texts: New soldering iron smokes from inside the handle (not from tip) - is this a problem?

texts:
I've started using a brand new soldering iron for the first time and it's not working as expected:

After about 10 seconds of power, smoke starts coming out from inside the handle, next to the metal shaft. After 30 seconds on, there's a lot of smoke pouring out, like a candle that's just been extinguished. I've turned it off and on and this still happens
There's no smoke from the tip, and a very small amount from where the tip attaches to the shaft
The tip doesn't get hot enough to melt solder after being on for a little over a minute. I haven't tried leaving it on for longer than that because the amount of smoke from inside the handle seems to just keep increasing. The handle doesn't seem to get noticeably hot in this time

I bought it in a 230V country (UK) and am using it in a 230V country. It's a 40W Maplin soldering kit.

I expected the tip to smoke, but not the inside of the handle. Looking this up online, I see a lot of similar questions being mis-read as being harmless tip smoking, and a lot of comments that they're often coated in oils that burn off. It seems to me that these wouldn't be inside the handle, though? Or would they? Some other comments seem to think this is a sign of a defective iron, but don't offer anything to back up this opinion beyond "I've never seen that".

Just found in the paperwork:

  The first time you use the soldering iron, it may smoke slightly and there may be a smell of burning as the heating element dries out. This is normal and should only last a short while

...which sounds unusual and is a little vague. This seems like it'd explain the small amount of smoke where the tip joins the metal shaft, but I'm not sure if this would explain large amounts of smoke from within the handle.

Update: I tried leaving it plugged in outdoors under supervision (fire extinguisher at the ready). After about 7 minutes it seemed to stop smoking, so I took it back inside (keeping the fire extinguisher handy), let it warm up again for a few minutes, started soldering, then noticed it was smoking again. It stopped smoking pretty quickly after killing the power, and was still hot enough that I could finish my soldering, but I think I'll be looking for a replacement.


texts: Choice of power supply block for RPI4 PCB and sensors

texts:
My project consists of making analog to digital conversion from 10 sensors (2 MyoWare sensors and 8 FSR sensors.) with a Raspberry Pi4. The analog to digital conversion chips are 2 ADS1299.
I need to power them with the bipolar mode +2.5V/-2.5V. I have 2 choices: two 9V batteris or a power bank 5V 3A.
How can I know if the two 9V batteries can support powering all the system (sensors,RPI4,ADS1299?)
What must I calculate to choose the optimal power supply system?


texts: How to generate a 555 fixed time delay even if trigger button is held on?

texts: Can any one help me how to make it when the switch is presed for long time but it will not affect the time delay


texts:
I want to simulate a simple encoder wheel with two buttons (one for up and one for down). The output of the encoder is as follows:

I want to accomplish this without the use of a micro. I have a solution in mind but it would require 3 555 timers to generate the wave form (one to create A pulse, one for delay time on B pulse and third for the B pulse). I am thinking 50 to 100 ms periods would be sufficient. Also, the waveform does not HAVE to repeat while a button is held down. So, the button CAN be repeatedly pressed to simulate a full rotation as opposed to being held down.

Anyone have an improvement on my 3 555s? It just seems so wasteful and I am sure there is likely a more elegant approach.


texts: How do I create pulse of 200 ns and 10 V with a microcontroller?

texts:
I 'd like to command the gate of a MOSFET with a microcontroller. The command will be be very short: a pulse with 200 ns of duration (period = 1 ms) and about 10 V of amplitude.
Can I do this with an Arduino? Or with another microcontroller?


texts: battery low voltage cut off breaker (manually reset)

texts:
First off, I am aware that premade devices like this exist however I have been unable to find any that fit my exact needs which are as follows.

