texts:
Here we have a limiter circuit, pinned to 2.75V.

There are 2 AAA batteries on the right and a 5V solar panel on the left.
There is a sensor to determine when the circuit is on or off at P0.6 (high(2.5V) is ON and 0.00V is off), P0.6 is connected to uC.

Here is the problem:
When solar panel voltage is rising from zero to 2.75V - everything is good and is working as it should be.
However, when the voltage is dropping the circuit is supposed to turn off at below 2.75V and so is P0.6 is supposed to read 0.00V, but P0.6 is continues to read high (2.5V) until the solar input drops to zero.
How to improve it to completely turn the circuit it off when the input from solar drops below 2.75V?


texts: Formula for voltage drop vs PCB trace width, temperature, current, and trace length

texts:
I need to find out the voltage drop in the PCB traces with respect to the possible factors like: copper thickness, trace length, trace width, temperature, etc.

I found some calculators available at:

http://www.leiton.de/leiton-tools-pcb-voltage-drop.html
http://www.eeweb.com/toolbox/external-pcb-trace-max-current
http://easycalculation.com/physics/classical-physics/circuit-trace.php

Since all the calculators are providing different values for same input, I am not sure which calculator is giving the correct value. Is there any formula so I can calculate the voltage drop in the PCB traces?


texts:
[Taken from Razavi's Analog IC CMOS Design Book]

My confusion is with the line that says "Such an arrangement is indeed practical if the circuit senses only high-frequency signals."

Firstly, I'm a bit confused, what exactly is the purpose of the circuit in 12.2(b)? Is it just to set a bias point?

Secondly, high-freq AC signals will see the capacitor as a short, so what exactly is that going to achieve?

I think I'm just struggling to see the problem with these circuits and thus I can't figure out why certain solutions are needed?


texts:
I have two ideas:

I use a temperature sensor, which is a thermocouple, where it will be connected to the input of the voltage range adapter. It will design a voltage range adapter capable of taking  low signal levels 0-30mV from the temperature sensor to translate them  in 0-1V or  0-10 DC. And the outputs of voltage range adapter  will be connected to the analog inputs of a Moeller PLC, which will displays the temperature obtained from  the temperature sensor.
Or I could use temperature sensor, which is a thermocouple, where it will be connected to the input of the voltage range adapter. It will design a voltage range adapter capable of taking low signal levels 0-30mV from the temperature sensor to translate them in 0-1V or 0-10 DC. And the voltage range adapter is controlled by a microcontroller to display the voltage obtained from the temperature sensor on an LCD.

What electronic schemes could you recommend?


texts: Awesome modems with Arduino compatibility?

texts:
I'm looking for a modem that can hook up to the input port on a portable ham radio and an ardunio board serial connection. Not really interested in APRS, it's too high level for my needs (long distance remote control).

Just need to be able to send 10 characters maybe 3 times a second (>1200 baud)
low power if possible
distance of like 40-50m max

Seems like that will all be taken care of by the radio, just wondering if there is a good hardware modem for this kinda of thing.


texts: What is the internal i2c address to CAT24AA16-D

texts:
I am interested in using this eeprom for a project. I have used used I2C devices before and usually the datasheet gave the embedded address somewhere. For the life of me I can't seem to find it on their datasheet.
Anyone want to show me where the heck it is? I feel quite silly as I even tried CTRL+F to find keywords on the datasheet.
https://www.onsemi.com/pub/Collateral/CAT24AA16-D.PDF


texts: Why do these two dramatically different sized heatsinks have similar thermal resistance?

texts:
I have a plate fin heatsink that measures 100mm wide x 114mm long x 4mm for the plate with 6 fins that are 35mm tall x 1mm thick.

I get 1.84C/W at 100LFM when I punch these values into a heatsink calculator.

Then, I went on Mouser and looked at their offering for heatsinks and found a ton that are way smaller with similar (or even lower) thermal resistance values. Here is an example.

Am I misunderstanding something here? Why does a heatsink 4 times larger have the same performance as the one I listed from Mouser?

Added (after Icy's answer): all the heatsink calculators i have found online assume at least 100LFM but i am interested natural convection values.


texts:
I am trying understand the schematic for a Waveshare Core 407I board, with an STM32F407IGT6 MCu. What is the meaning of this schematic symbol (labelled COMP.J1 JPAD3)?
Link to full schematic: https://www.waveshare.com/w/upload/4/4a/XCore407I-Schematic.pdf

I've identified it on the board to be a blob of solder next to a square contact. What component is this if I were to draw it myself in an EDA program?


texts: How to calculate flux density in a toroidal CT that has an electrical line pass through the center?

texts: I have seen the Biot-Savart equation but I don't know how to apply it. Also does the conductor length need to be considered finite and equal to the core length or will the calculation be for infinite length conductor?


texts:
I'm working with GSM modem and I'm wondering if anyone has come across any sort of measured or typical GSM current profiles for various actions such as:

Connecting to base station
Sending a SMS
Voice call
During an active data connection

I know the general trend of what the current consumption should look like when it is transmitting based upon frame rate and slot-time, what I'm looking for is more coarse view.  For example when sending a SMS message it transmits for N number of slots.


texts: Temperature and Voltage variation affects on Metastability

texts: Are there any effects of temperature and voltage variations on Metastability of the flip-flop? If Yes, What are the effects?


texts:
I am planning to use this small solar panels to charge a 18650 cell with this charger module and power a low power project with it.

I've never worked with solar cells, although I have read a lot from them. I understand the need for diodes on them to prevent a battery discharge, but I'm having a little problem.

As far as I know, any diode has a voltage drop. Let's say 0.6V on average in my experience.

If I connect those 5V panels in parallel with the charger, would I run in under voltage problems? In the description is stated that input voltage should be 5V.

But then series panels would be more or less 9V and we are clearly on the over voltage side.

Are diodes necessary in this application? Would the charger prevent the battery discharge? I'm kind of confused arranging this power setup and would appreciate any help.


texts: Microcontroller Adjustable 2A 24V Constant Current Source

texts:
I need to come up with a method to provide a microcontroller-adjustable, regulated current ranging from 0-2A at ~24V to a load in a closed-loop fashion.  I have been researching this issue for awhile and have found a few ways that it could be achieved, each has its issues.  I was hoping to lay out my thought process and different approaches and get feedback as to whether I may have overlooked something obvious or if I am going about this entirely the wrong way.  Thank you.

Method 1 - Purchase a constant current LED driver IC

This seemed like the most obvious solution.  It would have the benefit that I would not need to setup external current-sensing to implement closed-loop control as would be needed with the other two choices. However, I had trouble finding LED drivers that could handle 2A at 24V on a single channel as I browsed DigiKey.  If any exist I would be very happy to have a part number.

Method 2 - Convert a voltage regulator into a current source

Unable to find a suitable LED driver I did some more research and came across this instructables which looked like it would achieve what I needed.  The problem I ran into here was that this design and others like it use a small resistance (on the order of 10's og ohms) potentiometer for current adjustment.  My system, in order to be closed loop, would need to use a digi-pot which do not exist at such low resistances due to limitations of their construction.

Method 3 - Construct using an Op-Amp and Transistor(s)

Finally, after the previous two failed attempts I went back to the drawing board.  I came across other StackExchange questions like this one, the accepted answer for which used an op-amp and some type of transistor (the comments on the answer go through a variety of different choices from MOSFETs to Darlington pairs).  This seems like it would work for my purposes but I have limited experience in this area, is there a particular transistor type that would be far superior in this application?  Also, will I need to take into account the gain of the transistor or is that handled with the feedback from the sense resistor?

To conclude, my question is two fold:

Is there a way to achieve my stated goal using one of first two methods I mentioned which I may have overlooked?
Is there a particular transistor type that I should be using for method 3 if my goal is to be able to set the current for the load anywhere in the 0-2A range, not simply an on-off switch?

Thank you very much for taking the time to read my question and provide answers.  Do not hesitate to request clarification on anything I said!


texts: How to avoid interference in wireless communication?

texts:
I am working on wireless communication system. We are using around 10 pairs of transmitter and receivers. We are using atmega16 microcontroller for encoding and decoding by USART ports.

Now we are able to transmit the data and receive the same in the receiver end, but there is a major problem, when we are finding the 2 transmitter data coming at the same time. The receiver is unable to get it due to interference.

Suppose one transmitter sends "SENDA" at the meanwhile another transmitter sends "GETTS", at that time the receiver can not receive proper data. As all the transmitters and receivers are working in same frequency, so this interference is occurring. How can I resolve this issue?


texts:
I built a controller for a soldering iron (JBC C245/C210 specifically), which can supply up to 60W of power to the iron. I have a temperature control loop that runs at 10 Hz, which I am trying to tune properly. Thus, loop_duration = 0.1 s (used below). There is a current control loop within the temperature loop, which runs 20 times per temperature loop iteration. This current loop shall not be the subject of my question.
Up to now, I am only using P and I components, my D-component is set to zero. The temperature control loop looks like this, and it generates an output value for heater current:
void temperatureControlLoop(){
    // Calculation of new temperature error
    temp_error = temp_set - temp_is;

    // Only integrate error, if output current is within limits
    if ((current_set < current_max) && (current_set >= 0))
    {
        // anti windup protection and integration of temperature error
        temp_integrated_error += temp_error * loop_duration;
    }

    // calculate change in temperature error
    diff_temp_error = temp_error - temp_error_last;

    // Control equation, calculates new output current value
    current_set = D * diff_temp_error + P * temp_error + I * temp_integrated_error;

    // remember last temperature error for D-component
    temp_error_last = temp_error ;

    // Clamp to available power supply current
    if (current_set > current_max)
    {
        current_set = current_max;
    }
    else if (current_set < 0)
    {
        current_set = 0;
    }
}

It works fine so far, but I would like to optimize it further. Attached are two pictures of measurements: in each one, temperature (in °C) is shown on the top, heater power (in W) on the bottom. Please don't pay attention to the time scale on the power curve, it is incorrect. The time scale of the temperature is reliable, where a value of 10 equals 1 second.
The first image shows the iron temperature from cold to target value (350 °C). I feel like it could heat with full power for longer. If the heater power is switched off, there is no more rise in temperature, thus I think that there is no significant delay. It should be possible to heat close to target temperature with full power and then just stop.

The second image shows the reaction to disturbance. I contact a copper plane at t=100 and remove the iron again at t=190. I think that the reaction could be much quicker, as I have much heating power to spare. Also, the overshoot after removing the disturbance is too large.
My question is: how can I optimize the parameters? Should I record the step response and use offline optimization or is there a suitable practical tuning method? I want to have minimal drop in temperature when a disturbance happens. Overshoot is not as critical.

