texts: make arduino start when a line is broken

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simulate this circuit – Schematic created using CircuitLab

Hi. I'm trying to build an anti-theft project. Where if you break a thin wire connexion, It should power ON the arduino and let it do its thing.

As long as the wire on top is not broken, it should draw nothing from the battery and the whole circuit should be OFF. This is important because I need the battery to last many years as this event will occure very rarely.

Optional: would be nice if power to arduino shuts down when the line on top is connected back.

What should I use in the "some magic" box ?


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From the label on thermostat I can read the following, but can't decode it to understand the max current.

CAMPINI Ty 95

C1-16(3)/250~
C2-6(1)/250~

Does anyone know what is the 16(3) and 6(1) means? The device(oven) has 1.15KW power mentioned on the back? I am trying to substitude this thermostat with simple relay, but would like to get one with proper current. Wires connected to it and thermo elemt are 2mm thick, if that helps.


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I'm using CN3722 for 2 cell battery charging. I have two way supply, it gets power from Solar as well as DC 12V whichever is available. The MPPT is set at 11V. Solar panel maximum goes to 21V.

I have two circuits. When I apply 12V the 'CHRG LED' blinks(Battery - NC) in both of the circuits, When increasing voltage to (13V-15V) the CHRG LED stops blinking(should blink) in one of the circuits. The charge current is set to 1A.

Both circuits have similar diagram and components but show different behavior. When I increase the voltage above 13V the battery is not charging in the faulty circuit whereas in the other circuit all conditions are working fine.

But when I measure the voltage of GATE DRV pin of IC, it started drawing the charge current. What might be the reason?


texts: Why do motherboard voltages meet 5v standard when so much seems to work at 5.5?

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I am working with supercaps (>1F) for resin embedded purposes. I have an induction charger that says 5v, but it really is outputting 4.85 volt. Caps seem to be commonly in 2.7 and 5.5 volts... although there are some caps at other voltages, 5.5v seems to have way more supercaps than just 5v. Why is this?
I can't really fully charge big 2.7v caps in series (5.4v) but it seems so perfect for a 5.5 volt system. And I have to use a buck converter to get to 5.5 volt... or I have to just resistor drop everything to 2.7/3 and then they don't last anywhere near as long. SO what is the reason for this and how do I deal with this problem?
I could really use some insight. I'm sorry if this has been explained elsewhere... I'm struggling to dig through huge search results with just voltages and basic words for filtering. Thanks for any help.


texts: Clarification on region of operation in MOSFETs

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So this is going to be a series of questions:

Enhancement MOSFETs:

N-Channel:

So applying positive voltage and up to the gate, relative to source, lets more and more current through until it reaches saturation. 0V turns it "off", so no current.

) Now, what reason will there be to apply negative voltage to gate, relative to source?

P-Channel:

Applying negative voltage and down to the gate, relative to source, lets more and more current through until it reaches saturation. 0V turns it "off".

) What reason will there be to apply positive voltage to gate, relative to source?

The rationale of the 2 questions above is that the regions of operation are "reasonably continuous":

?? -> cut-off -> linear -> saturation

In N-Channel, if positive and up is linear and saturation and 0V is cut-off, then is negative also in cut-off or is there another region? And, vice versa for P-channel.

Depletion MOSFETs:

N-Channel:

Applying negative voltage and down, relative to source, narrows the conductive channel and lets less and less current until it pinches of and lets no current through. 0V, relative to source lets current through.

) What reason will there be to apply positive voltage to the gate, relative to source? Would it conduct more current than 0V?

P-Channel:

Does not exist in the market, but for theoretical consideration:

Applying positive voltage and up, relative to source, narrows the conductive channel and lets less and less current until it pinches of and lets no current through. 0V, relative to source lets current through.

) What reason will there be to apply negative voltage to the gate, relative to source? Would it conduct more current than 0V?

The rationale of the latter 2 questions above is that the regions of operation are "reasonably continuous":

?? -> cut-off -> linear -> saturation

In N-Channel, if 0V, positive and up is saturation and linear then is negative cut-off and is there another region? And, vice versa for P-channel.


texts: Surface Mount vs. PTH Components For Production

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I'm a hobbyist who has developed a product which uses ~20 PTH components. The device is essentially an Arduino UNO with some extra driver ICs and LEDs. I have had quite a lot of positive feedback on the product and am considering re-designing it so that I can put it into production.

I was wondering what technology was best for automated/volume production? I've noticed that several companies use both surface mount and PTH components on their boards, Arduino being an example. How do the board designers make a decision on what technology to use? Size isn't really an issue for this product, the existing board using PTH components is a quarter of the size of it's container.


texts: USB Power Delivery over Type-A connector

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I have a Xiaomi phone that came with a 33W charger. It says it does 5, 9, 11, 12 and 20 volt, so looks like a fairly normal USB-PD charger. Except, it has a type-A socket and came with an A-to-C cable! How is that possible?
It seems to be doing normal PD on the C end, because I successfully charged a laptop at 20V. Both charger and cable have the 5 extra pins from USB 3. Is there a standard for this at all? Does the A-to-C cable have a non-standard pin mapping to make USB-PD work?
Edit: Here's an old eBay listing for an identical charger.


texts: Detect if input voltage is 110V or 230V signal

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I'm building a small electronic project that will measure the power consumption of a device and send this back to Arduino or ESP2866.

I've figured out how to measure the current that goes trough a power cable using the ACS712. This works fine.

The only problem I have is sending the input voltage be it either 110 Volt or 230 Volt. The easiest for me to work with would be an output signal of 3.3 Volt. E.g. 0 volt when the input voltage is 110 Volt and 3.3 Volt when the input voltage is 230 Volt.

Then if my input pin is 0 volt (digital 0) AND I measure a current I can assume that the input voltage is 110 volt. If the input pin has 3.3 volt (digital 1) and I measure a current I can assume that the input signal is 230 volt.

Right now I am setting stuff up on a breadboard but when all is done it should have an as small as possible footprint. Around 2.0 x 2.0 centimeters.

Anybody has some good tips on how to do the voltage sensing?


texts: Purposely draining a battery by a resistor

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I'm new to electronics and wiring, and wonder if a 15 ohm resistor will drain a 1.5v battery (specifically a Duracell Alkaline AA) in a reasonable amount of time to a super-intense white LED.

Does anyone know if this will work?


texts: Passing input on one pin of FPGA straight out to another output pin for monitoring

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I need to monitor a signal as it is going into the FPGA, tracking down a potential noisy input or slow rising signal issue.  I want to use an external oscilloscope to see what the FPGA sees (as opposed to the internal chip scope), so I thought I could just do this :

However, this creates a timing violation that I don't understand.  I get a WNS of -3.758ns -- what setup/hold time does the tool think I need to meet here?  This is not going into a latch or anything, just connecting two pins internally (one in , one out).  Am I violating the setup time for the FPGA's IO buffer?  If so, what are my options?
All I'm trying to do is to monitor a signal as it "enters" the FPGA by echoing it out another pin.  I can of course connect the scope directly to the input pin by soldering a wire to it, but I do not want to do that.  The other pin I can use to monitor the input signal is available and goes out to an easily accessible connector.
***********Edit ********
Timing violation:


texts: Is it possible to make a "Sony CFS-201" cassette player/radio output sound from an external source?

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I have an old 1989 (bought new well into the 1990s) "Sony CFS-201" cassette player/radio with a broken cassette mechanism. I'm trying to use it as a "dumb speaker" by hooking up an audio cable from my Raspberry Pi to it, to play back a custom sound file on repeat to simulate white noise, but there is one "small" problem:

The only connector it has is for headphones, which means that it outputs audio instead of accepts audio input. There is a built-in mic, but no "mic connector" (it's just three small holes in the top of the device instead of a connector). I've looked closely everywhere in good lighting. Also, I read the manual.

Yes, I know that this is a cheap consumer electronics device from 30+ years ago, and half-broken on top of that. But it's also very sentimental to me, and it would've been nice to find a way for it to actually be useful again. However, I don't think this is possible.

And before you suggest it, I cannot just make it play radio static, because it sounds very unpleasant and not at all like "white noise". And I cannot repair the cassette mechanism to use a tape (plus that would get really annoying with having to rewind it all the time).


texts: Is there any micro-controller with ADC > 20 MSPS?

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Is there any micro-controller with ADC more than 20msps (at least 20msps ) ??

Maximum limit I have found is 12.5msps in texsas instruments C2000 f28335

http://www.ti.com/tool/tmdsdock28335#descriptionArea
http://www.ti.com/product/tms320f28335

If not , is there any method to mix more than one channel (ADC) to get higher sampling rate ?


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Id like to create a powerful IoT Edge device that has cellular capability (Wifi is undesirable). Right now the intel compute stick/neural stick almost fits the bill except that it does not have 4G capability.

So what id like to do is buy a compute stick and an USB 4G modem device and connect them via USB link.

I want to explore if it is possible to fuse the underlying circuits together of both of them (Compute stick + USB 4G modem device) and make a professional looking monolith out of it.

The idea is that the monolith comes with power of intel compute stick plus a 4G capability! at the same time not bulking out too much and/or becoming heavy.

Is this possible to accomplish that in the capacity of individual developer?

More importantly will it violate usage policy of the individual component manufacturers? (Intel or 4G modem manufacturer?)

If this is not a viable solution, is there an industry out of the box lightweight alternative computing platform that comes with 4G capability built into it?


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Previous thread: Flyback transformer

So, in short, I'm attempting to build a flyback transformer. The schematic I am using is this:

And the flyback core looks like this:

Upon recommendation from the previous thread, I got an actual ferrite core from a TV and wound it myself, 10x 80 turns of 0.125mm copper wire (as in 800), each layer (composed of 80 turns) separated by insulation tape. The primary coil (5 turns) was wound underneath these. All the turns are over the airgap in the flyback core.

The circuit is running to an extent. There's a high pitched squeal when it turns on, and the MOSFET heats up. But no arc. I haven't tried measuring output voltage because I'm worried about frying the multimeter, but it should produce an arc.

I'm really not sure what's going wrong here. I can confirm that the circuit is assembled correctly. The flyback core was damaged when trying to take it out (one of the bars snapped in two), but I glued it back together, having been told that would fix it, and I don't see why that would not be the case.

My power supply is 12V, provided by a 9V and 2x1.5V in series, as required.

I have been told before that the circuit schematic given is not very efficient (as shown by the MOSFET heating up). I'd like to point out that at this stage, getting the circuit to work at all is a greater priority for me than efficiency. I don't want to shell out on new components or build a whole new circuit until I'm sure that that's the issue here.

Overall view of the circuit build:

Okay, got round to testing it.
Anda aka were right about the power supply. When running, the PD across the batteries drops to ~9V. I tested it with 15V - dropped down to 10. At 12V the output current was about 0.2A. Makes sense I guess.

Question is: what could I use to fix this? I'd rather still use batteries due to portability.


