 voltage regulator. According to the datasheet, the maximum output capacitance is 10uF. Does it mean that is the total capacitance attached to the output rail? Is it bad if I, for instance, put the 4.7uF near the voltage regulator output pin, but also the 10uF at the MCU part and RF part? Those capacitors are not all near voltage regulator, but the total capacitance exceeds the datasheet specification. What is right approach?


texts:
I'm trying to understand how to connect a SPI device (a mifare RC522 RFID board) over long distance to my RPi via SPI.

I searched and find I could connect those via SPI over RS485 using a MAX490.
(http://forum.arduino.cc/index.php/topic,93234.0.html)

Could anyone explain, maybe with a schematic, how to connect those devices? And do I need some software changes?


texts: Amplitude Modulation Circuit Implementation

texts:
I am trying to understand AM modulation at circuit level.

As per theoretical framework, we have to multiply \$V_{G2}(t)\$, \$V_{G1}(t)\$, so that frequency shifting happens at carrier frequency, i.e., convolution in frequency domain.

Now as per the above circuit, using superposition, I can calculate the \$V_{out}\$ as \$V_{out} = R_1 \cdot V_{G2}(t) + R_2\cdot V_{G1}(t)\$, where \$R_1\$, \$R_2\$ are real valued and they are function of resistors, capacitors, and transconductance.

I am confused on how the circuit is multiplying the two voltages, it looks like the circuit is adding the two voltages, whereas it should multiply as per AM modulation. I am not clear on what's the purpose of \$C_3\$ and \$R_2\$.


texts: How does a USB C port provide the power to charge laptops?

texts:
I've heard about laptops such as the new Chromebooks that are charged via a wall charger that connects to a USB-C port. I'm quite happy that this will supposedly standardize laptop chargers but I'm a little unclear about how this works.

Existing USB ports provide a 5 volt source, but the laptop chargers provide up to 20 volts. is there some kind of higher voltage line or are the USB-C powered laptops running on a lower voltage?

All this information I've seen gives a fairly vague idea of providing more power, providing up to 100 watts rather than 10 watts. Even so, my laptop is not the most powerful machine and the charger still outputs fairly near 100 watts, I can imagine more chargers for power laptops providing much more than 100 watts. Could a general purpose USB-C charger really power all these machines?


texts:
I'm a total newbe in electronics but I like to make things up. All I want is to turn on a "black box" of leds (that operates at 8-9v) when my motion sensor is activated. The problem I've got is that the output of my PIR is only 3.3 volts. Here is my crappy schematic.

How can I achieve 9v where the red arrow is pointing? Is the the 150ohm resistor Ok?


texts:
(From a complete beginner)

I've had this idea to build my own keyboard from scratch for a while, and I finally got the time (and motivation) this winter break to go ahead and try it for myself. After a couple days of reading forums and googling circuit design stuff, I've created this schematic for my project in KiCAD.

I was wondering if any kind person would be willing to give me a review of my design?

I'm using a teensy 4.0 and using its pins for digital IO.
For the key switch matrix, I am assuming that cherry switches don't come with their own diodes, so I added my own. Don't know if I need to explicitly make input and output labels, or if normal ones are ok.(for reference rows are input, cols are output)
For the rotary encoder, I've got the switch pins integrated into the matrix (felt cool doing that), and the other pins are directly hooked up to pins on the teensy. I read that bouncing is often an issue with these. Is it better to debounce in hardware? (I was just planning on implementing my own debouncing in software).
Finally, (The part I'm most concerned with...) I wanted to route a female usb-c connector somewhere on the edge of the PCB so that I could use a male to male wire for my computers. I get this error "Different net assigned to a shared pin in another unit of the same component" for the D+ and D- labels. This really prompted this post as I couldn't find any answers online for this error. I'd love it if someone could explain what this means and how to fix it.

I appreciate any criticism and advice that I can get. Thank you.

Schematic:

UPDATE

I have added a Usb C receptacle and plan to run it on USB 2.0. I also found that I don't need pull down resistors on the columns as the teensy has its own input pull down functionality. I'm also planning on replacing the THT diodes with SMD ones later tonight.

Still open to any comments. Curious what people will say about the rotary encoder

Here is a new updated schematic:

Here is my PCB:


texts: What happens to a Micro-controller if you short VDD and VSS across a GPIO pin?

texts:
So I designed my first complex PCB containing a STM32F105.

I have a solder jumper connected to a GPIO pin and ground pulled upto 3.3v via a 10k resistor.

Everything was working fine until I closed the solder jumper. The board started using 600mA and the MCU was too hot to touch.

It turned out that the pull up resistor was a dead short, either a bad resistor or a solder bridge, when measured with a DMM it was 0ohm. (All other pull ups on other jumpers measured correctly 10k)
So as soon as I connected the jumper the GPIO was connected to both VDD and VSS.

After I remove the jumper the current returns to normal and I can connect to the MCU via ST-Link which identifies it fine.

But the board doesn't seem to do anything else, interact with any user inputs or anything else it is supposed to.

Have I fried the MCU, if so how can it connect to ST-Link?
Could the MCU be fine and its just a coincidence that nothings working?


texts: LED indicators for 2 Positive voltages and 1 Negative

texts:
I have a seemingly simple question but I am getting stumped.

I have a power supply providing +12v +5v GND and -12v. I would like to have an LED for each input voltage showing that they are working correctly. The '+' Voltages are all simple, However, I am having trouble with the -12v input.

Any help or a point in the right direction would be appreciated.

Thanks


texts: Is it possible to set some of four available user leds to show serial port activity, like we can set it to show mmc activity?


texts:
First off I'm new when it comes to connecting electronic circuits. I'm sorry in advance if this question sounds unworthy or irrelevant.

I'm building this project as a hobby, and I ran into a problem when connecting relays. This is the relay he has used in the video "8 channel relay control panel PLC relay 5V module", and this is what I have purchased:

And Output from Relay to irrigation pumps

My question is; in the output side of the relay, where does the power for the +ve and -ve for the pumps go? In the video he has used a 3 piece terminal block to connect the power.

I'm guessing that O is the output which takes in the pumps +ve. Which one of the two does the -ve go in? I'm using a DC pump so I need to be careful so that it won't short-circuit and fry my chip and the board.


texts:
Logically i understand that 'No Pin' literally means that there is no physical pin but i would prefer to hear a conformation of this fact by those who has encountered such situation.
The thing is should i make a hole in PCB for the pin marked as 'No Pin' or not?
In my case it's pin# 5 for PXE30-12S3P3 http://us.tdk-lambda.com/ftp/Specs/pxe.pdf
And does it has any drawbacks if i have a hole in PCB under the IC part with "No Pin"?


texts: Fourier Series Expansion of Periodic Signal

texts: Why is it necessary for a periodic signal to be a power signal for its fourier series expansion to exist?


texts: What is the relationship between ARM® and TI OMAP® / Samsung Exynos® / Apple A5X® / Qualcomm Snapdragon® / Nvidia Tegra®?

texts:
This is my first question in stackexchange community.
And i'm sure that my questions will find suitable answers here, thank you guys in advance.

I'm really curious about the mobile hardware platforms, and i can see that the market contains a lot of manufaturers and processor systems, from which i can count:

Samsung Electronics: Exynos® (5)
Qualcomm: Snapdragon® (S4 - Krait)
Nvidia: Tegra® (4)
Texas Instruments: OMAP® (4470)
Apple: A5X®

(in brackets the latest platforms' versions released/rumored as i know).
Now my questions are:

Do these parties develop/manufacture/integrate/...etc the common ARM® processors' architectures and distribute/ship them as end-user handsets processors?
Can any body clarify the business relationships between these companies?
What are the graphics controllers compatible/used with each system (i.e: PowerVR SGX series, ...etc.)

Any additional data (regarding market shares, systems' block diagrams, latest products) will be appreciated. THANKS.


texts: In the photo below, under the diode (D2), we're given V and to help solve for current, V is equal to zero in the solution. How can we assume V=0 if it's not given in the question?


texts: ESP32 stalls b/c of current spike (inrush current) - how to limit inrush current?

texts:
I have a circuit with several neopixels and an ESP32 MCU running with micropyhton. Under full load, the circuit including the ESP32 draws around 200mA at full load. Now I'd like to add another component, which is not controlled by the ESP32 but uses the same +5V net to be powered. The additional component is controlled by a switch. In normal state, it draws ~330mA. However, initially when I turn it on, it causes a current spike (I assume inrush current), which peaks at ~500mA. After the initial spike it goes back down to ~330mA. This causes the ESP32 to stall and not operate normally anymore until I take the load off.
For context, I'm running the circuit with +7.5V from a power supply capable of delivering 3A. The voltage is dropped to +5V via a LV7805CV 1.5A (including heatsink and decoupling capacitors). I'm looking to replace that with an LV78S05CV, which can handle 2A.
My question is how can I mitigate the initial inrush current of the component to prevent the ESP32 from being affected and continue normal operation. I understand that the current draw is very sudden and happens when the switch is pushed before the current draw levels off at ~330mA. Do I need inrush suppression?
Would an RC circuit before the additional component like this
How to limit inrush current?
make sense?
N.B. The additional component can be turned on/off anytime and multiple times during normal operation of the ESP32 causing a spike every time that happens.
Please let me know if something isn't clear enough.


texts: How to Find DC Step Response of Semi-Parallel RLC Circuit

texts:
Hi everyone, I find myself stumped on how to approach this problem since there is a resistor in series with the capacitor for what is otherwise a parallel RLC circuit.