EDIT: Here is the step response to 1/3 or maximum heater power (20 W). You can see the heater power step, and the temperature rising as a result. I repaired the time scale which now shows acutal seconds correctly. I don't really see any noticeable delay of temperature change to the application of heater power.
This is the complete step response, which cuts off at 380°C, because this is a safety limit in my design

This is zoomed into a smaller portion of time

And even more zoom.


texts: floating ground for AC and DC power supplies

texts:
I wanted to connect two power supplies, one is AC (240V , 6A) and the other is DC (3,3V, 300mA). But i read in some referrence that connecting AC and DC power supplies could be dangerous if the two signals have are from different grounds. So I was thinking about using a floating ground to avoid a ground loop.
Is the use of the floating ground can secure the power supplies from damage? Or the power supplies need to be isolated ?
If not, what is the best way to connect the two power supplies safely?


texts: How to determine rise time from a datasheet?

texts:
I am trying to determine the rise time for a component in my circuit. I am unsure if my current method is correct and could use some verification. I would love help in the general case as well.

Case 1: NC7SV86

I am using this XOR gate as a clock inverter. I am powering the device with 3.3 V. I can see from the datasheet that the HIGH level output voltage is 2.2 V, and that the HIGH level output current is -24 mA. Thus (?) the output resistance is:

\$R =\frac{V}{I}= 92\ \Omega\$.

From the datasheet, we also learn that the output capacitance is \$C_{OUT}= 4.5\ \$pF.
Thus, the time constant for the output is
\$\tau_{RC}=RC=410\ \$ps.

Then, the rise time is
\$T_{r}=2.2\tau_{RC}= 910\ \$ps.

Which seems reasonable, but I have no way of verifying. Worrisome, however, because this rise-time produces a knee frequency of:
\$f_{knee}= 550 \ \$MHz.

Case 2: 74VCX245

Again, I am powering the device with 3.3 V.

\$R=\frac{V}{I} = \frac{3.3\ V}{100\ mA}=33\ \Omega\$

\$\tau_{RC}= RC = 33\ \Omega\times 7\ pF=230\ \$ps

\$T_{r}=2.2\ \tau_{RC} \ 500\ \$ps

\$f_{knee} \approx 1000\$ GHz

Again, a really high knee frequency.

Do these calculations check out with you all? If not, what is your recommended procedure for determining the rise times.

The target speed for the entire circuit is 100 MHz (clock), so I understand that I will need ground planes and careful impedance matching.

Thanks to Niel_UK, I now see how to use the propagation delay as an order-of-magnitude check, at the least.


texts: Series and parallel RGB LED work abnormally (cross light up)

texts:
I am trying to make a msp430 controlled Bluetooth RGB lamp. The program works perfectly right now. But the problem is: when running for a while or as soon as I connect the led driver power supply (I soldered many boards to troubleshoot the problem. But I failed), some led begin to blinking (the unstable kind.) and it's like the color is abnormal. For example, if I only turn on Q1, then the blue should be the only color, but actually, some led will also light up red color, and some even show red only. I don't know what cause this problem.

I one board I soldered, I try to lower the MT3068 voltage to around 14V (15V originally). This time, the stable working time lasted longer (not broken as soon as possible). But eventually, the cross-light-up still occurs.

How should I work around this.


texts: I need to confirm something.Do circuits like the one shown below in which there is no connection between points A and B,treated as separate loops with no connection between them?


texts: Using a Logic Analyzer for Device Drivers (low level)

texts:
Sort of a follow up to this question:
https://stackoverflow.com/questions/19760764/learning-to-write-low-level-drivers-linux/19761953?noredirect=1#comment29386523_19761953

For example I want to take a random peripheral (like an SNES Controller I used in the example above) and make a device driver out of it. With/Without a guide for the controller how do I really know how to read the inputs.

Take this as someone that knows very little about Device Drivers so what im saying may make little sense. It was mentioned using a Logic Analyzer to use if I had no instructions on the device.

Thanks


texts: NodeMCU with two MQ gas sensors requiring multiple analog pins

texts:
I was very helpfully directed to this forum from Stack Overflow with this question.

So I've been working on some project for making air quality sensors and ran into a problem. As anyone who has worked with a NodeMCU would know, the chip only has one analog pin. Unfortunately, I have two MQ gas sensors, MQ2 and MQ7, and so I had to follow the guide here to install two analog sensors to the chip.

Now, the MQ sensors are working kinda strange. They output very high values when I uploaded the code from the Arduino IDE and often make no sense when converted into ppm (makes 0). Dunno if it's due to the fact that the heater in the sensors aren't being preheated or what.

Later, I was told that the GPIO pin outputs around ~3V of power while the MQ gas sensors needed 5V to function but I was told it can be done. What I was advised was to "use the IO-pins to switch on/off a transistor which drives the sensor".

Could anyone here detail me on how to do this? Or could I just use a voltage divider to constantly supply ~2V more of power to the sensors (currently I'm trying it with a 10K and an 18K)?


texts: Increase electret microphone bias voltage

texts:
I've got a Zalman zm-mic1 microphone, that was working just fine on my laptop. I bought a new rig a couple of months ago and the microphone is really quiet, digital amplification introduces an enormous amount of noise while my voice is still barely audible. Tried everything on the software side, nothing helped.

I measured the bias voltage and got 2.25 V, while i had 3.85 V on the laptop. So I checked the the audio codec's datasheet (ALC887) and it says "Software selectable 2.5V/3.75V VREFOUT to be analog microphone bias". Well this software selection is nowhere to be found, neither in the official driver, nor in the BIOS and google doesn't help either.

So the question would be, is there any way of increasing the bias voltage externally, that doesn't include me buying another sound card/microphone. Or should I just build a preamp with the LM386. You can see the wiring of the microphone jack on the following picture (taken from the datasheet).

PS: Since it's a new PC, and my knowledge on the field is obviously lacking, I don't want to get funky with the motherboard.


texts: How did dial-up modems make noise when initializing internet connection

texts:
A 56k modem sounded like this. I read somewhere that the reason for these whistles and chirps and buzzes is to give the user the feedback that something was happening during the handshake.

I guess the modem had its own speaker. Does anyone know how those sounds were generated before coupling to the speaker? Was it a recorded sound or really the actual sound of some real-time pulses or?


texts: Controlling direction of current flow through pin depending on the type of device connected

texts:
I have a small portable device - lets call it MASTER - which can be inserted into two different accessories - CHARGER and SLAVE. You can check very rough block diagrams in the attached picture.

MASTER has 40mAh LiPo battery inside with nominal voltage around 3.7V (but of course during usage it's something between 3 and 4.2V). This voltage is further regulated to 1.8V. That is the voltage that is used by MCU.

MASTER has 3 pins/pads that extend outside the MASTER’s enclosure. They don’t extend much but user can definitely touch them or short them otherwise.

CHARGER and SLAVE have spring fingers (something like this http://www.te.com/catalog/products/en?q=2199001) that form a contact when MASTER is put inside.

DATA pin is used for single wire SLAVE/CHARGER identification. The memory with ID is parasitically powered so it can be read even when battery is not connector to the SLAVE. MASTER can easily determine if the connected accessory is SLAVE or CHARGER.

Everything else on the SLAVE (except memory) must be powered from MASTER’s BAT and GND pins because SLAVE has no battery.

But also MASTER’s battery must be rechargeable through BAT and GND pins.

Which finally gets us to the problem - Is it possible to supply voltage to the SLAVE and also recharge MASTER’s battery using only single pin? And of course without possibility to short-circuit the MASTER’s battery and other components.

NOTE: Supplying voltage to SLAVE and recharging MASTER will NEVER occur at the same time, these are completely separated events.

Now some ideas I had but was unable to implement (probably because I'm too stupid :)):

You can use identification on SLAVE/CHARGER to “open” supplying/charging paths of circuit, but consider that charging the battery MUST be possible even when battery is completely drained and cut off.
Using some MOSFET/transistor magic to recognize type of accessory (SLAVE or CHARGER).
Cut off the BAT pin from battery when overcurrent is detected. But fast - resettable fuses are not fast enough. Also relay or SSR relay is not suitable because of its size.
Last idea was to use 4 pins instead of just 3. This should be the last resort. If you guys tell me it cannot be done with only 3 pins, I'll ask new question.

Thank you all in advance!


texts: Why do I get a failure in Quartus while trying to programming my FPGA?

texts:
I followed with this tutorial into the end of it, but I got an error while trying to programming my DE2 altera kit.

the design is input pin output pin (pin_name1 and pin_name2) and an inverter instead of the circuit in the tutorial.

this is the pin mapping:

this is the warnings I get after compilation:

Warning (20028): Parallel compilation is not licensed and has been disabled
Warning (20028): Parallel compilation is not licensed and has been disabled
Warning (20028): Parallel compilation is not licensed and has been disabled
Warning (169174): The Reserve All Unused Pins setting has not been specified, and will default to 'As output driving ground'.
Warning (292013): Feature LogicLock is only available with a valid subscription license. You can purchase a software subscription to gain full access to this feature.
Warning (306006): Found 1 output pins without output pin load capacitance assignment
    Info (306007): Pin "pin_name2" has no specified output pin load capacitance -- assuming default load capacitance of 0 pF for timing analysis
Warning (332068): No clocks defined in design.
Warning (332068): No clocks defined in design.
Warning (332068): No clocks defined in design.

this is the failure I got:


texts: How to use Arduino to control the switch on a 4.5v circuit

texts:
I've been building a wall mounted lightsaber using the below board.

At the moment the switch is turning it on and off, however I want to automate this with an Arduino.

Can I use a digital output pin to act as the switch and connect the Arduino ground to the ground on my board?

My power source is a 2amp 4.5v  DC.
The Arduino would plug into the USB on the same AC/DC adapter as this board.

Thanks!


texts: What can I do as a student to be a better candidate for a hardware design job?

texts:
If you were looking to hire a student still in school for an internship position at a high-tech company (say, Microsoft, Apple, or Google) for hardware design. What kind of skills would you be looking for?

What can I do with limited time and budget to attain those skills outside of what my school covers?


texts:
I have 300 amps 12V Gel deep cycle batteries bluged into suoer 50A smart 4 phase charger and a PC that works on a DC power supply takes around 5-30 A (15 amps most if not all the time).

Now I want to know if this is a good setup because during bulk charge phase the charger will push very high current 50A when the batteries are discharged by 30% and this may damage the batteries? if the PC was turned off. From what I know is that the charging current should not exceed 12.5% of total batteries capacities which is 36 of 300 Amps.

The thing is that I have a smart charger which changes the current and the voltages depending on battery state of charge, but having a load applied on it constantly may make it apply the wrong amount of current and voltages extending the bulk charge period and costant voltage phase and never enter the float charge phase so that does not look good to me, is it?


texts:
I have attempted to use a calculator without success.
Using a 5 V logic gate that will be driven by a Kinetis MCU, I would like to make a DAC. I have tried a 10k and 100nF filter but at 1 kHz I get a sawtooth on the output. I need <0.1V ripple at 500Hz.
Ideally I would like to lower the PWM frequency even more (say 200 Hz) but have a nice variable 0 - 5 V output. Any ideas on RC combo? Response is not that much of an issue. A full sweep from 0 V to 5 V in < 200 ms would be adequate.
PCBs are made so only option is to change the R/C values not redesign the layout.
Its currently logic TTL signal into a 10k then out of that to the "measure point" with a 100 nF cap to ground from there.


texts:
Given the situation where an LED is being used for a status indicator or similar, not toggling quickly.