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I'm studying for EE final exam
First Question: what is the current through the red LED?
I have been working on this problem. So far, what i got is that with 5V come in the non inverting input of the op amp so that the inverting should be at 5V, also. From that point, i can found the emitter current which equal to (5V-0V)/160.
Second question: What is the purpose of the BJT?
I am not sure what is the purpose of the BJT on this problem? is it acting like a switch or a buffer?


texts:
Recently been calibrating my solder reflow oven to work with a higher temperature solder paste. Had a few boards come out that were slightly over done.

At 250 degrees Celsius I noticed that the silk screen was starting to yellow and the electrolytic capacitors looked like they were bulging?!

Has anyone else noticed this before?

The capacitors seem to be fine, I've used the capacitance setting on my DMM to check, they all seem to have remained in tolerance. The circuit they are part of also seems to be operating perfectly normal.

Does anyone know what's happening here?

Sorry the pictures aren't any better, I've not got a very good camera:

Here's what they normally look like:

If you look closely you can see that the over cooked ones have a slightly curved top. I've since reduced the reflow temperature and reflow hold time on my oven and they don't come out like this anymore.

Here's the datasheet for the caps, unfortunately it doesn't really mention the maximum reflow temperature.

EDIT: The caps are from Farnell and should be legitimate. They were flat prior to reflow and rounded post reflow, they had not had power connected when I noticed this problem. The oven was at 250 Degrees for 120 seconds during the reflow. The temperature is monitored using a K type thermocouple (connected to a MAX6675 and Arduino) and has been verified against my multimeter's temperature probe and was found to maintain temperature to within +/-1 degree. The capacitors are connected in the right polarity according to my original circuit design that was mocked up and tested on breadboard. This phenomena has not occurred with any of the other boards or prototypes, the polarity has always remained the same between devices, it seems to just be the ones that were over heated.


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I am trying to toggle the power on a 24V LED strip using a IRFZ44N MOSFET. I am able to power the LED strip and vary the current using different PWM duty cycles, but the MOSFET gets really hot, especially when the lights are "dimmed", i.e. 0 < duty-cycle < 100. With duty-cycle = 0 there are no heating issues though.
The LED strip is rather power consuming, 24W/m, and I'm utilizing 4m so i figured a 4A power supply would suffice. The idea is to toggle the voltage, ~10V, on the T3 MOSFET gate by regulating the current at the base of T1 and T2. To my help is a Raspberry Pi 4B, using 3.3V GPIO, the 12V input is 1A

I am not an EE and apologize if there is anything unclear about the above schematic, would be happy to elaborate.
I found a similar post here on SE, which made me suspect the PWM frequency and T3 input voltage: I've tried many different PWM frequencies, from 1Hz to 10KHz, and also measured the voltage on the T3 gate, which according to my multi-meter is around 12v, 10V+ should be enough from what i understand. I didn't quite get the points they made about capacitance, but i have tried to lower the resistance on R4, which seems to delay the heating issue, but not fix it.


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I was wondering how inside the relaxation oscillator heating is not produced inside the BJT junction causing destruction of the transistor.

simulate this circuit – Schematic created using CircuitLab

and this is what I propose:

simulate this circuit


texts: usb device feature isn't working in case of external power supplied into the board

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I have my own designed board. It has USB device interface circuit.
The MCU is LPC1769 Cortex M3.

Basically when I use USB bus power for the board, its USB device feature is working. It means when I connect to PC, it is identified.

But when I supply the board with external power, then the usb device feature isn't working.

The external power is driven by 24V SMPS. On the board, 5V and 3.3V are regulated by regulator ICs.

Is there anyone experienced similar like this ?

The interface circuit is very simple.
Vbus is float on board. GND, D+, D- are connected.
For D+, D-, 33ohms resistors are connected in series.


texts: Does anyone know how MOS treshold voltage varies if the physical distance between source and drain decreases ?


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I am having a problem trying to operate a bi-directional solenoid from a RaspberryPi by using an L298N H-Bridge. I am sure it’s a misunderstanding on my part but I hope someone can help me!

The solenoid I am using is this Intertec ITS-LX-2218-12VDC-10mm.

The H Bridge is the same type as this L298N Motor Drive Board Module.

My supply voltage is 15V.

My plan is to use the Pi’s GPIO to control if the solenoid is open or closed.

However when testing (using 3.3V and 5V control voltage and a common ground) I have noticed a problem.

If I don’t have the solenoid attached then when using a multi-meter I when 15V on the output when the control pins are set to 1 and 0 respectively and as expected I get -15V if 0 and 1 are present. This is all fine.

However when I perform the same check with the solenoid connected I’m only reading 7.5V across the H-bridge outputs and the solenoid fails to fire.

To summarise the H-bridge seems to work as I had hoped, apart from when the solenoid is attached.
When the solenoid is connected the h-bridge would appear to not provide enough voltage/current to power the solenoid.

The solenoid works fine when using the source voltage directly for a fraction of a second.

I would be the first to confess my electronics knowledge is rubbish and even endless reading on Google has failed to provide any help so I am turning myself over to the good people of stackexchange.


texts: Toggle switch as momentary with debounce

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I have been trying to do the following:
When a toggle switch is flipped down, the pic I'm using (16F1503) sends a pulse and turns on a led, when it is flipped up sends the same pulse and turns off the led.
I managed to cobble some code together and works great. The problem is that I need to manage another toggle switch which it does exactly the same thing, but it sends a pulse on a different port and turns on/off a different led.
Any suggestion? I'm having trouble mostly on debouncing multiple switches.

Here the code I'm using:

void main()
{
uint8_t db_cnt;
PORTA=0;
PORTC=0;
ADCON0=0;
TRISA=0b001000;
TRISC=0b010000;

for(;;)
{
                //Wait for button press, debounce by counting:
                for (db_cnt=0; db_cnt <= 10; db_cnt++)
                {
                    __delay_ms(1);      //Sample every 1ms
                    if (TOGGLELEFT==0)  //If toggle off (RA3 low)
                        db_cnt=0;       //Restart count
                }                       //Until button on for 10 successive reads

                PORTA=0b100000;         //Turn OFF toggle LED, turn ON transistor
                __delay_ms(10);
                PORTA=0b000000;         //Turn OFF transistor

                //Wait for button release, debounce by counting:
                for (db_cnt=0; db_cnt <=10; db_cnt++)
                {
                    __delay_ms(1);      //Sample every 1ms
                    if (TOGGLELEFT==1)         //If toggle on (RA3 high)
                        db_cnt=0;       //Restart count
                }                       //Until button off for 10 successive reads

                PORTA=0b110000;         //Turn ON toggle LED and transistor
                __delay_ms(10);
                PORTA=0b010000;         //Turn OFF transistor
}
}


texts: USB cable current limit: wire or connector?

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I am trying to power a device which requires 5V and 2A through a 5.5mm / 2.1 mm barrel jack connector. SInce I need the device to be portable I am using a battery bank like this: http://www.amazon.co.uk/dp/B00OB5251W/ref=pe_385721_37986871_TE_item with a USB to barrel jack adapter like this: http://www.ebay.co.uk/itm/USB-A-to-5-5mm-2-1mm-Barrel-Jack-Male-DC-5v-2ft-power-charger-connector-cable-/281293234909?ssPageName=ADME:L:OC:IE:3160

However, I don't seem to be getting enough current. I think it is because the adapter cable is limiting the current to less than 2A. Does this sound correct?

I'm thinking of creating a new adapter cable by taking the cable from the original plug-in charger which came with the device, cutting off the plug end and soldering on a USB connector. Would this work? I think it should work if it is the wires which are limiting the current but not if it is the actual USB connector which limits the current. Does anyone know if this would work?


texts: Negative pluse generator does not reach 0V

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I'm using an Arduino board to generate a 125KHz square wave signal to feed into this curcuit:

simulate this circuit – Schematic created using CircuitLab

So this is what I'm receiving from my scope.
The output was connected to the channel-1 upper, and input is connected to channel-2 lower.

Any idea why above channel-1 output does not reach 0V when the pulse happens?

How do I make it to hit 0V?


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I have designed the schematic diagram of the inner components of the 555 Timer IC for understanding the working of the IC, but not sure if I have designed it correctly or not.
If it is correct can anyone please help me to understand how the Reset is working on the RS flip-flop.

Modified


texts: Is the open loop phase response of an op amp the same as the closed loop phased response?

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I am trying to do some calculation for my post lab and i dont understand why the lab manual only talks about open loop phase response.  are these the same?

I know the gain for open and closed loop differs quit a bit.


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I need to build a faraday cage to shield from the following source: 8 Watt, 14 MHz. The signal is AM modulated
I want to build an metal box enclosing the source. I want it to shield the signal so that the AM signal cannot be received, but I want to keep the costs reasonable.
My questions are:

I want to use steel, but what should the thickness be? 1mm, 2mm?

How should I attach the sides of the box to each other? Is welding acceptable? Or should I use some other method?

Any formulas or reasoning for arriving at an answer would be appreciated.


texts: What are some design concerns for off board SPI communication?

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Overview:

I am communicating among 3 custom pcb boards with dspic33's on them using SPI.  I have a master and 2 slaves, but I am sending both the slaves the same data (and letting them choose what to pay attention to).

Hardware setup:

The two slaves have built in BLDC motor controllers and the Master is controlling these motor controllers over SPI.  The wires are run about 3 feet from the master to each slave and the headers are typical .1" pitch through hole SAMTECH headers.  Each motor controller has it's own 3.3 volt regulator that runs the dsPIC/LV electronics.  I use one motor controller regulator(lets call him A) to also power the SPI master DSPIC.  To the other motor controller(lets call him B), I just run the SPI lines and ground from the master.  The SPI clk is running at 100KHz

Getting to the point (Finally):

With no motors running this all works fine, all data comes through as expected to both slaves.  However, when I start up the motors, Bslave no longer gets the correct data.  He is either picking up extra clocks or dropping them, I am supposing do to the extra noise.  In any event his checksums start failing.  Aslave works like a champ no matter what.

1)  Would you expect that all these devices need to be ran off the same 3.3 volt source?  If so, can you convince me by talking about the longer inductance loop and black magic such as that.

2)  Do you have any kind of rule of thumb as to how fast I can expect to be able to run the SPI clk and have success with a hardware setup such as above?


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I have a project on which I used two mcp617's for the purpose of buffering a signal.  Inputs An1, An2, and An4 work as expected, but An3(J7 connector) does not.  An incoming signal level of 4.4V on pin 3 of U22(tested with 3.3v as well) is outputting 2.8V on pins 1-2.  I have tested this across numerous different boards and chips with the same result.  I also have double checked that there is no load on the output

At this point I am unable to find the difference in layout or schematic between these circuits.  The MCP617 is listed as unity gain stable as well.

MUCH larger version of circuit diagram here - Imgur saves uploaded files at larger sizes than it displays.

