texts: Simultaneous charging and powering device for DIY project (12v)

texts:
I'm planning to build a DIY Raspberry Pi tablet powered by three 18650 li-ion cells.
I want to be able to use the device and charge the batteries at the same time, like it's common for tablets.
Here https://electronics.stackexchange.com/a/79108 it says:

While it is true that you can't actually charge and discharge a battery simultaneously, it is quite common to have a charging source, a battery, and a load, all connected in parallel so it looks like you are charging and discharging simultaneously.

I'm looking to combine available parts, as I don't know how to create my own circuits. I found the following component on aliexpress:

3S 12V 18650 Lithium Battery Protection Board 11.1V 12.6V overcharge over-discharge protect 8A 3 Cell Pack Li-ion BMS PCM PCB

https://de.aliexpress.com/item/32899770249.html
I could not find a datasheet for the board or the chips on the board, here are the specs listed on aliexpress:

Model
HX-3S-03

Overcharge voltage range
4.25-4.35v±0.05v

Size
30302.8mm

Over-discharge voltage range
2.3-3.0v±0.05v

Upper limit working current
6-8A

Working temperature
-40---+50 °C

Upper limit instantaneous current
9-10A

Storage conditions
-40-- +80 ° C

Quiescent current
less than 30uA

Effective life
more than 30,000 hours

Internal resistance
less than 100mΩ

Short circuit protection
protection, delay self-recovery

Charging voltage
12.6V-13V

Would such a board be suitable for my purpose?
Edit: the comments asked for better information, i.e. a datasheet, which I couldn't find. So I added the specs listed on the aliexpress page.
I also found that note on an ebay-ad for the same board:

After connecting the cable, you need to charge it first, then there will be output

https://www.ebay.co.uk/itm/3-String-11-1V-Lithium-Battery-Power-Circuit-Board-for-12V-Electronic-Products-/324302796542
So that sounds if it cannot be used as "load sharing charger" (like @ocrdu pointed out).


texts: How can a GPIO logic to high amp/voltage logic adapter be built using multiple voltages? (5v, 12v, 24v)

texts:
I'm working on a project that requires making a fairly universal board (to work on different model machines).  I need to hook up many pre existing motors and switches/sensors to the board that all work off of different voltages and have their own unique pin/plug configuration.  I figured using fpga would allow programming of the     correct configuration, but I need the 3.3v fpga pins to accept input/output from 5vdc, 12vdc, and 24vdc selectively.  Is there any simple solution out there?  They all need pwm capability, and the ability to drive small motors/devices.

I have thought of using load switches for the outputs, which seems correct.  As for inputs, I was thinking isolators, but they don't allow such a wide range of input voltages if I am     correct.  The only other thing I can think of is voltage regulators in series or parallel to convert the voltage to 3.3v logic.  However this may pose a problem where pins can not be ground (as in 0v) for high  current as well as serve as a logic input.        Any help or ideas would be appreciated.


texts: How do you develop software for the Arduino?

texts:
Is the main way of programming the Arduino's Atmel MCU thru a Visual Programming environment such as Max/MSP? Or do you have to write typical C code?

What are the different ways available?


texts:
My hardware team is planning to use an Atmel AVR 8-bit microcontroller for a future project.

So far as I know, it must be programmed in C. I have found a JVM for AVR, though it is more limited than the native C libraries from Atmel.

Can you suggest me an 8-bit microcontroller which supports Java?

PS. I don't know C and I am inexperienced in microprocessor programming.


texts: Does anyone have any idea how to solve this?

texts: Apparently you could use linearity here, but that doesn't make the question any less intricate.


texts:
Are the fuses required for a redundant power system, which takes power from a battery?

If yes, how to calculate the characteristics?

I am trying to isolate the faulty PSU, not the load. Load must have uninterrupted power.

Thanks.


texts: Why are these electric circuit transformations giving me different answers? (See details)

texts: I used star to delta and delta to star transformation on different parts of circuit.But I am getting different answers. Why is it so?


texts: Can two MAX7219 chips drive a 10x11 LED matrix?

texts: I want to drive a 11x10 LED matrix.  Can two MAX7219 do this? Is there a way to have on MAX7219 handle a core of 8x8 LEDs and the other would drive the remaining 3 cols and 2 rows?


texts:
I am planning to use TLC5916-Q1 LED Driver for switching of 8 different color led's and in application,switching takes place at fast rate.

Datasheet: http://www.ti.com/product/TLC5916-Q1

For interfacing SDI, CLK pins are used. As per datasheet, interfacing is as shown:

I have seen one application where these pins are assigned to SPI pin ( SDI--> MOSI and CLK-->SCLK)

My question is can I assign it ( OPTION 1 ) to I/O pins or ( OPTION 2 ) to  I2C pins.

What are considerations while assigning these pins to controller?

Thank you.


texts:
I need help with the wiring on my son's car.
I'm trying to run 2 x front and 2 x rear #QG550 12 V 45rmp motors using independent 18 V power supplies, 18 V front and 18 V rear.
I wish to keep the forward/stop/reverse 6-pin switch and the hi/lo speed 6- pin switch.

I had a wiring diagram drawn up for me but I thought the foot pedel was only a 3-pin switch. I have now learned it is a momentary 6-pin switch(16A 125/250vac)T125.
How do i wire

I have also a 5-pin relay and two 8-pin DPDT relays to run my second system.

Can some one look over my diagram and help me please. Sorry if my first post was brief - I was hoping to upload it. Also the bottom right DPDT relay doesn't look wired right too.


texts: Lora sx1278 implementation by Arduino Uno

texts: I'm implementing a Lora network, with two SX1278 modules and Arduino Uno. Lora is based on three classes. A , B and C, The question is : for change For example A to B, what should exactly change in communication? and How does it change the beacon?. I clearly mean, Does it need to send a particular and standard message to the receiver ? Or Will just communicating in scheduled time change the class or changing some control bits is needed?


texts: Why are there slots around the transformers in this PCB?

texts:
I took apart an office printer a while back and this is a photo of one of the power delivery PCBs:

(Please note I have removed some components from the PCB).

What is the reason for the slots in the PCB around the transformers?


texts:
I have been reading about Norton Operational Amplifiers, I get a good idea of how they work, even at the transistor level, I understand that difference current in = voltage output. What I have been having trouble is finding about the advantages of these opamps VS the traditional voltage ones, is it speed?, bandwidth?, what?

Where should one use a Norton Op-amp instead of a regular voltage Op-amp?, I ask this because if its a matter of applications in which the output is a current (like in a DAC) one can still use regular voltage opamps, for example, an inverting transimpedance amplifier with its input as a virtual ground.

Two example data sheets are:

LM3900
LM359

The following video explains fairly well how a Norton (Current Differencing Amp) works. Look at 19:30 on the vid

Norton Amp

However again, I need to know in which applications this amp is best, and what should drive me to use a Norton amp instead of a voltage amp.


texts: Presence of depletion layer in an N-MOSFET

texts: The source and the substrate of an N-MOSFET are connected together and biased with zero potential. In spite of that, a thin depletion layer exists. Why?


texts: Implementing ADD instruction for RiSC-16 processor

texts:
I'm trying to implement the RiSC-16 (not RISC) processor documented here using Verilog.
The processor is really simple, however there is a problem when you try to perform ADD instructions consecutively on a register, for example

add r1,r1,r1
add r2,r2,r2

Looking at the sequential implementation here, this code won't work. Here is why: Since write enable of register file is on throughout the execution, the result of the first instruction gets overridden at the beginning of the second instruction. This is because the target address does not change immediately at the beginning of the next instruction cycle.

Is there a way to prevent this from happening?


texts: Headset microphone is noisy, but touching speaker wires removes the noise

texts:
I'm repairing my simple wired headset which is composed of two little speakers and one microphone. The audio and mic jacks are separate. The speakers work fine. But the microphone is very noisy. As I was playing with wires, I found out that when I touch both ends of the speaker wire, the microphone noise goes away. Short-circuiting the speaker wire alone won't work. I have to literally touch the wires. This is rather bizarre to me. Do you have any idea what should I do?

I have seen this happening in lamps flickering too. The moment I touch the metal body of the lamp holder, the flickering goes away :-/


texts: Is there a schematic symbol for a supercapacitor?

texts: Is there a schematic symbol for a supercapacitor, as distinct from smaller polarized capacitors?


texts: What is the convolution of an antipodal (that is alternating 1 and 0) pulse train with rectangular pulse of duration T in the time domain?

texts: What is the convolution of an antipodal (that is alternating 1 and -1) pulse train with a rectangular pulse of duration T in the time domain?  I am having trouble picturing this.


texts: Does a DMM alter the real value of current flow, when measuring current?

texts:
I am working on a project right now, that utilises the low-power mode of the ATmega328-P. This essentially sleeps the micro-controller when it is not in use.  I have a Fluke 79 series ii DMM, which is what I use to measure how much current my ATmega is drawing in its low-power state. It gives the figure of 0.007 mA, or 7 μA.

My question is, does the multi-meter offset the true current draw, as it itself is in the circuit? It isn't usually enough to affect a reading, but is it when the current flowing is this low?

In the Fluke 79ii manual, it states (p23): "Input current through R5+R6 (for mA)...develops a voltage that is proportional to the input."

Further in the manual, it determines R5 as "WW, 9.99, +- 0.25%, 1W, 50PPM", and R6 as "WW, 0.010, +- 0.25%, 1W, 100PPM". Can anyone confirm the units they are, and what PPM means?

Can we determine if the meter influences the current draw, and if so, can we calculate how much?

Thank-you in advance for your help,

Smeato


texts:
I'm busy repairing a guitar amp from '79 and stumbled upon these. They look like resistors, but they are definitely caps. I confirmed that with the PCB schematics and by measuring the ones with larger values, but I don't have the equipment to measure the ones in the pF range (e.g. the one in the middle should be 470pF). So I thought about replacing them, just in case. From what I found via Google, I suppose I can use ceramic disc caps as replacement. Is that correct? And is there a way to determine their maximum voltage rating?

Edit: Not sure if I may post the complete schematics, so I added images of the areas around the caps in question. The ones on the photo are C6, C8 and C5.


texts:
All embedded devices includes a "Factory reset" option that allows the user to reset his device if something is wrong.

I am developing a Firmware on an STM32 board. The firmware includes a boot loader that allows to upgrade the application via UART (By sending a binary file that contains the new image) and I want to add another feature: A factory reset. When the user choose this option, the board shall load the original image.

What is a Factory reset? Is it about loading the whole binary file into memory again or it's just calling a function that reinitialize variables modified by the end user?

What are the best practices to do so?

Where to store the original FW? is it in an internal or external flash?


texts: What effect does having a constant +12V on the drain have on an N-channel MOSFET?

texts:
I have a circuit where I have 12VDC source that is connected to the MOSFET (A2SHB) via a timer that applies the voltage to an LED. I have also wired the 12V straight to the LED via a resistor for a constant 8 volts on the LED. The result is that the LED is always on and then the timer comes on and the LED gets brighter making the LED appear to be blinking.