0 power draw when in the off state
Minimal voltage drop when in the on state
Being able to set it to trigger at 10.5V
Simple design
Manually reset

When I attempted to design a circuit to fit those needs myself I came up with the following. (R1 just represents the load)

The idea is that when I connect a battery with a voltage above 10.5V and S1 is pushed to jump start the circuit the normally open relay will then start keeping it's self closed. I would then have R2 tuned so that it had just enough resistance so that when the voltage on the main circuit dropped to 10.5V the voltage to the relay coil would become too low to keep the contacts closed. The contacts would then come open and cut power to the whole circuit.
In theory this is a nice simple elegant solution to the problem for a layman like me. The issue that I'm running into is that there isn't an "exact" voltage where a relay shuts off so it would be nearly impossible to get it to shut off when the main circuit is at exactly 10.5V. I can't use a transistor or similar device because even a small voltage drop on a 12V nominal circuit like this makes a huge difference. I need 10.5V reaching the end device when the battery is at 10.5V.
I am hoping to keep this circuit as simple as possible so that I can have it packed up nicely as a single rugged unit. Currently the only application I have for it draws a constant 5 amps but I would like to be able to modify the circuit to accommodate larger loads if needed in the future so an electromechanical component seems ideal for switching the main circuit.
My question is, is there a component or simple circuit that I could put in the place of R2 that would only allow voltages over 10.5V through and completely cut off below that? If I can just get that relatively low amperage (under 200mA) circuit to completely cut off at a designated voltage then I can switch the main circuit with whatever relay or contactor I want with minimal modification.


texts: Can a PLL work with a sine signal as its XIN?

texts:
I need to generate a 150.012MHz signal. I am going to this with a PLL for RF purposes, so I am thinking to buy a 10Mhz osc with a sine output, will this work with all PLLs? as they are digital I'm not pretty sure. Or should I buy an square oscillator?

Thank you in advance.


texts: How can I build a RGB+CSync to SCART video cable for a vintage camera control unit?

texts:
I'm an associate professor at a university in Japan, and last year I discovered that my university has two working, vintage Sony DXC-M3A Saticon tube video cameras, along with accompanying power supplies and CCU-M3 camera control units (CCUs).

I'm trying to build a video cable that will run from the RGB+CSync BNC outputs on a CCU  to the SCART input on a SCART->HDMI upscaler that I recently purchased. The goal is to get RGB output from the cameras into an Elgato Game Capture HD, which is very picky about which resolutions it accepts through HDMI.

The CCUs output RGB+CSync through four independent 75-ohm BNC plugs. Right now I have a BNC->VGA/15-pin RGB cable, and I was able to use that cable with a Gonbes arcade scaler to get an RGB signal to an LCD monitor, but not into the capture device. I wired my own VGA->SCART cable to go from that cable to the SCART->HDMI scaler, but all I ended up with was a blank screen.

I have some RCA plug to BNC adapters, so I was thinking of cutting off one end of an AV cable (plus one more RCA cable), wiring the ends to the appropriate SCART pins, and then connecting the other end (RGB+CSync) to the CCU, but which pins should I use? Do I need to use a power supply to send the correct blanking signals and aspect ratio selection to the SCART end?

I'd appreciate any advice the StackExchange masses can give me.


texts: Why do high current wires have fabric/nyon sheathes?

texts: I saw two wires going into a halogen light bulb whose outer sheathes were not a plastic (like PVC, or polyurethane), but rather a woven fabric (like a nylon shoelace).  Why is woven fabric better for this high current application?  Sure, PVC may not have as high of a temperature rating, but why specifically does the material transition from solid to woven construction?


texts: Question about transitor NPN [ALFA;Strange configuration;Exit characteristic]

texts:
first of all thanks for read and for your time, I have a few questions about transistor:
1)

I can't understand why my book say:
Ic=Icb0+alfa*Ie
and not Ic=Icb0+alfa*Ie-Ib since the Ic doesn't have also the Ib

2)

My teacher says that this configuration can't exist, since G2 isn't in common with GND, but in according to my reasonament:
If G2=0,7 the Node P will be at 0,7V, and the node A will be at 5V higher than the node p so it will be at 5,7V

3)

Why if 0,2V is the voltage of saturation in which the transistor could be immagined like a shorted circuit the Ic isn't high?