Update:  After going through all boards, it seems this is indeed happening to all devices somewhat randomly, probably due to running these outside their characterized parameters.


texts: OLED 128 x 32 SYO12832B01 display problem

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I am using a SYO12832B01 I²C OLED display with driver SSD1306. Here I am attaching the my initialization code. I got the correct data in the display, but the issue is I can't enable the internal charge pump. The voltage obtaining across the charge pump capacitor is 3.3V, so the backlight is not enabled. Also the data displayed is inverted. Following is my initialization code:
write_cmd(0xfe);  //display off
write_cmd(0xd5);   // set oscillation frequency
write_cmd(0x80);// set to
write_cmd(0x20);   //set memory address
write_cmd(0x02);   //set to
write_cmd(0xa8);   //set to multiplex ratio
write_cmd(0x1f);   //set to
write_cmd(0xd3);   //set to offset
write_cmd(0x00);   //set to
write_cmd(0x40);  //startline
write_cmd(0x8D); // charge pump
write_cmd(0x14); // enable
write_cmd(0xa1);  //segment remap
write_cmd(0xc8);  //scan direction.
write_cmd(0xda); //hardware config
write_cmd(0x12); //configuration
write_cmd(0xdb); //set vcomh
write_cmd(0x12);//set to
write_cmd(0xa4); //entire display on
write_cmd(0xa6); //normal display
write_cmd(0xaf); //normal display

Am I missing something?


texts: Low capacitance value capacitors in LC bandpass filter

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I am going to try to build a Butterworth LC bandpass filter. However, using some online calculators result in some very low value capacitors (sub-1pF).

I am thinking that the performance will not be optimal because even the stray capacitance of the PCB traces (I want to use prototype boards) will be higher than that value.

Is that true? If it is, how do I build a RF filter easier with standard value inductors and capacitors?

EDIT:
I want to build a simple LC bandpass filter for 430-440MHz, trying online calculators like this shows for first element is shunt, the capacitance of second element (which is in series) is 0.091pF. (Center Freq=435MHz, BW=10M, Z=50Ohm, Order=4, Shunt First)


texts: Circuit that allow the passage of the current and not its interruption

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Hi guys. I have to make a circuit which allows the passage of current through human action but does not allow interruption of the current without removing the power source. I have designed the circuit in the photo. Are there other methods to do this? Is my method good?

From the image:
-Alimentazione means:power supply
-Interruttore means:switch


texts: Binary info to Decimal representation using circuitry

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I'm tryign to make a counter (and by extension all the other things) using a series of flip-flop circuits, and a seven segment display.

As I have it the digit increments through 0xF, which isn't what I want.

I imagine that I need to capture when 1010 happens, and at that point, I need to throw this digit back to 0, and also step up a 10s digit display using the same circuit.

What logic will reset everything to 0 when the And triggers?


texts:
I have finally built up a lab to design electronics in. I have quite a few designs I would like to test. I have tried the printer toner/iron technique a few times but have found that I cannot create small pitch sizes as they tear off while removing the printer paper. A few people have mentioned that this is due to using a Samsung laserjet versus a HP.

I am wondering what methods you use to develop PCBs for one-offs in your lab or at home (like me). I am trying to fast track a move to SMT/SMD components and would like some tips from seasoned experts on the best PCB creation methods to test board concepts before sending them off to a PCB MFG. I would like something that balances cost, time, and beauty of the finished product geared towards a hobbyist (at this point) and geared towards SMT/SMD components.

Please include pics/documentation of your preferred method. Thank you in advance for your post.


texts:
I've tried to find theory on how to convert 230V AC to 5V DC but without any good results.

I've been interested in how these wall plugs work and what the schematics are. Where can I read more about this?

What I'm trying to replicate or at least understand is the Fibaro Wall plug or similar. See teardown images posted in another forum for reference:
http://www.zwaveforum.se/viewtopic.php?f=46&t=4515

Here is a similar smart plug:
https://forum.athom.com/discussion/1745/app-z-wave-neo-coolcam-z-wave-devices-main-discussion-topic/p3


texts:
I'm trying to learn about noise, sensitivity, and the Shannon-Hartley theorem, and I'm using some specs for a LoRa node IC to try it out.

The Shannon-Hartley theorem says that the maximum data rate \$C\$ is given by

$$C = BW \ log_2 \left(1 + \frac{S}{N}\right).$$

Where \$S\$ and \$N\$ are the signal and noise powers within the fully-used bandwidth \$BW\$. LoRa occupies the bandwidth using a rather cool Chirp Spread Spectrum which you can read more about in this great answer and the question there as well.

The fundamental floor for noise in small signal analog electronics is usually thermal noise, and if I understand correctly that's usually given by

$$N \ = \ k_B \ T \ BW. $$

I calculated the Shannon-Hartley limit for the theoretical maximum data rate possible for the various values in Table 12 of the data sheet, and compared to the bits per second actually implemented at those quoted sensitivities, I was really happy to see that I'm in the right ballpark and tracking the trend nicely.

The Shannon-Hartley limit is always a factor of about 20 to 30 faster faster than the rate listed.

I'm just curious; could this be a safety margin, or conservative spec (did they pad the sensitivity to make sure they could meet it) or is there a factor I've forgotten?

Question: Am I using Shannon-Hartley Theorem and thermal noise correctly here?

As a bonus, any idea if the 14 dB is a safety margin, or if the noise floor is actually not thermal?

note: At these rates, the signal is well below the noise which is also pointed out in the data sheet.

Table 12 from Rev. 5 - August 2016 of SEMTECH's SX1276/77/78/79 Datasheet.
©2016 Semtech Corporation
www.semtech.com

def log2(x):
    return np.log(x) / np.log(2.)

import numpy as np
import matplotlib.pyplot as plt

kB = 1.38064852E-23  # Joules K^-1 "Boltzman's Constant"
T  = 298.  # about 25C

BW  = np.array(2*[10400] + 2*[20800] + 2*[62500] + 2*[125000], dtype=float)
SF  = np.array(4*[6, 12], dtype=float)
bps = np.array([782, 24, 1562, 49, 4688, 146, 9380, 293], dtype=float)
dBm = np.array([-131, -147, -128, -144, -121, -139, -118, -136], dtype=float)

lines  = np.arange(1, 9)
noise  = kB * T * BW        # Joules K^-1 * K * s^-1 = Watts
signal = 10**(0.1*dBm-3.)   # Watts

Shannon = BW * log2(1. + signal/noise)

plt.figure()

plt.plot(lines, bps,     linewidth=2)
plt.plot(lines, Shannon, linewidth=2)

plt.yscale('log')

lfs, tfs = 16, 16
plt.text(6, 50, 'bps', fontsize=tfs)
plt.text(5, 250000, 'Shannon', fontsize=tfs)
plt.xlabel('line in Table 12', fontsize=lfs)
plt.ylabel('rate (Hz)', fontsize=lfs)

plt.show()


texts: Li-ion and Lipo battery in parallel connection , can they work simultaniously?

texts:
I have a Li-ion battery(3.7V and charging Voltage 4.2V, 1800mAh) and I bought a Lipo battery(3.7V and charging voltage 4.2V, 2500mAh) for my smartphone. And I want to create a homemade battery case. So I am thinking to connect these batteries in parallel series to increase the battery capacity. is there will be a problem for that the one is Li-ion and other is Lipo?
And can I make a power house using Li-ion and Lipo in the same circuit ?


texts:
I want to buy one low budget multimeter for regular use. I don't need any high end functions only the basic ones (measure current, voltage and resistance).

I have found these two multimeters (1), (2) in local stores. The first one costs 20 euros and the second one 16.5 euros.

As I want it for electronics projects the specs of both, regarding AC, DC current and voltage measurement, are more than enough for me. The only difference that I see as important is that the first one (the one from Allsun) can measure up to 20MΩ resistance when the second one can measure only up to 2MΩ (if you can see something else in the specs that I should notice feel free to point it out).

My concerns are which one has better build quality, which one is more reliable and which one's manufacturer is more reputable.

Something that I found odd is that while searching online stores, including Ebay and Amazon, I saw that the one from Mastech is very popular and is sold by countless sellers but the one from Allsun is hardly found. Does this mean something about the quality?

All in all which one would you recommend me?


texts: Can I sell a CSA approved product in the US at retail or over the internet?

texts:
I have a product that was designed to sell in the RV market.  The RV industry does not require require UL per se, just a "recognized listing" which can be from a number of agencies including CSA (to Canadian standards, not like CSA testing to US standards).  Given that, we normally use Canadian approvals since some RV's ship to Canada and Canada DOES require their own listing, not just "a listing".

I now have an electrical product that I want to liquidate in the US via internet or retail, but it has only CSA approval.  Will this be a issue legally?  I understand that some (many) retailers would not be comfortable selling w/o a UL or equivalent mark.  I'm wondering from a "can I" perspective, not a "should I" perspective...


texts:
What is the output voltage Vo of the OPAMP circuit given below?

Attempt at solution: THE ANSWER IS GIVEN: 6V, but according to me as the positive terminal is grounded the negative terminal will be virtually grounded (0V), from ohm's law (applying to the two series resistance) it is expected that Vo is 0V!
I don't know where I am getting wrong!


texts: The ATMEGA datasheet suggests filtering the ADC reference voltage with an LC network, in other words VCC - L - AREF - C - GND. How does the inductor smooth the voltage better than just a capacitor?


texts:
Let's assume you have a battery bank not connected to anything and we are dealing with perfect ideal values.  You just want to calculate the total battery internal resistance of your battery bank.

To calculate the total resistance of a battery bank, can you simply take the internal resistance of the battery and replace the battery with the resistor value and proceed to find the total equivalent resistance as you normally would in a simple circuit that just has resistors?

For example,  would 2 batteries in series with an internal resistance of 2mΩ simply equal 4mΩ?  2mΩ+2mΩ=4mΩ?  Or is there some physics law I am violating due to it being a battery?

Then assuming you have another 2 batteries in parallel which equals 4mΩ, the total resistance to this circuit is 2mΩ?

Battery 1 + Battery 2 = 4mΩ

Battery 3 + Battery 4 = 4mΩ

(Battery 1 + Battery 2) || (Battery 3 + Battery 4) = 2mΩ

All of this is assuming ideal values (ignoring temperature flux, jumper resistance, health of battery, etc, etc).


texts: Error generating 1 sec delay using timers in PIC32

texts:
I have a PIC32MX795F512l and because XC32 doesnt provide an inbuilt delay function, I am  using Timer1 to generate a 1sec delay but there is a problem in it because it is generating more than 1sec delay. Can anyone help in getting exact 1sec delay in PIC32.