First off, I am attempting to find the step response equations for i_L(t) and V_c(t).

As far as the diagram is concerned, the 6V square wave is just there to act like a switched DC voltage source.

I've been farting around with Kirchoff's laws and DEqs but can't figure out how to set up anything that would find a solution.

That said, I've found the initial conditions for before switch closure, just after and final conditions in case those will be needed later.

Before switch closure:
$$V_L(0-)=0V,    i_L(0-)=2A$$
$$V_c(0-)=0V,    i_c(0-)=0A$$
$$V_{R_{eq}}(0-)=0V,  i_{R_{eq}}(0-)=0A$$

Just after closure:
$$V_L(0+)=2.8708V,    i_L(0+)=2A$$
$$V_c(0+)=0V,         i_c(0+)=0.01435A$$
$$V_{R_{eq}}(0+)=2.8708V,  i_{R_{eq}}(0+)=0.50718A$$

Final conditions:
$$V_L(\infty)=0V,    i_L(\infty)=3A$$
$$V_c(\infty)=0V,    i_c(\infty)=0A$$
$$V_{R_{eq}}(\infty)=0V,  i_{R_{eq}}(\infty)=0A$$

Let $$V_a$$ represent the node voltage of the parallel elements.
Setting up the node voltage equation we have

$$i_L+i_{R_{eq}}+i_{C,R_2}=\frac{6-V_a}{6}+2$$

Note that, $$i_{C,R_2}=\frac{V_a-V_c}{R_2}$$ and $$i_{R_{eq}}=\frac{V_a}{R_{eq}}$$

Then,

$$i_L+\frac{V_a}{R_{eq}}+\frac{V_a-V_c}{R_2}=\frac{6-V_a}{6}+2$$

Note that $$L\frac{d}{dt}i_L=V_a$$ so I could differentiate both sides and multiply by L, to to eliminate all the currents. However, I still have $$V_C$$ which is what is stopping me from going forward.

I am starting to think I need more equations...

Any help on this would be very much appreciated.


texts: Input characteristic curve of common collector configuration

texts:
I am really new to electronics and BJT. I would like to know why is the input characteristic curve of common collector configuration [Ib-Vbc] is different from other 2 input characteristic curves. What actually accounts for this difference?

update:

@jippie the input characteristic curve of common emitter configuration is as follows:

but the input characteristic curve for a common collector configuration is :

can I know what actually causes this difference?


texts:
I want to use a retriggerable monostable multivibrator as a hardware watchdog.  This is for an amateur satellite project so I need to use basic rad hard logic chips (as opposed to more sophisticated watchdog chips).

I'd like the timeout to be 5 seconds.

Is there an advantage to using a 74123 part vs a 4538?  It appears from the datasheet of one 74123 part that the pulse timeout might be limited to .5 seconds.  Is this true for all 74123 parts?  Some datasheets don't seem to specify.  At least one 4538 seem to be able to sustain a timeout of up to 10 seconds.

Are these timeouts true of all parts of that family?  Or is it chip specific?


texts: Is it safe to reconnect a presumably broken PROM connector pin?

texts:
I am trying to understand (and fix) a soda machine that doesn't seem to accept 1€ and 2€ coins while all stickers (inside and outside) seem to imply that they should work (5ct to 50ct do work).

I noticed that the coin validator (class "MS 1000" by Mars Electronics International) has a broken pin (see the picture below). According to the PROM's datasheet, that's the A7 pin, but that doesn't tell me anything (I haven't found any documentation on the MS 1000).
I have not yet removed the board from the case because it sits very tight and I don't want to break it, so I don't know whether the pin is connected on the board.

Is that necessarily a problem or is it possible that this is intentional?
Is it advisable to reconnect it?


texts: Differential amplifier with a notch on output

texts:
This circuit is used to:

Read an encoder output and level shift it to 3V3 from 24V;
Convert a 0-10V input signal to 0-3V3;

Both points 1 and 2 should be usable at the same time. Point 2 works correctly while point 1 has a strange output with a "notch".
Here's the schematic:

In both tests where GND is connected with GNDS and where not, there's no noticeable difference.
What oscilloscope is reading:

A capacitor on R6 doesn't make any difference.
A capacitor of between pin 2 and pin 3, create a sinusoid when signal should be low, even 1pF.
I can remove this "notch" by adding a capacitor between R58 endings of about 22pF and this solves my encoder problem, but then the 0-10V conversion doesn't work anymore because a fixed input voltage is converted to a
sinusoidal output.

I've double checked the power supply and ground of my board. I have a decoupling capacitor near the amplifier, a solid ground plane under it, GNDs via near each ground point on schematics. Also a clear +24V square wave, generated by a lab equipment, on amplifier input pin.
Another test I've done is to change MCP634 with a similar one, but nothing changed (just slew rate.)


texts: Thévenin equivalent of a Norton equivalent

texts:
A very simple question. When solving circuits, and you need to solve it using the mesh analysis, you want the circuit to only have voltage generators.I wonder if for an independent current generator like this one:

can it be transformed into this model

or this model?

And are the last two equivalent? Because some books use the first transformation while others use the second one.


texts:
This question is a bit related to an earlier question: Question

With my current scope (Philips PM 3253, 20 MHz 2 channels), I cannot measure the quality of edges from square waves from the test signal, because if I put the time to less than 1 ms, I either don't see anything or a straight line.

I assume this is a problem of the scope (it has a quite bad screen, the beam stays 'forever' or is fading away fastly, so all the time I have to press the 'reset 'beam'' button.

Is there something I do wrong? I already know I should use the 10:1 setting on the proble, but still have the same problems.

So I'm in the market for a new (old analog secondhand oscilloscope) and was wondering how to best do a test similar to this?

My idea: use a square wave (which I guess never is 100% square). I put the time to e.g. 10 us or whatever and I would see square waves which connect the 0 and 5V (or + or - volts) together with a 'rather'  steep line. And I want to measure the time from 0 to 5V or vice versa. This should be something in us I assume.


texts:
Analog Devices has published a note on high speed PCB layout, which shows examples of proper board layout for SOIC packaged op amps (figure 9, a & c). The note emphasizes that "keeping trace lengths short is paramount".

The first example routes the feedback path around the amplifier. The traces are very long, which should be avoided.

A second example routes the feedback path under the amplifier, placing the feedback resistor on the opposite side of the board. This reduces trace lengths, but requires vias. Vias "can introduce parasitic capacitance and inductance", so this should equally be avoided.

I was wondering whether it was not a better alternative to route the vias under the SOIC package (but still on the same layer) and place the feedback resistor above the op amp as shown below.

This way the trace lengths are kept reasonably short, without using vias.

But I guess if this was a better solution the author would have mentioned it. Is there a specific reason for not routing the feedback traces under the op amp package? Is this an acceptable, possibly even better layout for SOIC packaged op amps?


texts: ATMega168 SPI tranmission will not start

texts:
Scenario

I have an ATMega168 using an external 10MHz crystal. The DIV/8 fuse bit is not set. The processor takes the outputs from 4 quadrature rotary encoders. Their rotation direction information is decoded using pin change interrupts and the pin states. The rotation information is converted to control codes and is send over SPI to another processor handling some motor driving.

Problem

In the code listed, the rotation direction information gets decoded and converted to control codes as designed, and has been verified in hardware. The SPI transmission fails to start. Looking at the SPI pins on the scope, !SS pin stays high, and the SCK and MOSI stay low.

Two other people have looked at this code other than me. I know I have to be overlooking something simple. Why isn't the transmission starting?

/*Ports:
D.7..D.0 - 4x quadrature rotary encoders, triggering pin change interrupts
B.5 - SCK (SPI clock line)
B.3 - MOSI(SPI data line)
B.2 - !SS (SPI chip select)

This module interfaces with the rotary encoders, converts their
rotation to control commands, and transfers these commands over
the serial peripheral interface to the motor controller.
*/

#define LASER_X_L 28
#define LASER_X_R 56
#define LASER_Y_D 84
#define LASER_Y_U 112
#define MIRROR_X_L 140
#define MIRROR_X_R 168
#define MIRROR_Y_D 196
#define MIRROR_Y_U 224
#define NOTHING 0

#include <avr/io.h>
#include <avr/interrupt.h>

void initPorts(void); //set up function for GPIO ports
void initExtInt(void); //set up function for external interrupts
void initSPI(void); //set up function for SPI

int main(void)
{
    initPorts(); //call port set up function
    initExtInt(); //call interrupt set up function
    initSPI(); //call SPI set up function

    while(1)
    {

    }
}

void initPorts(void)
{
    DDRB = 0b00101100; //set SPI pins as outputs, unused pins as inputs
    PORTB = 0b11010011; //pull unused pins high
    DDRD = 0x00; //rotary encoder pins as inputs
    PORTD = 0x00; //pull ups off
}

void initExtInt(void)
{
    sei(); //global interrupt enable
    PCICR = 0x04; //enable Port D pin change interrupts
    PCMSK2 = 0xFF; //enable pin change interrupt on all Port D pins
}

void initSPI(void)
{
    SPCR = 0b01010001; //SPI interrupt disabled, SPI enabled, MSB trasmitted first,
                        //master, rising edge triggered, sample then set up, fosc/8
    SPSR = SPSR | 0x01; //2x clock speed for fosc/8
}

ISR(PCINT2_vect)
{
    unsigned char reg = PCMSK2; //read pin change mask register into intermediate register
    unsigned char send;