Thanks for read have a great day:)


texts: Suitable amplifier for relay controlling solenoid valve

texts:
I have a vacuum gauge with on board relays that trip at set pressures. They have a rating of 30 VDC, 1 A. The solenoid valve I need to control is 50 VDC with max current 3A (also is inductive load of course).
What is my easiest, cheapest option here to still use the vacuum gauge relay to control the solenoid? It seems like I need the relay to complete the circuit of an amplifier input that can provide the current and power drawn by the solenoid. I just need to figure this out fast, any help in the right direction in terms of products is appreciated.


texts: How to fuse batteries connected in parallel?

texts:
I have two GEL batteries 12V/130Ah and want to connect them together in parallel.

Currently I have one battery in the system and it is fused on the positive wire before the isolation switch.

I wonder what is the best way to fuse two batteries together connected in parallel. I came up with three possible solutions to prevent the short circuits:

1)

2)

3)

Which one is the best and why?


texts: Is a current varying output or voltage varying output for a 4-20 mA sensor more reliable for a rocket?

texts: For the internal plumbing system of a rocket which is expected to reach 100 km above the ground, industrial pressure sensors with a 4-20 mA current output and a 0-10 VDC output are available. What would be a more reliable choice?


texts: Maximum frequency of the synchronous counter

texts:
Find the maximum clock frequency at which the counter in the figure below can be operated. Assume that the propagation delay through each flip flop and each AND gate is 10 ns. Also assume that the setup time for the JK inputs of the flip flops is negligible.

My analysis :-As it is synchronous counter so,by 10ns all the flip flop will produce output.But now the output should reach the AND gate also ,so that when next clock comes then inputs to FF are ready.

The first AND gate will produce output by 10 ns,and then this input goes to second AND gate,which takes 10 ns.
So overall the time period of the clock is 30ns.
And frequency is 1/30 GHZ

But my book says that clock time period is 20 ns.
Can anyone clear the confusion here ,how 20ns is possible?


texts: LCD 4x20 display malfunction after ESD, Recover?

texts:
I have a device with 4x20 generic LCD display controlled by arm STR750 processor which is working well.

According to IEC EN 61000-6-4 standart criteia B display of device should be recovered in a while after any static discharge. ESD tests are done with 4kV per second to contact and 8kV per second for 10 seconds to glass surface of LCD and my LCD fails on both. My LCD chars displays wrongly and garbled ter a static discharge -my processor works normally-.

It keeps wrong display until end-user reset the ARM processor but IEC EN 61000-6-4 standard criteria B says it should be recovered without user interaction. So I should recover that malfunction with STR750 arm processor. Simple reinit of LCD makes it work good again.

How can I understand any malfunction occurs on my LCD that makes wrongly display by ARM processor? And Is there any robust way to recover it? I can sense it by STR750 arm processor with readback just after a write to LCD register for everytime but it is not robust.

I am asking for a method or procedure that helps me to write C code to my arm processor or a hardware trick for recovery after LCD malfunction because LCD is generic and have no info about ESD so I cant make any changes on LCD.


texts: Calculating Milliseconds using timers in PIC and synchronizing it with DS1307 timing

texts:
I have used DS1307 in my project which gives me the values of Hour, Min, Sec but I also need values of Milliseconds. I am planning to use timers with 1 millisecond timing and then synchronizing it according to seconds of DS1307.
I have made the program for 1ms delay but the problem is I am not sure if it is running with 1ms or not because I used led blinking and we cannot see led blinking at 1ms. My first question is, is there any way I can be sure that it is giving 1ms delay.?

Now lets say if its exact 1ms timer. Now how to sync it with DS1307 timing. My total application is like if I receive inputs then I have to show which inputs are turned ON on UART with exact timings (including Milliseconds). For example, if input 4 in ON then:

/*
**some code
*/
 if(PORTEbits.RB5 == 1)
 {
   putsUART1("Input 4 ON, Time:  ");
   putsUART(TIME);
 }

Now this TIME should contain the values of HH:MM:SS:MS. Till now I am able to show HH:MM:SS only. I also cannot use sqw/out because its custom made PCB and that pin is left blank. Pleas help

EDIT:

I have included count++ in ISR which is incrementing at 1ms. In while(1) I am printing the values of count after reading sec in RTC_read function

 while(1)
 {
    RTC_read();

    sprintf(TIME,"%s%s:%s%s:%s%s",hr2,hr1,min2,min1,sec2,sec1);
    putsUART1(TIME);
    putsUART1(" ");
    putsUART1(COUNT);
    putsUART1("\n");
 }

void __ISR(_TIMER_2_VECTOR, ipl3) Timer2Handler(void)
{
  mT2ClearIntFlag();
  count++;