CODE:

#define SYSTEM_FREQUENCY        72000000L
void Delayms(unsigned t)
{
    OpenTimer1(T1_ON | T1_PS_1_256, 0xFFFF);
    while(t--)
    {
        WriteTimer1(0);
        while(ReadTimer1() < SYSTEM_FREQUENCY/256/1000);
    }
    CloseTimer1();
}

and using it in while(1)

int main()
{
 SYSTEMConfigPerformance(SYSTEM_FREQUENCY);
while(1)
  {
    PORTDbits.RD0 = 1;
    Delayms(1000);
    PORTDbits.RD0 = 0;
    Delayms(1000);

  }
 }


texts: Finding zero cross of AC signal digitally

texts: I'm measuring 50/60 Hz with STM32 microcontroller. The signal comes from current transformer. I'm adding a DC shift to the signal equal to 1.65V. As the signal is riding in 1.65V, this will be my zero cross. I would like to detect the zero cross in software so what comes to my mind is to sample quick enough, say 8 kHz, to have more chance of finding the zero cross. So my plan is: take ADC sample -> Substract 2049 (1.65V) -> compare to 0 (I'm using integer math). Would this be a reliable way of doing it? Would I need some extra hardware? I've seen other solutions with some kind of hardware which I don't have at the moment. I only have the signal properly amplified riding on 1.65V.


texts: Some questions about Carry-lookahead adder and Ripple-Carry Adder

texts:
I was reading about the Carry-lookahead adder and about the Ripple-Carry Adder. I saw some designs and it made me wonder the following questions:

Both questions are the same for both adders so i'll call them Y.

Is there an equations for the number of full adders in a Y Adder?
If we will call X the pause (t_pd) of one full adder, what is the total t_pd of the Y adder?

For Carry-lookahead adder I think we will need 32 adders for Y, is it correct?. How can I calculate the t_pd?


texts: How reliable is a daisy-chained USB bus? What are the risks and how can they be minimised?

texts:
Introduction

USB has been around for quite a long time now, used extensively even in the automotive, marine and space industries to some extent. However certain communication ways are more reliable than others in terms of:

Possibility of hot redundancy
Protection of the connected equipment against failures in other connections (surges, short circuits, misbehaviours [data, voltage levels, timing...]...) or in the hub/switch itself
Large mean time before failure ("freeze" or hardware failure)

Usually, the error rate is a bit less important as detection and correction (which may require retransmission) is handled by the protocol library/stack.

Question

I would like to know how reliable is a system based on a USB hub (say, 16 ports, be it daisy chained or not). What can commonly go wrong, and what could be done (protections/topologies...) to prevent single point failures from spreading (ideally I would just swap the faulty equipment and it would be ready to go).

Specific problem

For a specific piece of equipment at work I need to interface 16 devices to both a primary PC and a redundant PC (taking over if the other one crashes). 75% of the devices have both Ethernet and USB and 25% are only USB, and I'm wondering if I should simplify everything (which may increase reliability as well) by using USB alone or have both to maximise reliability. For USB, switching between the 2 computers would be done using a manual switch.

To illustrate, the hub I'm considering is this one, handling  < 350W surges but doesn't seem isolated; I have the hunch they're overusing the term "industrial" so I may switch it for several daisy chained 7 ports. The connected equipment is a bunch of industrial PID temperature controllers, a UPS and a  precision thermometer. However this question is more of a general one.


texts:
Everywhere I look, nobody seems to use a soldering gun for electronics work, only soldering irons.

Is there a good reason for that ?

I'm a beginner in electronics and I happend to have a soldering gun at home. I thought I'll spare myself, for now, an investment in a good soldering iron/station.

Thank you!


texts: Why does my amplifier oscillate when I try to reduce the bandwidth?

texts:
I have a x100 opamp amplifier, which seems to work:

simulate this circuit – Schematic created using CircuitLab

Datasheet for the opamp: here. The diodes are there to protect the inputs of the (expensive) opamp. The opamp is powered from  +-250V rails, with 1nF and 100nF decoupling caps right by the pins, and have less noise than I can measure with my scope and probes (<10mVptp).

I built and tested the circuit.  It works, but I would like to reduce the noise present at the output.  Since the DAC is relatively noisy at about 10kHz and harmonics, I thought I could reduce the bandwidth of the amplifier.  I tried adding 15nF in parallel with R3, on the expectation that this would reduce the gain high frequency. Simulating in LTSpice with a generic opamp suggested it should work.  But it started oscillating at about 1-2MHz, rail to rail.

I have realised I don't really understand the criteria for an amplifier to oscillate.  Why is my amplifier oscillating? And how should I reduce the bandwidth without oscillation?


texts: Why is it said that when voltage source connected in series would only increase the voltage and not the current?

texts:
By adding cells in series, a larger-voltage bat-
  tery can be made, whereas adding cells in parallel results in a battery with a higher
  current-output capacity.

This is what a book that I am reading says and hence what I am understanding is Voltage is added when Voltage sources are connected in series and Current s added when voltage sources are connected in parallel.

Considering the ohm's law,

1)for V1=10v and V2=10v, R = 1K, if I keep only keep V1 as voltage source, V across R would be 10v and I(current) would be 10mA.

2)Now if I connect V1 and V2 in series , V = 20V and I would be 20mA.

Did I miss something or the current actually doubled up?

I even simulated the curcuit in the Multisim and i faced with a similiar result. Any help in understanding the concept would be helpful.


texts: What's the benefits to using analog-to-digital conversion like PCM?

texts:
I was reading a textbook, Data Communications And Networking, by Behrouz A. Forouzan, which says:

A digital signal is superior to an analog signal. The tendency today is to change an analog signal to digital data.

I don't quite get it, how is a digital signal superior to an analog signal? What's the benefits of changing an analog signal to digital data?


texts: schematic and algorithm for auto-range voltmeter

texts:
I'm creating Digital Voltmeter on ATmega16 with autorange to purpose.
I just have a problem with designing autorange.
Does anyone have a schematic of a voltage divider, and an algorithm for how auto-range should work?

I heard about FET selectable resistor ladder but currently I don't know how use it in my project. I mean schematic and how to control it from microcontroller.

The Voltmeter should be very simple - it is a project for my studies, therefore I don't want to use any digital potentiometers or sophisticated circuits.
The ranges may be 2 levels for example.


texts: Opto-Isolater always on by higher voltage

texts:
I use an AQH3213 Opto-Isolater. When I use 3.3V on the 'dc motor side', everything works fine and it 'turns off and on in an interval of 1 second'. But when I use 5V, it's always on....

Do you have any suggestions what I do wrong?

The simple test code is correct, because it works with 3.3V; so must be a curcuit problem I guess.


texts: What is this schematic symbol with intersecting triangles?

texts:
What is this symbol?  I think it is some kind of amplifier or buffer, but I was unable find any information using search terms like "overlapping triangles," "intersecting triangles," or "double triangle symbol."

For context, I came across it in the ATmega2560 datasheet (pdf), in Figure 13-2 on page 68, reproduced below:


texts:
An electric current is a flow of free electrons. Are these free electrons totally free from the orbits of metal atom or they moving by jumping from one orbit to another orbit of the atoms?

If they are totally free, what does enforce them to keep staying in (or on the sufrace of) the metal

Thanks


texts: Merging multiple audio inputs into one audio output

texts:
I am working on audio preamplifier project using Altium Designer, which is also a great opportunity to learn this particular piece of software. Now, I've selected Hierarchical design to be able to get benefits of Multi-Sheet and Multi-Channel Design:

Now, I have 8 audio relays, implemented with Repeat(AUDIO_INPUT_RELAY,1,8) command:

and here is Audio Input Relay Schematic itself:

Now, these 8 audio input relays converge into single SELECTED_AUDIO_OUTPUT_LEFT and single SELECTED_AUDIO_OUTPUT_RIGHT lines and here is whole subsheet:

I am aware a volume control is missing (the project is not finished), however, this is not topic now and my question is: when I compile this project, why do I get following error (I am aware I can disable error reporting in Project Options, which is also not the point here, I want to know what did I wrong):

Net SELECTED_AUDIO_OUTPUT_LEFT contains multiple Output Sheet Entrys (Sheet Entry AUDIO_INPUT_RELAY1-SELECTED_AUDIO_OUTPUT_LEFT(Output),Sheet Entry AUDIO_INPUT_RELAY2-SELECTED_AUDIO_OUTPUT_LEFT(Output),Sheet Entry AUDIO_INPUT_RELAY3-SELECTED_AUDIO_OUTPUT_LEFT(Output),Sheet Entry AUDIO_INPUT_RELAY4-SELECTED_AUDIO_OUTPUT_LEFT(Output),Sheet Entry AUDIO_INPUT_RELAY5-SELECTED_AUDIO_OUTPUT_LEFT(Output),Sheet Entry AUDIO_INPUT_RELAY6-SELECTED_AUDIO_OUTPUT_LEFT(Output),Sheet Entry AUDIO_INPUT_RELAY7-SELECTED_AUDIO_OUTPUT_LEFT(Output),Sheet Entry AUDIO_INPUT_RELAY8-SELECTED_AUDIO_OUTPUT_LEFT(Output))

and screenshot of error:

I have no unmatched ports and sheet entries, as @Radiohead gave a hint:


texts: Is inductor saturation current frequency dependent?

texts:
The wiki article explaining inductor core saturation talks about magnetic domains lining up with the external magnetic field to concentrate the magnetic flux. This sounds similar to electric permittivity where dipoles rearrange themselves to cancel internal electric fields.

I know that electric permittivity is frequency dependent since the electric dipoles have inertia and cannot realign themselves instantly.

Is this the case for magnetic permeability (inductor saturation)? If an inductor is claimed to saturate at 750mA in its datasheet, would it be less if the current was AC?


texts: How much power does the voltage source with \$12V\$ provide to the circuit? Which part of my calculation is wrong?

texts:
How much power does the voltage source with \$12V\$ provide to the circuit?

The answer is \$84W\$

My thinking:

The question asks me "How much power does the voltage source with \$12V\$" provide to the circuit, so I think I should ignore the voltage source with \$-6V\$, that is, see the voltage source with \$-6V\$ as a short circuit, then the circuit will become like this

simulate this circuit – Schematic created using CircuitLab

Obviously,\$R4||R2,R3||R2,R3||R1\$,so these resistances are parallel connected to each others,so the \$R_{th}=R4||R1||R2||R3=6||6||12||12=3||6=2\$.

And the power of voltage source with \$12V\$ is  \$P_{12}=\frac{V^2}{R}=\frac{12^2}{2}=\frac{144}{2}=72W\$, however, as I said in the beginning,the answer should be \$84W\$,so does someone know which part of thinking am I wrong in my calculation?


texts: Best way to connect two adjacent PCBs by their outermost hole rows?

texts:
I have two separate circuit boards that each have the same 8 hole row near their edges and I need to make a bridge from one PCB to another.
Placed like that, the distance from the first PCB’s first hole to the second PCB’s mirrored one is about 4mm - 4,5mm.

What is the best way to permanently connect these to one another in a neat and compact way? Some sort of staple shaped pins that I don’t know the exact name of yet because I’m new to this?

Usually I can easily find the answers by searching online but somehow the key words in this are involved in far too many rather general topics, so I'm afraid that a mere search engine won't understand the relations of the terms involved here; better ask a human.


texts: Current Consumption of ICs from Datasheets

texts:
newbie in electronics here and taking self study (don't have time to go to school anymore xD). i just want to ask, regarding the image below:

it came from this datasheet:

https://d3uzseaevmutz1.cloudfront.net/pubs/proDatasheet/CS5480_F3.pdf

how could i determine how much current the IC is consuming on power lines like on voltage regulators? I see a lot of ampere value here.