    //laser x - left
    if(((reg & 0x80) > 0) && ((PIND & 0x40) > 0))
    {
        send = LASER_X_L;
    }

    //laser x - right
    else if(((reg & 0x40) > 0) && ((PIND & 0x80) > 0))
    {
        send = LASER_X_R;
    }

    //laser y - down
    else if(((reg & 0x20) > 0) && ((PIND & 0x10) > 0))
    {
        send = LASER_Y_D;
    }

    //laser y - up
    else if(((reg & 0x10) > 0) && ((PIND & 0x20) > 0))
    {
        send = LASER_Y_U;
    }

    //mirror x - left
    else if(((reg & 0x08) > 0) && ((PIND & 0x04) > 0))
    {
        send = MIRROR_X_L;
    }

    //mirror x - right
    else if(((reg & 0x04) > 0) && ((PIND & 0x08) > 0))
    {
        send = MIRROR_X_R;
    }

    //mirror y - down
    else if(((reg & 0x02) > 0) && ((PIND & 0x01) > 0))
    {
        send = MIRROR_Y_D;
    }

    //mirror y - up
    else if(((reg & 0x01) > 0) && ((PIND & 0x02) > 0))
    {
        send = MIRROR_Y_U;
    }
    else
    {
        send = NOTHING;
    }

    if(send != NOTHING)
    {
        SPDR = send; //start transmission
    }
}


texts: Is there a method to know the temperature value of a microcontroller?

texts: I want to know if there is a method to know the temperature of the microcontroller to avoid its over heat.


texts: Problems with op amp thermocouple circuit

texts:
I am trying to use an LM358 to amplify a thermocouple and read in the resulting voltage into an Arduino.

I bought an Amico thermocouple from Amazon: http://www.amazon.com/Probe-Thermocouple-Sensor-Temperature-Controller/dp/B00899A4LY/ref=sr_1_7?ie=UTF8&qid=1448423872&sr=8-7&keywords=thermocouple

It is type K, and if connected to my multimeter with the temperature setting, it shows 22C for room temperature.  We tested it in a toaster oven, and it works at a range of temperatures.

Testing with Vcc = 6.3V (4 AA cells in series), I created the following circuit.  It didn't work.  The input voltage is correct.Admittedly, my knowledge of op amps is spotty.

Next, I looked for a schematic, even though I don't understand it.  It doesn't have two resistors in the voltage divider  that is familiar to me.  I tried to duplicate it but  didn't have a 100k potentiometer or a 270k resistor, so I tried 120k ohm resistor that was handy instead.  I didn't bother with the source follower on the output since it's going to my DMM which is high impedance.

  The voltage differential is 40mV for example, dunked into hot water, and the output I am getting is 1.0mV (although it's noisy as well).  Note that the author of this circuit says to put the positive side of the thermocouple to the negative terminal of the opamp (TP2).  I tried both ways just in case.

Here is a picture of my circuit.  I apologize that the terminals block some of the view but at least you can see some of it.

Any clues on what is wrong?


texts: Do I need some kind of licence or any papers if I want to sell a pcb board that I made to different people?

texts:
I have made a watch with a microcontroller and a display which shows a
real time clock.
I want to sell it to my friends officially.

Before I do that, do I have to obtain specific certificates for my hardware before I "put it on the shelf"?
Can I get any fine if I start selling hardware without any
certificates ?

I want to sell it as a consumer device. I am from
   Romania and we are part of the European Union.
   It does not communicate wireless in any way.
   My watch also has a Li-Ion rechargeble battery.


texts:
I have a question that I am curious about. I am designing an IoT device from my microcontroller. My question is how far can jumper wire (standard solid-core copper wire) go before it loses significant signal or power? The purpose is to drive a relay about half-way around my house. It isn't high frequency on/off, at most once per minute, so I'm thinking it won't pickup interference. The signal is +5V. Does thin jumper wire make the cut?

Cheers

Edit: by popular demand, the current draw is 71.4 mA and the coil resistance is about 70 Ohms.

More Edit: Significant voltage drop would be probably more than 1.0 V, and ringing is acceptable, so long as it is not outside of this range.


texts:
I'm using the NTE0506MC DC/DC converter which boosts 5V to 6V. The output voltage I'm measuring with no load is 9V not 6V. In page 3 of the datasheet they mention that it needs a minimum load of 10% of the rated load, which in my case is 16.7mA (0.1*167mA).

So I decided to put a dummy resistance of 232 Ohms (after trying several larger values) in parallel with the output decoupling capacitor. The measured output voltage in this case is 6.33V which is much better but still not 6V (my acceptable tolerance is +-300mV). The 232 Ohms should maintain an output current of ~27mA (6.33V/232) which is more than the required minimum current (16.7mA). Why is the output still not close to 6V? How can i solve this issue?

My circuit is exactly the same as the one in page 4 of the datasheet for the part NTE0506MC and my load needs a max of 20mA.

Update: 25/5/2013

I added two 200 Ohm 0.25W in parallel to the output of the regulator and the ouput voltage is now 6.18V which is within my specs.


texts:
First of all DMX signal use differential-pair signal, RS-485.
Many website said that each device have programble unique ID then we can send data to each ID by following protocol. (seem like they same way which Dynamixel motor used) But some device can connected by daisy-chain without configured ID for example, DMX LED strip which can connect and control in cascade maner also some DMX lamp don't have ID setting at all. This make me so confuse how the DMX work with daisy-chain in eletrical level.
I got more information from manufacturer.
The LED chip is UCS512C4. and it got 4 pin when connected(the extra pin is labeled as ADDR).
The controller is K-8000C which can write address to LED lamp some how.


texts: Dual OP AMP setup circuit supposed to pull 2mA, but where is the other 4mA going?

texts:
This circuit uses half of the TI dual OPA2626 (not showing the other half of the OP AMP).  This dual OP AMP supposed to use 2mA, but it's pulling around 6.8mA (measured at the Grnd pin and also at the Vcc pin). The other half of the OP AMP is currently not used and none of those pins are connected to anything.  Should they be pulled up or down in case that's where the current leak is?

The V-out is going to an Arduino digital pin and draws about 8.8uA, but even when I disconnect it the entire circuit is at 6.8mA.    The current from the voltage divider (P1 potentiometer) to the OP AMP draws about 2.4uA and to N2 inductance (20 Ohm) is 0.1uA.  Disregard the other (N1) inductance, it does not use any power from this circuit.

The other question:  do you see any obvious problems as far as wasted power or noise sources, better solutions?   This circuit supposed to amplify a 2-4mV to 4-8mV varying amplitude one-shot AC voltage sinus wave by 1000, and seems to work fine.

Thank you for any advice!

http://www.ti.com/lit/ds/symlink/opa2626.pdf


texts: Order of write and read in Microprocessor interfaced with ADC

texts:
An ADC is interfaced with a microprocessor as shown in the figure. All signals have been indicated with typical notations. Acquisition of one new sample of the analog input signal by the microprocessor involves:

a) one READ cycle only
b) one WRITE cycle only
c) one WRITE cycle followed by one READ cycle
d) one READ cycle followed by one WRITE cycle

So as I understand it, an ADC is treated as an input device. The Microprocessor (MP) sends an initialising signal first to the ADC, the ADC starts the conversion.
Is this the "WRITE" cycle?

Now once the conversion is done, the ADC sends the EOC signal, and now the MP does the READ cycle, completing the Acquisition.

I was not sure of what all is going on, I wanted confirmation that (c) is the answer.


texts: Connecting PC and embedded system via USB

texts: I have embedded system with USB3300 PHY and FPGA, which I have to program as a Link. I want my system to be able to communicate with my PC but I am not sure if I have gathered all information. Here is how I see it. I program FPGA to handle ULPI interface to be able to communicate with PHY. Then I write simple computer program to send data via USB that my system will be able to understand ? I am not sure if PC sends some extra information at the beggining of the transmission that I have to ignore ?


texts: I2C problem on STM32F303 processor, what is happening with SDA?

texts: I am trying to add an I2C display to my remote control drone.  I can't get the display to work.  I took the same code and copied it to a stm32f303k8 nucleo and got the display to work.  I moved the code back to the drone and tested on the STM32F303cc processor.  It doesn't work.  The signals below are form the exact same line of code going over I2c on both chips.  Well, recompiled in the cubemx framework for the different chips of course.  The yellow line is scl.  The blue line the clock.  The yellow line with the squiggles is from the drone that doesn't work.  The other 2 are from the working nucleo.  What is wrong with the signal on the drone, the stm32f303cc chip?  Why is it really squiggly.  Both have pull resistors 2.2k and 4.7k.  Specifically, why is the yellow line below, top image, split 50/50 between high and low on what looks like the acknowledgement bit?  Thanks


texts: Can I use the mosfet for 5 volt to 3.3 volt logic converter

texts:
I have a BSS138 circuit below the schematic

I want to Convert 5 volt to 3.3 volt logic level shifter that using this BSS138.

SCHEMATİC

Now. I am trying the circuit on the board, but does not work. Can you help me?


texts: How to find input impedance of this OPAMP circuit?

texts:
Assume OPAMP to be ideal with infinite gain (a) and infinite input impedance
I am clearly able to see that the input impedance of this circuit is R1 (correct me if I  am wrong) but I am unable too solve using feedback analysis on OPAMP

I have two queries regarding this circuit

Q1. As the OPAMP is taken to be ideal thus the input impedance of basic amplifier becomes infinite.