My concern is that with a constant 12V on the drain of the MOSFET, I am causing it to fail because sometimes the LED won't blink until I cycle power.

I am a complete novice at this. I have included a schematic that I think is how I have it wired.

Thanks in advance for any help on this.


texts: MCU Performance: running with emulator vs running without emulator

texts:
If I connect to my MCU with its SWD emulator/debugger, is there ANY difference in performance/behavior as compared to when I run the MCU without the emulator?

EDIT:
I am using a freescale KL25z Cortex M0+ with Arm GCC compiler on Eclipse.  I am running at full speed.


texts: Wiring a USB 2.0 Type-C receptacle so that both orientations work

texts:
I'm trying to wire a USB Type C receptacle just for USB 2.0. If I wire A1(GND), A6(D+), A7(D-) and A9(VCC), this works, but only for one orientation (as expected). If I use the B-side data pins, that also works for the other orientation. However, as soon as I tie A6 to B6 and/or A7 to B7, it stops working, with Linux reporting device descriptor read errors.
I've tested using A and C break-out boards, all VCC pins are tied, all GND pins are tied and the opposing side data pins are floating. This is a USB A to C cable, so we can ignore CC for now, I'm wondering what the correct way of tying the data pins together is? Should I be tying them up/down? If so, with what resistance?
I couldn't find this addressed searching through the spec or various posts generally on the web. I expect it is, but my knowledge is too lacking to comprehend it.


texts: Adding Ground or Earth to the shielded cable

texts: I am using 8 core shielded cable to transfer I2C signal along with analog sensor data. We have connected earth to the shied cable, we have option to connect DC ground also. Everywhere I have read shied should be connected to ground. If we have earth line should we connect it to shield. We have connected device chassis to the earth.


texts: Electronic product test plan/scripts...how to go about writing them?

texts:
I'm testing an electronics toy product. Any advice on writing test plans and test scripts.

I'm thinking along the lines of listing user actions:

for normal input/response
that are suppose to cause exceptions/errors

What else am I missing?

We have the flow chart that our vendor is using to program. I think I'm going to look at the flow and test each decision point to make sure that all the YES and NO paths are correct.

Any other things I need to include?
Any other strategies that would make this more efficient? Should I write a test script that can check off a few different decision points or do I need to test each in isolation? (I don't know if this is even possible because to get to some s/w decision points I need to get pass others.


texts: uploading sketch using mcp2221 to Atmel Mega1284P

texts:
Hi I am unable to upload sketch to Atmel mega1284p using a mcp2221 usb to uart converter IC.

I have a simple code prints "message received" It works to program the Mega1284p using arduino nano as ISP. But not using the MCP2221 over usb.  I took a long time and eventually errors out. I tried pressing reset button on ATMega while uploading, I tried swapping TX and RX. I double checked COM port. Please help.

avrdude:

     System wide configuration file is "C:\Users\hhuynh\AppData\Local\Arduino15\packages\MightyCore\hardware\avr\2.0.1/avrdude.conf"

     Using Port                    : COM5
     Using Programmer              : arduino
     Overriding Baud Rate          : 38400

An error occurred while uploading the sketch

This is my setup.

This schematic is simular to how mine is setup.


texts:
A discrete-time linear and time-invariant (LTI) system is given by the following
input-output relationship: y[n] = 2x[n] − x[n − 1], where x[n] is the input and y[n] is the
output.

(a) What is the frequency response?

(b) What is the response of the system to input signal 1 + e^(j*(pi/2)*n)

For the problem above, I figured out that the frequency response is H(jw)=2-e^(-jw). So for the new response in part b, I know that x[n]= e^(j*0*n) + e^(j*(pi/2)*n). How should I proceed from here?


texts: Mapping of Real-Time Process Data in PROFINET

texts:
I am in early stages of developing a PROFINET device. Can anyone explain me how "process data" is mapped in PROFINET protocol? I am referring to the variables exchanged in real-time (with RT or IRT protocol), and I would like to know how the master controller can configure a slave device to get the desired data, in general. Is it a standard procedure?
I have experience with EtherCAT, where the master write some objects to define which variables will be exchanged as "process data" with PDO protocol (procedure known as "PDO mapping"). I am looking for the similar procedure in PROFINET.
I'm asking to someone who has experience with PROFINET protocol, even just to get a reference to the proper standard document.
Many thanks!


texts: 1250w ATX Power Supply Serial 24v Question

texts: I have a ZM1250-Platinum model ATX Power Supply. It's the first I've considered making into a bench power supply that has two +12v outputs instead of just one: +12v1 @ 45A and +12v2 @ 65A. Even though they share a common ground, is there any configuration possible that could get these two supplies in serial and up to 24v? If not, what can I add to my knowledge as a take away lesson? Would it be possible if I really took the whole thing apart and somehow separated the common ground from one of the +12v supplies?


texts: Schmitt trigger - why is there no current over the second transistor?

texts:
I'm reading through The Art of Electronics, and I'm trying to wrap my head around a Schmitt trigger.

simulate this circuit – Schematic created using CircuitLab

Why is there no current over Q2 when Q1 is oversaturated? I see two paths out of R2 to R1 and in linear circuits there would be some current over both.

I'd assume it is because current from base to emitter in Q1 is oversaturating Q1 so it 'shorts' collector and emitter while dynamic resistance between collector and emitter is high so for near 0 V the Q2 behaves as if it was open (just as in silicon diodes). But I cannot find anything that would support this interpretation in the book (I probably missed something) outside "transistor man" model containing diode.


texts:
I read that if you try to solder an IC directly to a PCB, the heat from the soldering iron tends to destroy the delicate IC — unless you have elite-level soldering skills. (Hint: I do not have such skills!)

For my current project, my plan was to solder IC sockets to the board, do all of the other soldering work, and then insert the ICs into the sockets once I've put the iron away. Presumably the worst an iron can do to a plastic IC socket is maybe melt it a little bit. It's unlikely to completely (and invisibly) destroy it like an IC.

However... I'm using a matrix board. Almost every single connection requires another hoop of wire, and several of these need to connect pins on opposite sides of the ICs. Having got part way through the project, I'm becomming concerned that once I finish platting the board with its tangle of wire, I might not actually be able to physically insert the ICs for the amount of wire in the way.

The other option is to insert the ICs now, and continue soldering, hoping that the IC sockets will save me. Realistically, how much protection against thermal damage is a socket going to give? I mean, it's designed to make a good electrical connection, so it probably makes a reasonable thermal connection too. On the other hand, maybe it has more thermal mass, or a larger surface to dissapate heat? I don't know.

(The ICs are DIP-14, in case that makes any difference to anything.)


texts: How to quickly fill up the entire DDR memory using Xilinx tools?

texts: I have a board with a DDR3 memory and a Virtex 7 FPGA. I have used Xilinx MIG to create a memory controller and I am able to succesfully read/write to the memory using Microblaze registers. I would like to fill the entire DDR memory module with either 0's or 1's but Microblaze is really slow in doing this especially when the memory size is large. Is there a way I can quickly fill up the entire memory using RTL logic?


texts: 3.5mm Stereo output to 3.5mm mic input crossover

texts:
I have two devices, each with two 3.5mm jacks for the usual audio out / in.  I need a way to cross-over between the two, such that the stereo output of one, goes to the mic input of the other.  I have looked into and considered other options and (unfortunately), this is the best option for this project.  The devices aren't terribly smart (one has no accessible software component, and one is a knock-off RPi).  A software solution wont work, I need a hardware implementation.  I have looked around and found several related issues, but I haven't found an actual solution anywhere that works.  I did rig up a cross-over cable myself which does work, but barely, and with great audio issues.  This seems like it shouldn't be that difficult, but the mic works with much lower voltage than the stereo out, so feeding it directly across isn't a viable / good solution.

Any help is warmly welcomed, or something as simple as a usb audio card that can do it (one of the devices is a RPi type board).


texts:
I got a 750W (12VDC, 62.5A) power supply (I don't have it with me right now so I can't remember the model) from a old server and I was thinking on using it to create a lab bench power supply. My question is if it's worth it. I don't have any power supply and I can't afford spending much money on one. I'm a beginner in electronics so it would also be a project to get some experience from. I was thinking on using some components to have some fixed voltage levels and also a adjustable one. I would like if someone could give me some advices on this.

The components I was thinking of are:
3.3V - LM317 (1.5A max) and other regulator for more max current.
5V - LM7805 or LM317 (both 1.5A max)
12V - Directly from the power supply

Adjustable: LTC3780 (1-30V) (10A), using a display to show voltage and current and a few potentiometers.

Is this worth the money and time? Both for usability and experience.

Also, is it possible to have both positive and negative voltages?

Thanks in advance!


texts: How can I drive and measure the output of a bare ultrasonic parking sensor?

texts:
I want to use a parking distance sensor, specifically the common ones found on vehicle bumpers.

There are only two wires. How can I drive the sensor and read distance from it?
I specifically need to know what the input and output pulses should look like (voltage/duration).

Conceptually, I need to send a pulse of some magnitude and duration, and then measure the time before a signal is received back. That seems simple enough to be done with a 5V microcontroller and few other components, but I don't know for sure because I can't find much data on these sensors.

A common bidding site has the following 'data' for these sensors:

Allowable Maximum Input Voltage ( Vp-p): 140 (40KHz)
Pulse width: 0.5ms
interval: 20ms
Decay Time: ≤1.2ms

140V input pulse? Is that right or just a mistranslation? If it's right, I think it would be more cost effective to buy a driver for it.

This link suggests that the sensors in vehicles perform "both emission and reception", though that's not any sort of confirmation.

Note that I do not have of these sensors, and I do not have any supporting hardware for them (like a stock PCB).


texts:
I'm building a circuit for my project. However I'm a bit insecure about whether it is correct. (I'm from software myself).

It is the following circuit:

simulate this circuit – Schematic created using CircuitLab

A couple of side notes:

there are 15 Solenoid assemblies (Solenoid, Mosfet, Diode) connected in parallel.
there are 3 servos all connected to one 5V regulator.

Since I'm not that experienced with circuitry, and neither are the people who will use this project after me, I'd like to make this circuit almost impossible to break.

So my questions are:

Did I use the right parts to use solenoids and servos?
Am I missing any parts that could make it more unbreakable?
I've added a capacitor, but how many Farads would I need?
When testing, I noticed that the MOSFET doesn't transmit all current, and it also takes a while before it is really switched off. Why is this?
The solenoid needs to press a button but it only has enough force when ~19V is applied. I find it inconvenient to use this 19V supply. Could this be done in a better (=safer) way?

Thanks in advance!


texts:
Is it possible, with an oscilloscope, scalpel and a lot of patient, to open up a network cable (twisted pair), and sniff the traffic? All without interrupting the network traffic.

So;

Use the scalpel to get inside the cables, one by one.
Use the oscilloscope to find out which cable does what.
Attach to the data cables and dump the packages.