1) is it the Power Supply Current? Input current? input current supplies? output current?

2) how do i make simple math given on these values?

3) upon looking on other datasheet, they don't have same descriptions, i see Ic, Icc, Iaarms, Ii, etc. What could be the common current description i need to check to determine the current consumption of IC (even on max)?

I want to learn this because i want to make a computation of how much current should a 30 pcs of the given IC here will consume overall, at max, for me to determine what output current value should my voltage regulator have. Or do i have the wrong idea on computing the current consumption in relation to voltage regulator current supply??

EDIT: giving also example of how to compute 2 to 3 different ICs current consumption having different datasheets would be also good for me to understand it clearly OR maybe the image below, how can i compute it even a rough estimation. (included the setup to be future reference for others and to be understand clearly the situation)

uC -> arduino uno https://www.farnell.com/datasheets/1682209.pdf

4 to 16 dmx -> http://www.ti.com/lit/ds/symlink/cd74hc154.pdf

EMIC -> https://d3uzseaevmutz1.cloudfront.net/pubs/proDatasheet/CS5480_F3.pdf

TEMP -> https://datasheets.maximintegrated.com/en/ds/MAX31722-MAX31723.pdf

Relay Hub are collection of SSRs connected to a I/O expander controlling the gnd terminals of SSR via npn transistors

I/O expander -> https://datasheets.maximintegrated.com/en/ds/MAX7317.pdf

SSR -> http://www.crydom.com/en/products/catalog/gnr_22mm.pdf

NPN transistors -> https://www.diodes.com/assets/Datasheets/ds30384.pdf


texts: PIC16F877A don't work properly - led blink and 7 segment display problem

texts:
I'm trying to control a 7 segment display using PIC16F877A. I'm programming my PIC with a replica PICKIT 3.

I'm uploading my hex code using PICKIT 3 software and MPLABX IDE. I have no problem while I'm uploading my code, only when I set up my circuit.

I noticed only B1 pin is working. I did a blink LED circuit and I still get B1 pin high when I set D0 pin to high. I'm using 4 MHz crystal and 0.1 uF capacitors. I uploaded hex files from internet too, but I'm always getting high from B1.

I'm using 4MHZ Crystal with 0.1 uF capacitors. Should I change capacitors with 15 pF?

My Code:

#include <16F887.h>
#fuses XT,NOWDT,NOPROTECT,NOBROWNOUT,NOLVP,NOPUT,NOWRT,NODEBUG,NOCPD
#use delay(clock=4m,oscillator)
#define Dig1 PIN_D0
#define Dig2 PIN_D1
#define rfid PIN_D2
#define reset PIN_A1
#use fast_io(b)
#use fast_io(d)

static const int digit[10]= { 0b0111111, 0b0000110, 0b1011011, 0b1001111, 0b1100110,
                              0b1101101, 0b1111101, 0b0000111, 0b1111111, 0b1101111 };

void display(unsigned char value)
{
    static char tens = 0;
    char dig = (tens) ? (value / 10) : (value % 10);
    dig = digit[dig];
    output_high((tens) ? Dig2 : Dig1);
    output_b(dig);
    output_low((tens) ? Dig1 : Dig2);
    tens = !tens;
}

void main()
{
   char sayi = 0;

   output_b(1);
   output_d(0b11111100);
   output_b(0b11111100);

   set_tris_b(0x00);
   set_tris_d(0b11111100);

   while(1)
   {
     display(sayi);

     if(input(rfid) == 0)
     {
        sayi++;
        if(sayi == 100)
    {
      sayi = 0;
    }
     }
     delay_ms(30);

   }
}

My Schematic:

PIC16F877A Datasheet:
http://ww1.microchip.com/downloads/en/DeviceDoc/39582b.pdf

Real Life Circuit:


texts:
I was using ATmega32A before and now I am migrating to ATmega324PA just to enhance power management. Now I am testing the new controller in every aspect. This is a simple code to check the watchdog timer but it keeps resetting the controller.

Code:

int main(void)
{
  uart_init();
  PORTA|=(1<<PORTA1);
  _delay_ms(1500);
  PORTA&=~(1<<PORTA1);
  _delay_ms(2000);
  uart_array("FFFFFFFFFFFFFFFFFF");
  wdt_enable(WDTO_2S);
  _delay_ms(5000);
}

void uart_init()
{
 /*set PinA1 as output for LED*/
 DDRA|=(1<<1);

 /*set PinD3 as output for UART*/
 DDRD|=(1<<3);

 /*set pinD2 as input for UART*/
 DDRD&=~(1<<2);

 /*enabling TX and RX*/
 UCSR1B |=(1<<TXEN1) | (1<<RXEN1);

 /*asynchronous mode selection*/
 UCSR1C&=~(1<<UMSEL11);
 UCSR1C&=~(1<<UMSEL10);

 /*setting data format to 8 bit*/
 UCSR1B &=~(1<<UCSZ12);
 UCSR1C|=(1<<UCSZ11)|(1<<UCSZ10);

 /* setting one bit as stop bit*/
 UCSR1C &=~(1<<USBS1);

 /*Disabling parity*/
 UCSR1C &= ~((1<<UPM11) | (1<<UPM10));

 /* loading 8 LSB to UBRRL*/
 UBRR1L = UBRRL_VALUE;

 /* loading 4 MSB to UBRRH*/
 UBRR1H = UBRRH_VALUE;
}

The code works well for the first time, but after that, LED keeps blinking.

Note: watchdog (WDTON) fuse bit is disabled.


texts: How do I select diodes for battery charger repair?

texts:
I have an old vintage 1980's Sears battery charger that has two blown diodes. I wish to repair this charger and make it live again.
I would like to know how to determine what value of diode should be used.
I will say the obvious answer would be to just read the type number from the old ones and buy that model and install them. I WISH I could. I don't know why but when these things went they exploded the centers between the cathode and the anode was gone and there was a nice larg gap between the two. It's as if an EM pulse hit it.
Anyway, what I am having trouble with is, how do I select the correct diode?
I know that this charger is rated for 6-12 volt at 6 amperes. The diodes were fastened to two separate leads direct from the main transformer to the metal housing that the transformer is attached to.
I have tried to look up this information and have came up short on the whole answer.
I only find information about the voltage and not the amperage.
If I am recalling correctly some have said for the voltage selection you take the required through voltage and add 10V above the desired point and that's your value. Is this correct?
When it comes to the amperage I have found nothing. Any insight to this would be great.


texts:
I try to build a 300V voltage regulator using a LM317, which should be designed for 100 mA, but the circuit does not behave as I thought.

I loaded the circuit with 27K which is a current of 11 mA, and set the voltage regulator to 300 volt over the planned 22K in parallel with 1K.
It took me a few tries until I found the right resistor.
Some heat development at the transistor (heat sink) is not noticeable.

Then I bridged the output with a 5 kΩ resistor parallel to the 27 kΩ resistor which gives 4.2 kΩ and loads the circuit with 71 mA.
But instead of the voltage remaining at 300 V, it breaks down by more than 100 V, and the resistor before the Zener diode planned 3 kΩ used 3.3 kΩ gives smoke signals.

Also with this load no heat development at the heat sink.
At the transistor, 0.6 volts drop between base and emitter.
Can someone give me an assistance there?


texts: Switch that change its state with a signal of some seconds

texts:
I'm making an IoT project for a friend, but I need some tips: I want to use an old mouse sensor and convert it to a movement sensor (just for a door) and if it's activated, a second device (an esp8266) needs to be powered for just a minute (to send an alarm state to his phone). The problem is that the sensor provides just a few seconds and the second device won't be able to finish its work. So I need something that provides energy to the second device. What can I use?

Because it's an IoT project, I need something that doesn't consume power when it's not activated.


texts: How to Filter Harmonics in Wideband VCOs

texts:
I have a need for a RF signal generator, but I figured it would be a fun project to design a crude one myself. The main technical challenge I'm stuck on is how to filter out the harmonic content spewed out from the VCO (I'm looking for around -50dBC for the harmonic levels). For reference, I'm mainly working in in HF/VHF bands, roughly 10MHz to 300MHz. Since this is an educational project, I'd also like to keep the components for this project discrete instead of relying on purpose-built ICs. Along the same line... DDS is not allowed!
My concern is this: suppose I have a VCO that is capable of generating frequencies from 10MHz to 300MHz (don't worry about the implementation here). Let's say it is currently generating a 10MHz sine wave. To filter out the harmonics of this signal, I'd design a low pass filter with a cutoff frequency somewhere slightly above 10MHz. Now I want to output a 100MHz sine wave. The filter from before won't work -- I'd need another filter with a cutoff frequency slightly above 100MHz. Continuing with this logic, I'm envisioning a bank of filters, each with a different cutoff frequency that are switched in for their appropriate frequency range.
My question is: is there a better way to accomplish this goal of filtering out the harmonics without relying on a bunch of filters that need to be switched in?
If not, what would be the best mechanism to switch filters in? Ideally, I'd like the control to be electronic (along the lines of PIN diode switches, but would those be practical at these frequencies?).


texts: Is acetone or isopropyl alcohol better for removing rosin flux?

texts: For removing rosin flux from my board, should I use Acetone or Isopropyl Alcohol? I need an easily available solvent.


texts: Why does a Double-Balanced Mixer Reject the LO?

texts:
Look at the image of the so-called Double-Balanced Mixer (this is the active version). I understand why there is no leakage of the RF frequency in the output (because the LO square wave by which the RF gets multiplied at the output does not have a DC component). But what is the reason that LO frequency doesn't show up in the output?

Image Source: https://commons.wikimedia.org/wiki/File:Double_Balanced_Mixer_in_Integrated_Circuit.svg


texts:
I am trying to simulate the 810911001 line filter (Wurth Electronik) on LTSpice which I downloaded on the following link :

https://www.we-online.com/catalog/en/WE-CLFS/

I tried to simulate the circuit but I do not have the same result which is written in the datasheet for 50 ohm / 50 ohm sym :

www.we-online.com/catalog/datasheet/810911001.pdf

Thank you for your time.


texts: LM358 as a voltage follower only reaches 1.5 V of supply voltage

texts:
I am using an LM358 as a voltage follower, giving it a supply voltage of 6 volts and input voltage of 5V
At the output I am getting 4.5V.  By applying different configurations of input voltage and supply voltage I observed that there should a difference of 1.5V between supply voltage (Vcc) and input voltage.(IN+.) I am not able to find the reason behind it.


texts: Every RC car I've cannibalized has had a small ceramic capacitor soldered on to the contacts of the motors. What is the purpose of having this? What happens to the performance of the motor with out this?


texts:
If input to a transformer is square/triangular, draw its output voltage waveform.