Which is the best configuration for the IO pin, push pull or open drain? As I see it either will work, and I don't see any benefits to one configuration over the other.

U1 in the following is just representative, not a specific microcontroller.

simulate this circuit – Schematic created using CircuitLab


texts: I have noticed a lot of electronics use kapton tape in places where a heat resistant tape isn't necessary. Why is that so? Is it just because it's a good adhesive?


texts: Why do capacitor datasheets avoid directly giving the ESR value?

texts: Most datasheets give a parameter called "loss tangent" instead of directly giving the ESR value. Why don't they just give a numeric value for it? Why is loss tangent preferred over ESR? Is there something that prevents giving the ESR, like it is being dependent on frequency?


texts: A battery and other things are connected to the two ends of a resistor. Is the voltage between the resistor's terminals exactly that of the battery?

texts:
For ex,

So see the 6V battery connected to the two ends of the 1k resistor. Now, is it try that the potential difference between the terminal of the RESISTOR equal to that of the battery? I mean there is also a currently source that might generate som counter-voltage to the battery.

By counter voltage, I mean like:

In this case, the battery is trying to make the current throught the resistor go down, whereas the current source is trying to make it go up. I know in picture 1, a current source isn't exactly this close to the battery, and not exactly in parallel with it, but for some reason, it may be have an effect like this.


texts:
this is the basic shematic, i added a freewheel diode with the connector of the motor .

Im driving a DC motor 24DC 1A, im using PWM 500Hz from microcontroller and MOSFET IRF740 with a driver TLP250 and of course the freewheel diode in parallel with the motor.

the problem is that i don't have a clean zero state when the MOSFET is in conduction as you can see in the picture, and because of that he's overheating, but when im using a resistive load i have a very good commutation.

So the problem is because of the inductive load, what should i do to get rid of it ?


texts: Can anyone please help me identify this component, SMD (R40 515 Z5J)?

texts:
Can anyone please help me identify this component. It's marked
R40 515 Z5J
Dimensions are roughly 6.5mm x 6.5mm x 3.0mm my verniers have disappeared but it's pretty close.


texts: Is there a voltage difference between grounds of different areas?

texts:
Say that I pull a 100m long conductor wire between 2 areas, will there be a difference in voltage?  E.g. will there be a flow of some current back and forth?
Reason I ask this is because I know that the voltage of ground is zero, but what I don't know if that's just a relative convention for a circuit in a given area, or is it also an absolute voltage even across the grounds of different areas.


texts:
I am planning on making a board which will have some 2.4GHz RF capabilities, and would like to know if there is a cheap way to tune an IFA cheaply.

If I had access to the right equipment I could easily tune the antenna, but at the moment a multi-thousand dollar VNA is a pipe dream.

Is there anything that can be made or used on the cheap to get a crude antenna tuning going for this board?

Also something I saw which was interesting, on the antenna design specification it claims that no external matching components are needed. I'm assuming it would still be desired to have a pi network to deal with detunings caused by anything else on the board or in the environment right?


texts: Why we use Dual supply Emitter Bias in Transistor

texts: As i am studying about DC Biasing of transistor, i am just able to fully understand only Base Bias after that i am stuck at Emitter Bias which is also called Dual Supply Emitter bias where we apply voltage Vee to emitter, Now my question is, In Emitter bias we know Ic become independent of Beta when Base voltage become zero, it means as it gets independent of Beta so its operating point will be stable.. and the problem is solved.. than why we move to other bias conditions like Collector feedback bias or voltage divider bias etc etc why we dont end the game at Emitter bias after studying Base Bias. Thankyou.


texts:
I'm trying to design a "double-buffer" structure similar to that used in UARTs (for receiving).  In my case, it is for samples from an ADC.  I shift them in, and at some point my logic detects a condition that tells me that I want to "save" the block I currently have;  thus, a second buffer of type PISO works (serial-out is fine, since the microprocessor can always read the samples from the FPGA sequentially).

A pure HDL solution (using PFUs/LUTs) does not work, because the buffer is too large (I get the "Design does not fit in device selected" error at the mapping stage. Even with the XO2-7000, my required size is slightly larger).

EDIT:  I will need 512 elements × 16-bits per element (times two, if we're talking double-buffer). Notice that the ADC has parallel output; the analogy with the UART is not at the bit-level (in the analogy, each bit in a serial transmission would be like each sampled value of the ADC)
END EDIT

IPExpress only offers FIFO (including dual-clock) and RAMs (including dual-port).  But ideally, I would need to copy in parallel to the second buffer.

Any suggestions, or pointers to any additional IPs that could do the trick? (doesn't have to be free).  The IPs I see through Lattice's website don't seem to match .


texts:
Currently I have this 4 bit CPU as shown in the schematic diagram below.

What I wish to achieve:

Add one more output register to make the CPU output a total of 8 bits
Show alphabet using the 8 bits output

My current trial:

Cout of the first IC connected to Cin of the second IC
Cascaded in synchronous fashion

What I unsure/don't understand:

Should I connect the A~D pins of the second register to ALU?
The LOAD-bar pin is connected to LO-bar of the ALU. Should I add one more LO-bar to the ALU and connect it to the LOAD-bar of the second register?


texts:
I read everywhere that there needs to be a certain voltage at the gate so that current can flow between drain and source.
But in my MOSFET (FQP30N06L) drain and source are connected and current always flows between them.
So I can drive a motor without using the gate at all.
But how do I actually switch? How do I turn the motor off?

simulate this circuit – Schematic created using CircuitLab

I'm referring to gate as 1 (the pin on the left).
Drain is pin 2 (the one in the middle).
And source is pin 3. (the one on the right).


texts: How can I use a dual 4-channel analog multiplexer independently?

texts:
I have a CD4529BCN Dual 4-Channel Analog Data Selector (datasheet).
Here is the truth table:

Here is the problem:
I have two sensors which are resistive. I want to read their voltage via a resistive-divider and a buffer. I want to switch 4 different resistors for each resistor-divider circuit.
According to the truth table (in dual mode), when I choose say resistor X1 to be attached to Z, Y1 would be automatically attached to W. But I want independent behavior.
How can I do it?
Thanks


texts: I'm planning to make a permanent arduino project that I'm not planning to take apart. Can I solder the jumper cables and the arduino digital pins together? Will that harm the project or arduino in any way? Thanks


texts:
This is the code I have for a green LED blinking every 2s with watchdog mode for MSP432.

#include "msp.h"

void main(void)
 {
     volatile uint32_t i;
     WDT_A->CTL = WDT_A_CTL_PW & 0xFF00;
     WDT_A->CTL = WDT_A_CTL_PW | WDT_A_CTL_IS_5;
     P2DIR |= BIT1;
     while (1) // continuous loop
     {
         P2OUT ^=BIT1; // Blink P1.0 LED
         for (i =6000000; i> 0; i--); // Delay with 3Mhz clock.
     }
 }

How to design Watchdog timer that reset the system if Watchdog counter is not cleared at least every 1/4 seconds?


texts: I want to use a radio shack 38kHz IR receiver to make basically an on/off switch. All I need to do is that when the receiver "sees" any signal from a remote is switch on a 9v supply on. I am trying to make a rudimentary 9v switch with as few as possible parts. Any ideas?


texts: How safe are voltage detector pens and how can I test one's safety?

texts:
I'm not an electrician and I have some basic understanding of how voltage testing pens work. I haven't had an incident with them before but I'm still quite concerned about their safety mechanisms.

I do realize there are several types of testing pens but I'm using are relatively cheap and common and look like this:

I have 2 questions:

How safe are such common Voltage Testing Pens?
How can I test the safety of those devices myself at home?


texts: Integrator and differentiator - op-amps vs. RC networks

texts:
Integrator and differentiator circuits can be made using an op-amp:

and a simple RC network:.

Is one better than the other? What are the differences between the two, if any?


texts: Increasing in slope result in increasing in impedance of BJT Early voltage?

texts:
I'm studying about the AC equivalent model of BJT and in the re model, it said that:

"As the base current increases the slope of the line increases, resulting in an increase in output impedance with increase in base and collector current"

I thought that the impedance is equal to the ro in the denominator, so base on the formula of the slope in the picture then if the slope increases, the value of ro decreases and therefore the impedance should decrease rather than increase.

Am I missing something?


texts: How Can i Protect my Oscilloscope from high voltages?

texts:
I made an oscilloscope with AT90USB series(activated ADC in micro and send data to my own program in PC via USB).I dont need more than 0-5v but you can never tell.I know I can mislead higher voltages with diodes but what if I want to reduce the every high voltages to 0-5v?
Can I set AREF pin to negative voltages?


texts: Is it possible to calculate the position of touch on a conductive thread?

texts:
I have a conductive thread of about 2 feet (0.65 m). I would like to be able to sense the position of touch.

I was hoping that the resistance of the thread would change at constant rate along the thread. Is this true?

Thank you.


texts: Rotor Current and Torque Producing Current in Induction Motor

texts:
Is rotor current of an Induction motor always same with torque producing current?
In torque equation of Induction motor, there is also one factor called rotor power factor. if rotor current and torque current are not always same, how we get current drawn by motor by vector sum of magnetizing current & torque current ? I mean rotor current may be bigger than torque producing current due to power factor and we may get wrong result if we just make vector sum of torque current and magnetiziation current.
Thanks in advance


texts: How does the AM modulated wave cancel out when the signal amplitude exceeds carrier wave amplitude?

texts:
In AM modulation, the ratio of signal amplitude to carrier wave amplitude is called modulation index as m. When m>1 i.e when signal amplitude exceeds the carrier wave amplitude the modulated wave cancels out as shown below:

Why does the modulated wave becomes zero(cancels out) when m>1? How can this be explained graphically or mathematically?


texts: Why does putting resistors between Vcc/SDA & Vcc/SCL in I2C result in a square wave?

texts:
I'm trying to understand why placing resistors between Vcc and the data/clock lines helps my waveform be square, when I'm communicating between Arduino and an EEPROM chip. If resistors are not placed in the circuit, the waves look like shark fins. The circuit still functions, but they're definitely odd-looking waves.

For background, this question arose after wiring up an Arduino to a Microchip 24LC256 (EEPROM) using I2C. Upon inspecting the signals with my oscilloscope (trying to debug something unrelated) I noticed the waves looked, well, horrible. They looked like shark fins to me (is there a more accepted EE phrase for this?). I checked several times to make sure my probe scopes were tuned/compensated correctly, and verified I didn't get such behavior on other circuits. This is what the wiring looked like:

In a chance conversation I told an EE about this -- and they said this isn't uncommon for I2C. He recommended putting a 10k Ohm resistor between Vcc to SCL, and trying a lower resistor between Vcc and SDA. Additionally he recommended reducing the I2C speed to the lowest setting (31KHz for Uno). Sure enough if I put a 10k resistor between Vcc/SCL and a 4.7k resistor between Vcc/SDA -- they look nice and square. I also lowered the speed from normal down to 31KHz but that made a much smaller (if any) impact.