}

RTC_read function:

/*
* some code
*/

 //read sec
   while(!I2CReceivedDataIsAvailable(RTC_I2C_BUS));
   Nop();
   sec = I2CGetByte(RTC_I2C_BUS);
   AckI2C2();
   while (!I2CAcknowledgeHasCompleted(I2C2));

   /*
    * Milliseconds
    */
   if(count >= 999)
   {
       count = 0;
   }
   else
   {
       sprintf(COUNT,"%d",count);

   }


texts: I'm having trouble finding a specific component for a project I'm working on. What I need is a sensor that can act as a hinge (or can measure the rotation of a hinge) and tells the degree of rotation between the two planes on either side of the hinge. It needs to read from 0-100ish degrees. I've looked at various sensors with knobs, and I don't think they could solely support the weight being put on the hinge. Has anyone ever worked with a piece like this? Any tips or workarounds are greatly appreciated.


texts: Dump loading chip resistors and heat dissipation

texts:
I'm building a circuit at the moment which involves switching a 500ma load from a microcontroller to balance a bank of batteries. This circuit runs at 12V nominal. I've built a PCB with 1210 chip resistors in a 4S8P type configuration (32 resistors) each running 51ohm for an overall resistance of 25.5ohm.

I've selected 32 Panasonic ERJ14 1210 1/2W resistors which should be dissipating around 180mw each, however these chips are very quickly getting very hot, measured in at over 120˚C in a 20˚C room. The data sheet lacks ambient temperature delta / load data so my question is, how does one determine the temperature rise for a particular chip resistor? And less directly, what are the physical limitations to heat rise from dissipating a certain amount of energy? In this example, how hot is a particular surface area going to get to dissipate 6W?


texts: Connecting Charger + Inverter to deep cycle battery

texts:
It's a really simple question I believe, but I just want to make double sure it's okay. Can one simply clamp a mains charger as well as an inverter onto a deep cycle battery, or does one need any other equipment?
My charger has charge management circuitry. My pure Sine Inverter does inverter things. And the battery is a, well, battery. So can I connect both charger and inverter directly to the terminals of the battery, or do I need to put something between the battery and the inverter?
Not asking about nice-to-have equipment. I really just want to know whether they will work together and play nice.


texts: MOSFET driver "overcurrent" error but no current is flowing

texts:
I have a motor controller design that I was hoping would be able to drive very high currents of 50A continuous up to 100A peak.

In order to do this, I have put 4 mosfets (PSMN0R9-25YLC, http://assets.nexperia.com/documents/data-sheet/PSMN0R9-25YLC.pdf) in parallel in each section of my h-bridge. I suspect this use of parallel mosfets may be part of my problem. I am using an Allegro A4956 mosfet driver (http://www.allegromicro.com/~/media/Files/Datasheets/A4956-Datasheet.ashx?la=en) to drive the mosfet gates. I have a 1 ohm resistor in series with each mosfet gate to keep them decoupled from each other (since I read some decoupling resistance was good practice) and a single 10 ohm resistor in series with the A4956 gate driving output. I am not sure if this series resistance is necessary, since it wasn't shown in the example schematic in the A4956 data sheet, but I have seen in most other examples, and removing it didn't seem to help either.

My problem is that the A4956 seems all too ready to go into fault mode for "overcurrent" (OCLn driven low and AIOUT above ground, and gate voltages too low for the high side to turn on but not grounded either). On occasion it reports a V_ds fault (OCLn driven low and AIOUT also grounded), but not nearly as often. I have assembled four of these circuits and they all have the same behavior, so I can tell the problem is with my design and not with any specific defective part.

This is puzzling to me because this happens even when no motor is attached, or when I manually pull the current sense voltage to ground.