This problem was asked in one of my recent interviews, please help me with this problem.


texts: Getting 240VAC output from 220-230VAC input

texts:
For lab testing at work I need to be able to test an appliance (often more than 3KW, e.g. deep fryers and waffle irons) at 240VAC. The problem is that our power grid only provides between 220 and 230 VAC.

So I'm looking for the best way to get a steady 240VAC output from a slightly variable input (we're in an industrial area).

A variable output would be nice, but is not a requisite.

Any help/hints/direction would be more than welcome!


texts: Circuit for flashing LED strips controlled by Arduino Nano

texts:
I'm building a project to flash three concentric rings of LEDs in sequence to give the effect of light moving from the centre to the edge. The circumference of each loop is based on an even number of LED blocks (three LEDs per block @50 mm), so the three strips will be:

Strip 1    610 mm   12 blocks     36 LEDs
Strip 2   1400 mm   28 blocks     84 LEDs
Strip 3   2050 mm   41 blocks    123 LEDs

What I figured out so far is that I can use an Arduino Nano to control the pattern, and a MOSFET to turn each strip on and off with the right timings.

I came unstuck looking at power and voltage specifications for the MOSFET, then saw diagrams using other components in the circuit and am completely out of my depth. How can I do this?

I'm planning on using white SMD5630 LED strips (60 LEDs/m) and have calculated the power/current for the largest strip (2050 mm, 41x3 LEDs) based on power information for this LED from How to select an appropriate transformer for 12 V LED strips as being 41 A/492 W, but maybe a grownup should check this.

I'm assuming I'll need three identical circuits, one for each strip.


texts: I think our company fields machines that can shock people. Can I try to fix it?

texts:
For more background details, you should read my original question on Workplace Stack Exchange.

I am a technician at an arcade. My company is fielding machines that seem to be shocking people from the outside. My question is "What could be causing this?"

People get shocked if they touch metal surfaces on the outside of the machine (such as locks!), so I was wondering:

Can this be caused by faulty wiring leading to the machines?
If this is truly a faulty ground, why is the ground carrying current at all?  I thought the ground was only for if something went wrong.
I got shocked by a faceplate underneath a joystick my first day, and my boss fixed it by cutting a "ground wire" from the panel.  How horrible is this?  (It's happened more than once, in widely separated areas.).

Perhaps most importantly, do any tools exist so that I could check for a consistent potential on the face of the machines?  (Wetting the local area then shocking myself while I'm wearing socks is not my idea of a great test.) This way I can at least definitively prove a problem exists; see my original question for why this might be difficult.

Note: I know about voltmeters, but I'm wondering if there exists something more specialized; normal voltmeters would be difficult to use with the geometry of the environment. (I'd need very long probes)


texts:
I have basic electronics knowledge and have repaired many things, but I'm a little confused about this. I have a 220 V LED PCB like this:

One of the LEDs is burning out and causing the whole array to flicker and die. I assumed like most things, I could replace the LED after finding out what voltage and current it was. When I desoldered and tried to power up one of the good SMD LEDs on a DC supply, I could not get it to light up, even after supplying between 3-28 V (the maximum my supply can provide). However, when I hooked it up to a variable AC transformer, I got the LED to light up fine at around 22 V.

Now I'm confused. Is this an AC-only LED? I've never heard of that.


texts:
My code works fine without interrupt (I tried polling the ADC value) but when I enabled the interrupt, it didn't work - while debugging in Keil, it never reaches the ADC_IRQHandler(), Also I found that the EOC flag is always set(in the while loop)

This is my code:

#include "stm32f4xx.h"                  // Device header
volatile int16_t k=0;
int main()
{

RCC->AHB1ENR |= RCC_AHB1ENR_GPIODEN | RCC_AHB1ENR_GPIOAEN ;
RCC->APB2ENR |= RCC_APB2ENR_ADC1EN;

GPIOA->MODER |= GPIO_MODER_MODE0; //analog input
GPIOA->PUPDR &=~ GPIO_PUPDR_PUPD0;
GPIOD->MODER |= GPIO_MODER_MODE13_0;//ouput
GPIOD->MODER &=~ GPIO_MODER_MODE13_1;
GPIOD->OTYPER &=~ GPIO_OTYPER_OT13;
GPIOD->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR13_0 ;
GPIOD->PUPDR &=~ GPIO_PUPDR_PUPD13 ;
GPIOD->ODR &=~ GPIO_ODR_OD13;

ADC1->CR2 |= ADC_CR2_ADON | ADC_CR2_CONT;
ADC1->SMPR2 |= ADC_SMPR2_SMP0_1;
ADC1->SQR3 &=~ ADC_SQR3_SQ1_4; //CHANNEL 0 (PA0)
ADC1->CR1 |= ADC_CR1_EOCIE;
NVIC_EnableIRQ(ADC_IRQn);
NVIC_SetPriority(ADC_IRQn,0);
ADC1->CR2 |= ADC_CR2_SWSTART;

while(1)
{
}

}
void ADC_IRQHandler()
{
     k= ADC1->DR;
     if(k>2000)
     {
        GPIOD->ODR ^= GPIO_ODR_OD13;
     }
}


texts: Software to help place ICs on a wirewrap prototype board

texts:
I have a moderately complex circuit (about 80 LSTTL Chips - a bit retro), designed and working in Logisim. I have 2 Augat WireWrap prototype boards (Similar to the image below) that I want to use to build the working circuit.
Does anyone know of any software which would allow me to play around with different placements of the various (16 and 24 pin) DIP chips on a "virtual" prototype board, before I commit to the first wirewrap?
I have looked at Fritzing, but I am not really planning on using a breadboard.
I plan to learn kCad, to draw up some circuit diagrams as a checklist when I am wrapping. Does that allow layout on such a board?


texts: Laplace domain: poles on both sides of the jw and x plane

texts: For a pole/zero plot, if a system has a pole on the left side only it is stable, and if the pole is on the right only it is not stable, but if the pole is on the right and left, would that be stable? And what determines if the system is causal or not, as far as the pole/zero plot concerns?


texts:
For this circuit we're asked to calculate Vo using the 0.7V diode model.

simulate this circuit – Schematic created using CircuitLab

I understand that when the potential is higher at the anode than the cathode then the diode is in the forward biased direction, current will flow through the diode and a (in this model) a 0.7V drop across the diode will occur.

My guess was that D1 is in reversed bias mode b/c the V2 is at a lower potential than ground, so D1 can be modeled as an open circuit.

I don't know where to go from there, my gut says nodal analysis but I'm not quite sure how to set it up. Plugging this into circuit simulators I get ~525mV when using 1N4004 diodes, but I'm not sure how to calculate this by hand.


texts: Can you get 240 volts and 50 amps from paralleled inverter generators?

texts:
I'm here for help solving the problem of suppling a 240v, 45amp kiln off the grid. The catch is, we can't just use a large portable generator. So,

-can you put three or more inverter generators in parallel?

-can you get 240 volts out of paralleled 120volt inverter generators? Is there equipment that can do this? (transformer?)

-can you put inverter generators into series to raise voltage?

-how would you supply 240volts and 50amps of power off grid if you couldn't use without a large portable generator?

Any ideas/suggests welcome.


texts: What is the simplest EEG detecting circuit possible?

texts: Suppose I took an Arduino and hooked it up to two electrodes: one to the front part of my head going into A0 and another connecting my earlobe to ground, why wouldn't this system be capable of measuring mV scale EEG signals?


texts:
I am receiving a string of data via UART in PIC32, extracting and concatenating two of its bytes, dividing the result by 2, converting the resulting integer to a string and transmitting via i2c to another PIC32. My problem is that this conversion has a strange bug: for numbers greater than 1K, I get weird results like 32760 even though it should be like 1000, 1252, 1100, 1090 etc. but it is good for some specific numbers like 1050, 1080, 1085.
Any suggestions are welcome.
My code is as below:
'''
                  default:    if (flag.bits.nopmeasure_received)
                            {
                                nopmeasure[Ptr_nopmeasure++] = c;

                                if(Ptr_nopmeasure >= 4)
                                {
                                   flag.bits.LR_OK = true;
                                   I2c_Data.Lr.flag.bits.mesure_received = true;
                                   unsigned short result = 0;
                                   char buff[2];

                                   result = (nopmeasure[3]<<8)|nopmeasure[2];
                                   result = result / 2;
                                   itoa(buff, result, 10);

                                   strcpy(I2c_Data.Lr.Mesure1, buff);

                                   flag.bits.nopmeasure_received = false;
                                }

                            }
                           break;

'''


texts: Unexpected behaviour of operational amplifier in an LDR light sensor

texts:
Here is the circuit I have set up in my breadboard

It is a light sensor using an LDR. I am using the op amp as comparator.

When indoors light is reduced, the LED lights up and I am able to set the lighting threshold with the help of the potentiometer.

But when indoors lighting is on, something strange (to me) happens. The LED is OFF except for a tiny region of potentiometer resistance. In this region, the voltmeter reads from -0.53 V to -0.29 V. This seems strange. When the voltmeter reads a value smaller than -0.53 V, the LED is OFF. This is logical. Additionaly, in a small region where the voltmeter reads positive values (from 0V up to 0.5 V) the LED is OFF. But if there is positive differential input, shouldn't the op amp go high?

Why the op amp behaves strangely in the aforementioned regions of the differential input voltage close to 0 V?


texts: What is my best possible antenna setup for a 900MHz 24dBm XBee?

texts:
I have two of these 24dBm XBee modules in a semi-LOS setup (1 receiver will be on the ground, obscurred by some tents/structures and other Burning Man camp crap), with these supposedly 3dBi antennas but I figure that will not get me far. Considering that one of my modules will be mounted 15ft up in the air on top of a bus, how can I maximize the communication distance?

Would either this or even better this antenna make a noticeable difference? Can I even attach my limited power 250mW XBee to such a large antenna and expect it to work?

Any other alternatives? I am even thinking of having a rotor setup with a directional antenna on a vehicle, but trying to avoid it at all costs...

Thank you!


texts: Is it current (and power dissipation) which damages things, not voltage?

texts: With higher voltages (more than about 5V), microcontrollers may be damaged. Is this because the voltage actually physically damages them, or because it allows excessive current to flow? - and thus increases power dissipation beyond safe limits. How does this apply for other devices?


texts: Termination on Ethernet line with Magnetics

texts:
I'm trying to understand this schematic:

The ethernet lines end in a device with the input already 100 ohm terminated. The magnetics have a ratio 1CT:1 so the input of the rj45 Connector should have termination resistances of 50 ohm on each line like the ones in figure, that should be not mounted. Moreover there are this 22 ohm resistors that I don't understand. I read that put a 22 resistor is a rule of thumb for high speed signal termination but I don't understand their utility in this case.


texts: What type of motor is more desirable, if the requirement is to rotate a load with high torque by about 30-60 degrees?

texts:
Torque required is about 17Nm.
The speed for rotation is very small about 10degrees/sec.