Unfortunately I never got a chance to ask why! I'm a noob to electronics but I'm very curious why a resistor placed like this causes them to be better looking square waves? This photo below is after using resistors, but before picking the 'optimal' resistor values for the best looking square waves. I think it looks much better.

I looked for explanations on Stack Exchange but to no avail. These seemed (potentially) similar to my issue:
Problem with I2C EEPROM communication (his waves look similar to what mine looked like, but the answer didn't address my question)
I2C interfacing between two chips (this one also seemed fairly promising but didn't dig into the "why")
Strange I2C signals emitted from FPGA (this seemed related to something else... though similar in that her waves look "ugly")

Thanks for the help!


texts: Problems with controlling 24VAC 3way valve (with arduino)

texts:
community, your help is required on this one. I need to control opening and closing (up to 50% opening) of a 3 way valve (see pictures). I use the following hardware:

15W 230 - 24 v transformer;
Arduino DUE (the software side works correct);
LTC1665 (octal 8 bit digital to analog converter);
Regulated switching power supply on LM2596(see photos);

The idea is to control valve with 0-5V signal from DAC, the software part of the project works perfectly, I am able to get the 0-5V DC signal. The problem is that I need to power the valve directly from the transformer 24VAC connectors as indicated in the picture below:

When I do so, I am able to open and close the valve as required, but the transformer fails shortly after that. When I measured the current flow at the output of the transformer I measured 1,65A , surely the transformer fails due to overheating.

The (BAD) solution to the problem was to rearrange the circuit in the following way:

The valve now works according to the 0-5V signal and the current measured at the output of the transformer is 0.14A.

The problem is that I really need to power the valve directly from transformer, while in the bad solution I have to connect 24VAC (-) pin of the valve to GND pin of the Arduino and 24VAC (+) pin to transformer, that might cause some troubles in the future.

Any suggestions to my problem ?

Thank You.

P.S.: As I understand, when the valve is powered directly from the pins of the transformer, the 0-5V signal I'm giving from the DAC just got no reference on the valve side. The power supply thing is connected properly and it provides stable 12V DC power to the system , also the in (-) and out (-) pins are connected (checked using multi-meter).


texts: Why can’t we use synchronous counters for high clk frequencies?

texts: My professor said we can’t use synchronous counters for high clock frequencies. Is it because with many flipflops the delay becomes quite big and so the outputs change after the next triggering edge of the clock?


texts:
I have a question which I was unable to solve but it seemed trivial. I am getting a stream of characters from a processor over UART and this stream represents a JPEG file.

I captured this stream, as file.txt and can open it in (say) notepad and see FFD8...lots of data...FFD9. FFD8 and FFD9 are JPEG start of image and end of image codes and the data in between is presumably the jpeg image. I want to view this image, but the problem is that this data represents HEX characters (FFD8 for instance) but being a text file it is actually just ASCII and hence I can not open it as a JPEG.

Is there a program or a utility which will let me convert this file which contains "ASCII HEX" to true binary so I can view it as a jpeg file?

Thanks!


texts: Why can a capacitor connected to ground in a 555 astable circuit change pin 2s output?

texts:
beginner here.

Basically my question is exactly as it says in the title. I was watching a video ( https://youtu.be/qfWIjb48mjE ) about 555 timers and was wondering how the capacitor can change the voltage of pin 2.
The screenshot below is from around 8:40 in the video.

I was thinking does the capacitors energy go back into the pin? but how and why?

Thanks for any help and sorry if it is a really simple question.


texts: Is this DC instalation a dangerous situation?

texts:
At an industrial plant, we have three electrolytic cells supplied with a 6 V Rectifier (max current 10 kA).
Each of the three cells is currently absorbing ~1000 A at 6 V through 8 240 mm² copper cables (for each one).
My concern is with safety because the connection points are now reachable by operators. We are thinking on how much effort should we put into insulating and securing the instalation but I am thinking, isn't 6 V safe for any human to touch a conductor (and not being earth protected) or even grab the two poles? I know the current can be high but as far as I know a human being would not absorb a dangerous amount of current at 6 V.


texts: Simplifying Positive and Negative Voltage Divider BJT Input

texts:
I understand norton equivalent and I understand thevenin equivalent and how it can be used to simplify CIRCUIT A into CIRCUIT B.  What I don't understand is my books explanation of simplifying CIRCUIT C into CIRCUIT D.  They basically claim that Circuit B Vth is just the voltage division so that Vth=R2/(R1+R2)*(V+).  I get that, and it works if you also convert (V+) and R1 into Norton equivalent, see that R1 is now parallel with R2 and combine then, and then convert the current source and Rth into Thevenin equivalent.

What I don't get is how they got Vth for Circuit D.

My Method:

Norton Equivalent of V+:R1 and V-:R2
Parallel simplification of Inorton(1) and Inorton(2)
Parallel simplification of R1 and R2
Thevenin equivalent of Inorton and Rth to get Vth and Rth

Where am I going wrong.  My solution is in the picture below for Circuit C.


texts: Making Solenoid valve work with Arduino and TIP120 transistor

texts:
I am trying to turn off an on 12 solenoid valves using Arduino and TIP120 TO-220 Darlington Transistors NPN. I connected everything as I show in the diagram but my solenoid valve wont work since when its connected and I checked the voltage, it only shows 10.8 Volts, but when I check the voltage without the solenoid valve, it shows 11.98 volts.

I am not an Electrical Engineer and have minimal knowledge in the field so sorry if this is a stupid question. I was wondering what causes this voltage drop that prevents solenoid valve from working. Also what is the role of the resistor here and am I using the correct one if its needed ?

I will provide the links for all the parts in case if it is needed.
TIP transistor

Solenoid Valve


texts:
I plan to use the  MAX1555 chip

The chip output a logic bit to indicate if current is pull from the charger ( POK pin- Chip 1551 , CHG pin - chip 1555)

The datasheet talk about the low state, being around 150-300 mV.

What is the HIGH level voltage? I need to know because I implement a little circuit that ligh led 1 when current is pull and light led 2 when the device is done charging.

That HIGH level will affect my inverter and MOSFET choice.


texts: Derivation of electric field intensity for Line charge

texts:
These snapshot is taken from Principle of Electromagnetics by Matthew N.O. Sadiku.

In this derivation I don't understand the highlighted step. In previous step we are defining a position vector R from element dl to point in space (x,y,z) which is equal to xax + yay + (z-z')az , this position vector is defined for a unique point.

However in the next step we are defining same position vector in cylindrical coordinate but we are defining only two cylindrical coordinate and \$ \phi \$ coordinate is missing. I know that Electric field intensity will be constant for all values of \$ \phi \$ for a given value of z. But I think position vector should be directed toward a unique point in space. Can anyone justify why we are not defining \$ \phi \$ in the highlighted step?


texts: What is ADC Supply Current in Microcontroller and how much current will a GPIO take

texts:
I am having this Microcontroller

In this Microcontroller, I am using the ADC peripheral and normal GPIO port.

My questions:

On Page 58, table 42, There is a parameter called as Supply Current per ADC which is mentioned as 1mA. What does it mean? It also mentions that it depends on the conversion rate.
Does it mean, if I connect a voltage (within the mentioned limits of the pin) with a series resistor to that ADC pin, that pin will consume 1mA?
So, if I connect two ADC inputs to the ADC peripheral, it will consume 2mA?
Suppose, I configure a port as Input port. How much maximum current will the Microcontroller pin draw?
Injection current will come only when I impress a voltage above that the supply voltage of the GPIO. And Leakage current, will come into picture only when the device is operating in low power state or shutdown.
So, If I donot use the microcontroller in the above two conditions, (applying voltage to the pin within limits and in normal working mode), how much will the microcontroller pin take for a normal GPI input?
This Microcontroll has two supplies. ADC Reference supply high and ADC Reference supply low? Usually, I have seen only ADC reference supply as a single reference supply pin. But here, there is reference high and reference low? Any idea on why is this implemented and any use case of it?


texts: Generating Electricity Using a Steam Turbine and Small Motor

texts:
I have started a project where I intend to use a Small steam turbine to power small devices in the wilderness. the goal of producing usb standard 5 V and 2 A to 4 A current.

Here is the turbine: http://www.microcosm-engine.com/live-steam-turbine-engine-jti-p-131.html#.WJ_x3FUrJdg

I have seen the engine power a prop in water quite well... and 60 W worth of lights.

The turbine does not have as many specifications listed as I would like.
but it does seem enough for the generation side.

What I am not sure about is what I should use to convert the mechanical energy into electrical.

I think that perhaps a good brushless RC motor with a low kv rating would do the job. Of course, with those, I have to estimate output based on Max ratings and whatnot because they do not intend these things to be generators.

here is a motor i am considering:
https://hobbyking.com/en_us/multistar-elite-3508-268kv-high-voltage-endurance-motor.html

this motor is 268 kv which means it should produce 1 V per 268 rpm less some efficiency.
it has max of 11 A and max 330 W output.

There are a number of these motors in so many sizes and shapes. I can only assume I want a low kv motor to have the most headroom in using rpm to create volts (and they seem to have higher amp limits too).

What I don't quite understand is how the current comes into play. Amperes are resistance based?  These motors are rated for max current, but they list "No Load Current" ...basically just spinning without a prop, I believe. I don't understand how the current is generated by the motor.

And then converting the power. Say I produce 10 V at 1 A ac.  Can I convert this into 5 V at 2 A dc?  (what if its 20 V at 0.5 A) etc. etc.

Can I just feed the AC into an AC/DC charger (phone charger wall-wart) and it will be ok using the less than 120 V feed?

Im a bit confused even after looking at all the circuit diagrams. They are almost all aimed at a battery making power for a bulb but not the other way around.


texts:
I am new to Embedded systems. I am starting my learning with AT89C51.
My first target will be LCD interfacing.

I have a programmer an LCD and a microcontroller.

But the program is written in C or assembly language and I need a .HEX file to burn.