Or will this disturb/beak the connection and make it unstable/impossible for the ends to talk to each others.


texts: Migrating from USB 3.0 Micro B to Type B connector

texts:
The current design uses a Micro B connector for the USB 3.0 connectivity. Unfortunately, this connector is susceptible to mechanical stress if the PCB is not handle with care, which results in ripped pads rendering the board unusable. I decided to replace it in the next revision with a Type B connector, which is THT, thus providing greater mechanical support.
The PCB is a 4-layer, in which all of the high-speed signals are located on the top layer. I have never used a THT component or VIAs for high-speed signals before. Is there anything I should consider or I just proceed with it? Also, we tend to hand solder the PCBs since it's a low production volume, with solder paste and hot air for SMT and iron for THT components on the board. Do you solder the USB 3.0 connector with the soldering iron as any other THT component, or is there anything special about handling a high-speed THT connector? Thank you.
Edit:
Although I will probably go with the solution proposed by Maple below, I am still interested to know the answer to my questions regarding Type B connector.


texts: If a 5 Ohm solenoid is connected to a 1.5 V AA battery, the resulting current will be 300 mA. For a 1000 mAh battery this should provide about 3.3 hours of operation. Is it practically possible to connect a 5 Ohm solenoid to a stabilized DC power adapter with 1.5 V output? Will the voltage still be 1.5 V with such low resistance load?


texts: Downsides of using 5mm fuses in 6.3mm sockets

texts:
For my multimeter I need to replace a fuse. It is 6.3mm in diameter, 25mm long, rated 500mA/250V AC and 1500A interrupt rating.

I have a couple of such fuses, but they are 5mm in diameter, and looking online here in Germany I can't seem to find 6.3x25mm ones. So I was wondering in general (but of course mostly specific to my multimeter):

Are there any downsides in bending the fuse holders just a bit (1.3mm)? Assume that the fuse can not easily fall of, at most lose contact. I am mostly interested in safety issues here, I can live with the fuse needed to be reset from time to time.


texts:
I am working on a diorama.

I found this circuit online and it's what I want. (I'm NOT making a railroad diorama.)

I want to add two more LEDs to this circuit to have 4 flashing LEDs.  Like this:

Question: Is it that simple to parallel two more LEDs and two more resistors to create a four flashing LED system?

EDIT:
I'd like to use just a 9v battery for ease.


texts: Maximum tolerance for a loop trace-antenna's capacitor

texts:
While going through the document at https://www.silabs.com/documents/public/application-notes/AN639.pdf I have read from "Figure 13. Loop Antenna Simulated Mag(Zin) vs. CP1" below that even a 2% tolerance for Cp1 results in a Zin of about 200 - 250 Ohm for the 434 MHz frequency range that I am heading for. The desired Zin is 500 Ohm.

I am not sure if this is the case but as I understand it this will cause a good fraction of the power to be reflected back into the IC. If so, could I have a maximum tolerance level for Cp1 so that my transmitter will not require full power in order to cover a mere few meters ? (in ohter words, for my transmitter not to perform poorly)


texts: Xbee series 2 drops off network without apparent cause - diagnostic suggestions?

texts:
I've built a meter reader, based around an ATMega 328P and an XBee series 2.  The initial protoype built with an Adafruit trinket pro (3.3V) and it worked like a charm.  It was stable for 10ish days, before it ran out of battery.

To improve battery performance, I moved it to a breadboard-duino.  This is where the problem starts.  I start it with a newly charged battery back (4*1.5V hybrid NiMH) and it's fine for ~7ish days, as the battery pack voltage slowly drops from 5.7V down to ~5.1V.  Some time around this point (and it varies by >0.1V) the XBee dissociates from the network.   I know this because 1) Power cycling the xbee only restores connectivity 2) The XBee association LED activates, rather than blinking and 3) The 328P can be regularly seen trying to put the XBee to sleep.

However, if I restart the xbee (or entire circuit, ether way) the issue repeats itself - but in a timeframe of a day.  This implies to me it's related somehow to the battery decay, as that's the only thing that doesn't get reset.

However:

Power output is regulated to 3.3V by a TS2950CT 3.3V regulator
Measured circuit voltage is 3.27V, nonfluctuating on my meter
The trinket pro worked all the way down to a supply voltage of 3.6V
There's a 100uF capacitor between the +3.3V and ground for smoothing
After the blocking diode, supply voltage is still 4.69V
Drop out voltage on the regulator is listed at 450mV, worst case, with a 100mA load.  This is, at worst, half that.
All the components are rated at 3V, except for...

The only dodgy thing I've done is (accidentally) used a 16Mhz ATMega.  I've got an 8Mhz crystal in the post, and I'm going to replace that ASAP.  But it's Christmas, and if I'm lucky it'll be here by new year.

So, what I'm asking people is - what else can I check?  What could it be?  Where could I start looking?

Oh, and, relevant seasonal greetings.  They'll be merry if I can get this thing to work!


texts:
I purchased a DIY op-amp kit from eBay. The parts arrived in a baggy, I soldered it all together, but have no idea how to wire the power supply?

I am hoping to use 9V batteries, and realize I might have to run two or more in series? I am pretty new to this electronics thing.

What is confusing me is that the hookup has "VDD", "-GRD-", and "-VCC". I have no idea what connects to what in terms of batteries, etc.

I have attached several photos with the amp, chips, etc. It did not come with instructions, datasheets, etc.


texts: Do rail gun systems require high voltage?

texts:
I couldn't justify, as to why most rail-gun examples I found would have high current and high voltage. When the rails & projectile can be designed to have low resistance by varying the volume of those components.

If capacitors are used, having them parallel also reduces the ESR's contribution to the total resistance.

I'm curious why many designs would have high voltage ratings, when the objective is to have high current, and the resistance can be reduced by adjusting the component's volume.


texts: Primary current expectation in unloaded toroidal transformer

texts:
Background

I found a hefty, 7 kg toroidal transformer in visually good condition at a flea market which I am trying to map out. This is part one: I am not sure about what is happening on the primary side.

It has seven individual windings with an estimated ratio of 36:5:5:3:3:2:2. Windings are roughly 1.4 mm² copper except the bolded which are 7.5 mm². Just a logotype and custom part number.

Assumptions

Because of the winding ratio, individual thickness, and being manufactured by a reputable Swedish company for what is likely a Swedish market, I am assuming that the main primary winding is meant for use with a 220 or 230 volt mains, and the whole transformer is designed for either a class B audio amplifier of several hundred watts, or a lab power supply, or anything else where you need dual 40 volts at 5-10 ampere each, and a regulated ±15 volts. From the weight of this, I'd say it's rated for around 1000 VA.

Measurement setup

After doing a couple of other tests with a variac I wanted to see how it behaved on higher voltages. I connected the primary side to the variac, left all the other windings open, and slowly increased the primary voltage while also measuring the no-load current through the primary side. After about 200 volts, it started growling a bit, and I didn't dare to try it above 220 because of the evil sound - as you can see, the primary current is increasing exponentially.

simulate this circuit – Schematic created using CircuitLab

Questions

Now I need help with interpreting this data and my assumptions. I am not very experienced with how transformers should behave. Can anyone shed some light here? I do have a few ideas, but they are just guesses. It's either:

Normal for an unloaded transformer of this size, because something about the magicmagnetic currents not being absorbed on the secondary side, causing distortions leading to increased power consumption on the primary.
Normal for a transformer of this size. The no-load losses will still be pretty large, and the growling should go away when properly mounted and not just lying on the workbench.
The transformer is designed for the US market, to give 2x15 VAC at 20 ampere each, and a couple of even lower voltages with a primary of 110 VAC.
The transformer has been damaged (seems fine on low voltages and no load).
Something else of your choice.


texts:
I need an inexpensive RGB LED driver IC with minimal BOM that:
Can source or sink at least 3 * 350 mA
Has an I2C or SPI or digital interface
Has at least 16384 grayscale intensities

Can anyone recommend some devices to consider?
Is it possible to get 14-16 bits for a single 350 mA LED?
I found the TLC5955, which has 65536 brightness adjustment steps, costs about $9.10/piece and it has inconveniently located 48 pins to combine them and connect a RGB LED. RGB LED If: 350/350/350 mA, Vf: 2.1/3.4/3.2, power is one cell Li-Ion 3.7 V.


texts: Why are there three transistor pairs in Class B Power Amplifier circuit?

texts: I have a Class B amplifier circuit to be done in lab. Why three pair of transistors are used in this? I suppose one is a Darlington pair but what is the requirement of the third one. Also, why there is unequal mumber of diodes even if equal number of PNP and NPN transistors are used?


texts: Options for higher current regulation in an aircraft strobe system

texts:
I've deployed a homemade strobe system using Cree 10W LEDs in my homebuilt aircraft.  My implementation uses a simple PIC controller to do the flashing, an IRL2505 mosfet (driven by an NPN transistor) for the switching, and a linear regulator (LM338) to limit the current to 5 amps.  The system is using 7 Cree's in parallel for the landing light, and 8 in parallel for each wing strobe unit, each driven by an independent IRL2505/LM338 5 amp drive circuit.

Details can be found in this instructable:

http://www.instructables.com/id/LED-Landing-Light-for-Experimental-Aircraft/

After adding a protection diode to manage inductive field collapse on the wing mounted strobes, the system is working fine... however, more brightness is always better!

Here's the schematic:

So, my specific question is this... to make this brighter, I need to go beyond 5 amps.  What options are there for a more efficient, higher output, physically small current regulator?

Some implementation constraints:

There is little to no space in the wingtips or nose for the electronics, and heat is also an issue... I can't afford to have something melting my wings!  I've had to work hard to control the heat from the LEDs and also from the linear regulator/mosfet.  So... space and heat are my enemies...!
Switching regulators may be the right option, but I've been reluctant to try designing one because by reputation they are inherently electrically noisy... I depend on my HF radios, GPS, bluetooth and Wifi (all currently in the airplane) - so adding electrical noise could be an issue.
Commercial LED based strobe systems for homebuilt aircraft are out there... and I've looked at them closely.  I don't see current limiters.  At all.  And, they are plenty bright.  What gives???  What don't I understand??? Are they just keeping the duty cycle so low that the LEDs can't overheat?

ANY thoughts, suggestions, comments, or ideas would be welcome.