Thus feedback impedance should be infinity/loop gain which comes out to be infinite

Q2. If I am given the second diagram that is the circuit diagram with current source at input to OPAMP shown in above figure then can I still find input impedance without using source conversion and converting non ideal source to non ideal voltage source

If so then as the voltage across the resistance R1 in circuit with current source is zero thus resistance turns to be zero


texts: I’m needing help finding/naming a specific type of on/off toggle switch, but can’t seem to find it by googling. Basically, I want a toggle switch like in the picture below that I can use to power on and off a Raspberry Pi. That’s easy enough. But I would like to find a variant of this toggle switch design that has the lever in the down position as “neutral” and then when the lever is moved to the up position it changes the switch state (on/off), then the lever automatically returns to the down “neutral” position. So similar to a momentary on toggle switch, but works like a push button. I want to push the toggle up to power on the RPi and then eventually push the toggle up again to power off the RPi. Can anyone help? Thanks!


texts: Multiplexing thermocouples, what to look for in multiplexers?

texts:
I would like to use a MAX31855K IC for amplifying K type thermocouple response. This alone seems rather straightforward, but I'm also considering connecting 2 or 3 thermocouples to one IC. I don't need high frequency (a measurement every 0.5s is enough) and I also don't need it to be super accurate. I'll be measuring high temperatures, in ranges of 300-600C (570-1100F) and I'm fine with accuracy of 10-15C in that range.

I found a project that uses ADG407 analogue multiplexer for that, which was described as a successful try.

Before I try this on my own, I would like to ask on what should I consider when looking for multiplexers for this project? Or even, is a multiplexer the right choice? There're multiple ways of routing signals. I could also probably use an analogue switch IC, or maybe even some kind of transistors?

Initially I was thinking that a really low Rdson (like a few ohms) would be a key, to not alter a signal, but on the second thought the current there is probably close to 0, so ADG407's 80 ohms sounds fine. Is there anything else to consider? Is there any Rdson level that would not be acceptable for my requirements?


texts: Any specific precautions should be taken when using 2x AA LiSOCL2 batteries in parallel?

texts:
I am working on the wireless sensor design and one of the sensor is such that it needs to be kept ON through out the operation and it takes supply of 3V and current of about 100uA, which I think is ok to draw from LiSOCL2 (Lithium Thionyle Chloride) battery.

To provide the system with higher battery capacity, if I go with bigger battery, it doesn't fulfill my form factor requirement of the sensor node. So, I have decided to go ahead with 2x AA size LiSOCL2 batteries.

Are there any specific precautions that should be taken while using this configuration and/or using LiSOCL2 batteries?


texts:
I am using the equation Qg = ig * t in order to calculate the gate resistor which charges the MOSFETs input capacitance (Ciss). The MOSFET I am using is the IRFP4368PBF. So if I use the equation Q=CV I can find the charge, in this case being (19860pF * 15V = 297.9nC). By rearranging (Qg = ig * t) to
 (ig = Qg / t) gives (297.9nC / t) . My question is that how do I find t , is it on the MOSFETs data sheet ? or else where ? because if i know t than i can calculated the current flowing into the MOSFETs gate which will than allow me to calculate the gate resistor.


texts: Interrupt Arduino if voltage is below some level or a switch which will not allow current to pass across if no sufficient voltage

texts:
I'm a very beginner in electronics. Actually from software field. With some craze started with Arduino. What am trying to implement is a simple interrupt mechanism which will interrupt Arduino if AC voltage if under a predefined level (don't need to measure the voltage). For example if mine is a 220 volt circuit and if it's below 180v it should interrupt on an interupt pin on Arduino.
 I'm not looking for a complicated system like measuring the voltage and making the decision. Instead of something like a resistor or what ever which will not allow the current to flow if under some range like above. But please remember it's on AC supply. Or is there is any simple component like MOSFETs or bjts which only allow the current flow if base voltage is above a point. I'm a humbly mentioning my knowledge of these electronic components are very very less..


texts: Power Supply : How to keep SMPS always above the post-regulator that follows it

texts:
I'm trying to find a way of building a new power supply for my workshop, in order to keep it small and not so hot I will be using a spare xformer to step down mains to 24v and then a variable buck converter to adjust it (and CC mode, displays and blinky stuff).

I thought it would be a good idea to use a linear regulator on the output stage to smooth things out, but I can't seem to think of a control scheme that allows me to change the voltage using only one potentiometer. The buck stage is this topology but with a external PNP transistor.(It has already been prototyped, it works alright, I know the mc34063A is old)

The only idea I got that ""works"" is using the buck converter output as a reference for a linear regulator (IC or discrete parts), but using a SMPS output as reference for anything is a bad idea, due to the amount of noise and fluctuations.

This is the sort of output stage I can and have built (or bought) over time. Just a big discrete regulator.

In short: How to control a MC34063A step down (buck) converter so it follows the output stage +1-3 V of headroom.


texts: How to Modify IR Auto-Close Circuit for Trash Can Lid

texts:
Just bought a new trash can with an automatic lid that I'm fairly happy with but there's one modification I'd like to make.
If I place the trash can in a cabinet and close the door it detects the door in front of the IR sensor and holds the lid open indefinitely even though I would prefer it to be closed. You'd think it might eventually close the lid based on some kind of timer, but you'd be wrong.

I have a few ideas for possible modification but I'm looking for any recommendations.

Change the microcontroller software to just close the lid after a set amount of time. This would be the simplest change if I were the manufacturer and could just add it to the microcontroller code and burn to the em78p372n ROM. Unfortunately in my case, I'm not the manufacturer so the workaround for me would be to use one of the dozen ESP32 or ESP8266 modules I've got lying around and create my own motion detector with a PIR sensor or something.

Add a photoresistor somewhere in the circuit for the IR detector so that it needs to detect an object AND have some amount of ambient light in order to truly trigger a detection. The cupboard closet will be pitch dark when closed. The difficulty here is that the controller board is a lot tighter than I'd hoped and it's not super obvious to me where the best place to splice in the photoresistor would be.

Maybe there's just something passive I could place on the closet door that would trick the sensor into thinking there isn't an object right on top of the sensor? The closet door basically touches the IR sensor window when closed so maybe a reflective tape or something to absorb the IR light would help?


texts:
What is the difference between a diode rectifier and an op amp rectifier?
Thanks for the easy explanation


texts: Connecting USB-powered Beaglebone to car's CAN bus through OBD connector using common signal ground

texts:
I want to connect my Beaglebone Black, powered from USB port on my laptop, to OBD connector present in my Ford in order to see CAN traffic with can-utils.

Beaglebone operates on 3.3V, that's why I am using a logic level converter to interface to MCP2551 CAN transceiver operating on 5V.

I am using pins P9_26 and P9_24 from Beaglebone's header P9.

My DB9 to OBDII cable has the following pinout:

Questions:

Is the connection presented on the schematic correct?
Can I connect the Signal Ground from my Ford's OBDII connector with GND from Beaglebone (which I think equals GND from USB) safely?
Is connecting grounds of these two separate circuits (car <-> Beaglebone/laptop) necessary?
If the grounds are not connected - can it pose any danger to the car's transceiver/CAN computer or USB port in laptop?


texts: Search for "pinhole" SMT switch (like "reset" switch operated with paperclip)

texts:
I search for a small switch, momentary on, SMT mounting type, I can put on my STM32 board for entering DFU. I search for a small switch with only a small hole to put a pin or a paperclip.
I thing I don't get the right name of this kind of switch to search. Can someone can tell me the name or have an entry point?
EDIT:


texts: Is it possible to install `tcpdump` on an Arduino 101?

texts:
Currently architecting a side-project idea I have that requires tcpdump on an Arduino 101. This will be my first project and just wondering if this is possible or if maybe I should get a Raspberry Pi?

I won the Arduino 101 at a hackathon so I already have it and I think I need to order an Ethernet Shield but want to ask before I order parts.

Update: hrm, it appears I will need to do the packet sniffing with possibly libpcap. Found example here https://www.tcpdump.org/sniffex.c


texts:
I'm studying Jim Williams application note AN-104 - Load Transient Response Testing for Voltage Regulators, in which he describes an FET-based load transient generator, what might commonly be called an electronic load or dummy load.

In the highlighted areas, Jim mentions "peaking" components:

And apparently, when properly adjusted, these peaking trimmers allow the circuit to produce a very clean-edged and flat output (current through the MOSFET, trace B):

Note the LT1210 is a current feedback amplifier, not one of the perhaps more familiar voltage feedback variety.

My question is: "What is the peaking Jim is talking about here and how does trimming it optimize this circuit's output waveform?"

I vaguely suspect it has something to do with adjusting the resonant frequency of the gate drive node (and separately the feedback network) to push just the right amount of charge into the MOSFET gate at the fastest possible speed, but really don't have much of a clue :)


texts: Half-wave recitifer diode (0.7v) problems

texts:
I can't seem to decide which is the correct answer for this question.

An AC voltage of 5 V (peak) is applied to the circuit shown. What is the peak inverse voltage (PIV) of the diode? Silion diode (0.7v)

a) 5v
b) -4.3v
c) 0v
d) -0.7v

I know it could be either A or B.


texts: Undeletable EEPROM or other storage for micocontrollers?

texts:
Is there such thing as permanent EEPROM storage?

The data written should be un-deletable.

Once written it should be there as long as the chip is not destroyed or damaged.

Any other alternatives to EEPROMs are welcome.

I use DVD drives for PC. But I need a similar chip or system for microcontrollers.