How do I do this?
I have also heard about Keil IDE but its evaluation version is not working.
Please help me with any additional information.


texts:
i am trying to read quaternion's out of the BHI160b, that's why i purchased the BHI160b shuttle Board from Bosch. I want to connect it with my NUCLEO-L053R8 from STM. So i implemented the library into my STM project. The next step was to figure out how to use the HAL_I2C functions to communicate with the sensor. I changed the read/write operations in the driver's file bhy_support.c like this:
uint8_t GTXBuffer[256];

int8_t SensorAPI_I2Cx_Read(uint8_t slave_address7, uint8_t subaddress, uint8_t *pBuffer, uint16_t ReadNumbr)
{
uint16_t DevAddress = slave_address7 << 1;

// send register address
HAL_I2C_Master_Transmit(&I2C_HANDLE, DevAddress, &subaddress, 1, BUS_TIMEOUT);
HAL_I2C_Master_Receive(&I2C_HANDLE, DevAddress, pBuffer, ReadNumbr, BUS_TIMEOUT);
return 0;
}

int8_t SensorAPI_I2Cx_Write(uint8_t slave_address7, uint8_t subaddress, uint8_t *pBuffer, uint16_t WriteNumbr)
{
uint16_t DevAddress = slave_address7 << 1;

GTXBuffer[0] = subaddress;
memcpy(&GTXBuffer[1], pBuffer, WriteNumbr);

// send register address
HAL_I2C_Master_Transmit(&I2C_HANDLE, DevAddress, GTXBuffer, WriteNumbr+1, BUS_TIMEOUT);
return 0;
}

I connected the Shuttle Board to my NUCLEO board like this:

___J1___|___NUCLEO___
   1/2  |    3.3V
    3   |    GND
   17   |    PB7 -> I2C1_SCL
   18   |    PB6 -> I2C1_SDA
   21   |    PB5 -> DI/BHI160_INT

In my main loop i startet to initialize BHI160 Sensor with the function bhy_initialize_support();:
int main(void)
{
  /* MCU Configuration--------------------------------------------------------*/

  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_I2C1_Init();

  /* USER CODE BEGIN 2 */

  bhy_initialize_support();

  /* USER CODE END 2 */

  while (1)
  {
        if(HAL_GPIO_ReadPin(Button_GPIO_Port, Button_Pin) == 0)
        {
            //HAL_GPIO_WritePin(User_LED_GPIO_Port, User_LED_Pin, 1);
            GPIOA->BSRR = (1<<5);
        }
        else
        {
            //HAL_GPIO_WritePin(User_LED_GPIO_Port, User_LED_Pin, 0);
            GPIOA->BSRR = (1<<21);
        }
    }
}

When my programm jumps into the function it checks the product_id of the sensor and returns *            return BHY_SUCCESS;* which means that the I2C connection is working!
Bosch also provides some example code for different sensor readings here.
Because i want my rotation data in quaternion's i looked at the rotation_vector_example.c example.
There are two functions static void sensors_callback_rotation_vector() and void demo_sensor(), but i cant get this code to work. I am not sure how to use this two functions to get continous data readings from the sensor. Maybe there is an other way to use this driver? In the documentation they say that the driver helps you in 3 phases to read out data: initialization, configuration and data readout. But i cant figure out how to actually do it!


texts: As we know there are companies that make cheap and bad stuff and there are others which make good stuff i.e. tested and with warranty. Is there a certified way such as ISO stamps to check for the  quality? What do they tell us about the product?


texts:
I'm driving four N-channel MOSFETS (IRFLIZ44N) with a HIP4081, and the circuit looks like the following:

The MOSFETS are driving a peltier module, and the input pins of the HIP4081 are being driven by an Arduino microcontroller. The connections are similar to the ones incorporated by Open-Source Motor Controller, and following is the associated truth table:

However, I'm facing a problem in case of "Direction 1". I'm not receiving stable PWM pulses from the output of the H-Bridge Driver.

Probing the input BLI and AHI (which are supposed to be LOW), I get the following signal:

At "direction 0" however, I get a very clear PWM signal output from the IC. I'm not sure how exactly to go about troubleshooting this.


texts: For an Ideal transformer where permeability of the iron is infinity, why is the excitation current 0 if the secondary winding is open circuit?

texts:
I have read this question Why is the Exciting Current zero in an ideal transformer?. However I don't quite understand where his initial equation for the excitation current came from.
Can someone guide me though the process step by step from a lower level, starting from the moment a voltage is applied?

My intuition tells me that when a voltage is applied, a current will begin to flow, causing an induced magnetic field in the coil. However, since the permeability is infinity, that will result in an infinite B field, and an infinite flux.(this is apparently not true, and I am quite confused)


texts:
I am preparing for an exam and I am not sure if my solution is correct for this problem:

  We have a differential amplifier with 2 NPN transistors (T1, T2). T1's
  collector is directly connected to the power supply \$V_{CC}=15V\$,
  while T2's collector is connected to the output and \$R_C\$. T2 base's
  potential is constant \$V_2=-0.5V\$. After changing \$V_1\$ - T1
  base's potential - to \$V_1=0.5\sin(2\pi1000t)-0.5V\$, the peak-peak
  voltage of the output signal is equal to \$1V\$. Transistors' emitters
  are connected to \$R_E\$, which is connected to power supply
  \$V_{EE}=-15V\$. \$I_E=0.5mA\$

  Draw the circuit
  Calculate values of \$R_E, \ R_C\$
  After changing \$V_1\$ to \$V_1=0.01\sin(2\pi10t)-0.5V\$, calculate the maximum and the minimum value of the output voltage and draw the
  output signal
  Calculate T2 collector's potential, if we change \$V_2=-2V\$

1.

No. 2

\$V_{diff}=V_1-V_2=0.5\sin(\omega t)-0.5-(-0.5)=0.5\sin(\omega t)\$
We know that \$A_{ in}=0.5V > 50mV\$, hence we knot that the maximum difference \$\Delta U=I_E\cdot R_C=1V\rightarrow R_C=\frac{1V}{0.5mA}=2k\Omega\$.

If we change voltages to \$V_1=V_2=0V\$, then we can easily calculate \$R_E\$:

\$0-0.7-I_E\cdot R_E=V_{EE}\rightarrow R_E=\frac{-V_{EE}-0.7}{I_E}=28.6k\Omega\$

No. 3

\$V_{outMAX}=V_{CC}=15V\$

\$V_{outMIN}=V_{CC}-I_E\cdot R_E=14V\$

and output voltage will oscillate around \$14.5V\$

Circuit's gain is \$G=-\frac{g_m R_C}{2}=-10V/V\$

So, I think, the output voltage is \$V_{out}=14.5-10\cdot0.01\sin(2\pi10t)V\$

No. 4

\$V_{in}=V_1-V_2=0.01\sin(2\pi10t)+1.5V\$

I don't know, maybe \$V_{out}=14V\$?


texts: Estimating the Capacity of Charged Used Li-ion Cells:

texts:
I acquired 6 used li-ion cells 1 year ago.  Since I wanted to know for certain how well the cells would hold a charge after 1 year, I conducted an experiment.  I recently tested the cells.  Below is some data related to my testing:

Charger info:
 Voc = 5.25 (Open circuit Voltage--no cell in charger)
Imax = .68A (max charge current=680mA--no cell in charger)

Cell Info:

Manuf:  Panasonic
   Id:  CGR18650CE
    V:  3.6 (nominal)
  mAh:  2150 (typical capacity when fully charged)
+Chrg:  CC=1.43A (max), 4.2V (max)     // "+Chrg"=Charging
-Chrg:  CC=2.04A (max), cut-off @ 3V   // "-Chrg"=Discharging

Notes:
- All cells were charged at a CC=.68A to a CV=4.2V.  Charging was cutoff when the charge current reached .01A@4.2V
- The resting V of all cells after 24 hrs was at least 4.05V.

Here are the cell measurements after 1 year of resting:

Cell V___ A___ VA(W)  Est mAh (i.e. VA/3.6*1000)
1    4.16 3.29 13.67  3802
2    4.01 3.23 12.95  3598
3    3.95 3.18 12.56  3489
4    3.85 3.09 11.90  3305
5    3.95 3.17 12.52  3478
6    3.77 2.95 11.12  3089

The multimeter was verified to be operating properly using a bench power supply.

We can see from the data that some cells held their charge better than other cells. My question is, how can the cells have such a high capacity when the datasheet indicates their capacity is 2150mAh? I know the cells are at least 5 years old.  I also realize that my estimated mAh capacity is not based on actual discharge tests, but is there some other way of estimating the capacity of such cells using a multimeter & a bit of math?


texts:
The HC-49 xtal is an 8 MHz crystal, and the radial crystal is an RTC 32.768 kHz crystal. C11, C12 are 22pF, and C13, C14 are 18pF.

The traces go directly into a micro (a PIC24F.)

I tried to follow Microchip's guidelines on this, but they advised using surface mount xtals and talked about "guard rings" which are alien to me.


texts:
For a project I need to design a dual H bridge to drive two motors with the specs provided below:

Output speed: 150±10%rpm
No_load Current: 200mA (Max)
Stall current: 4500mA(max)
Stall torque: 9.5kgNaN
Rated speed: 100±10%rpm
Rated torque: 3000gNaN
Rated Current: 1200mA (Max)
Noise: 56dB
Working voltage: 9V
Outside Shaft Length: 14.5mm
Shaft End Play: 0.05-0.50mm
Screw Size： M3.0
Dia. Of Shaft phi4mm, D3.5
encoder: 2 pulses/circle

We will be over driving the motors at 12V instead of 9V.(Marked as Vcc on the schematic)
The logic chips are powered by the Vcc pin which is coming from the header which will be either 5 or 3.3V, but the ground is shared across logic and power sections. The choice of mosfets isn't finalized but they will be sufficiently rated for the job(Currently considering IRF4905 for the high side and IRFZ44N for the low side).
I've already designed an H bridge with a lot of safety features and logic circuit to prevent shorting out the mosfets, but I thought I share the design with you ... maybe someone finds a flaw or recommends some better components that I can use. Here is the schematic diagram of the driver:

https://easyeda.com/editor#id=|83f5fc53d367464aa14022658cb7057f
Edit: Please just comment on my design and don't go off topic. It's not about buying an off the shelf bridge with better design, we are doing a robotics project for fun and would like to build everything ourselves.


texts: What role does this diode play in this reverse voltage protector circuit?

texts:
I have been trying to understand this schematic, which is I believe intended to be provide reverse voltage protection.  I understand most of the aspects of this.  The basic idea is that D3 allows current to flow in the proper direction, which then will turn the mosfet M1 on.  The mosfet will then provide a lower-resistance path for the majority of the current in the system to flow through.  The zener diode D2 and resistor are there to allow for a wider range of input voltages while keeping within the mosfet's gate-source voltage tolerance.

What I don't understand is why D1 would be in the circuit at all.

simulate this circuit – Schematic created using CircuitLab

A few notes about this schematic. The 24V voltage source is intended to be input from an external voltage source, and VCC and GND labels are the effective voltage source for the rest of the board.

I found this schematic in the open source Smoothieboard's design, which can be found here for further reference https://github.com/Smoothieware/Smoothieboard.


texts: Is a snap on ferrite bead suitable for USB Arduino programming and charging

texts:
When I connect a 3 foot USB cable at the "micro B" end into my Arduino board (Adafruit Feather 32u4 with the ATmega32u4 3.3 volt chip) sometimes the system malfunctions and subsequently resets. The symptom of the malfunction is that the LCD graphics is messed up. "Sometimes" means less than 10% of the time.