However, if I use a low motor supply voltage of only 4V or so (my design is for 12V motors), the controller operates mostly correctly, only tripping to overcurrent if I make too sudden changes to the PWM duty cycle. But once I cross this arbitrary voltage, I am stuck in the overcurrent fault. I am using a power supply that reports amperage, so I know that when this is happening, there really isn't any DC current going anywhere at all.

I thought that maybe the issue was the transient involved in turning on the mosfets, since 4 times the mosfets would require 4 times the current, but increasing the blank-time to a maximum did not seem to fix the issue. Perhaps using 12V instead of 4V also increases the current transient. When I look with an oscilloscope at the voltage on the mosfet gates, though, I don't seem to see any transients occurring. To make sure enough current can be provided by the mosfet driver, I have used the current setting resistor R_Iset (set to 20k) to specify the maximum current, which should be 46.9mA to the high side and 88.5mA to the low side.

I think that 46.9mA should be plenty to charge the mosfet gates because running at 16kHz pwm, I should be able to charge up to 46.9mA / 16kHz / 2 = 1465nC and I should only need a maximum of 51nC (total gate charge of each mosfet) * 4 = 204nC total gate charge, nearly a full order of magnitude less.

I am pretty puzzled about what to try next and why the A4956 is not operating in any way I can understand.

edit: The most relevant sections are below, but the full project is public on upverter: https://upverter.com/acshi/43f3f94ec99df03a/53A-Motor-Controller-11/

Also, in testing the controller, I managed to blow out the indicator LEDs for when the motor is turned on and in what direction, which are just put across the output voltage. I find this also to be a very strange occurrence, but I don't know if it is a related problem or a different one (like a voltage spike from when the motors were in fact turning at around 4V and then suddenly stopped).


texts:
I am working on a DC battery charger project, and there is a dispute that the battery charger does not charge up to the stated 12V / 25A rating (300 watts).

We've connected the DC battery charger to an electronic DC load at a constant voltage of 12V, and it draws 20A maximum (which is below the stated limit, and sets a firestorm of regulatory issues since the product need to meet 25A as per the stated ratings).

I understand there is variation in battery voltage vs. the nominal voltage (so the current can change), but we do not see this device ever output anything close to the stated power output.

If we connect two or three nominal 12V batteries simultaneously then we can coax the charger up to 24A.

The designer thinks we have set up the measurement incorrectly and is waffling on why the watt output is so flaky.

I am thinking to illustrate the point further, we will get a 12V battery and remove the electronic DC load.  I wanted to nail down the measurement connections and terminations with the designer so there is no dispute about "the test setup" and then wire in a ammeter in series to measure the current.

I am seeing on high-end Fluke multimeters they are only able to measure 10A of current safely.

What can be used in series to safely measure up to 25A of current?  I'm seeing clamp style multi-meters, is there anything else like a more traditional meter that can be wired up in series for the measurement?


texts: Should resistor R1 be in the gate of the CMOS transistor of the following schematic? (CMOS Transistor)

texts:
I'm analyzing the following circuit that is used to activate and deactivate a CMOS transistor which is used as a switch:

simulate this circuit – Schematic created using CircuitLab
I think that R1 should not be and the M3 gate should be connected directly to the driver's output.
Am I right?
Any comment or suggestion is welcome.


texts:
I am new to Embedded domain and wanted to know what exactly is SOC(system on chip) means?

Is it like we different hardware component on CPU chip(like RAM on CPU chip) or on the same embedded board we have cpu chip manufactured by one company and rest of the component are manufactured some other company.

For example I have heard of TI soc's and Brodcom soc's both share the same cpu chip .


texts:
I know I have been asked not to provide video links and ask questions.

But I have no proper guide/mentor or anyone who can provide me better answers other than users in this site. So, please pardon me for this. I rely on this site for answers which can Solve my queries and help me with my understanding.

If you seen my previous questions, you would notice that a majority of my questions would have been related to control loop stability analysis of a dc-dc converter. I was not able to grasp the concept of zeroes with respect to electrical components. All I understood is that, If I have a pole, it means the electrical component will oscillate (at some frequency) and the system will be unstable. But what happens when a component provides a zero instead of a pole? How does one understand or find whether a component will provide a zero or a pole? What effect will that zero have in the system?