The load is dynamic and I do not want to apply any torque more then 20Nm, this I want to achieve by using a torque feedback. I want to make an cost effective setup for this purpose. Hence should I use servo motor or a stepper motor with a feedback? I read here to use servo motor when i need feedback anyways. Is it true? wouldn't I will save some money by going for stepper with feedback as the speed is slow?


texts: Battery support capacity for inverter supply of 30A over 3hrs

texts: I need to determine the 12VDC Ah capacity of a battery pack, to provide current to a 30A 120VAC circuit thru an inverter with 88% efficiency, where the voltage must not drop below 10vdc, over a period of 3hrs. This is the worst possible scenario. I would expect that the current of 30A would begin to ramp down to 20A after the first 15 min., then hold steady at 20 amps for the remainder of the three hours. As a bit of a buffer, perhaps 80% efficiency should be used for the performance of the inverter. The battery pack will be in a well ventilated position to control fumes and temperature, as will the inverter. I would expect to use deep cycle batteries, but am unsure of size this battery pack will need to be.


texts: Obtain the matrix in a control system with tandem/cascade representation

texts:
I'm trying to find tandem/cascade and parallel realization for the following transfer function:
$$G(s)=\frac{(s+6)^2}{(s+2)^2(s^2+4s+6)}$$

For Tandem/cascade realization, I draw the following block diagram:

And there is my resolution attempt:

$$X_1=\frac{1}{s+2}U\Leftrightarrow (s+2)X_1=U\Leftrightarrow sX_1+2X_1=U\xrightarrow {\mathcal{L}} \dot{x_1}+2x_1=u\Leftrightarrow \dot{x_1}=2x_1+u$$

$$W_2=\frac{s^2+12s+36}{s^2+4s+6}X_1$$

$$W_2=\bigg(1+\frac{8s+30}{s^2+4s+6}\bigg)X_1$$

I don't know how to obtain the matrix and the final result. What are the steps that are missing?


texts: How to bias(voltage offset) unity gain buffer

texts:
First post so sorry for any bad formatting.

I'm trying to figure out how to bias my signal going through a non-inverting op amp with a gain of 1. Because I want a gain one just 1, it would just be a unity gain buffer with the signal as the input.

1) Lets say the incoming signal is biased at 0V with signal going from -2.5 to 2.5V. How do I bias at 2.5 with signal going from 0 to 5V.

2) How about re-biasing from 2.5V to 1.65V?

Thanks for any input!


texts: Voltage stability factor of voltage regulation circuits

texts:
Here a shunt voltage regulator circuit with two Zener diodes.
One Zener diode Z gives the reference voltage at the comparator given by T1  for the feedback signal out Ra-Rb potentiometer.
I can't explain the role played by the second Zener diode Z1.
I think that one of them gives a  compensation for V1  variation and the other for the variation of V2.
But in which way? That is my question.
I have to calculate the voltage stability factor (Sv.)
Any suggestion is welcome.


texts: LED circuit:: current goes through, no light

texts:
I have made the following circuit. Using the multimeter,+ on first and - on last LED, I get 8.7 volts. What are possible reasons for no light?
I have checked that I got the connections correct ( + to - ) for each LED. Since I have cut the leads to solder the LED together, I used lead frame orientation to double check that connections were correct. Any other possible reason that this might not be working? If one was damaged during soldering, do all stop working? Would current still go through ?
9V battery, 1.9 voltage drop on LED, 82 Ohm resistor, circuit was working on breadboard, no light after soldering.


texts: How to reduce EMI susceptibility for board to board connectors?

texts:
I am planing to design an MCU based board. Although I don't need all the GPIO's, SPI's, PWM pins, etc. I like many of them to be connected a card edge connector or board-to-board connector. So, I can be flexible to use those pins when I needed in the future without re-designing the board.

For example that might be the connector;

However, the idea having spare GPIO's on the connector sounds very handy to me, on the other hand, even I set them as an output and pull-down or pull-up programmatically, I feel like that unused (for the time being) wires connected to a connector will look like an antenna and susceptible to EMI accordingly.

I have read some EMI considerations related books and articles. But, I couldn't really find something related to my subject or I totally overlooked it.

Important note that: There is a big chance I will have to go for FCC/CE certification.

My chain of questions;

Am I right to worry about antenna behavior and susceptibility to EMI?
If so, is there way to get over that concern while still using that unused pins on the connector?
Or should I completely avoid from using those unused pins on the connector?

I appreciate your inputs from now.


texts: How does force feedback [hardware] work?

texts:
Force feedback steering wheels are fairly common, but I don't understand how they work.

Specifically, how does a "direct drive"($$$) steering wheel apply a force one way while moving in another direction and know in which position it is (I can understand the software but not how the hardware actually does what it's told to do).


texts: Although the adsorption of moisture by FR4 is quite low, what is the best way to minimize it or eliminate it completely?


texts: Need help with maximum safe load on a C10 battery in a Solar power system

texts:
I have a solar system with 20Amps/12v MPPT, 150ah/12v C10 battery, 500watts/24v panel and 1000va inverter. I have a few questions.

Can I use a 750w cloth iron on this for 30 minutes? As per my calculation, it may draw up to 45Amps from battery, because I am getting only 18amps from MPPT. Will this affect the battery in any way?
Can I run a 1HP water pump on this for 30 minutes with a soft-starter?

Thank you all for your valuable inputs.


texts: Want to know more about this op-amp configuration

texts:
When I see op-amp inverting and non-inverting amp configurations, I see the one on the left.
(only inverting circuit is shown).

This op-amp circuit has a gain equal to \$ {-R2}\over{R1} \$.

However, if I do the math I can see that the configuration to the right also works (notice the inverting and non-inverting pins are swapped.) as an inverting ampifier, with gain equal to the same \$ {-R2}\over{R1} \$.

PS: I have checked this in a simulator and found that the circuits are indeed the same and the one on the right works exactly like the one on the left.

Thus my question is why do we use the Left circuit and not the one to the right, if they behave the same?

My derivation is here:

Here is the simulator:


texts:
I tried throwing together a little circuit that has an IR sensor (the Vsignal should really be a photodiode going to the supply) and switches the output high until C1 charges back up again. The Vout is supposed to apply high voltage to the input of a power relay (one of these this).

The circuit works perfectly fine without the relay output load (the output goes high until M3 is shut off again). However, with the relay hooked up to Vout, the voltage doesn't go back down even when Vgs of M3 is 0! Can someone explain why this is happening?

I quickly tried buffering the output with an emitter follower but it only partially allowed the voltage on Vout to drop down to about 2 or 3V.

Thanks


texts: Could a network of WiFi routers replace an ISP?

texts:
If it could be done, it would. But what are the driving forces preventing a company from creating a device that could connect to numerous other routers/devices and relay the information throughout an entire network assuming the devices are within range of eachother. Essentially I'm thinking of a web of wireless routers/devices that handle the internet instead of a cable company?

Is the main issue that there would be too many competing signals and they would drown each other out?


texts: Do 6-, 10- or even 20-pole rotary switches exist for 220V applications?

texts:
I am trying to create a "dimmer" with non-dimmable bulbs.

The idea: use 6, 10 or even 20 bulbs (some cheap non dimmable LED or CFL), use a rotary switch that in position 0 lights up none of the bulbs, in position 1, lights 1 up ... to position n where it lights up the first n bulbs without complicated electronics (I am after the cheapest solution possible).

Does such a switch exist?
I tried to search for such a thing googling 20-pole switch and 20-position rotary switch, but did not come up with a workable result.

Any help appreciated.

Alternatively I would, but I failed to find it so far, I would like to find an affordable and dimmable high power flood-light (150W LED actual power - 13k-15k lumens) that I can control from a single dimmer switch.


texts: Electronic Switch with Load Before and After

texts:
I'm having trouble including a switch in a circuit that will be turned on and off via a PIC microcontroller (3.3v). The circuit that it will be switching can go up to 24v and around 20amps. This has been easy to do with a transistor (N-Channel MOSFET) and works very nicely when I put the load before the switch.

The problem is that this switch will control an external circuit where the load could be anywhere. Having the load after the switch causes a voltage drop of around 10%, something I need to get around. Is there a way of getting consistent voltage and current on the second circuit before and after the switch? It doesn't have to be a MOSFET.


texts: Why does it take such a long time to build a new power grid transformer?

texts:
From time to time, when people are discussing the consequences of power outages, like the ones from the Texas winter storm or a hypothetical catastrophic space weather event (Carrington event scale), someone invariably brings up the point that one of the most important goals during a power crisis is to ensure that the high voltage transformers do not get damaged, because even with our current technology, it easily takes well over a year, probably even over 2 years, to build just one.
Why would it take so long to build one of these? Are they that complex to assemble?


texts: Is there a safety issue with running a AA alkaline cell through 0.3 ohms?

texts:
I'm running an Electricity merit badge session for my son's boy scout troop.  One of the requirements is to make a simple electromagnet.  For this, I was going to have the boys take a 12 foot length of 24 gauge wire and wrap it around a large nail and connect it to a AA alkaline cell.

The wire gauge chart tells me that 12 feet of wire is about 0.308 ohms.  The nominal voltage of the AA is 1.5 volts, which would put the current at about 4.9 amps.  However, when I actually connect it up, the measured voltage of the battery is actually dropping to about 0.9 volts, for a current of about 2.9 amps, which is within the amperage limits of 24 gauge wire.

My question is: Are there any safety concerns with connecting the AA cell this way?  I realize that this will drain the energy out of the cell fairly quickly, but it doesn't need to last very long for this demo.


texts:
I am planning to create a device which is connected to wifi and triggers a current when I send some signal to it using wifi.

This will be something like unlock an electronic door remotely. What all components will be needed to do something like this?

I will be using Android for triggering the signal. Any help will be appreciated. Any recommendation for any pre-built device will be useful too.


texts:
I am having some difficulty figuring out V_out. I know that it is going to be inverted because V+ = 0 and I know that V- ≠ 0. I don't really know how to go about finding the currents in the system to calculate V-.

Doing KCL I get stuck with 2 equations and 3 unknowns (the third is Vout)

Circuit Simulation


texts: How can I output 5V from ESP8266 NodeMCU 3.3v input?

texts: I want to control a High Torque Servo using the esp8266 with PWM. This servo's operation voltage is in the range: 4.8V - 7.2V. With the esp8266, the GPIO pins can only output a maximum 3.3v. What's the most simple way to achieve the 5v output from esp8266?


texts: How to use a multiple serial port in Arduino

texts:
I have obtain 2 shield from Itead; GPS Shield & IComSat GSM Shield. I have a requirement to
develop an Arduino Uno prototype and used a serial interface to communicate with this two shield. My sketches using SoftwareSerial but it seem not working properly, is there any optimal way to combine these two shield?

Arduino GPS Shield
http://imall.iteadstudio.com/im120417017.html

IComSat GSM/GPRS Shield
http://imall.iteadstudio.com/im120417009.html


texts: LED Matrix creation using resistors & MAX7219

texts:
I've been attempting to create my own LED matrix, but now I've plugged it all together I'm getting some unexpected LED's lighting up, it seems some are getting power when they shouldn't (not very bright but a little bit bright) and it seems those that need power might not be getting enough (they are colour changing LEDs but they are not changing, it seems like they aren't getting enough volts/amps to change?).