Thanks!


texts: TimerA: How to get PWM in upMode configuration?(TI MSP432 Launchpad)

texts:
I try to use UpMode timerA configuration on MSP to get PWM with arranged Duty Cyle. So here is my code below:

#include "msp432.h"
#include "driverlib.h"

void SetConfiguation(void);

int main(void)
{
    WDT_A_holdTimer();
    SetConfiguation();
    while(1);
}

void SetConfiguation(void)
{

    Interrupt_disableMaster();

    CS_setDCOCenteredFrequency(CS_DCO_FREQUENCY_24);
    CS_initClockSignal(CS_SMCLK, CS_DCOCLK_SELECT, CS_CLOCK_DIVIDER_128);

    /* TimerA UpMode Configuration Parameter */
    Timer_A_UpModeConfig upConfig =
    {
            TIMER_A_CLOCKSOURCE_SMCLK,              // SMCLK Clock SOurce
            TIMER_A_CLOCKSOURCE_DIVIDER_64,          // SCLK/64 = 24MHz/128/64 = 2929 Hz
            24,                           // 50000 tick period
            TIMER_A_TAIE_INTERRUPT_ENABLE,         // Enable Timer interrupt
            TIMER_A_CCIE_CCR0_INTERRUPT_ENABLE ,    // Enable CCR0 interrupt
            //TIMER_A_CCIE_CCR0_INTERRUPT_DISABLE,     // Disable CCR0 interrupt
            TIMER_A_DO_CLEAR                      // Clear value
    };

    P1DIR |= BIT0;
    P1OUT &= ~BIT0;

    Timer_A_configureUpMode(TIMER_A0_MODULE, &upConfig);

    Timer_A_CompareModeConfig compConfig =
    {
        //uint_fast16_t compareRegister;
        TIMER_A_CAPTURECOMPARE_REGISTER_1,
        //uint_fast16_t compareInterruptEnable;
        TIMER_A_CAPTURECOMPARE_INTERRUPT_ENABLE,
        //uint_fast16_t compareOutputMode;
        //TIMER_A_OUTPUTMODE_SET_RESET,
        TIMER_A_OUTPUTMODE_TOGGLE_RESET,
        //uint_fast16_t compareValue;
        6
    };

    Timer_A_initCompare(TIMER_A0_MODULE, &compConfig);

    //Timer_A_enableCaptureCompareInterrupt(TIMER_A0_MODULE, TIMER_A_CAPTURECOMPARE_REGISTER_0);
    Timer_A_enableCaptureCompareInterrupt(TIMER_A0_MODULE, TIMER_A_CAPTURECOMPARE_REGISTER_1);

    Interrupt_enableInterrupt(INT_TA0_0);

    PCM_setCoreVoltageLevel(PCM_VCORE0);
    PCM_setPowerState(PCM_AM_LDO_VCORE0);

    Timer_A_startCounter(TIMER_A0_MODULE, TIMER_A_UP_MODE);
    Interrupt_enableMaster();
}

void Port1IsrHandler(void)
{

}

void Timer_AIsrHandler(void)
{
    Timer_A_clearCaptureCompareInterrupt(TIMER_A0_MODULE, TIMER_A_CAPTURECOMPARE_REGISTER_0);
    Timer_A_clearCaptureCompareInterrupt(TIMER_A0_MODULE, TIMER_A_CAPTURECOMPARE_REGISTER_1);
    Timer_A_clearInterruptFlag(TIMER_A0_MODULE);
    P1OUT ^= 1;

}

In the Code, upMode works fine, interrupts work fine so I get 60 Hz what I want. But, to get PWM with arranged duty cycle, I need to use compare mode So I structed compConfig as seen on the code. However, it seems like there is no interrupt created for compare Mode. I use compare_register1 to catch interrupt but whether I put the compare interrupt enable or not result is same. It has no effect on the output. So, where am I doing wrong here? What is the correct way to achieve adjustable PWM.


texts: Identify inductor color code - green on 3rd position?

texts:
I need to replace the inductor on the picture, but the color code is pretty weird: yellow, violet, green, silver (47 * ?? μH +/-10%). According to inductor color codes https://cdn.instructables.com/FRQ/J6VA/H4VQNQFK/FRQJ6VAH4VQNQFK.LARGE.gif , the third position should contain only black, brown, red, orange, yellow.

Can you please help me what this coloring could mean?

Edit: it is a control unit of a garden whirlpool (mspa oasis b-120 sapphire lite)


texts: Would a cracked sealed lead acid battery be a safety issue?

texts:
I know that 'sealed' is a different term but most know SLAs as that. I've had a PowerSonic 12V 7ah in my bedroom for maybe a year, not really doing much (anything actually). I realized that it had a small hairline crack while actually messing with it to see if it was still good, and had some small white 'crust' built onto the edge. Crumbles just as corrosion on a household battery does. What am I looking at here? Sorry if not clear enough. Pics included. Thanks so much y'all. Pic1
Edit: I feel like it's worth saying, I am locating my closest battery recycling location now.


texts: Making a circuit entirely with XOR 2-input gates

texts:
The equation is

g = a'b'c + abc + ab'c' + a'bc'

and I try to make it all work in a circuit with only XOR-2 gates

so the truth table looks like this:

by working on the equation and applying De Morgan's law:

g = (a'b'c + abc + ab'c' + a'bc')'
  = ((a'b'c)' (abc)' (ab'c')' (a'bc'))'

I hit a dead end.

is there something I'm missing from boolean algebra or is it impossible to design this entirely with XOR gates?


texts:
I'm an electronics noob and I'm looking to create a doorbell which hooks in to an Arduino board in order to alert me when I don't hear the doorbell.  I've read 'Software alert when doorbell rings. Doable?' and this looks like it's going to put me on the right tracks, but I need a hand in figuring out what doorbell I should buy and how to wire that to the Arduino board without damaging it or me.

I'm looking at buying a doorbell like this (but not specifically this).  I would like the doorbell to keep on working alongside the Arduino board.  But I'm such a novice that I don't even know the correct questions to ask beyond that.  I don't know if it matters but I live in the UK.


texts: RIGOL DS1054Z Fixed trigger time for sweeping using a FeelTech digital signal generator

texts:
How do you properly setup a frequency sweep with a digital signal generator and a RIGOL oscilloscope?

I've got a setup similar to one in this video: https://www.youtube.com/watch?v=ni07A7sZCPM, showing it's possible. Still, I can't find anywhere a clear instruction on how to set a fixed trigger time just like the author of the video did.

So, I've got very popular Rigol DS1054Z (in the video, the author uses a RIGOL DS1102E) and a FeelTech FY3200S function generator, which is a cheap generator from china, with good reviews in general.

Since it's a digital generator, it's providing only a TTL square wave, and no ramp is available. It would seem, the author of the video only has a single wire connected to the oscilloscope anyway. Please advise.

Your help is greatly appreciated. Thank you.


texts:
I have a two filament turn signal/parking lamp on my car (3157A bulb).
When the parking lights are on, the turn signal is not very noticeable, so I am trying to get the parking filament to turn off when turn signal is on.
I understand I can achieve this by using a normally closed 12V relay.
The 3157 bulb draws about 0.6amps for the parking lamp filament.
I have two questions:
1) Since this is a very low current circuit would it be ok to use a generic automotive relay ie: bosch 30 or 40amp?  Or should I use a smaller rated like 10amp or 5amp PC relay like this one https://www.e-sonic.com/ds/505330.pdf?p=45319483
2)Do I need to install a flyback diode in parallel with the coil to prevent damage, if so what size does it need to be?

Thanks in advance.


texts: Doubts related to the Arduino Ethernet with PoE

texts:
I implemeted a system by using the Arduino Uno and the Ethernet Shield without PoE. Now, I am thinking to use the Ethernet with PoE but I have following doubts, even if I read the Official Documentation:

Is the Ethernet with PoE a Shield? or not? That is, do I need the Arduino Uno in order to fully use the Ethernet with PoE (from uploading code to getting power)?
How the Ethernet with PoE gets power? That is, should I own also "the silver and black box in the middle" of this photo (from Wikipedia) in order to give power through Ethernet?
If I buy the above linked Ethernet with PoE should I buy this USB 2 Serial Converter in order to program and upload code to it?


texts: Not understanding a circuit from a book im reading

texts:
Well Hello and merry xmas! ,  I got a qeustion of a circuit witch i dont understand (yes its probaly a stupid qeustion but i cant figure it out)

So this is the text from the book

  . Because of the difference in resistances and the
  relatively high turn-on voltage for the LED, the base is forced below its turn-on
  threshold, and as a result, the transistor will not pass much current. The LED
  will glow dimly at best.
  Now what happens when the switch is opened? The base of the transistor
  loses its negative power supply and has only its positive power supply. It be-
  comes much more positive, above the turn-on threshold for the transistor,
  which tells the transistor to lower its resistance and pass more current. The LED
  now glows brightly. Thus, when the switch is turned off and breaks the con-
  nection, the LED is turned on.

how doos the voltage from the base effects the voltage to the led?
i dont understand what he means with , the base loses its negative power and it becomes more positive when the switch is open? how? (witch is probaly also qeustion 3)

3.and when the switch is open how comes the voltage increases across the base of Q1? ,

also i  looked online for some explanation and i found that to calculate the base(vbb) of transistor you have to do 12 (1k)(11) = 1.09 V   thats above 0.7. so shoulnt the transistor be on? bec its above the thresold of 0.7

whys the D1 Diode there ? in the book it says this about the diode , but how can the current from the relay go up , and why dosent it just go the negative cell of the battery?

  One little problem remains: in the new version of the circuit, if the transistor
  goes off while the relay is still on, current from the relay can flow back up the
  wire to the emitter of the transistor, where it will try to flow backward through
  the transistor to the base, which is “more negative,”

sorry for my bad english :/


texts:
What would happen if I short the terminals of a DC motor together while power is disconnected but it is still freewheeling?

According to several sources, it would brake the motor. This makes sense. But they also mention using an array of power resistors and not just shorting the terminals. What would happen if I just shorted the terminals?


texts: Aircraft Starting Mockup Display With Buzzer Question

texts:
I am stuck in the middle of building a circuit for an aircraft starting mockup that will train our students to correctly start the aircraft without accidentally re-engaging the starter and thus causing very costly maintenance actions.The system is 12v.

We would like to have a 10 second delay timer switch that will turn on a light when the start sequence has been successfully completed. This part seems simple because when the ignition switch is turned to start, it closes the contacts and starts the 10 second delay timer that turns on the light if held closed for 10 seconds. I found one of these timers on amazon but could not find anything for the next part of the mock up.

The complex component of the circuit I can’t figure out is that I would like to have a buzzer in the circuit. If the student accidentally releases the ignition switch even for a moment during the 10 second starting sequence then this buzzer would go off using something like a latch circuit that turns on and keeps a buzzer on until it is reset.

What is confounding me is how to create this circuit so that the buzzer is not going off when:

The system is initially powered up.
The contacts are closed when the ignition switch is turned on for a start sequence
The 10 second starting sequence is completed successfully and the starting key is released thus opening the starting circuit contacts.

We only want this buzzer to go off if the student fails to hold the ignition contacts closed during the 10 second starting sequence.

Could someone please help me design this circuit and let me know what components I need to in order to build it?


texts: RC Timer Circuit (fundamental) Misunderstanding

texts:
I'm working through Electronics for Dummies book and I'm stumped with the RC Timer example. See the diagram below. I believe I understand the idea of it taking a period of time for the capacitor to charge and that once it has charged sufficiently (i.e. the voltage it has is sufficient to drive the buzzer) then the buzzer sounds.

The bit I don't understand is why V1 and V2 in the diagram are not 9v instantly (ignoring the voltage drop across R1) as they would be in other parallel circuits.

Clearly I'm missing something fundamental in my understanding...

Thanks


texts: Looking for simple Ethernet (RJ-45) controlled on/off switch for low-voltage DC line

texts:
I need to replace a mechanical toggle on/off switch with one that can be controlled with a flavor of Ethernet (e.g. 10Base-T, 100Base-T, or 1000Base-T) using standard RJ-45 port.