This was observed in a cold plug situation where the "standard A" end was loose. It was also observed when the standard A end was connected to a cellphone wall charger. In a programming situation where the standard A end is connected to a computer it is uncertain whether this was observed.

I noticed most of my USB cables do not have ferrite beads. They are mostly cellphone charging USB cables.  I have one USB cable with a ferrite bead but it is not suitable for Arduino use because it has a "standard B" end.

This is what Wikipedia says...

  Ferrite beads are one of the simplest and least expensive types of
  interference filters to install on preexisting electronic cabling. For
  a simple ferrite ring, the wire is simply wrapped around the core
  through the center, typically five or seven times. Clamp-on cores are
  also available, which attach without wrapping the wire: this type of
  ferrite core is usually designed so that the wire passes only once
  through it.

This description suggests there is a difference between a built-in bead and a "clamp-on core" but I do not know how to assess whether this difference is important.

Should I buy a snap on ferrite bead for my purposes or should I simply replace the cable with a proper ferrite USB cable?


texts: SVPWM: Does setting modulation index to 0 still consumes power?

texts:
I've implemeneted a 3rd harmonic injection SVPWM (Space Vector PWM) scheme and it performs quite well. One peculiarity i have noticed was, when i set the modulation index to 0, the motor stops as expected but after leaving it like that for a couple minutes the H-bridges (Infinieon IFX007T)  on my custom 3 phase inverter board got quite hot - okay to touch but still you wouldnt want to keep your finger on it for too long..

The modulation index at 0 corresponds to all 3 PWM duty cycles being at half the max value. In essence that should be "zero power transfer" but the H-bridges getting hot clearly indicates a power transfer and considering you can measure the current at this state ( when the motor is running ) got me wondering.

A quick "hack" would be just manually setting the duty cycles to 0 or shutting down the inverter entirely but i would like to know the inner workings behind it and if thats normal behavior.

TLDR; Setting modulation index to 0 returns duty cycles that are half the max duty cycle. Would it be ok to leave the motor like this for hours or would it still drain some power ?


texts: Can anyone help me to identify that pin connector? It's exactly 20 mm and got 20 pins. (It's used from Battery Management System to battery cells.) Thanks.


texts: Phase Cut to Control Speed of AC Induction Motor with Arduino

texts:
simulate this circuit – Schematic created using CircuitLab

So I'm trying to speed controlling a single phase AC Induction Motor(For Fan). And I am trying to use phase cutting to control it. So I use arduino to detect zero cross of AC Wave, and then cut the wave with triac, also I am adding a snubber circuit. But I can't reach 90% of the speed, and when I try to set the speed to 50% the motor goes humming.

What is the cause that I can't reach 90% of the speed and why the motor goes humming when 50%? Also, is there another available option to control single phase AC induction motor using arduino? I already try to search about VSD/VFD but after some google searching it won't work with a single phase(only 3-phase motor).

For the diagram, all ground in schematic is arduino ground, and voltage source is from the same source.

int AC_LOAD = 3;    // Output to Opto Triac pin
int dimming = 128;  // Dimming level (0-128)  0 = ON, 128 = OFF

void setup()
{
  pinMode(AC_LOAD, OUTPUT);// Set AC Load pin as output
  attachInterrupt(0, zero_crosss_int, RISING);  // Choose the zero cross interrupt # from the table above
}

//the interrupt function must take no parameters and return nothing
void zero_crosss_int()  //function to be fired at the zero crossing to dim the light
{
  // Firing angle calculation : 1 full 50Hz wave =1/50=20ms
  // Every zerocrossing thus: (50Hz)-> 10ms (1/2 Cycle)
  // For 60Hz => 8.33ms (10.000/120)
  // 10ms=10000us
  // (10000us - 10us) / 128 = 75 (Approx) For 60Hz =>65

  int dimtime = (75*dimming);    // For 60Hz =>65
  delayMicroseconds(dimtime);    // Wait till firing the TRIAC
  digitalWrite(AC_LOAD, HIGH);   // Fire the TRIAC
  delayMicroseconds(10);         // triac On propogation delay (for 60Hz use 8.33)
  digitalWrite(AC_LOAD, LOW);    // No longer trigger the TRIAC (the next zero crossing will swith it off) TRIAC
}

void loop()  {
  i = 90;
    dimming=i;
    delay(10);
}

I got this code from http://www.alfadex.com/2014/02/dimming-230v-ac-with-arduino-2/ and I just modify the loop so I can get a constant speed. I give i = 90, so I can get approximately 70% of the speed( 90 / 128 ).
Thanks!


texts: LM317 maximum resistor/pot - Current regulator - Reference voltage

texts:
Here is my circuit design. Are there any problems here?

Here are my questions:

1, I notice that R1 is either 120 or 240 ohm in the datasheet. Is that because of the 1.25v reference voltage, and the LM317 requires a minimum 10ma/5ma to operate? (1.25/240=5ma; 1.25/120=10ma)

2, Which resistor should I use? 120 or 240? Is 240 the maximum value for R1?

3, With 240 for R1 and 5k for R2, I get 25v with this calculation, 1.25/240*5000=25v; but with the Vout = Vref (1 + RL/RH), I get 27v. which one is correct?

4, For the pot, or R2 here, Is its value limited to 5k and lower? ( I don't have low value pots. 10K and 50K are all I got, and my test showed very bad voltage range with 10k.)

5, From my circuit above, is there a 6v drop across 2 LM317? so to get 10v output, I need at least 16v.


texts:
So my system needs 120 V and 12 V. And I'm trying to avoid having 2 input plugs for my system.

Thus, I'm looking for a dual power supply that splits 120 V input (wall plug) into 120 V and 12 V.

Are there any dual power supply that splits input voltage to 120 V and 12 V?

If there is no such a thing, how could I feed my 120 V system and 12 V system with one input plug?


texts: Is the transformer working and possible identification

texts:
Unfortunately 2 nights ago, my 120V stereo was plugged into a 220V socket directly.
(I'm just about talking to the offender again).
The stereo now ceases to function more or less

Radio, tape player, amplifier and lights not working
Only the record platter turns (I know the record player is 120V).
There was a burning chemical smell afterwards.

Unfortunately I have being unable to track down a service manual or schematic for the stereo. So I don't know what is supplied by the transformer inside...but as the record platter and tone arm continues to function, I'm wondering if the transformer is step down and powers the radio, tape player, amplifier and lights. This is my theory as of now anyway.
The transformer...

It's labelled as AC-159C (but I cannot find any reference to this on the Internet).
There are 2 wires (both white) on one side which I am assuming are the input wires.
There are 5 wires (2 x red, 1 x black, 1 x green and 1 x yellow) on the other side which I am assuming are the output wires.
I've been unable to find any specifications on it or the stereo so I'm not sure what the voltages should be.

So my 2 questions are...

Can anyone identify the transformer?
There is no resistance measurement between the two white wires. Is my transformer working? Or are there other tests I should perform? (details of testing below).

Transformer test: I removed the transformer from the stereo and tested the resistance between all the wires.

White -> White = No measurement (Open circuit I assume)

White wires to all other wires = No measurement (Open circuit I assume)

Red (#1) -> Red (#2) = 3ohms

Red (#1) -> Yellow = 2.2ohms

Red (#1) -> Green = 3.2ohms

Red (#1) -> Black = 3ohms

Red (#2) -> Yellow = 2.1ohms

Red (#2) -> Green = 3.2ohms

Red (#2) -> Black = 3.2ohms

Yellow -> Green = 1.6ohms

Yellow -> Black = 0.9ohms

Green -> Black = 1.9ohms


texts:
I'm wanting to start my own lab at home so that I can learn things faster than uni teaches (we're not allowed into labs unless we're in our own lab).

A friend said that I'd be better off getting a power supply than a function generator, since I'm a first/second year elec student because he thought they'd be cheaper, but there's only about $50 difference between the two.

I'm actually wondering whether it would be a good idea to get the Rigol DG-1022, and to supply a dc source, I set the frequency as close to zero as possible. Of course, electricity is dangerous; while I'm cool with blowing an LED or op-amp, I'm not at all happy to assume that a mock dc supply is actually direct current, without first checking if this is safe.

Wondering what you think? I'm not just asking about safety, if you've got other comments, I'm happy to hear them.


texts: Constant values read from LIS3DSH Accelerometer

texts: I'm working with the board STM32F4DISCOVERY from ST microcontrollers. I'm trying to read acceleration on the 3 axes from the accelerometer LIS3DSH via I2C communication. The code is working on one board, but on another one, I constantly read the same constant values, even though I'm moving the accelerometer (turning it around, for instance). Does that mean that the accelerometer does not work properly ? Is it possible that the component have been damaged by a connection to an external supply voltage of 5V on the STM board ? If not damaged, is there a way to reset the module and get the corrrect values ? (datasheet of the component) Thanks in advance


texts: Crystal Oscillator not giving correct frequency

texts:
I have a 48MHz Crystal Oscillator (see here) that I am using as a clock for my microcontroller (EFM32GG332F1024). Looking at the datasheet for this crystal it seemed to me that the load capacitance is to be 18pF, I have taken this to meaning that I should have an 18pF capacitor from each pin to ground, however, I am not entirely sure if that is the correct thinking.
A diagram below shows my meaning:

Doing some reading around I have found a calculation to work out the load capacitance for each pin but this gives me a value of 30-36pF once I have entered all the known values and to me this seems too high of a value to use.
\$C_{L1}=C_{L2}=2\cdot(C_{Load}-C_{Stray})\$
Where \$C_{Load}=18pF\$ and \$C_{Stray}=2-5pF\$

The problem that I am having is that instead of the oscialltor outputting a frequency of 48MHz as expected, it is only outputting 16MHz, precisely a third of what it should be, and I am not entirely sure why this is.
I have tried changing the crystal, changing the load capacitance, both up and down, and nothing appears to have an effect on the output frequency.

I am not entirely sure of what is causing this issue or how to fix it as the capacitors appear to be doing nothing which is unexpected, so if anyone has any ideas about this problem, please feel free to give advice/ solutions.

Something useful to know might be that I am measuring the frequency with a x100 probe on a digital oscilloscope by measuring from one of the crystal pins to ground. Neither of the pins give the expected reading so I feel at the moment it is irrelevant which one is which. I think I am right in saying that the crystal has no polarity as it is just a two pin device that can be seen from the link at the beginning of this post.


texts: How can I power 7 IL151 5mm Clear White LED leds for a sculpture in a series circuit?

texts: I am in the midst of planning a sculpture. The sculpture will require 7 IL151 5mm LEDs with a forward voltage of 3-3.5v . I have NO experience in electronics and I've been looking around and people have stated that a series circuit would be best for most LED projects. Now since the type of circuit I'm using would require a voltage equal to the voltage of all the LEDs, I would need a power supply of 21-24.5v (if I'm correct). Now how exactly should/could I power these? I don't think I can exactly power these would an obscene amount of batteries. I was wondering if I could use a DC power supply but how could I do it if it were possible. I would really appreciate any help I can get.


texts:
I have make a full wave rectifier and aimed to obtained +9V, -9V and +5V DC from an AC transformer (I have  diplayed output of transformer only as AC1 and AC2) as i have shown below.