So, I am trying to learn it by watching questions and answers in this site, reading app notes, watching lectures and so on to get clarity.

In this Video, around 3:08 , he says that when the capacitance magnitude matches the resistance magnitude, we get a zero.

I don't understand that. Can you tell me :

Is he meaning that at some frequency, the capacitance impedance will be equal to the resistor's resistance? If so, at this point, what will the combination of the resistor and the capacitor connected to ground look like? And when he says zero, what effect will it have on the system?

Please do not think that I am asking multiple questions. If anyone can provide the answer which can help me clear my doubt regarding the poles and zeroes in an electrical circuit (in simple electrical terms for a beginner to understand) and how one can figure that this component will provide a pole or a zero, then that answer would solve all my questions.

Would be really grateful.


texts:
I am looking to interface a 3.3V device with a 5V one.  This will require the shifting of the logic levels between the two devices.

Doing this in one direction is a trivial matter, but I need to do it in both directions (reading and writing - it's a data bus).

I know there are bus drivers that can do this but I'm a skinflint, so I'm looking to see if I can do it with the discretes I have at my fingertips.

I came up with this circuit:

I don't know if it will actually do what I want, but from reading other sources (including Is it possible to drive TTL inputs from 3.3v microcontroller and Bi-Directional Step up and Step down (3.3v <-> 5, etc) [the latter mentions a sparkfun tutorial that no longer exists]) it might.

My thinking is, data from 5v to 3.3v goes through D2 and the series resistor R2 to drop the voltage.  Data from 3.3v to 5v goes through D1 and gets pulled up by R1.

Would this work?  Is it complete gibberish?

Update

Ok, so we have agreed that circuit is total gibberish.

I have made some tweaks, and come up with this:

Playing around with my scope gives me levels of around 1V-4V on the +5V side, and 0V to 3V on the 3.3V side.  Both sides default to a high level and connecting to ground on one side causes a low level on the other side.

The resistors are all 10KΩ, and I have had both ends feeding through 100KΩ resistors to simulate some form of load.  The diodes are all Schottky.

Thoughts?


texts:
I am new to electronics and have the following doubt.

Say Vgs= 3V to a NMOS produces Id= 3A.
Now if we place a 3A current source at the drain,will it cause a 3V at the gate, when the gate is open (assume source is grounded) ?
Why?
Also what happens when gate is also at ground potential?

Thanks in advance


texts: for an audio signal within the rails of an opamp, can its quality be improved by the + and - rail voltages?

texts:
I have a high end audio application in which I'm using the NE5532 opamp. I'm processing an audio signal with 10Vpp swing (so between +5V and -5V) in an audio ADC input stage. Does it make any difference for the audio quality whether I use +/-14V or +/-11V as supply rails? If yes, why?

Additional info: my converter takes differential inputs, each input between 0 and 5V. My circuit feeds it two signals centered around 2.5v, each 2Vpp so after subtraction the ADC sees a 4Vpp signal. This is a 32-bit converter and the sample rate I'm using is 192kHz. I cannot change the converter. Given this scenario, does it matter sound quality wise to use 11V or 14V rails?


texts: What does "Sourced from process " mean in transistor datasheet?

texts:
On first page of Fairchild BC516 transistor datasheet it's written:

  Sourced from process 61

What does it mean? Is it important for part's users or it's some kind of production process description?


texts:
i found an SPICE model for a component with diferent parameters than the ones that i found earlier (wich have the same parameters). So i am questioning wether there is a way in wich it is posible (and right) for a component with the same name (identifier code) to have diferent spice models with diferent parameters.
In case not, then the first one you stumble with when looking for a spice model on the internet is very likley the rigth and unique one, right?


texts: How can I create a SPDT for this motor without using a relay?

texts:
I have this 12V ball valve which is controlled by three wires.  Contaray to the description below, the motor still draws current after the valve opens or closes, so I will not only want to control red/blue is "on" but also power to the circuit.

I'll be using an arduino to control the valve.  For power (and other) reasons I don't want to use a relay.  I will power the motor with its own 12V battery pack.