Now I've realised I've done something wrong, I have used pre-wired LED's that each had a resistor already soldered in! See here Each is 3-6v 20mA.

I've used a MX7219 on a pre-build board see here, removed the small LED top and connected up my own wires. I'm realising now this board probably also has two resistors built in, one for column one for row.

I'm powering it with a 5v, 5A power supply.

Checking Dig0 & SegA on the Max7219 there is roughly 3.15volts running through it.

Is there something obviously wrong with this setup? Are the resistors on each LED doing something funky to the rules of the LED matrix? Can I get around this or is replacing all the LEDs with non-resistor LEDs the only choice now?

**If you are looking at the picture. Some of the LED's are not color changing, they are pure white see here but they are the same voltage and amperage. I just didn't want to confuse the question with this info.


texts: BLDC Motor Driver: Justifying better design approach

texts:
When and why it is better for a design engineer to design a BLDC driving circuit using individual MOSFETs, instead of selecting a ready made driving IC to simplify the design?

Here I just do not mean to run a BLDC but also control its different parameters. For instance: Speed; which can be controlled using a potentiometer but programming seems more practical in certain cases.


texts: What is the total power consumption of a flipflop?

texts:
See the datasheet of D flip-flop (74V1G79).
Here the total power calculation is given as follows,

Average operating current = Switching current + Supply current.

But if there is a load in the output side of the FF, (Assume the case of ring counter with output side also with same FF 74V1G79) then total current will be as follows,

Average operating current = Switching current + Supply current + load current.

This is my understanding. Following things need to be clarified.

1) Whether this understanding is correct or not?

2) How can I get the load current? (Checked in the datasheet, but nothing related output drive current found)

Edit

Assume the switching frequency as 500 kHz.


texts:
I have a small project that I'm working on. It has a NOKIA 5110 LCD.
I want to make a nice GUI to view measurements, and also control the hardware.
I've designed tow screen layouts which you can see in the images below

the thing is if I complete the code the way I did it(the code is at the end), it will be big.
And I don't think this is the optimal way to make a multiple screen layouts.
It would be great if any one could help or give me a head tips.

This is the code for "ok" button:

if(bit_is_clear(PINC, 5))
    {
        UART_Send_String("OK\n");
        switch(screenIndex)
        {
        case HOME_LAYOUT:
            switch(cursor_index)
            {
            case 5:
                lcdSetupLayout();
                cursor_index = 0;
                break;
            default:
                break;
            }
            break;
        case LCD_SETUP_LAYOUT:
            switch(cursor_index)
            {
            case 0:
                PCD8544_send_command(video_inverse);
                break;
            case 1:
                PCD8544_send_command(display_norm);
                break;
            case 3:
                cursor_index = 0;
                homeLayout();
                break;
            default:
                break;
            }
            break;
        default:
            break;
        }

        _delay_ms(300);
    }

And this is the code for "up" button ("down" button has a similar thing)

if(bit_is_clear(PINC, 6))
    {
        UART_Send_String("UP\n");
        if(cursor_index > 0)
        {
            set_x_y(0,cursor_index);
            PCD8544_send_char(' ');
            set_x_y(0,--cursor_index);
            PCD8544_send_char('>');
        }
        else
        {
            set_x_y(0,cursor_index);
            PCD8544_send_char(' ');
            cursor_index = 5;
            set_x_y(0,cursor_index);
            PCD8544_send_char('>');
        }
        _delay_ms(300);
    }


texts: Low voltage controlled open drain circuit

texts:
I have a power regulator with an output enable that can be used to shut the regulator off without actually unhooking it.  I am trying to figure out how to control that using a GPIO port of a Jetson TX2 (1.8V logic).

The manufacturer of the regulator says that I will not be able to connect the output enable wire directly to a 1.8V GPIO pin because the output enable is internally pulled up to the regulator Vin (24V).  They said to drive it properly I will need an open-drain circuit, which will allow your GPIO to switch the output enable pin between float and ground.

Using https://www.microcontrollertips.com/what-is-an-open-drain/ as a source I looked on Digikey to find an N-channel MOSFET that would work and I think one of these:

https://www.digikey.com/product-detail/en/toshiba-semiconductor-and-storage/SSM3K329RLF/SSM3K329RLFCT-ND/3522426

https://www.digikey.com/product-detail/en/nexperia-usa-inc/PMV40UN2R/1727-1900-1-ND/5056345

would. Is creating the open drain circuit a matter of connecting the output enable wire of the regulator to the mosfet drain, the Jetson GPIO to the gate and the mosfet source to ground like this? Or do I need a current limiting resistor between the GPIO and the gate?

simulate this circuit – Schematic created using CircuitLab

Thanks for your help.


texts: What is the reason CMOS took over as an inverter for fabrication of gates?

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I get to know that the static power dissipation is zero in case of CMOS where as there is some static power dissipation in NMOS with saturated load and linear load and with NMOS with depleted load.

What exactly does it mean?


texts: Do the resistors fail to distribute voltage?

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I am working on infrared array PCB designed to track line i was supposed to get analog output (1 in the diagram) instead i get all 5 volts from all sensors in my PCB. I bought a infrared sensor TCRT5000 Reflective Optical Sensor with Transistor Output" from this link. I am not able to debug it.

The circuit:-

TX+ > Anode

TX- > Cathode

RX+ > Emitter

RX- > Collector

Every thing is connected correctly but I get a voltage on the transmitter of the sensor of 5 volts instead of being distributed on the 330 Ω resistor and the LED, and the same on the receiver instead of analog output.

My question is whether the resistor may be defective, or the sensor itself, knowing that they are all new?


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I have a central heating system that displays it's info and error codes on 4 7-segment displays. These displays are driven by a SAA1064, like so:

This SAA1064 (datasheet here) receives it's information through I2C from the main computer, and the displays are multiplexed.

Here's my problem: I have a raspberry pi (whose I2C bus is already in use, at 100KHz) and I want to use it to read the values being displayed. I would prefer not using an extra microcontroller just to parse what's being displayed or to sniff the I2C bus inside the central heating system (as I have little-to-no-experience in programming those). Would using I2C IO expanders be an idea? If so, how would this be wired?


texts:
I wired up this light dependent switch

which works fine.  when in daylight and covered.  how can i make it work when the light source is dimmer?  ie is it a case of changing 1 of the resistors?


texts: I need to make a circuit that results in a 0(off) when one or both switches are closed. I am pretty sure this is a NOR circuit, but I am confused on how to make it assert a 0 when the switch(es) are pressed.


texts: Making a lock system with a 7-segment circuit

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I got an assignment in my university to create a lock system using a 7-segment LED, a 7-segment decoder IC and a bi-color LED.

The idea of the assignment is that the password is stored somewhere. Then using a 4-dip switch, you input data to the decoder IC to be displayed on the 7-segment. If the binary input that you made, is the same as the password that you have stored, then the bi-light LED would light up green. If the password entered on the 4-dip switch is wrong, the LED would light up red.

Using IC 4511 and a common cathode 7-segment display, I made the connections needed for the 7-segment display to operate without much trouble, but I still don't know how make the logic for the lock system. The only thing I could come up with for the lock system's logic is the following Boolean expression:

\$ f(A,B,C,D,E,F,G,H) = (A \oplus E)' + (B \oplus F)' + (C \oplus G)' + (D \oplus H)'\$

where A, B, C, and D are the 4 bits of the password that we have stored somewhere, and E, F, G, and H are the inputs that we make to the 4-DIP switch

Is this logic circuit correct? Are there any simpler solutions to comparing two binary numbers outputed by a 4-dip switch?


texts: Reducing noise in an audio amplifer using opamp

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I am trying to make an audio amplfier using an opamp for a project. It works kind of okay but the only issue is there seems to be a lot of noise in the output of a 0.5 watt speaker. I have tried changing the various capacitor values but there still seems to be noise. Whts the best way to bring down this noise in the circuit? My circuit is identical to the one http://www.elexp.com/t_audio.htm. Could someone please help me out?

The input is from my laptop jack output . Could this cause any ground issues which cause noise?


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I am trying to get my Arduino to control a relay without luck. I'm able to see the LED flashing on the relay board indicating that the relay should be throwing, but the circuit is not being closed. I'm wondering if its because the circuit on the relay is too low of a voltage? I've got a 12 volt circuit.

Here is the relay I'm using


texts: What if I have a voltage between ground neutral?

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What does it mean when there is voltage between ground and neutral (220V) and between phase and neutral (220V) but no voltage between phase and ground (0V)?

What could happen? Is it safe?

Is it normal that when I plug in a lamp, it works just fine?


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I am more of a software programmer, but I have a basic question on electronics.

What happens when a device draws more current than the power supply can provide?
And under what circumstance can it happen - bad board design or not determining the worst case scenario of the device operation?
How does one actually see this on a scope?
What in turn happens to the device if this is not rectified?


texts: How to write a program for 4-Bit CPU made in Logisim?

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So I finally got my 4-Bit CPU working on Logisim, and am trying to get it to do commands and display them, but am unable to do so. My CPU looks like the following:

I am trying to implement the following commands or opcodes into the Decoder (Address Bit Width = 4, Data Bit Width = 8):

And my PROM (Address Bit Width = 4, Data Bit Width = 16) Gives an output as follows:

  Question 1: How do I create a simple program following these guidelines that will take 3 + 4 and add them, displaying each number, digit and symbol, as well as the result. (I.e. What goes in decoder, and what in the PROM?)

  Question 2: How do I figure out how to display simple letters on the display? (I want to type Hello World).

I'm not much of a low-level programmer, but understand the concepts so help would be appreciated.

I have a file named Hello.txt which can be used to load a program into the PROM, however it doesn't display the correct output, which should be: "Hello BJ". Instead it shows random characters. https://pastebin.com/HbtaA04i

The way the PROM and the Decoder commands are as is follows:

An example of the PROM would be:

  0011 0000 0001 0110
  - Display the contents of registers 1 and 6. At the
  end of the operation, a 3716 will be sent to the
  display, and a “7” will be displayed (refer to an
  on-line ASCII table for doing display writes).


texts: how to isolate Maxim dallas one wire interface

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I would like to isolate my thermocouple amplifier using a adum1200.
Given the following illustration of the chip, does this chip allow me bidirectional comms on the same pin?

I hooked up power on vdd1 and gnd1 to 5v rail on my uno.

then provided another sperate 5v (plug pack and 7805) to vdd2 and gnd2.

ViA ----> to my digital pin 2 then voA to my one wire amplifier.

The code says it can't find the amplified but it works pefectly fine when I don't use the amplifier.

I'm guessing I need a chip that has an open drain output

I fell into the trap of believing the banner specs on the datasheet if that's the case.

out of interest how are they claiming it's bi directional then. iS it because the adum1201 has 1/1 directionality