However, when i connect the +5V output and +9V output together, i have observed a significant decrease on the voltage level on both. I am condisering to change the configuration like one below. Do you think this will overcome the voltage level decrease problem? Thank you.


texts: What free tools are there to simulate RF circuits?


texts:
For the short circuit test of a 3 phase transformer (star-star connected) I am given ( or have already calculated from previous questions) $$I=9720 A\\cosφ=\sqrt 2/2\\P=300kW\\R=0.001 (phase)$$I am asked to find the leakage reactance of the transformer. I started by finding the apparent power from cosφ $$P/S=cosφ=>S=\sqrt 2P$$Then S for any phase is $$\frac{S}{3}=\frac{V}{\sqrt 3}I=>V=\frac{\sqrt 3S}{3I}$$ And now I can find the total impedance Z $$Z=\frac{V}{\sqrt 3 I}=0.001496$$ Finally for the leakage reactance $$X=\sqrt{Z^2-R^2}=0.00111$$

The solution manual did just one calculation for all this. $$\tanφ=\frac{X}{R}=>X=0.001$$

How is this true and what have I assumed wrong in my calculations and the result is different?


texts: Can a faulty motor cause issues to another motor?

texts:
This is regarding the circuit of my 3D printer mainboard.
I had an obersvation: It has a cooling fan (40X10 24V) which is having issues lately - it stops working sometimes, and when pushed to rotate, spins back.
Now one of the stepper motors (NEMA 17 ~3.5kgfcm) in my core XY has been malfunctioning, where it misses rotation sometimes out of the blue, which shifts the whole print. I thought this is due to the driver limiting the current to the motor, so I rotated the screw terminal clockwise a bit more to allow more current for the motor. This works fine for a while, but the problem comes back.
Now, I also noticed a few times that this issue occurred when the cooling fan for the drivers stopped working.
Can the stopping of the cooling fan cause the stepper motor to falter?


texts:
I've been working on a model maglev train as my Grand Hobby Project; something around the H0 scale.

The initial idea was to use the Inductrack mechanism to keep it simple. To summarize, a Halbach array of rare earth magnets produces current in a conducting track, which in turn generates a repulsive force. Unfortunately the theory doesn't scale well downwards; either you have to go really fast (Mach 3) or need 3 cm of copper to drive the resistance down.

My current plan is to keep the array, but manage the currents in the track actively. Back-of-the-envelope calculations indicate I can get satisfactory lift with 2-3 amps, and I can even use PCB with 1 mm traces as the track without turning it into a hot plate.

However, that's still a respectable current where I come from, and the load is on the order of milliohms. I have no idea how to build a circuit that can drive those currents without blasting 99% of the energy in a sense resistor.

Other "requirements" are reproducibility and ease of setup. If I have to tweak a trimpot or solder 10 components for each trace in the track to get the forces to balance out, this thing will never get done. Optimal solution would be some off-the-shelf voltage-controlled IC.


texts:
I recently purchased a used IEC Centra centrifuge with a refrigeration feature. Works great, except the refrigeration condenser never cycles off and as a result the chamber gets down to the minimum reading of -10C no matter what I set the target to. I've deduced through testing that the thermocouple works fine and it still manages to get extremely cold (I actually had a sample almost freeze) so I'm assuming the actual refrigerator coil is sufficiently charged and all.

I pulled the temperature controller board tonight and figured that it was probably an issue with the relay to control the condenser. Datasheet for the relay is here. I wired a lightbulb to the AC output and noted that as soon as line voltage was applied the lightbulb came on even though I had not connected anything to the DC side of the SSR. Am I correct in assuming that this means the relay is shorted and I should begin by replacing it? I have never verified if an SSR is working before.

Thanks


texts:
I am in the middle of trying to wrap my head around basic electronics. I understand the concepts of voltage, amperage, and resistance, however I'm confused about how heat is generated and related to these three things. These are my assumptions and questions:

When you plug an appliance into a 120 V wall outlet, some amount of amperage will run through the wire depending on the amount of resistance in the circuit (I=V/R, where the voltage is a constant 120 V). Resistance in the circuit depends on the material resistivity and the length/shape of both the wire and appliance.
The difference between a high amperage appliance (like a refrigerator or space heater) and a low amperage appliance (like a light bulb) is the resistance in the circuit. A light bulb draws less amperage because there is more resistance. In other words, resistance is used to control the amperage drawn by an appliance. The appliance is intentionally made to have the right amount of resistance so as to draw the right amperage.

Is this assumption correct?

More resistance creates more heat. This is due to the electrons bumping into the atoms in the material they are moving through. I kind of envision this as being like having more friction, so therefore more heat. This is the reason a frayed wire can heat up and cause an electrical fire.

Does this mean that since a light bulb has more resistance than a space heater, it is more likely that it can heat up and cause an electrical fire? Are small appliances therefore more dangerous than large appliances due to their higher resistance?
Does current in itself create heat? So when you reduce resistance and therefore increase current, does more heat get produced (although heat due to resistance decreases)? Conversely, does increasing resistance (e.g. fraying a wire) also help it cool down since current is reduced?

Any explanations would be greatly appreciated.


texts: Does a secure erase on a SSD with lots of free space cost less P/E cycles than an SSD that's almost full?

texts:
Doing an ATA Secure Erase on an SSD should reset all of the cells to factory condition, which results in a program/erase cycle on cells at least in blocks that contain data.

On self-encrypting drives, a fast version of the secure erase regenerates and replaces the encryption key, and then it marks all blocks as unused so that they can be erased later before using. This seems like it should cost a P/E cycle only on used blocks.

When doing a secure erase, do typical SSDs typically attempt to reset all blocks, or do they reset only used blocks, saving P/E cycles on the blocks containing no data?


texts: Calculating RMS current from AC712 chip (AC system)

texts:
I have read several articles with code examples on how to calculate the actual current with a ACS712 chip with AC involved. I understand what RMS is and I feel like I am able to implement it myself. However I first started with copying code that was supposed be usable with a 5A ACS712 chip. The results were really disappointing and the values returned were far from what my Ammeter returned. Ultimately I decided to implement it myself and I ended up with the following code:
values.emplace_back(std::pow(value - 512.0f, 2.0));
if (values.size() == UPDATE_RATE) {
    const auto n = values.size();
    const auto sum = std::accumulate(values.begin(), values.end(), 0.0f, [&n](const auto& cur, const auto& next) { return cur + next / (float) n; });
    values.clear();

    const auto rms = std::sqrt(sum);
    std::cout << "RMS: " << ((rms / 1024.0f) * 2500.0f) / 185 << std::endl;
}

The values are read from an Arduino and value is essentially the result of analogRead(A5) where the ACS712 is attached to. I am using an ACS712 chip that supports -5A to 5A therefore the / 185 as the 5A chip has a resolution of 185 mvA. I divide by /1024 because analogRead returns values between 0 and 1024 and I multiply by 2500 because the ACS712 has a range of 5000mV - thus mapped to [-1, 1] it has to be multiplied by 2500.
I was wondering, is what I am doing reasonable to measure AC current with an ACS712 chip? My results are reasonable, I get values around 130mA for an utility that according to the Ammeter uses 130-140mA.


texts: Should the thermocouple wires be insulated against a metal shaft

texts: I am working on a project where I am using Omega bare TC. Its just two wires welded at the tip. I am using MAX6675 coupled with an Arduino. Should one of the two leads be insulated? The bare thermocouple will be inside a metal shaft. Now I am worried if there will be a short circuit.


texts: signs of complete PCB photo-resist development

texts:
Currently. I'm making a PCB using the photolithographic method (print on transparency, expose with UV which works, then develop under a bright red LED as the only light source), but half the time, the developing stage is not perfect. I find this out when etching the board is about 5% complete. I then re-develop the board. This is even after I sanded the photo-resist layer off of a small corner of the board (before exposure) to give me an idea of how the background should be after the removal of the unwanted photo-resist.

I'm using 1 part standard sodium hydroxide developer to about 10 parts water and the liquid is greenish since I use the same mix for multiple boards, and it takes two minutes to development to (roughly) complete, but I cannot use time as a factor to development completion.

Rather than having to re-develop the board to get it perfect, what other signs should I look for on the board to indicate completion of photo-resist removal? and would it be a benefit if I used a different colour light source to make the signs I need to look for more visible?

I want to avoid colours which would make the photoresist react (such as the exposure light color purple).


texts:
I want to connect 5 of pcf8574t on my AVR ATMEGA32L. One for LCD 2x16 and 4 for general purpose I/O. The question is: if i get an interrupt signal from one of 4 chips, how can i know which chip has send the interrupt?

I think that circuit may be usefull to apart interrupt signal.

This circuit x4 times (one from each PCF8574T chip). "mcu Interrupt pin" connected together to AVR Global Interrupt pin, such as INT0, or INT1. "PINx mcu" pin, connected seperate to a GPIO pin of AVR such as PB7, PB6, PB5, PB4. and "PCF INT OpenDrain" connected also seperate to INT pin of PCF8574T.

but i don't know if this circuit it's working 100% .


texts:
Problem:
I have built a wooden model of a lighthouse.  I want to make the light in the house flash.
I am can use a soldering iron.  I have no circuit experience.

Question:
How can I build a simple circuit with the following requirements?

9 V battery (or AA, just not C or D size)
bulb could be anything like a Christmas tree light bulb or bigger.

The resulting circuit and battery will fit into a 2" x 2" box that the light will screw into.

It has been suggested to use LED flashers, but how can I control the speed of the flash?

This looks like the right speed to me:


texts:
I'm creating a new project that requires a LiPo to be charged from USB, the circuit can then be powered from either the LiPo, USB or an external Voltage (don't know which will be available at any given time). Charging should however only be done from USB. My setup at the moment uses Schottky diodes to switch between these sources leading to the voltage regulator. The system uses fairly little current but the diodes will still have a voltage drop associated which I would like to minimize. (Zeners on the schematic should be schottky diodes, Kicad doesn't seem to have the symbol)

I'd appreciate some critique and suggestions about this configuration and any ideas would be appreciated.

MCP1802 LDO Data sheet

MCP73832 - LiIon/LiPo charger - selector guide - page 16


texts: Estimate minimum current draw for a device

texts:
I'm trying to sum up the minimum current draw for all devices fed by a buck converter in order to determine the necessary inductance value. The max current is typically easy to find on datasheets, but I'm having trouble getting values for minimum current. For instance, the datasheet for the LTC2292 ADC specifies a max current of 95mA and a typical current draw of 78mA, but leaves the min column blank. I could play this safe and take of min current of 0A, but that heavily constrains the inductance value I can use and seems very unrealistic. Is it safe to take the typical value as the minimum current? Or, is there some other way to estimate this?