The line in/out is just a low-voltage DC line controlling a fan.

I want my software to turn the fan on/off, and the software commands are sent out over Cat5e cable to an RJ-45 port.

I'm having trouble with search terms for Google. Something like: on/off switch with ethernet port, just returns a lot of ethernet switches of various port sizes. Or, I find lots of sites promoting how to add a mechanical toggle switch to an RJ-45 cable, which is opposite of what I'm trying to do.

Looking for a simple solution, and wonder if anyone has come across such a thing for their hobby projects.


texts: Minimum voltage supply for a MOSFET-based ring oscillator

texts:
I am trying to build a ring oscillator based on N-channel MOSFET like below:

How to compute the minimum \$V_{DD}\$ required for the circuit to oscillate? Is this the gate threshold voltage (\$V_{GS(th)}\$) + the voltage drop from the \$R_D\$ resistor?

My goal is to have a \$V_{DD}\$ of 3.3V to interface this circuit directly to a microcontroller.


texts: Is voltage divider applicable on circuits where there is no ground?

texts:
For the circuit below, if the bottom terminal is -Vin and not grounded, is applying voltage divider possible at all?

If this is the case, what would the equation be? I never heard of a voltage divider with no reference ground at the bottom.


texts:
Im not sure how to find the frequency response (\$H(jw)=V_o/Vin\$) of this circuit

Can anybody help please?


texts: What is the maximum current limit of this motor?

texts:
I am confused about the maximum current limit of this DC Motor.
Rated Power is given as 220W and Rate voltage is given as 24VDC. According to this maximum current should be 9.166A. But 2.5Amax is also mentioned on the name plate. So what should I consider as the maximum current limit so as to design the protection circuit for this motor?


texts: Why do manufacturers specify typical values, not just maximum and minimum?

texts:
Why do manufacturers specify typical values? I am still going to have to design my circuit so that it can accept values within the maximum/minimum values.
What is the probability of getting a "typical" value component? Is it standardized?
For example, the datasheet for a TL081, on page 12 there is a table of electrical characteristics. Which tells me the input offset voltage is typically +-1mV. But if I need 1mV then I'll have to go find a different op-amp because its not within the max of +-4mV.


texts: High resolution timer on the BeagleBone?

texts: Is there a high-resolution timer (microsecond resolution or better) available on the BeagleBone (TI AM3358 ARM Cortex-A8 based) development board?


texts: Using capacitors to reduce reactive power

texts:
I have been trying to understand the concept of reactive power in power systems. From what I have read so far, I understand that any inductive load like a motor needs some reactive power to function (set up the magnetic fields to work etc.). Now I also understand that, while transmitting the current required for this motor to work, the transmission line also has to carry the current required for the reactive power. Now this increases the loss, as it is given by \$I^{2}R \$. Now, capacitors are used to help generate this reactive power, (as they dissipate power when the inductor consumes it) and are hence placed near the load to reduce the reactive power that needs to be transmitted. I have the following questions:

Is my thought process correct? Am I right in my understanding of reactive power?

If we already know the value of the inductance of the motor, why don't motors come attached with capacitors that make them less of an inductive load? If we can approximate the inductance of the coils can't we find a capacitance that cancels the effect and makes the net impedance value close to zero? Why do we need to have separate stations built for this when we can try to eliminate this at a device level.


texts: Does USB require protection if it is only connected to the regulator input?

texts:
I have the following schematic powering my circuit.

Is it required that I protect the USB power pin with some fuse?


texts: I am designing simple monitoring application circuit, used 3analog inputs. Im confused that how to choose decoupling capacitor for that dc voltage stability and analog inputs. What kind of capacitor need to add, how to choose?


texts:
I am using LT Spice for simulation of my circuit. I have used a probe to check for the voltage on the Capacitor.

What is the green dotted line that can be seen in the plot? Thank you.


texts: Li-Ion battery remaining charge question

texts:
I'm boosting a 7000mAh Li-ion battery pack to 16V to drive a dc brushed motor that has a startup current limited to 1.4A. Due to my switching regulator efficiency a 1.4A output current means about 6.5A input current requirement from the battery.

I noticed the inrush current on the motor and the startup time do not change even when the battery reaches 3.3V

How is it possible that the battery at voltage near cutoff is still capable of supplying that much current, whereas my discharge curve does show at that voltage level the remaining charge is less than 2000mAh ?
I have to admit my knowledge of Li-Ion battery is limited.


texts: How to Read Wheatstone Bridge negative voltage with Arduino?

texts:
I have a half bridge setup with strain gages and a INA126 to amplify the voltage.  I can read the voltage fine when the lever is bent one way, but when beding the lever in the opposite direction I don't get any reading.  I'm guessing it's because the voltage is negative.  Is there a way to read the voltage when the lever is bent in either direction or would I have to make another half bridge to accomplish this?

Created schematic in Circuit Lab -> Schematic


texts: Why do we put transistors in logic gates?

texts:
I was recently doing some experiments on a breadboard and I decided to try to make a not gate with a single transistor. It worked. Then I tried taking the transistor out of the circuit, connecting what would've been the base and emitter together, and it still functioned. So why do we use transistors in logic gates? I thought it might be to keep the signal strong, rather than it weakening, or to get less resistance, but I don't know. I'm new to all of this, so sorry if this isn't a great question. So why must we include transistors in logic gates inside a computer?
Edit: Here's the transistorless schematic. I built it on a breadboard, and I might've translated it to a schematic diagram wrong, so please tell me if I did. Anyway, the only path for electricity is through the LED when the switch is open, but when it closes, it becomes the path of least resistance, and the electricity basically goes around the LED.

simulate this circuit – Schematic created using CircuitLab


texts:
Hi, in this exercise I need to find the values of Ra and Rb so that Vo is equal to Vx and Vy times an x value. I know how to find a equation with Rb, but I don’t know how to get an equation that contains Ra. More specifically, I don’t know how Ra affects the circuit. Could someone explain me how Ra have an impact in the circuit and how that impact is represented in an equation?

The exercise actually comes with an answer:
Vo = (2Rb*Vs)/10k - (Rb/10k)(Vx + Vy)

I know Ra isn’t in the equation, but there are also several sets of values for Rb AND Ra that are needed to get that given “x” amplification in Vo. I really don’t get it.


texts: Second Order Circuit \$\omega_0\$, \$\omega_d\$ and \$\alpha\$ naming

texts:
In 2nd Order Circuits I usually solve them with solving differential equtaions by checking jumps.

But today my teacher solved a question by using \$\omega_0\$, \$\omega_d\$ and \$\alpha\$. I think they are specific to a specific circuit but not sure. What are those \$\omega_0\$, \$\omega_d\$ and \$\alpha\$ and what are their interpretation in differential equation method? How do we find what kind of response is that?


texts: Power supply protection (limiting the voltage)

texts:
This should be fairly simple but I can't find any satisfactory answer on the web (I'm quite new to this things and I don't really know where to look for). I have two sensors in my circuit, one working at 12VDC and the other at 5VDC. The power supply is 12VDC and in my circuit I have a DC/DC converter bringing my 12VDC to 5VDC:

Murata Power solutions OKR-T/3 Series

I would like to add some protection for the sensors (they are quite expensive). I would like to protect them from over-voltage supply and negative voltages. The only thing I have found is:

Voltage detector Linear Technologies LTC4360ISC8
Voltage detector Linear Technologies LTC 4365HTS8

But they only have SC-70 packages and it's simply to hard to solder them and test them


texts: Can anyone tell me if there are any logic gates built into this circuit board?

texts:
We have these circuit boards that we use at work for indication of whether a door is open or closed... To be honest, I have no idea how they work.  I drew up a diagram of it to see if anyone can explain how it works.  The left LED is green (closed) and the right LED is red (open).  I've added a picture to show you what I'm talking about.  Thank you so very much for your help!

simulate this circuit – Schematic created using CircuitLab


texts:
I have tried to simplify a boolean function. Unfortunately it is wrong.

Question: Where is my mistake?

\$ f = x_4x_2 + \overline {(x_3 + x_2)x_2 \cdot 1} + x_2 x_0\$

\$ f= x_4 x_2 + \overline {(x_3 + x_2) x_2} + x_2 x_0\$

\$ f = x_4 x_2 + ( \overline{x_3} \overline{x_2}) + \overline {x_2} + x_2 x_0\$

\$ f = \overline { \overline {x_4 x_2 + (\overline {x_3} \overline{x_2}) + \overline {x_2}+ x_2 x_0}} \$

\$ f = \overline { \overline{x_4} + \overline{x_2} (x_3 + x_2) x_2 \overline{x_2} + x_0}\$

\$ f = \overline{ \overline{x_4}+ \overline{x_0}} \$

\$ f = x_4x_0\$

The correct solution would be:

\$ f = \overline {x_2} + x_0 + x_4\$


texts: Why do most logic ICs (e.g. AND gate) have more than two inputs

texts:
I imagined the simplest AND gate in context of a small microcontroller project operating at 3.3V with two input pins and two one output pin. This is not the case in reality though, I didn't find one AND gate chip that wouldn't also have VCC and Ground pins.
I'm trying to understand better (coming from programming side of things) and I'm assuming this is a design choice. Two questions related to this:

Can AND gates be built without VCC and GND be built (power from input pins) and does this even make sense in a arduino-like environment?
Why are GND and VCC usually needed?


texts:
I have to design a PSRR test fixture with a 2.4KHz signal imposed on a dc power supply. I can do it using a bias tee at rf but the size of the components at audio confound me. The application is a Sample and Hold Amplifier Test Fixture. I would like to stay away from transformers and/or large inductors since I probably have to wind them.
Any suggestions welcomed.


texts:
I'm so new in analog electronics. So I stuck with one issue. Let's say I have an input signal, like blue one:

To get a DC form I can rectife it (got a grip on it). But what I need is a smooth(regulated), without spikes signal, like red one

Saturation is optional :)
So to get this signal I need to use intagrated circuit with op-amp and NF, like this:

But my question is next: how to pick values for each component (R39/R40=gain; R40*C37-integral time(not sure); all I know) and what excactly are they responsible for? Or just advise where to dig for info. Will appreciate any answer, friends.


texts: Why can't you go sticking a voltage across the base-emitter terminals in a transistor?

texts:
I just read some first pages of "The art of electronics - Paul Horowitz". In chapter 2 transistor it says there are four properties of an NPN transistor (for PNP, it is reversed).

The 2nd property say:

  The base-emitter and base-collector circuits behave like diodes. Normally the base-emitter diode is conducting and the base-collector diode is reverse-biased.

Then it says:

  Note particularly the effect of property 2. This means you can't go sticking a voltage across the base-emitter terminals, because an enormous current will flow if the base is more positive than the emitter by more than about 0.6 to 0.8 volt.

I don't understand why? Current flow from base to emitter because the base-emitter is conducting-diode so why can't I stick a voltage on those two terminals. If I don't apply a voltage, how can there be a current flowing?