Important: I don't want this to be implemented in my microcontroller Software by custom code. The Chip or IC or System it self should have that by default.

Link on Security.SE:

https://security.stackexchange.com/questions/128160/undeletable-logging-or-file-writing/128161#128161


texts:
If transformer is coil (primary and secondary), then when we connect ac source across primary winding which is a nothing but a coil, so entire coil impedance will come across ac source and it will be short circuit condition at input winding ( considering low resistance of primary winding ) and at secondary even if secondary is open then ac line is short circuited by low resistance primary winding.

Does it actually do short circuit of ac mains?

Please someone elaborate , I have this basic question.


texts: Transistor toggle by NPN and PNP - how is it build?

texts:
I want to toggle between 2 devices using one GPIO 3.3v pin and powering them with 5v.

I thought about using an NPN and PNP transistor, tying up the base and collector/emitter to 5v power supply. If the GPIO pin goes HIGH or LOW, switch trough either transistor.

So far, I have tried a lot to get it work somehow. But i do not seem to be able to have either the NPN or PNP transistor not be triggered to a degree somehow.

I am too embarrassed to show any of these noob tries, and just want to ask you guys for Ideas how to approach that problem.
Am I going a completely wrong way with this?

Is thinking of it like a Y switch wrong?

Thanks für input on this very confusing matter.

EDIT:
Some basic Idea, without any resistors (since they are part of my problem: I con't find out, where to place them and how strong.) Placed on my breadboard to get started with LEDs ...

One LED should be ON while the switch is pressed, then should switch to the other if pressed.

Edit 2: Thank you for all your amazing additions to the post. It will probably take me some time to look up all terms and try to understand the explanations :) So please bear with me.

(btw: Only screenshot - CircuitLab shows me a CSRF Error when trying to register :/ )


texts: Adding a dimming knob to a step up power supply

texts:
I am a ME student with little EE knowledge, and I currently have a setup which includes a 12V SLA battery, a 100W LED chip and a constant-current constant-voltage step up converter. The board can be found here:

http://www.amazon.com/DROK-Converter-Transformer-Regulator-Controller/dp/B00E8D7XYG/

I have adjusted the trim pots on the board to provide the LED with around 95W, as this is near it's maximum operating point. This is a portable floodlight project, and because the board is housed inside of the body, this trim pot is not adjustable during use.

My goal is to add a dimming switch that protrudes out of the body of the light that will vary the current (and thus voltage) given to the LED. My first thought is to introduce a logarithmic potentiometer into the circuit with resistors, as I understand that the LED current draw exponentially increases with increasing voltage. But the problem is that I have no idea how to go about determining which value of resistors or trim pot I will need or where this would be added to the circuit.

The overall thought idea is to have an additional switch that varies the current from 0A to my pre-applied value that was set using the board's trim pot. I have used an Arduino in the past to control an LED's brightness using PWM, but this isn't ideal because I would like this design to be as simple as possible.

Thanks


texts: Adding hysteresis to a window comparator

texts:
I have designed a window comparator and am finding it seemingly impossible to add hysteresis. Below is the basic circuit before attempting to add hysteresis.

Now I add a feedback resistor to the positive input of both op amps in an attempt to add hysteresis and this is the result:

The hysteresis seems to only be applied to U2, where the reference voltage is on the positive input. When the reference voltage is on the negative input, as it is for U1, it doesn't do anything. Putting the feedback resistor for U1 on the negative input screws up the whole thing too. This is what is confusing me. Is there a way to do this? The reason I want to add hysteresis is because the LED flickers when you are near the reference voltages, since the input voltage is from an accelerometer and is very sensitive to change.


texts:
I am using a MCP79410 real time clock to generate a 1Hz square wave signal (50% duty cycle) for a low power display (Sharp Memory LCD). Without this signal charge builds up and the pixels show burn-in.

The problem is that the RTC output is open-drain, so a pull-up resistor is needed.
Because I need to save power I cannot use a resistor smaller than ~1MOhm.
Unfortunately with this resistor the display does not recognize the signal anymore, 10kOhm works perfectly fine.
Now my guess would be, that this is due to the slow rise time of the signal.
The frequency and duty cycle don't have to be very accurate.

What would be the most simple way to solve this?

Maybe a (schmitt trigger) inverter could improve the edges of the signal.

EDIT: I soldered a Schmitt trigger inverter (74HC1G14) onto the board. It works!! Thanks for your help!

Overall power consumption in standby is under 10uA now. I can't say much about the dynamic consumption but it should be OK. For the final design I might switch to the SN74AUP1T14 as user2943160 suggested.


texts: Are some implementations of SPICE more accurate than others?

texts: Just like the title says. Is there one single SPICE back-end that's the same for different versions of SPICE, or are the different versions performing different simulations?


texts: Phono preamp picking EMI (4G/LTE/GSM ??)

texts: My phono preamp works fine, it's placed in grounded aluminum enclosure but every time i turn on the internet on in my phone and place the device ~1m or closer to the preamp i can hear some interference which sounds like short impulses (mainly low frequency murmur). How can i get rid of this problem? As i said - the device is placed in grounded enclosure, i've also tried some EMI gasket (metal tape) to seal the gaps in enclosure. Thanks!


texts: Industrial RF replacement for Xbee based UART communication

texts:
I have used Xbee's several times and I am working on a basic project which involves multiple MCUs talking to a central MCU and sending some updates such as Temp, GPS and etc...

Very basic setting bunch of Atmels ATMega controllers and they each have an Xbee connected to them. I am trying to take this a step forward and like to have professional design and printed on a PCB, also I have had several orders for the network, so I like to take this from an XBee based system to something more robust. I have looked into some TI's RF transceivers and Atmel's as well, but since I have never done an communication project from scratch I am scared to step into this dark area. I know RF is nothing but pain, dealing with the antenna's and noise, and etc...
I was wondering if anyone can help me with some design notes, and examples, maybe a chip that can be interfaced and would be easy to program. again this is a really basic 2-way network and I don't need a long range. It's a residential building solution so I am thinking about 2.4Ghz, or 900 Mhz would do just fine, all I care is to bring down the cost of production while keeping the design and implementation process fairly easy.

Thanks


texts:
I have some query about the priority of if else in verilog.
For example.

  If (a)
  b
  else if c
  d
  else if e
  f
  else
  g

At here, those a,b,c...g are all searched ?
How do those have priorities in if~else in verilog?


texts: Use the oversamplling followed by the "decimation method" to increase the ADC resolution and not normal averaging

texts:
To increase the 12-bit resolution of ADC from 12 bit to 14 bit, this can be done through the 'oversampling and decimation method'. An Atmel Application note says that

The higher the number of samples averaged is, the more selective the low-pass filter will be, and the better the interpolation. The extra samples, m, achieved by oversampling the signal are added, just as in normal averaging, but the result are not divided by m as in normal averaging. Instead the result is right shifted by n, where n is the desired extra bit of resolution, to scale the answer correctly. Right shifting a binary number once is equal to dividing the binary number by a factor of 2.
It is important to remember that normal averaging does not increase the resolution of the conversion. Decimation, or Interpolation, is the averaging method, which combined with oversampling, which increases the resolution

This reference clearly says that for the decimation method, the result is right shifted by the desired extra bit of resolution, and not divided by m as in the normal average.

So, the question is, why do we need to use the decimation method instead of the normal averaging after the oversampling to increase the ADC resolution?

It says above "Right shifting a binary number once is equal to dividing the binary number by a factor of 2", but what if we don't use a binary number? How do we use the decimation method in this case?


texts: How does this battery charger from an emergency rechargeable light work?

texts: I opened an emergency rechargeable light and saw the charger circuit which is quite simple: a bridge rectifier and then a big capacitor (I don't know the rating). There is no transformer, but the battery terminal voltage is appx 4.5V, but how does it work? When I measured the output of the rectifier I got nearly 270VDC. In India domestic voltage level is 220-240VAC. How is it possible to get more voltage? How does the battery charge with high voltage?


texts: Why is the impedance in the parallel resonant circuit maximum at resonance?

texts:
Why is the impedance in the parallel resonant circuit maximum at the resonant frequency?

For example if we have two resistors in parallel the equivalent resistance is less than the values of the resistors in the circuit. Isn't this similar to the LC parallel circuit?


texts: Trouble with understanding heatsink datasheet

texts:
I am trying to understand the heatsink datasheet provided in the following link:
https://www.fischerelektronik.de/web_fischer/en_GB/PR/SK434_/datasheet.xhtml?branch=heatsinks
My problem is that the heatsink is available for lengths:
50 mm / 75 mm / 100 mm / 1000 mm
I am trying to find the thermal resistance for the 1000mm one. From the graph you can see that the thermal resistance is only given on the interval from 40-200mm. How can I find the thermal resistance for 1000mm?

If anyone know I would really appreciate the help:)


texts: I have recently heard of the concept of a one-bit ADC, and have seen it implemented in the context of a sort of digital-to-analog converter (oddly enough), and I'm wondering, what is the point? Why not simply use a higher-resolution ADC, if higher resolution is desired?


texts: How to process voice commands using ATmega or Arduino?

texts: For a project I need to start my PC using voice command. I thought to made up an voice controlled system to turn on my PC. As far as I know, when I press the turn on button-2 pin's on the motherboard get short and PC starts. I think a relay circuit may solve it, but how can I process the voice command?


texts:
I am going to have a something thats runs on 120vac pulling 1-2amps is there a chart or something for choosing the right gauge of wire?