EDIT:

I'm seeing multiple answers to the question of how to choose an inductor for a buck converter use a 10% rule, where the current in question seems to be max current, although is not always specified. For instance, this answer explicitly states 10% of max current and this other answer also uses 10%, but does not explicitly state whether it is in reference to max current or typical current. Is it safe to use 10% of either max or typical current for choosing the inductor, rather than worrying about the actual minimum current draw?


texts:
I was ordering some resistors online, and I saw that 0 Ω resistors have a power rating. Why is that? Power through a resistor is calculated with the equation \$P = UI\$ or \$P = RI^2\$. Since \$R = 0\ Ω\$, \$P=0\ W\$.

According to this post (How to calculate Power Rating for Zero Ohm Resistors?), a 0 Ω resistor has no power rating... But Farnell tells me the opposite:


texts: What's the source of this noise in my Arduino oscillator?

texts:
I've been experimenting with techniques to rapidly switch on and off the digital output pins in an Arduino. This is the code I use:

#define PIN3_ON PORTD |= 0x8
#define PIN3_OFF PORTD &= ~0x8
#define NOP __asm__ __volatile__ ("nop\n\tnop\n\tnop\n\tnop\n\tnop\n\t")

void setup() {
    pinMode(3, OUTPUT);
}

void loop()
{
    cli();
    while (1) {
        PIN3_ON;
        NOP;
        NOP;
        PIN3_OFF;
        NOP;
        NOP;
    }
}

When I observe the output under a scope, I see some sort of quickly decaying oscillation after the pin is switched off:

I have observed this on an Arduino Uno and Nano328. What is the reason for this oscillation?


texts: Thermal calculation for a D2PAK with a SMT Heatsink

texts:
I am trying to calculate the junction temperature of a D2PAK FET that is dissipating 5W. The junction-to-case thermal resistance is 0.4 C/W. The junction-to-ambient (PCB mounted, steady state) resistance is 40 C/W. It seems that D2PAK datasheets don't give a case-to-sink figure.

I am using this sink which has a thermal resistance of just 3 C/W with forced air flow. My question is, when calculating the junction temperature do I include the junction-to-ambient figure in the calculation?

Tj = Pd(Rth(jc) + Rth(ja) + Rth(heatsink)) + Tambient

Or can I ignore the ambient figure when using a heatsink?


texts: Common base bias reduces input impedance

texts:
When biasing the common base as shown I was expecting the input impedance to be (1/gm1 + R3/Beta)//(R1//Rpi2). So we with Beta of 100, and biasing current of 250 uA I was expecting the impedance to be around 100+50 (ignoring R1 and Rpi2). But when I simulate the circuit it is coming up to be < 2 Ohms.  Could someone please help me understand why?
I

simulate this circuit – Schematic created using CircuitLab


texts:
i have a made transformer less power supply to power a arduino board and and two relays. The circuit is designed to get 6v and a current of 150mA. after building the circuit i have connected one arduino and two relays across the output. The two relays are controlled by arduino. When i activate either one relay the output voltage across zener decreases to 5v but when i activate both of the relays at a time then the voltage decrease below 4V and the arduino restarts
Now i want to make the output voltage across the zener constat and stable how can i do that...? and why the voltage decreases with change in load...?


texts:
I am trying to cheat the auto-shutoff feature of a commercial power bank, something along the lines of these instructions.

Contrary to the article I am simply using one port of an Attiny85 to output several types of pulse trains. The port is switching the load (R=60 ohms is what I have proven to keep the power bank alive when driven continuously) by means of a MOSFET (BS170). The circuit as such works as expected (proven with a DSO), but the conditions under which it keeps the power bank alive are tricky.

My first attempt - ordinary PWM at 1 kHz with duty cycle up to ~20% failed. I didn't drive it to higher duty cycles because my goal is saving power.
My second attempt - manually switching the port at low frequency (<< 1 Hz) with on-time ~1 second, off-time ~4 seconds was successful
Third attempt - reducing on-time to 0.5 seconds or increasing off-time to more than 4 seconds failed (1 second "on" seems like the minimum for the power bank to recognise intermitting load)
Fourth attempt - on/off = 1 s/8 s with intermittent 10 ms pulses works for some time (longer than the auto-shutoff time of ~15 s), but eventually fails (shuts off)

What I conclude from these findings:

the power bank's controller somehow integrates current (otherwise the high load peaks of the ordinary 1 kHz peaks would be enough to keep the unit awake)
20%-duty cycle at 1kHz (not working) is not the same as 20% duty cycle at 0.2 Hz (working), so the power bank integrating current cannot be the whole story
the sensitivity to peak load seems to get lower for longer pauses (8 seconds), but can be reactivated by very short maximum load peaks

Does anyone know something about commonly used strategies for implementing the auto-shutoff in commercial power banks?

Is there any easy explanation for the behavior that I have observed?

Any ideas on how I could reduce the duty cycle substantially further while keeping the unit alive?


texts:
I would like to use a FIFO in VHDL, I used coregen to make it but when I want to use it into my project, I get this error :

  ERROR:NgdBuild:604 - logical block 'U101' with type
  'fifo_generator_v9_3' could not be resolved. A pin name misspelling
  can cause this, a missing edif or ngc file, case mismatch between the
  block name and the edif or ngc file name, or the misspelling of a type
  name. Symbol 'fifo_generator_v9_3' is not supported in target
  'spartan3a'.

I can't find where this error come from... Here's some parts of my code (those with the FIFO) :

component fifo_generator_v9_3 is
PORT (
        M_CLK : IN STD_LOGIC;
        rst : IN STD_LOGIC;
        din : IN STD_LOGIC_VECTOR(17 DOWNTO 0);
        wr_en : IN STD_LOGIC;
        rd_en : IN STD_LOGIC;
        dout : OUT STD_LOGIC_VECTOR(17 DOWNTO 0);
        full : OUT STD_LOGIC;
        empty : OUT STD_LOGIC
        );
end component;

signal WRITE_EN, READ_EN, FIFO_FULL, FIFO_EMPTY : STD_LOGIC;
signal DATA_IN, DATA_OUT : STD_LOGIC_VECTOR(17 downto 0);

U101:fifo_generator_v9_3
port map (
            M_CLK,
            rst,
            DATA_IN,
            WRITE_EN,
            READ_EN,
            DATA_OUT,
            FIFO_FULL,
            FIFO_EMPTY
            );

Q : Can someone tell me where that error come from (in my case) ? Is it possible that I'm missing a file? In that case, where can I find it?

Thanks in advance !


texts: If Input is above specific Voltage than only get output

texts:
I am from India. In our country we get 3 phase electricity only for 8 hours and remaining 16 hours either we have single phase electricity or no electricity at all.

In three phase mode:

The Voltage difference between any two phase is 440V AC
The Voltage difference between any Phase and Neutal/Earth is 230V AC

In single phase mode:

The Voltage difference between any two phase is 230V AC
The Voltage difference between any Phase and Neutral/Earth is 150V - 180V AC

I want to light a bulb.

When there is single phase electricity:

If I join the connections of a Bulb to a Phase and a Neutral:

simulate this circuit – Schematic created using CircuitLab

If I connect the two connections of bulb to the two Phases as shown in diagram:

simulate this circuit

When there is three phase electricity:

If I join the connections of a Bulb to a Phase and a Neutral:

simulate this circuit

If I connect the two connections of bulb to the two Phases as shown in diagram:

simulate this circuit

So, my problem is:

When there is single phase electricity, I connect my bulb with two phases as shown in diagram2 which lights up my bulb very bright. Now I am doing some work and if Electric board cuts the power supply for 3-4 minutes and then Electric board gives 3 phase electricity, I loose my bulb. So, every time such scenario happens, I had to change the connections of my bulb or I would loose it.

What I tried:

So, I tried to develop a circuit which does this thing automatically for me:

simulate this circuit

Requirement:

The green boxes in the above diagram are the unknown components. If I apply 440V or very near to that to the primary coil of XFMR1, then only U1 should get the voltage else U1's input should not get any Voltage.

Similarly, If I apply 230V or very near to the Primary Coil of XFMR2, then only U2 should get input else U2's input should not get any Voltage.

Idea after the requirements are satisfied:

So, the idea here is, If Government supplies single Phase electricity:

XFMR1 gets 230V difference between two phases and so, it will produce near about 7 Volts in the secondary coil. So, the green box will not output any voltage to the input of U1.
Similarly, XFMR2 gets 150-180V difference between a Phase and Neutral, which will produce near about 7-8V in the secondary coil. So, this green box will also not output any voltage. As a result U2 will not get any voltage.

So, both the inputs to AND gate will be 0, which will not turn on RLY1. The input to the NOT Gate will be 0, so it will output 1 and thus RLY2 will start.

If Government supplies 3 Phase electricity:

XFMR1 gets 440V difference between two phases and so, it will produce near about 12 Volts in the secondary coil. So, the green box will give output as 12 Volts to the input of U1.
Similarly, XFMR2 gets 230V difference between a Phase and Neutral, which will produce near about 12V in the secondary coil. So, this green box will also output 12V. As a result U2 will get 12V input.

So, both the inputs to AND gate will be 1, which will turn on RLY1. The input to the NOT Gate will be 1, so it will output 0 and thus RLY2 will stop.


texts: Regarding boost converter and current sink IC operation

texts:
I have a doubt regarding the use of a boost converter and a current sink.
This doubt arises based on the following -very simplified- circuit.

Following the attached circuit, the boost will take the incoming 3.7V and provide a constant 12V output at whatever demanded current. Now, in the hypothetical example of having N number of LEDs with N resistors of different values, if I want to maintain a constant current so the LED brightness is constant (neglecting manufacture mismatches,) the most logical idea -IMO- would be to implement a current sink.
In the example, a TLC5940 is used, which will set a fixed current and, as consequence, will make the voltage change to adapt to that current. Would that make a conflict to what the boost is performing?


texts: Charge 18V battery with charger rated at only 18.5V?

texts: I am wondering if an 18.5V, 3.5A charger be able to charger a 18V battery without any bad side effects? The old charger (not functioning anymore) was 24V 0.2A. I know the charger must have a higher voltage rating than the battery to be able to completely charge it.


texts: Why would you enable pullup for a GPIO pin in push-pull mode?

texts:
In this STM32L486xx HAL User Manual (note: 36 MB!) is an example for GPIO configuration to power an external LED on page 53. The code lines that are confusing me are these two:

GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_PULLUP;

So they are using push-pull mode in combination with a pullup. Why would you do that? I can't think of a use case. Either the output is high anyway, then the pullup won't be necessary. Or the output is low, than the pullup will stand no chance and the output signal will still be low, with or without pull up. So is there a reasonable use for this configuration?