Also,

  because an enormous current will flow if the base is more positive than the emitter by more than about 0.6 to 0.8 volt

What does this explanation mean? Why is the explanation that a voltage can't be applied to the base-emitter terminal?


texts: Powering long lengths of WS2812B Pixel Tape

texts:
I've been doing a lot of research regarding powering WS2812B pixel tape. From my tests, running a 5m length of 30 LEDs per metre tape requires powering at both ends to avoid yellowing/browning when running full white.

The way I want to setup the control means that I have a separate "controller" and PSU for every 2 tapes (for ease imagine one µC per two tapes). The controller is powered by the same 5V PSU as the tape. The tapes are lined up in linear fashion, so the 5V PSU is in between the two tapes, with 2x 5m extensions running to the outer ends. At one end is the controller.

Can I run the data out of one pixel tape into another one that is powered by a different 5V supply?
Is there an issue with tying the grounds together of multiple power supplies? (I imagine if I want to achieve what I want in point 1 then this would be the answer). I've read in a few places about some issues with current flow if the voltages are different between the two PSUs.
There's a lot of mention of fuses. What's the best practices with these? Similarly, a capacitor across the 5V supply?


texts: LTC3112 undefined behaviour when power supply reaches current limit

texts:
I am getting a behaviour of LTC3112 that I do not understand. I am using it very close to the schematic recommendations in the datasheet. It works perfectly fine until my power supply (TOE 7610-60) goes into current limiting (at 2.5 Amps). The current limit is only reached due to switching peaks in the current, but not actually used by the circuitry.
Then the LT3112 seems to get stuck and constantly draws 2.5 Amps (and gets really hot).

I have done a simulation with LT Spice, that does not show this behaviour. Note the voltage source V2 (going from 0.5 V to 0V in steps) and the voltage source V (with current limiting for 2.5 Amps).

In short: the power supply reaches its current limit and even if I decrease the output current of LTC3112, the power supply keeps outputting 2.5 Amps.

Here's the link to my Spice file:
https://drive.google.com/file/d/1YAqItHs-o8JfcMuBkUnUXJvRFGC33utz/view?usp=sharing


texts: Boot problem with STM32 HAL, I2C HDD44780 and 1602 LCD

texts:
I'm using the following (relevant) combination:

STM32F103C8T6 devboard (bluepill)
1602 LCD with I2C (HDD44780)
STM32CubeIDE HAL

Also I have a keypad and some other components attached, but these are irrelevant for the problem.

I use a stripped down library, removing some unnecessary delays (I think, since in debugging circumstances it works).

What I see is when I debug the application, all is ok. Occasionally the LCD will not go through initialization, but when I remove the power to the LCD and reconnect, and restart, debugging is fine.

However, when I do not debug, thus running the application 'normally', the I2C display shows either rubbish or shows the first line lighted and the second line empty. The application itself seems to work, except for the display.

The only way to solve this is to press the reset button on the STM32F103C8T6. Removing the power from the STM32 (and thus LCD) and reconnect power does not help.

How can I fix this? It seems I have to programmatically reset/init the I2C somehow?

Relevant code

MyMain.cpp

Global code, creating the LCD display, MyInit that is called from main.cpp (Init).

…

// Refresh every 99 ms, not 100 ms (than fractions are changing when displayed items have a period of
// % 100 ms == 0
LcdDisplay       _lcdDisplay   (&hi2c1, 0x27, &UpdateLcd, 99, 1);
...

void MyInit()
{
   //_lcdDisplay.I2C_Scan();
   _lcdDisplay.Init();

   …

LcdDisplay.cpp

The constructor saves some variables for the instance, MyInit initializes the screen. In this function is high likely a problem.

LcdDisplay::LcdDisplay(I2C_HandleTypeDef* hI2c, uint8_t i2cChannel,
      UPDATE_LCD_FUNCTION_PTR callbackFunction, uint16_t refreshTime, uint8_t sysTickSubscriberIndex)
: _hI2c(hI2c),
  _i2cChannel(i2cChannel << 1),
  _callbackFunction(callbackFunction)
{
   SysTickSubscribers::SetSubscriber(sysTickSubscriberIndex, this);
   SysTickSubscribers::SetInterval(sysTickSubscriberIndex, refreshTime);
}

void LcdDisplay::Init()
{
    // 4-bit mode, 2 lines, 5x7 format
    SendCommand(0b00110000);

    // display & cursor home (keep this!)
    SendCommand(0b00000010);

    // display on, right shift, underline off, blink off
    SendCommand(0b00001100);

    // clear display (optional here)
    SendCommand(0b00000001);
}

void LcdDisplay::SendCommand(uint8_t cmd)
{
    SendInternal(cmd, 0);
}

HAL_StatusTypeDef LcdDisplay::SendInternal(uint8_t data, uint8_t flags)
{
    HAL_StatusTypeDef res;
    for(;;) {
        res = HAL_I2C_IsDeviceReady(_hI2c, _i2cChannel, 1, HAL_MAX_DELAY);
        if(res == HAL_OK)
            break;
    }

    uint8_t up = data & 0xF0;
    uint8_t lo = (data << 4) & 0xF0;
    uint8_t data_arr[4];

    data_arr[0] = up|flags|BACKLIGHT|PIN_EN;
    data_arr[1] = up|flags|BACKLIGHT;
    data_arr[2] = lo|flags|BACKLIGHT|PIN_EN;
    data_arr[3] = lo|flags|BACKLIGHT;

    //res = HAL_I2C_Master_Transmit_IT(_hI2c, _i2cChannel, data_arr, sizeof(data_arr));

    res = HAL_I2C_Master_Transmit(_hI2c, _i2cChannel, data_arr, sizeof(data_arr), HAL_MAX_DELAY);

    //HAL_Delay(LCD_DELAY_MS);
    return res;
}

As you can see I removed the HAL_Delay (it seemed unnecessary).
I tried to use I2C using interrupts, but didn't got it working (so far).


texts: How to make a simple USB gadget without vendor and product ids'

texts:
I would like to control a simple servo or led with USB.

I opened the cable up and connecting the red and black wires to the servo made it spin properly with about 5V, as those are VCC and GND. Ok.

Now I would like to use one of the data channels to control the state (on/off) of the servo via my computer.

In the end I would like to have a script to turn it on and off.
The problem is that every tutorial uses an USB architecture that makes drivers overly complicated by using vendor and products ids' to auto identify the hardware at the end of the USB (to allow for plug'n'play, I imagine), and I don't have that - that is, I don't want to make a circuit that is able to inform to the PC the specs of my device. And I do not want to use Arduino's or other complex boards for such a simple task.

I couldn't even identify my ports (in linux), as every software and utility I found lists only the plugged usb's, with their crazy ids, and my bare ended (servo apart) half-cut usb extension is not listed, as (it seems) it is not connected to a 'proper' usb gadget.

I would like to make a program that would run, ask for a physical usb port on my machine (identifying then somehow) and then let me set the output in each of the two wires, instead of a driver that can automatically detect my gadget. Simple as that.

Is there a way to do that with USB? Or should I choose another way of communicating with my device? (though I can't think of any other ways that my computer would handle... and with the advantage of built-in power...)


texts: What capacitor types perfom best for large-value signal path applications?

texts:
Most signal path/timing capacitors are of stable types such as film or C0G ceramic.  However, size and cost force an upper limit on this -- C0G caps out at 10-100nF, while film caps can manage up to 1-10µF albeit at a severe size penalty -- this isn't enough to cover things like audio coupling capacitors and large timing capacitors, which may be 47µF or more.  In the "bad old days", the only choices for these tasks were wet aluminum (bulky and with poor tolerances) or MnO2 tantalum (intolerant of reverse polarity but more precise) electrolytics.  However, modern technology has given us more options for this -- conductive polymer electrolytes are now in common use with both aluminum oxide and tantalum oxide grown dielectrics, and niobium oxide based capacitors are a niche product as well.

Which of these technologies for large capacitance/high-CV capacitors, old or new, provides the best performance in terms of:

stability (for timing applications)
not distorting coupled signals or introducing excessive noise (for signal chain apps, such as audio or other low frequency signals)?


texts: What is the effect of supply voltage asymmetry in opamp amplifier topologies?

texts:
What is the effect of a \$\Delta V\$ voltage shift in one of the supply voltage inputs of an opamp on its functional behavior (\$\Delta V\$ can be positive or negative)?

Suppose that, I'm designing a non-inverting amplifier with \$R_1 = 100k\Omega\$ and \$R_2 = 1k\Omega\$. Supply voltages are; \$V_+ = +5.0V\$ and \$V_- = -4.5V\$. And my opamp is MCP6V31. What will be the output voltage, if my input voltage is 1kHz sinusoidal voltage, 10mV peak-to-peak?


texts:
I buy a 2 channel relay module for Arduino.
I surprised that why this relay module is designed active low?
Circuit:

i means that when we connect In1 to low V (GND) relay turn on. Is there any reason for using this way instead of turn on relay with high V?

sorry for bad English.


texts: Delay TTL signal from board power supply

texts:
To preface, I don't come from an EE background so I'm sorry if this question is extremely simplistic.
I have a shutter controller board that allows me to open and close a shutter (optical iris) with a TTL signal.  However, I want to keep things modular with a prior system that was controlling the shutter via simple power to the control board (we don't open and close the shutter often).  Unfortunately, this prior system's control board has been discontinued and is no longer available.
My idea was to simply use the board's power to also provide the TTL signal.  Voltage isn't a problem and I've confirmed that from lab power supply that this method should work.  However, I need to introduce a delay to the TTL signal to allow the board to be powered up first.
I'd like to make this as simple as possible.  I was considering doing an RC opamp delay circuit, but that seems like it may cause problems if the rising edge is too slow.  Am I approaching this in a completely unreasonable way?  Ideas?  Thank you so much for any insight you may be able to provide!


texts: What Does Rated Load of a Tactile Switch Mean?

texts:
I want to connect a tactile switch to an GPIO pin of MSP430 (which runs on 3.3 volts). The datasheet of the micro-controller says that IO pins can withstand max current of 6mA.

The tactile switch I am interested in has rated load of 12V and 50mA.

What does it mean? Does the switch draws power when it is closed?! Can I use the switch with that micro-controller?


texts:
I'm using the TPS56221 buck converter.

500 kHz switching frequency
12V in 5V out,
16A max, 14A load step

I've found out all the values I need, the problem I'm having is finding suitable capacitors. For example I need around 600uF output capacitance and 200uF input capacitance. However at 12V any capacitor I get will be more than half it's capacitor value due to the DC biasing. Even at 5V, most capacitors are half their value such as the C1210C107M4PAC7800 (100uF) that I want to use. I could put 12+ of those to get the 600uF that I need, but I'm wondering if there is a better solution here - for example the MegaCaps from TDK that keep the capacitance relatively stable with increasing voltage

Thanks in advance!


texts: Different dc results with Operating point analysis and DC Sweep analysis

texts:
I am simulating a dc analog circuit comprising transistor, opamp and resistors.
In Ltspice, if I run a Op point analysis for a boundary value of my input voltage I get unexpected reults. (This is shown in image as current through Resistor R6 which is I(R6) )

However, if I run a DC Sweep Anaylsis for whole range of input voltage including boundary values, I get the results as expected. This is shown in image below that I get different value of Resistor R6 current for same value of input voltage Vin = 6.1

As both of these Analysis are DC and calculate node voltages and current, this discrepancy between both analysis is to my surprise.