The wire will run from an inverter in the front of my car(by the battery) to the back (near the taillights).

I need the smallest diameter wire possible.


texts: Altium Designer: polygon pour on signal layer

texts:
I'm designing a board around 2 Texas Instruments TPS65988. In the datasheet a layout example is shown where "fins" are placed around pads to provide further thermal dissipation. A pour to create this region sounds to me the best option to draw these regions. However, designing them with lines is very time consuming and not precise at all, even with a grid of 0.025mm setted in Altium, given the total dimensions of these fins (TPS65988 is a 7.15 x 7.15 mm QFN IC).

I tried to draw Solid Regions (faster to draw, more precise) but unfortunatelly I don't know how to exclude vias not connected to the same net of these fins from those solid regions (look at the bottom left via in picture below). It's very easy with Polygon Manager... But I can't find a easy way to do the same with solid regions.

So, my question is... How do they draw them? What is the best way to draw them in a fast and straighforward procedure?


texts: Difference between 32 KHz clock output load vs. clock input impedance requirement

texts:
I have a WiFi chip that requires a input impedance of > 100 kohms and < 5 pF as seen in the requirements table found in the datasheet below.

I'm confused if this 5 pF requirement correlates to the output load of the clock I'm using.

Am I confusing things here? I feel like 15 pF output load violates the 5 pF input impedance requirement.

Another question is, how do I know if my output impedance is greater than 100 kohms, do I just place a 100 kohm resistor to do that job?

Any help is appreciated. Very new to this sort of stuff.

Link to Clock datasheet


texts: Can you use a amplifier and a satellite antenna to boost a GSM signal?

texts: I have a small GSM Modem whose internal antenna sucks. I bought a small external antenna that boosted the signal a little, however I want to boost it more. Would using a typical high frequency audio amplifier that is connected to a satellite antenna boost the signal?


texts: Lithium-ion battery charging and discharging

texts:
I want to discharge a 3.2 V (600 mAh) Lithium-ion battery.

Will the battery voltage go down if I discharge the battery? I have a Computerized battery analyzer (CBA-II) to discharge the battery.
In which condition, I should charge the battery again? I mean when the battery voltage will go down to 3V/2.8V/ 2.5V/ 2V/ 0V.

Thanks in advance.


texts: What is special about camera flash capacitors?

texts:
Capacitor manufacturers offer capacitor series that are specifically targeted on camera flash applications. For example, Rubycon has the FW series, and NCC has the PH series. These have working voltages of about 300V to 330V and a typical capacitance of 100μF to 150μF, so at first glance these seem to be standard high-voltage electrolytic capacitors. Nevertheless, they are designated for camera flash applications.

What makes these capacitors particularly suitable in terms of ESR, construction, etc. ?


texts: Measuring 0-250V and 10A (AC) with arduino

texts:
So,

I've decided to make a "homemade variac", but for simple things, such as lightbulbs, etc. Just to try things. So I'm going to use a voltage regulator to regulate AC voltage between 0 and 230V, where current can be up to 8A (according to voltage regulator's "max. power", but I think never will go higher than 3-5A).

Now, the question here is: How can I properly measure AC voltage and current, which I intend to show on LCD display? Which modules would be proper to use?

( I intended to use these voltmeters, but couldn't find one for AC current 0-10A, so I decided, to make it on a display and show also input voltage, input current, power and Wh.)


texts:
Consider a two windings transformer (I'm not talking about flyback transformer):

Magnetizing inductance is not equal to mutual inductance. Mutual inductance refers to the energy which is transfered from the primary to the secondary. The energy which is not transfered from the primary to the secondary refers to the leakage inductances and?
Magnetizing inductance correspond to an inductance which is placed in parallel to the primary side of the transformer. So the energy stored in the magnetizing inductance (1/2LI²) is not transfered to the secondary. As some people says it "sets up" the transformer for then transfering energy to the secondary.
Apparently in a forward transformer, if the magnetizing inductance was infinite, the flux into the transformer would be equal to 0 as the flux at the primary would be cancelled by the secondary.

What do you think about it?


texts: Finding the magnitude of the Transfer Function

texts:
This is the circuit, where some of the components values where given and the others, I found myself. (Sorry I have no link to the design, I needed membership there)

The following part says to draw the corresponding AC-circuit and find the magnitude of the transfer function U2/U1 at  ω= 0 , ω = infinite , ω =1/sqrt(LC)

This is the AC drawing that I have done

I am asking this question for the purpose of hoping that I get some feedback about the way I solved this problem and the fact that I am not sure if it’s done correctly. By no means this is homework. I am just trying to learn transistors and not knowing what the correct answer is causes doubts if I did it right or not


texts: How can the CMRR of an opamp be negative?

texts:
I was reading a paper from 1977 regarding the analysis for the CMRR of a three opamp instrumentation amplifier, I got the paper through my Unviersity but I cant post the paper since its copyrighted, however here is the link to download it legally through IEEE Xplore: C.M.R.R. analysis of the 3-op-amp instrumentation amplifier

The circuit im refering to is as follows

Basically the short (1 page) paper describes the procedure to obtain the CMRR of an instrumentation amplifier. The formula is the following:

$$ CMRR=\frac{Ad\cdot cmrr_o}{1+Ad\cdot cmrr_o(\alpha_2-\alpha_1)}$$

Where $$Ad=\frac{(R1+R2+R3)}{R2}$$
is the differential gain of the buffer stages (both opamps at the input)
$$cmrr_o \text{ is the CMRR of the differential amplifier stage}$$
and
$$ \alpha_i=(cmrr_i-1)/cmrr_i $$
where
$$cmrr_i $$ is the CMRR of the ith opamp

The paper follows the equation with a simple example:

An instrumentation amplifier was designed and built
with the following parameters: Ad = 100,  R4=R5=R6=R7= 10k (nominal value), with R5 adjustable. 741-type
op-amps were used with the following measured cmrr's:
$$cmrr_1= -111\times 10^3$$
$$cmrr_2= 40 \times 10^3$$
$$cmrr_3= -52.5 \times 10^3$$

R5 was used to obtain $$cmrr_o = 100 dB$$

The measured CMRR of the IA was $$-2.4 \times 10^4$$
 in reasonable agreement with the previous equation which predicts a CMRR of
 $$CMRR=-2.9 \times 10^4$$

I can do the math and arrive at the same result as the paper, but my question is this: how is it possible to obtain negative CMRRs (when not stated in decibels) such as the values of cmrr_1 and cmrr_2, does it mean the differential gain or common mode gain is negative in that particular opamp? in that case what does it mean that an opamp has a negative differential or common mode gain?


texts:
Could you suggest if it's possible to effectively use SiGe/GaAs RF MMIC (which have 50 Ohm input impedance) as first stage of photodiode amplifier?

The idea is to reverse bias diode from some +50V, and connect it directly to MMIC input, so that photodiode is loaded to MMIC's internal 50 Ohm termination. 50 Ohm might be quite low value though.

I am mostly worried about noise figure, frequency range is 1-100Mhz (maybe even 1-4Ghz???). Final target is to detect individual photons (with some probability) or dozens of photons (photo-diode QE is 30-70%).

I understand that typically one would need transimpedance amplifier for this job, but using common off-the-shelf SiGe/GaAs part in my dreams might yield lower noise...

PS. I understand that silicon photomultipliers / APD might be more useful here, but they are prohibitively expensive.

PPS: Parts I look at are :
Mini-circuits MAR-6 2GHz 3dB NF
Mini-circuits PSA4-5043+ 4GHz <1dB NF


texts: Using a differential pressure sensor in a mobile phone cover

texts:
So I am basically developing an interactive game and the game is going to have an external input in the form of a mobile phone cover. Right now, I am using push buttons as the main input. I do, however, wish to include a force or pressure sensor and am exploring the options available to me.

What I want to know is how could this sensor https://www.mantech.co.za/ProductInfo.aspx?Item=15M0057 be used for the application? Would it be possible and if so, how? I have tried reading up about this sensor but I can't seem to find much information on how to use it. Could someone who has used something similar provide some tips on this matter and also tell me if there is scope for integrating this  sensor into a mobile phone cover?

Any help would be appreciated


texts: Do mosfets only output a portion of their drain voltage when measured at their source? Why?

texts:
I built a BMS battery cutoff detection circuit for an RV using a mosfet inverter and a second mosfet to deliver a low impedance path to the vehicle's starter battery.
Am I underpowering the gate of FET1, or is 10.4V at Vout normal behavior? I tried changing R3 to 5K and it made no difference.


texts: Tracking location with GSM tower triangulation

texts:
I want to track location with GSM tower triangulation.
I searched and I found this API for GSM positioning.
{
  "gsm": [{
    "mcc": 262,
    "mnc": 1,
    "lac": 5126,
    "cid": 16504,
    "nmr": [
      { "bsic": "6", "bcch": "82" },
      { "bsic": "7", "bcch": "85" },
      { "bsic": "12", "bcch": "93" },
      { "bsic": "13", "bcch": "88" },
      { "bsic": "19", "bcch": "88" }
    ]
  }]
}

It requires the shown GSM information.
I don't understand what "nmr" is.
How can I find "nmr" information of GSM?


texts: Output State of comparator circuit for AC signal when open?

texts:
I am trying to design a circuit which would interface AC signals from pick-up coils.
Below is the circuit.

R4, R3 are for DC bias, and R2 is for feeding that bias to inverting input of the OP amp.

R5 and R8 is for hysteresis regarding noise immunity.

V2 is the input signal.

V1 is power rail.