If I could figure out how to make a SPDT switch, I would use a transistor to control the valve by using the red/blue and yellow wires.  I assume I probably need a diode or two to protect against EMF. I've been driving other 12V motors with Darlington TP120 so hopefully I could use those here as well.


texts: Equivalent of STP16C596 in DIP package for through-mount

texts:
I’m trying to add a large number of RGB LEDs (70, so 210 outputs) in a fairly small space (basically a keyboard, although it’s a bit bigger than most).

I read on this tutorial and elsewhere about shift registers, and to me the STP16C596 seems particularly good because a) it will drive 16 outputs and b) it obviates the need for resistors because it provides a constant current.

However, this part is obsolete it would seem and unavailable. What’s a good alternative that I will still be able to hand-solder?

This question suggests using an ‘SCT2026’, but the original link is dead, and I get no result on Mouser or Digikey for that part.

Notes

Apologies if any of my terminology is not right – I’m new to this!

I would certainly consider alternative approaches to this problem if there are any. From what I can see, a matrix-based or charlieplexing approach would be


texts: Is it true that power transformer has maximum efficiency at full load? In other words, is that possible practically?


texts: Mosfet blows on high load using gate driver

texts:
I am using LM5060 from TI for switching big modular N channel MOSFET in SOT-227 package (IXFN420N10T) for relative high 100-200A loads.

On small loads like 10-20A it was working fine then we tried a bigger resistive load of around 50A and it was working completely fine when first connected when the gate was switched it was opened up and current flew and worked just fine. But then the gate of MOSFET didn't work anymore always opened.

Our schematic is based on the reference from datasheet with added 0.01uF capacitor on the gate.

Maybe someone does know why mosfet get's blown? It supposes to handle 420A and at 50A it blows (not literally but the gate doesn't work anymore)

EDIT: Here is schematic as asked

EDIT2: At first I saw in documentation that Vgate is like 12V so it was within the range, and now I see in further documentation it writes this but I don't really understand if I am understood correctly:

  A charge pump provides bias voltage above the input and output voltage to enhance the N-channel MOSFET
  gate. When the system voltage is initially applied and both EN and UVLO are above their respective thresholds,
  the GATE pin is charged by the 24-µA (typical) current source. During normal operating conditions, the GATE pin
  voltage is clamped to approximately 16.8 V above the OUT pin (i.e. VGS) by an internal zener

So if I understood it charges voltage VIN - 16.8V ?


texts: VHDL difference between component and subprogram

texts:
I've read different article (and book chapter too) about "component" and "subprogram".
What i don't understand is what is the difference between the two...

I mean, i know that the component make easier the "hierarchical design" grouping "hardware pieces" somehow, while subprogram groups piece of code, but what i do not understand is how all this stuff behaves in synthesis. It is easy for me to understand how component behaves in synthesis (probably a compiler expand the component and just infers the logic embodied) but i don't figure out how a subprogram or function are synthetized.

Could you help me to understand?


texts: 5V Powerbank not turning on automatically when > 100mA are drawn

texts:
In this project, I power cycle a RaspberryPi Zero over a 5V USB powerbank, please have a look at my previous question:
Blocking current from Backup battery (3x1.5V=4.5V) when powerbank (5V) is turned on my timer switch
I use the TPl5110 as a timer switch and 2xAA as backup battery.
My circuit looks as follows:

The power bank is 10.000mAh, 5V, noname. EDIT: I've checked with the Varta consumer service and according to the datasheets of most powerbanks, they require a minimum current of 50mA -> this question is more universal than it initially looked.
The P mosfet is a NDP6020 with a low Vth of max 2V
The Diode is standard silicon 1N4001

According to the manufacturer, the powerbank needs a minimum of 50mA to be turned on/stay on.
I've set the potentiometer of the timer switch to 5min and I've verified it is working.
The problem is: after the first cycle, the RPI0 won't power up anymore since (for the 2nd and subsequent cycles) 0mA current (measured with multimeter) is drawn from the powerbank when the switch kicks in again. Clarification note, as requested: In the first power cycle, 130mA current are drawn (if I turn on the powerbank manually by pressing the on switch).
Can you see a flaw in this simple circuit that prevents current to be drawn from the powerbank on the power cycling events?
Please see the overall setup here:


texts: If a specific cell tower contains transmitters with an output power of 120 W along with antennas having 16.5 db of gain, would this not result in an effective radiated power in the kW range? The frequency is 2100 MHz and the antenna height is 105 ft. If a residential community is located less than a quarter of a mile from the tower, would there be cause for concern?


texts:
First time asking a question but I've come across something I just can't find the answer to. Whether or not it's because a silly question I hope to find out.