Can anyone share his experience ? which result is the right one ??


texts: Stacked metallized film caps -- what's the "outside" foil?

texts:
One piece of advice that gets tossed around when low noise analog design is discussed is that the outside foil of a metallized film cap should be connected to AC/RF ground, or to whichever circuit node is closer to AC/RF ground, to basically act as a noise shield of sorts.  This is great for wound metallized film capacitors, where there is an "outside foil" to talk about.

However, almost all SMT film caps use a stacked structure similar to a MLCC -- see this datasheet for an example.  If you were using these capacitors in a low-noise or otherwise sensitive design, does it still matter which end is connected to the node nearer AC/RF ground?


texts:
The UC3C Datasheet doesn't provide a clear explanation about "drive strength", how it behaves and the side effects in projects. After fabricating my board I realized I placed a LED on a x1 strength pin (AVR32UC3C2512C pin PB00) and I calculate a 23mA current ((5V[input] - 1.5V[LED drop])/150ohm).

In table 40-6 there is a tip that x1 handles 3.5mA, so what happens if I turn this LED on? Will the LED drain more current than the pin can handle and burn the MCU or will the MCU limit the current to 3.5mA? Or does it means something entire different?

The Circuit:

simulate this circuit – Schematic created using CircuitLab


texts: Why should I learn a microcontroller architecture?

texts:
I recently started working in a small company that produces automotive diagnose related electronics. My boss, who is in his mid 50's, said that he was using 8051 derivatives, and they were doing the job. I went on to search Google to learn if 8051 is still popular today. And in Quora, I saw these:

  ...it is probably the simplest MCU architecture around. Every peripheral seems like the bare-bones version. My concepts of timers, clocking, UART etc. cleared up a lot! And, I then began appreciating other architectures - because I actually understood the differentiation.

  ...obviously , it won't be used by any industry to develop a product because of its simplicity...

But why? So far, at least as a student, I used to do a lot of things without messing with architecture. I happily coded with C, I used LCD peripherals, connected to other IC's with different protocols (SPI, I2C etc.)

Why should I bother with architecture of my microcontroller, apart from limited fields of real-time & time-critical applications?


texts:
I'm sure this is a basic question but I am unable to find an answer anywhere online that explains it in a simple way.

I am researching NTC sensors and figuring out how to use them.

I want to know that the advantages or disadvantages of changing the NTC resistance will be ?

So far I have the assumption that a larger resistance ( 50K ) could meausre a greater range of temperatures ? ( than say a 10K )

But if both are 1% tolerance the larger resistance would not be as accurate because the range is bigger ?

Am I on the correct track here?

Also I take it that in my voltage divider circuit I should get a better tolerance resistor if I want the reading to be more accurate ?
( 1% instead of a 5% )

I am looking to measure temperatures of around 90 - 130 degrees C, with an accuracy of around 1 or 2 degrees, if that makes a difference.


texts: What is the purpose of a capacitor in an ideal op amp schematics?

texts:
I'm trying to understand the purpose of the capacitor C which is in parallel with the resistor R3. Current sources IB are indicative of the current offset which was the part of the lecture we had where we tried to compensate the offsets and the op amp is ideal.

When analyzing the DC regime the capacitor is an open circuit and all of current IB goes through the resistor R3 and when analyzing the AC regime it's a short circuit and no current passes through it.

Was it it's sole purpose to short-circuit the R3 resistor? Why would that be so important if that's the case other than reducing the total resistance of the circuit?

The capacitors are thought of as having infinite capacitance and IBs are DC current sources.


texts: RS485: Where to connect the cable shield in a battery-powered system?

texts:
I have implemented a Modbus with the RS-485 bus. The length of the bus is about 80 meters and I have connected the master and 10 slaves. The system is battery-powered and will be outdoor.

My question is about the shielding of the bus cable. Is it sufficient to connect it to the negative terminal of the battery, or must it be physically connected to ground?


texts: Is it possible to detect a battery type and requirements(voltage,current etc) using an MCU based circuit?

texts:
I am trying to build a generic circuit to detect different types of batteries (lithium ,lead acid etc) based on automatic and quick tests for a potential product.

Is this  possible using an mcu and and electronic circuit?


texts: How Does Varactor AFC Work in This circuit

texts: I have a question about how the varactor on the transistor's emitter can change the frequency of the modified Colpitts oscillator on the collector of this circuit. The junction of the varactor and R30 has 3.4VDC on it at 10.7MHz (FM IF). This voltage comes from the ratio detector. When the frequency increases above 10.7MHz, the ratio detectors output drops and the voltage at the cathode of the varactor drops. Conversely, when the frequency drops, the voltage increases. Both voltage swings were about +/- 10mV so small in either direction. So exactly how does a varying capacitance on the emitter change the frequency of an oscillator on the collector.


texts: Any resources to understand Clamper circuit?

texts: Can anyone please provide some resources for understanding of Clamper Circuit, i'm having a hard time in understanding it when it comes to biased circuit.


texts: Why does a spark occur when an SMPS is connected to the load circuit?

texts:
I am using a 36VDc SMPS as a power supply. A spark is generated when I connect 36V with my load circuit.
Specification:

Voltage source: 36VDc
Current consumption: more than 3A

I want to know why a spark is generated when I attach my load circuit, and how can I reduce the spark.
I have tried some RC circuit solutions given for arc suppression circuits but I can not identify how can I use those solutions.
Is there another way to reduce the sparks?

I tested with a 1545CT Schottky diode to put at the beginning of my circuit as mentioned in this answer, but the solution isn't useful in my case.
@Manumerous, can you guide me for which type of MOSFET I have to use in my circuit with configurations to avoid a spark?


texts: SPI on STM32 won't work without pullup resistors and even then performs poorly

texts:
I've been trying to get the SPI1 on the STM32F103C8 (Blue Pill board) working correctly for some time now. As I'm just starting to learn ARM, I am simply trying to shift data to a 74HC595 shift register and latch it to light up a byte of LEDs. I am not reading back any data, so I only have MOSI, SCK and SS lines.

At first I wasn't getting anything out, but reading some online examples I could fix these first problems to get the communication going (I needed to correctly set GPIOA pins and set software SS).

The main problem right now is that if I don't include pull-up resistors on all lines (MOSI, SCK, and SS) the microcontroller doesn't output anything on any line (checked with a scope). On top of this, after adding pull-up resistors the rise time on the pulses is very slow so I can't use too high a frequency (with 10 kΩ pull-up resistors I'm limited to about 250 kHz SCK, and switching to 330 Ω about 4 MHz). I am working on a breadboard, but even then with AVR and messier wiring I could get a 4 MHz SPI working no problem without any added resistors and the waveforms were cleaner.

Here are two pictures (sorry for the abysmal state of my scope screen) transmitting the byte 0b01110010 at a 250 kHz clock. The top trace is SCK and the bottom is MOSI. The first picture is with 10 kΩ pull-up resistors and the second with 330 Ω pull-up resistors that make the waveforms much nicer (but they shouldn't be needed).

I'd appreciate some help to figure out what's going on.

The relevant parts of my code are:

#define SS_LOW        GPIOA->BSRR |= 1 << 4 + 16;
#define SS_HIGH        GPIOA->BSRR |= 1 << 4;

// SPI GPIO configuration
RCC->APB2ENR |= RCC_APB2ENR_IOPAEN;
GPIOA->CRL |= 0b0011 << 4 * 4;    // Set pin A4 as PP out 50mHz for SS
GPIOA->CRL |= 0b1011 << 5 * 4;    // Set pin A5 AltFunc PP out 50mHz for SCK
GPIOA->CRL |= 0b1011 << 7 * 4;    // Set pin A7 AltFunc PP out 50mHz for MOSI
SS_HIGH;

// SPI1 configuration
RCC->APB2ENR |= RCC_APB2ENR_SPI1EN;        // Enable SPI1 clock
SPI1->CR1 |= SPI_CR1_SSM;        // Software SS
SPI1->CR1 |= SPI_CR1_SSI;
SPI1->CR1 |= SPI_CR1_BR_0;        // Set prescaler
SPI1->CR1 |= SPI_CR1_BR_1;
SPI1->CR1 |= SPI_CR1_BR_2;
SPI1->CR1 |= SPI_CR1_MSTR;        // Master mode
SPI1->CR1 |= SPI_CR1_SPE;        // Enable SPI

// Transmit byte
SS_LOW;
SPI1->DR = 0b01110010;
while(!(SPI1->SR & SPI_SR_TXE));
while(SPI1->SR & SPI_SR_BSY);
SS_HIGH;


texts: RD-ZD-25F, 220V/50W motor as a generator

texts:
I have 2 RD-ZD-25F, 220V/50W DC motors from 2 broken bread-making machines. Can they be used as a generator?
I gave one with the hand few spins and I got a little bit of a shock from it.

Thanks

PS: The only specs I could find for it:
Model: RD-ZD-25F
Voltage rating: 220 VDC
Current rating: 0.23 A
Power: 50 W
Motor diameter: 63 mm
Motor length: 105 mm
Shaft diameter: Ф7 mm with jam 14 mm
Shaft length: 20 mm
Wiring: 2-way cable
Motor mounting: 3 x openings M3 mm
Body material: metal
Application: used in bakeries and ovens


texts: Interrupt Management - Large AVR Projects

texts:
This is for the more experienced one's out there.

I am currently involved with a large AVR project (using ATMega328) and it's getting confusing with respect to interrupts.

The project involves interrupts from the following sources

USART
TWI
SPI
External Interrupt (INT0 and INT1)

With so many interrupt sources and the fact that global interrupts get disabled when an ISR is executing, I am afraid of missing out on interrupts that might fire when my code is servicing another interrupt.

So is there some more structuralized method of managing interrupts in a large project?


texts:
I'm trying to understand the operation of a single coil magnetometer (marketed as "fluxgate", but with only a single coil). I've backed out the schematic as shown. The coil is driven by a 17kHz oscillator (not shown other than as "oscillator").
I'm stumped on the part I've called U4. It appears to be a SOT-143 device with the marking "E9" on the top. There is no continuity between any of its 4 pins to the others. Sadly the diagram doesn't lend many hints either - I was initially leaning to an NPN RF transistor, but the pinouts/functionality don't make sense. Any thoughts would be appreciated. Photo of the part included with U4 circled.


texts: Is there a way to recycle/use negative half of AC voltage from a rectifier?

texts: Forgive me, as I am far from an electrical engineer, but when rectifiers were explained to me I found that a rectifier allows current only in one direction, which allows it to filter out negative voltage of an AC power source and only output the positive, but where does this negative voltage go? Is it just lost in the conversion process? If so is there a circuit that can "recycle" this "lost" negative voltage?


texts: Acquiring and fusing data from different controllers

texts:
TL;DR: What are some options to fuse data acquired with separate controllers?