My question is that how should I determine the state of Vout(18V or 0V) when V2 is open?

I simulated it on CircuitLab. and below is the result
V+ = 8.946 V
V- = 8.955 V
Vout = 1.783 mV

My concern is that V- is higher than V+ only by  9 mV, which I believe is leading Vout to near negative rail(0V).

Can I rely on current circuit for the output to be low always?

Or should I add some kind of pull-up or pull-down resistor for circuit stabilization?

I tried adding pull-up or pull-down resistors to V+ or V- but it prevents the signal from making Vout with 18V peak to Peak.

Below is the link to the circuit i made public

https://www.circuitlab.com/circuit/74bt8h/comparator/


texts: Ultra low power input ORing/power muxing

texts:
I'm working on a project with three power inputs and I need to automatically switch between them (favoring the highest voltage). There are plenty of posts on this topic (especially on this exchange) and it seems like your options are diode ORing, FET switching or using an IC like the TPS2115A. My issue is power consumption since my main power supply is a primary CR2032 Coin Cell battery that I'm hoping to get 6+ years our of. This rules out diode ORing because of the voltage drop and every IC I've looked at consumes >10uA -- I can tolerate around 150na ideally.

TI's TPS22933A is one of those ICs; it does exactly what I need, but has a quiscent current of ~0.7uA even when bypassing the internal LDO. (below)

Currently, the system sits at 240na without any switching logic and draws 4ma during transmit for 40ms -- all at 3v. I want to keep that nominal current below 400na if possible. Is there a solution with very low leakage/power consumption while nothing is plugged in and the system is using battery power? Any help would be amazing, thanks!


texts: Why is a LIN cluster limited to 16 nodes?

texts: It says everywhere that a LIN network can be made up of at most 16 nodes (1 master node and up to 15 slave nodes). The id field however is 6 bits long allowing for more than 15 slaves to be addressed. Why this limitation to a total of 16 nodes? What was to happen if i were to add a 17th node?


texts: Generate smooth sine wave from ZYNQ Analog to Digital Converter(ADC)

texts:
I have system built on ZYNQ SoC. The ADC of the ZYNQ Soc is fed with 10KHz sine wave and I am getting below wave as the output of ADC. This signal is further processed by further modules. As this signal is very noisy, the other modules are not behaving as expected.
Now, I would like to generate a smoother sine wave from this. After doing some literature survey, I understood, by doing averaging I can smooth the wave to some extent. But I think, there would be some better approaches to obtain a smooth sine wave. Any suggestions or help will be much appreciated.
Thanks!


texts: 1.7 MHz Full bridge driver circuit for mist maker validation

texts:
I'm building an ultrasonic mist maker that can support 10 ceramic discs with a resonant frequency of 1.7MHz. I found the following circuit online, unfortunately, I'm a beginner in circuit design and due to COVID and time constraints I cannot order these parts and test the circuit. It'd be great If someone can validate the circuit logically. I'll order a finalized PCB using the same design and then test it out.
As far as I know, TLC555 can be used to drive MOSFETs up to 1.7MHz but I doubt if there can be problems due to high frequencies in the MOSFETs.
Here's the link to the easyeda design page: https://easyeda.com/319ashwin/ultrasonic-mist-maker

[enter link description here][3]

Thanks in advance! Much appreciated.


texts: Voltage Drop and Safe Current Load on CAT5 Cable

texts:
I am going to use this passive PoE injector cable set to power a Raspberry Pi model B.

The Raspberry Pi model B consumes between 700mA-1000mA (mine will also be powering the RPi Camera Module). Using this cable set, I plan to power the Raspberry Pi and provide Ethernet data at the same time. My questions are:

For a 60 meter CAT5 cable, how much DC voltage should I supply to account for voltage drop and still meet the needs of the Raspberry Pi?
For a 60 meter CAT5 cable, and let's say a 6V DC power supply - the above passive injector cable will split the current between pins 7 and 8 (meaning each of the two 24 AWG wires will carry between 350mA-500mA). Does this breach the zone of how much current the CAT5 cable can safely carry? I don't want to start an electrical fire.


texts: PCB Pads vs Components Footprints in PCB design

texts:
I want to understand the process of PCB design using a software like Altium. I have come across two approaches as follows:

Approach 1: While making the component parts library we make the footprints of the component slightly bigger in size from that given in the component datasheet. Later we use these footprints as the PCB pads in the PCB design. So in this approach if a specific part is used multiple times on the PCB then for each instance we will have the same pad on the PCB as we would be using the footprint of the part as its pad on the PCB.

Approach 2: While making the component parts library we make the footprints of the components of exactly the same size as given in its datasheet. We also make a library of pads of various shapes and sizes. Later when a part is used from the library in the PCB then at that point we get appropriate pads from the pads library for the pins of the component. So for each instance of a specific part that is put onto the PCB we can use different pads as needed for that specific position.

I want to understand which of the above two approaches are correct, especially for the case of SMD components and PCB design.


texts: Skin effect with superimposed frequencies

texts:
Does a high-frequency signal affect the skin depth of another low-frequency signal?

E.g.:
On a solid 6mm2 copper conductor, there are three currents running through it at the same time:

15 A DC
15 A rms @ 50Hz
5 A rms @ 15kHz (edited)

Can I calculate the skin effect individually for each signal and sum the losses? Or do the currents influence the skin effect of one another?


texts:
In my favorite CAD, Eagle, there is a function called "ratsnest", which removes all multisegment airwires and replaces them with one straight airwire.

According to wiki of some other CAD,

A multitude of airwires are called ratsnest.

But why is this feature/object has such a weird name? I was not able to find any reference to its history. (It is also possible that it is a well-known construct which I cannot recognize due to my non-English background. If so, can you point me to any dictionary?)


texts:
i'm trying to construct the following dc to dc converter.

Input: 12Vdc 3A
output: 5Vdc 3A

but i'm getting no output, any ideas ?


texts: Why try to maximize number of grounding vias in RF PCBs?

texts:
I couldn't find an explanation as to why one would like to place as many vias (~50) as possible along the copper trace (or everywhere on a PCB) which transmits a high frequency RF (100 MHz up to GHz) signal.

In my case, I have two ground planes (pours) on both side of my circuit board. My intuition is that, somehow with vias, you have generate a mutual ground between both ground planes such that there is no signal from leakage going from the top ground plane to the bottom ground plane along the PCB edge.

This is because the PCB perimeter would be like a loop for the RF leakage current. To minimise the induced current loop, one must provide a "shortcut" so that the both planes can contact directly? Am I right?


texts: Branch current method of a circuit with phasors

texts:
i was trying to resolve this sample circuit:

I was trying to resolve a simple circuit with the branch current method, but my result doesn't match the exercise result.

In fact, the phasor of the resistor R2 should be $$-0.01 - 0.70 j$$, while my result is:$$-0.8 -0.06 j$$

Setting, condisdering the bottom node,$$u_3=0$$

It becomes:
$$
\left\{\begin{matrix}
u_1= 10e^{-\frac{\pi}{4}j}\\
u_3=0 \\
I_E+ \frac{u_1}{2j} + \frac {u_1-u_2}{20}=0 \\
\frac {u_2 -u_1}{20} - \frac{u_2}{100j} + \frac{u_2}{20} = 2  \\
\end{matrix}\right.$$

The current of all the two-poles are directed to the node 3. R2 current goes from the first node (left) to the second one (right)

Then:
$$\left\{\begin{matrix}
u_1= 10(\frac{\sqrt2}{2}-\frac{\sqrt2}{2}j)\\
5j u_2 - 5j u_1 - u_2 + 5j u_2 = 200j  \\
\end{matrix}\right.$$

$$\left\{\begin{matrix}
u_1= 5\sqrt2-5\sqrt2j\\
10j u_2 - u_2 - 5j (5\sqrt2-5\sqrt2j) =200j  \\
\end{matrix}\right.$$

$$(10j - 1) u_2 -25\sqrt2j- 25\sqrt2 =200j$$

$$(10j - 1) u_2  =200j + 25\sqrt2j + 25\sqrt2$$

$$u_2  =\frac{200j + 25\sqrt2j + 25\sqrt2}{- 1 + 10j}$$

$$u_2  =\frac{200j + 25\sqrt2j + 25\sqrt2}{- 1 + 10j} \cdot \frac{-1 - 10j}{-1 - 10j}$$

$$u_2  =\frac{(200j + 25\sqrt2j + 25\sqrt2)(-1+10j)}{101}$$

$$u_2  =\frac{-200j - 25\sqrt2j - 25\sqrt2 + 2000 + 250\sqrt2 - 250\sqrt2j } {101}$$

$$u_2  =\frac{-200j + 2000 + 225\sqrt2 - 275\sqrt2j } {101}$$

$$u_2 \approx \frac{2318,91 - 589j } {101}$$

$$u_2 \approx 23.18 - 5.89j$$

$$i_2 = \frac{u_1 - u_2} {R_2}\approx \frac{7.07 - 7.07j-23.18 + 5.89j}{20}$$
$$i_2 \approx \frac{-16.01 -1.18j}{20}$$

$$ i_2 \approx -0.8 - 0.06j$$

So, my result is:
$$i(t)= 0.80 \cos (200t - 0.75)$$

Instead of:$$i(t)= 0.70 \cos (200t - 1.58)$$

EDIT: The resistor connected to the first and the second node is R2 , not R1. The resistor connected to the second and to the third node is R1.


texts: If we have four grounded nodes in a circuit, can we connect two of them together and forget that those two were grounds?

texts: Refer to the image attached. I personally think the answer is no because it is not necessary for the currents through both the grounded capacitors to be the same in the upper circuit, but that is not the case for the bottom one.


texts:
For the class I am taking, we are to design a circuit with a thermistor in a wheatstone bridge. When the thermistor senses a temperature above 100°F or below 60°F it is supposed to turn on a red LED otherwise a green LED is supposed to be on. The circuit I have turns on the red LED at the 100° set point then turns on the green LED at the 60° set point. I am not sure how to fix that. Any help is greatly appreciated.