I'm developing my own IMU for a quadrotor.

My inputs are an accelerometer, gyro, magnetometer, and barometer all via I2C and my GPS module via serial. The I2C bus updates & transfers much faster (~few ms) than the serial (~1s, 4800 baud).

My outputs would be commands to 4 motors and data logging.

I've been reading the I2C stuff with an AVR because I need quick updates to prevent drift of the quantities I'm integrating (gyro, accel). However, I can't read the gps with the same AVR at 4800 baud without skipping an eternity of I2C data. I concluded I need to read the gps with something else. (currently a raspberry pi)

I've already implemented a kalman filter on the AVR for the gyro/accel/mag/baro. Now I want to fold in GPS.

The simplest option would be to move everything to the pi and run the I2C and serial on separate threads and save to global variables. But getting away from real time data acquisition worries me.

Another option may be to acquire the I2C and Serial with two independent AVRs and save the data to an outside memory module. I'd then need some 3rd device to get all the data off the memory module and run the calculations. (Maybe this is a crazy 'hardware' version of a global variable?)

I'm just getting the sense I'm going about this the wrong way, even if I could brute force it to work. Is there a 'right' way to solve this problem?


texts: Generalized transistor equation for Collector Current including the reverse saturtion current?

texts:
44I am referring to Millman's Integrated electronics and there I came across and equation
$$
\begin{equation}
(I_c) = -\alpha(I_E)+I_{Co}(1-\exp^{V_C/V_T}) -->eqn(5.6)
\end{equation}
$$
where $$ I_{Co}(1-\exp^{V_C/V_T})  $$ represents shows reverse saturation current . Can any one explain me how this equation came . Also is not reverse saturation current independent of applied voltage then why is there $$V_c$$ there in equation ?


texts: It seems standard for a lithium-ion charger to cut off the applied voltage when the CV-mode current draw dips below 0.1C (or thereabouts).  Why is this necessary?  Why can’t the charger continue to apply 4.2V indefinitely?


texts:
So i have the following circuit:

and I am asked to do the following:

a) I should determine the type of negative feedback here and draw a diagram that confirms that it is indeed the type of neg. feedback I said it is

b) I should find the voltage gain using "negative feedback theory". I believe that it means that I should do it using the formula:

$$A_r=\frac{A}{1+\beta A}$$

c) Find input and output resistance using formulas I previously used for b)

My attempt:

It's somehow obvious to me that, looking from the output, we have a so-called voltage connection, which means that the feedback network (which has R1 and R2 resistors in it) is connected in parallel to the output, however, looking from the input I cannot conclude what type of connection I have since we have the gate connected to the feedback network, meaning that feedback is connected to the input only with one of it's ports.

Since I can't conclude what kind of connection I have, I'm not able to progress further with this problem. Any help appreciated!


texts: 1 master, multiple slaves RF communication

texts:
I want to communicate with multiple Arduinos over RF. Price is important, and so is power use.
So I've ordered a couple of nRF24L01 modules which seemed up to the task. One thing I like is that they allow setting a channel (0-127). They also cost very little and use little current.
However as I will communicate with one master device (PC endpoint), I need to use a single channel for all those slaves (think in the dozens), which would mean I'd have to share bandwidth, which I'd rather not do.
My last resort is having a master transceiver for each individual slave.
Is there a better solution than that?
Update
Required bandwidths, single connection:

Client -> Master: 80kbit (single packet: 360 bytes)(could be without CRC and ACK)
Master -> Client: 5kbit~, very little (single packet: 20 bytes)(needs CRC and ACK)

There is no communication needed among  clients.
I would like to stay off Wifi/Bluetooth, as they consume more current, are pricier and the range is shorter.
But I would like to keep master-client ratio as high as possible (1:5 at least). A Pi is a possible alternative if throughput is an issue only for master.


texts:
I am using display port interface in my design. As per display port specification biasing circuit is implemented to auxiliary signals. Since AUXP and AUXN are LVDS signals they can be connected to 1.8V IO bank in FPGA

Can someone tell me the importance of below circuit?


texts: Help building Digital Logic Circuit (from truth table and state diagram)

texts:
I am somewhat stuck and desperately need help. I am faced with the Traffic Light Problem, and I completely understand the actual logic of it. However, I am having great difficulty turning this into digital logic. I have thought through the state diagram.
My biggest problem that I can't wrap my head around is that the State is represented by a two-bit binary number. So when building my circuit, how do I "create" this two-bit number using gates and what not?

This is my simplified truth table for the problem. 4 states: new red light(00), existing red light(01), new green light(10), and existing green light(11) [the yellow light is being ignored in my version of the problem].

Reduced Truth Table
State Input  new State
  00    00     10
  00    *1     10
  00    10     01

  01    00     10
  01    *1     10
  01    10     01

  10    **     11

  11    0*     11
  11    1*     00

Now, I get how to brute-force design the output of each state+input to get each newState. I just am having a very difficult time bringing it all together.
I have my State Diagram all drawn out and I get when the transition needs to happen, its the digital logic that I'm having trouble with

I still have much trouble with Multiplexers, although I know they would be usable in this schematic I have drawn below (because I have created a brute-force design from the State rather than the inputs)

simulate this circuit – Schematic created using CircuitLab

I have another much more complicated schematic that includes both the State and the Inputs, but I'm not sure if it is right or how to use it further (i.e. connect to flip flop and create an output of the traffic light color) [NOTE: THE OUTPUT IS WRONG, the output of the first OR gate should be S0 and the output of the second OR gate should be S1]
[]1


texts: Higher than expected leakage drain current with Vgs=0 for N channel MOSFET

texts:
I'm fiddling with an STP36NE06, the datasheet says for Vgs=0, worst case maximum drain leakage current should be 10uA. (Maximum Vds, maximum temperature)

However I'm getting a reading of just under 1mA (for Vds=5v, Tcase=25), only out by a factor of over 100! I've even soldered the gate and source directly to each other to make sure.

What's going on here?


texts: Effects of using a different PWM frequency than specified on device

texts: I am wiring up a fan speed control circuit that creates a PWM frequency that is used by a PWM fan (the fan and its specs are pictured below). The fan claims that its PWM control is done through a 25kHz frequency. What will happen, in any situation in general, if I don't match 25kHz exactly?


texts:
I have a circuit to calculate my battery level using NodeMCU.
I use this formula:
    float r1=10.0;   // resistor
    float r2=2.0;    // resistor
    int analogvalue = analogRead(A0);
    temp = (analogvalue * 3.3) / 1024.0; // nodemcu works 3.3v and analogRead 1v
    volt = temp / (r2/(r1+r2));

I have to power on/off different sensor to save power. When I calculate the battery level with the following schema I have a correct result:
AnalogRead: 213
Battery: 4.12V

The problem is when I put a MOSFET to turnoff the battery calculator. I think that the MOSFET is like a resistor but I am not sure. With the following schema, I have the results:
AnalogRead: 136
Battery: 2.63

Can somebody help me?
Thanks!


texts: I understand that I can not connect an LED directly to a battery because it will draw too much current. Thus, there must be something else in the circuit to limit the current. What options are there? Are some methods more efficient than others?


texts: Calculation of supply current in stepping motor driven using chopping driver

texts:
I'm using STK 672-330 to drive a unipolar 2 phase stepping motor. The situation can be seen roughly in the circuit diagram below.

I set Vref so that the peak phase current becomes 1.2 A.
When I measured the current in the phase A (blue arrow), i confirmed that it correctly peaked at 1.2A . But then I measured the current from 24V (red arrow) it looks more like DC 400 mA ish.

I did a few research and I found out that according to this source (around last page) supply current is calculated using this formula:

Isupply = IM · ( VM ⁄ Vsupply )

where IM is motor winding phase current, VM is motor winding voltage.

In my situation:
Vsupply= 24V, IM = 1.2A, VM = 3.6V (winding resistance is around 3 Ohms)
so it gives me Isupply = 180 mA for each phase. Which gives a total 0f 360 mA.
This result more or less agrees with my measurement.

But why does this equation holds? I find it strange we need to divide with Vsupply. If the current flowing in the phase peaks at 1.2A, why there is no such peak appear in the 24 V line? Where does the current come from and go to?

I have a hunch this has something to do with the PWM chopping by the FETs inside the driver IC. But I can't find satisfactory explanation for the continuity of current.


texts:
I need to change the polygon clearance. Here are my setting rules.

But it seems that the lower rule for all clearances is superior to the second one and nothing has been changed. what is my mistake that the first rule is superior?


texts: Customizing both voltage and amperage in a circuit

texts:
I intend to control a motor via H-bridge L6205N (PowerDIP20). H-bridge's logic input requirements are:

High level logic input voltage: 2-7 V
High level logic input current: 10 μΑ

Motor's supply requirements are: 9 V, 0.4 A (approximately). Logic signals are the output of a BeagleBoard-xM (0.44 V). Thus, I have to customize signals to >2 V and <10 μΑ.

I thought of putting a 47 kΩ resistor, to customize amperage to 9.3 μΑ (via Ohm's law) and thereafter an non-inverting amplifier (close loop gain equal to 5) to customize voltage to 2.2 V.

Is my syllogism write and if not what is the way customizing both voltage and amperage? Is there something I have to pay attention for this circuit design?


texts: How can I make a power system efficient and safe?

texts:
I am currently designing a power system and so far I have been using fuses before relays to protect against high current. Those relays lead to multiple loads to power. I was thinking of adding a Bypass capacitor to shunt noise entering the system, but I am lost on what to choose to control my current inflow to those relays and loads.
It is my first time  ever designing a schematic myself and I have been trying to read about ways to make it safe, but I am rather confused.
To sum up, my sub-questions are:

Can I use a resistor before a fuse to control current inflow?
Is there another way than using a resistor that could limit high power dissipation?
What else should I think of when designing a power system?

The circuit will be connected to a current/voltage sensor and a microcontroller.


texts:
To convert 1-5V to 0-20mA:

When I use 3.3V ouput from Arduino Nano Power Pin--> Iout = 13mA (which is ok).

Similarly, with 3.3V Battery -> Iout = 13mA (which is ok).

But, when I use 3.3V ouput from Arduino Nano Analog pin(PWM)--> Iout = 16mA (I can't understand this value).

At 2.5V output from Arduino Nano Analog Pin--> Iout = 13.7mA.

Is seems their is a problem using Analog pins of Arduino nano?

At present, I am not using low pass filter. Will using low pass filter solve the problem?


texts: Why dust sensor is throwing different values on change of usb cable?

texts:
I have a dust sensor(particulate matter sensor) from Honeywell and which is connected to Vin(5v) of ESP32 dev board. The problem I am facing is sensor throwing different values when I change USB cable which I use to power on esp32. Different cable is giving me different values(if the actual PM2.5 value is 12 device throwing value around 90) but sensor works fine when I use it with Arduin0 UNO. When I measure voltage in Vin pin it hovers around 4.6V t0 4.8V in all the cables.

Can someone please explain to me what am I missing here?