Function table (to be edited by OP).

Temperature   Green   Red
    < 60°F    Off     On
60 - 100°F    On      Off
   > 100°F    Off     On


texts: Altium : sharing schematics beetween several pcb with different component ref or footprint

texts:
I'm designing several boards which share some common features like a lipo undervoltage protection. I put this feature in a schematic and this schematic is used in several projects. That works pretty well.

Now, for one of the boards, I need to change a ref (and a footprint) of a component because the requirements are not the same. In my case, current is higher so I need a bigger MOS but everything else is the same.

Is there a way to do it without duplicating the schematic? I tried with variants. I was able to change the reference and the footprint but the changes are not visible in the PCB layout.


texts:
I have this circuit and I know that for \$V_1\$ (taking current exiting the node as positive) it is \$\frac{-(8-V_1)}{2} +\frac{V_1}{4}-\frac{V_2-V_1}{1} -4=0\$ but for \$V_2\$ I'm slightly confused. To find \$I_d\$ is it just \$V_2\$?
Also since terminals A and B are not connected, what's the voltage at A? Is it 8 or 0?


texts: 18650 pack building - is it better to have similar batch or similar capacity?

texts:
I'm gonna build battery packs. I have quite a lot of experience with 18650 Li-ion cells, but there's one thing I still don't know.

I will buy CCA 100 new cells from seller (for example LGEBHE21865). There are multiple batches of cells (the number below battery model). Although the batteries are 2500 mAh nominal, actual capacity differs ±100 mAh.

My question is:

It is better to build a pack (5S2P for example) using only cells from the same batch or measure actual capacity of each cell and use cells with most similar capacity? Or is there another important aspect like internal resistance?


texts:
I'm kinda new to PCB design, but here we go:

I've created a simple sub-pump water level monitor and it uses a constant 5V from a MOSFET. In the end, it's all monitored by a raspberry pi and I know if I put 5V straight into a GPIO pin as input, that's going to kill the pi very fast so i'm wondering if anybody knows an appropriate resistor to use for this.


texts:
Does anyone know of an online battery usage calculator for predicting the lifetime of low power systems?

(something simpler than doing the manual calculations).

For example:

  "I have a microcontroller which is
  awake for 1ms in every 1000ms, during
  this time it consumes 5mA. I have an
  LED which is on for 2ms in every
  1000ms and it consumes 30mA. How long
  will my 2200mAh battery last?"


texts: The 3.3V DC is output from a MCU, how I can convert to a +/-5V signal?


texts: What adapter would power device that runs on 3 D batteries?

texts: I have a clock that runs on 3 D batteries and, as you can imagine, it's a pain to maintain them. I've found a DC adapter that delivers 4.5v (1.5v x 3) but it doesn't budge when connected. I imagine there's some issue with amperage or resistance, but those aren't listed on the batteries! What should I be doing?


texts: Why does torque increase with rotor current in an AC induction motor?

texts:
In my understanding, the EMF induced on the rotor of an AC induction motor induces a current, and the larger this current, the greater the rotor's torque will be.

Could someone please explain: why does a larger current lead to a larger torque?

I'm looking for a qualitative explanation rather than a quantitative one, but any help would be very much appreciated!


texts: Need a simple buzzer/LED circuit for espresso machine

texts:
I have an espresso machine that I tore down, reassembled with fewer components then modified it to fit a specific setup -- kind of DIY project.

The machine has an autofill circuit. After I removed the controller and SSR, the machine does not have an autofill circuit, which is fine when I turn on the pump to refill manually. The only problem is checking the water level to find out when I need to refill the boiler. I fitted a sight glass for that purpose, but I still need another aid to notify me whether the water level is OK or not, mainly in case someone else is using it.

I want to add  a small buzzer/LED which is activated only when the water level drops below a certain point, OR just a LED which lights up so long as the water level is fine.

There is a water level probe. The boiler is grounded so if there is water touching it there will be a circuit/current through the probe, and if water is below the tip then there is no circuit (this is my understanding, so please correct me if it is not correct.)

There are buzzer/LED gadgets that can be bought cheap, but I want to know how it would work with the water level probe? I tried connecting the probe to a LED then  to one of electric current poles; I thought it should light up when there is water touching the probe, but it does not seem to work, or maybe it is just the wrong way to do it. :)

Any help is appreciated.


texts: My EDA software (PCAD, but I guess others do this too) adds thermal reliefs on vias in a copper pour. What's the use? Vias aren't soldered. (I know why you use them on regular PTH pads)


texts: How does your company manage hardware reuse?

texts: At my company we do a lot of original hardware designs each of which are designed by only a small sub-section of our engineers. We are looking at ways to better document and distribute what has been done on each project so that information can be distributed and potentially reused. How does your company handle this?


texts: Need help initializing display on ATmega162

texts:
I have a DEM 16217 SYH-PY 2x16 character LCD and I have problems initializing it.

I'm using AVR Studio 4. The 8 datalines are connected to port A of the microcontroller while the 3 control lines are connected to port E. Enable is PE2, R/W is PE1 and S is PE0. Port A connections are DBn to PORTAn. As far as I can see from the datasheet, no instructions seem to take more than 2 ms. For some reason, busy flag check isn't working correctly, so I used 2 ms delay instead.

At first, I wanted to have an LED blink after each step, but it turned out to be much better to have output at a serial port.

Here's my code:

#include <avr/io.h>
#include<util/delay.h>
#include "LED.h"
#include "Terminal.h"

void Screen_Execute(void)
{
    _delay_us(2);
    PORTE=PORTE | 4;
    _delay_us(2);
    PORTE=PORTE ^4;
    _delay_us(2);
    //_delay_us(2);

}

void Screen_busy(void)
{
    _delay_ms(2);
    //is the screen busy?
    //PORTE=PORTE | 2;
    //DDRA=0x7F;
    //Screen_Execute();
    //while ((PINA & 128))
    //{
        //Screen_Execute();
        //BLINK_LED(500);
    //}// wait until zero
    //DDRA=0xFF;
    //PORTE=PORTE ^ 2;
    //Screen_Execute();
    //no longer busy
}

void Screen_init(void)
{

    //BLINK_LED(1000);
    SEND_STRING("Starting initialization\r\n",0);
    DDRE=0xFF;
    PORTE=0x00;
    DDRA=0xFF;
    PORTA=0x30;
    _delay_ms(250);
    _delay_ms(1000);
    SEND_STRING("Step 1 executing.\r\n",0);

    Screen_Execute();//voltage stabilized
    _delay_ms(5);//first output complete
    SEND_STRING("Step 1 complete.\r\n",0);

    //PORTA=0x30;
    //Screen_Execute();//second time
    //_delay_us(110);//end

    //PORTA=0x30;//third time
    //Screen_Execute();

    SEND_STRING("Step 2 start.\r\n",0);
    //BLINK_LED(1000);
    Screen_busy();
    PORTA=0x38;//two lines, 8 bits, 5*7 characters
    SEND_STRING("Step 2 execute.\r\n",0);
    Screen_Execute();
    SEND_STRING("Step 2 complete.\r\n",0);

    SEND_STRING("Step 3 start.\r\n",0);
    //BLINK_LED(1000);
    Screen_busy();
    PORTA=0x08;//screen off
    SEND_STRING("Step 3 execute.\r\n",0);
    Screen_Execute();
    SEND_STRING("Step 3 complete.\r\n",0);

    SEND_STRING("Step 4 start.\r\n",0);
    //BLINK_LED(1000);
    Screen_busy();
    PORTA=0x14;//cursor goes to home and screen is cleared
    SEND_STRING("Step 4 execute.\r\n",0);
    Screen_Execute();
    SEND_STRING("Step 4 complete.\r\n",0);

    //Screen_busy();
    //PORTA=0x04;//
    //Screen_Execute();//end of init
    //Screen_busy();
    SEND_STRING("Step 5 start.\r\n",0);
    //BLINK_LED(1000);
    PORTA=0x0F;
    Screen_Execute();//cursor blinks, screen works
    SEND_STRING("Step 5 execute.\r\n",0);
    Screen_busy();
    SEND_STRING("Step 5 complete.\r\n",0);
}

My problem is that after initialization, cursor appears on a random position on the screen.

When I try to do initialization as described in the documentation, by sending the PORTA=0x30; line 3 times, it doesn't work. Also, if I try to use tighter timing, it again doesn't work.


texts:
How can I make a two phase clock on a breadboard (i.e. no surface mount components) without using a microcontroller?

Phase 1:

   _     _
__| |___| |__

Phase 2:

  ___   ___
_|   |_|   |_

The exact duty cycle is not important.

Phase 1 must go low at least 50ns before phase 2 and go high at least 50ns after phase 2.

Ideally, the clock needs to be adjustable (via resistors, capacitors, etc.) between 1Hz and 100KHz.

I have been thinking about ANDing and ORing two 90 degree out of phase 50% duty cycle clocks - but I still need to generate those.