So I understand that with crosstalk occurs when an 'aggressor' AC signal is driven, and capacitive and inductive coupling happens.
I know that a steady state DC signal cannot couple to another signal, however can the reverse happen? Can an AC signal couple to a DC signal?
For example a signal line next to a VDC line.

Thanks in advance for any assistance, and again, apologies if it's a silly question.


texts:
I recently bought some Texas Instruments TTL chips.  So far they've been OK, except the XNOR (SN74HC266N) chips (I've tried 3, including one that's never been in my "real" circuit) always output low no matter what the state of the inputs are.

They weren't working right in the real circuit, so I pulled them out to test them in isolation.  Maybe I'm not testing them right, but here's how I did it:

              ----
      Input1 -    - Vcc
      Input2 -    -
MM Probe (+) -    -
             -    -
             -    -
             -    -
      Ground -    -
              ----

Where Input1 and Input2 where tied either to ground or Vcc of my supply (5.25v as measured by the meter).  I expect the "Y1" pin above to measure near Vcc with respect to ground if Input1 and Input2 are either both high or both low, but the meter measures ground no matter what.

Am I testing this thing wrong, or do I have a bad run of chips?  Am really new at digital electronics, so I'm fairly certain I've done something wrong.


texts: MOV in series with the VCC-IO pin of FT232R

texts:
Could someone explain to me why there is a MOV in series with the Vcc IO? Is it to cut power if the pin falls below a desired voltage?

(Here's the application note for the circuit.)


texts: How to add frequency control feedback loop to a circuit for an inductive heater

texts:
I am interested in a design made by an MIT student, Bayley Wang, several years ago for a 30kVA induction heater. One engineer on this site with professional expertise examined this circuit and commented:

  One problem with the Instructables project linked : No feedback to
  control (or limit) the frequency. With series tuned load, frequency
  needs to be above tank resonant. The changing properties of the heated
  load could cause tank frequency to change, and system would operate
  below tank resonant freq. At that point, the anti-parallel diode will
  begin dissipating a LOT of power - probably go PooF.

I emailed Bayley Wang and asked him if he agreed with this assessment and, if so, what he would recommend to do to improve the circuit and he made no response. Therefore, I am asking here how we could improve this circuit by adding a feedback loop to stabilize the frequency. The circuit is as follows:


texts: Safety of using microcontrollers such as Arduino

texts:
I have been learning how to work with Arduino Uno R3, and it seems very intuitive and exciting for me. As many agree, I see lots of benefits of learning to use it at a young age.

I would like to start a volunteer class for the local kids in my neighbourhood to teach them how to start small projects with the Arduino. This also includes learning how to work with a breadboard and other related devices and objects that go along with creating cool projects with Arduino.

What are the safety concerns of teaching 10 to 15 year olds to work with an Arduino (or similar) microcontrollers? Is there an existential risk that is high enough to make it a bad idea, legally or otherwise, to teach such a course to kids that age?


texts:
I'm currently using an MCP3008 ADC with Raspberry Pi and interfacing them with the wiringPi library.

To test the MCP3008 was reading the values properly I set up a voltage divider with a 100kΩ resistor and 100kΩ variable resistor to test a range of voltages.

The values however were around 130 off - which is quite high considering this is a 10-bit ADC.

I repeated the test with a 10kΩ resistor and a 10kΩ variable resistor and the values were accurate. I repeated the test again with 1kΩ resistors and they were accurate again.

So for the same values of voltages for 100kΩ and 10kΩ the MCP3008 gave different values.

The current was obviously lower in the 100kΩ resistors but the MCP3008 was drawing negligable current anyway so I don't think this is a factor.

Just wondering if anyone had any idea why this might be?

Sorry if this isn't worded the best, this is my first time asking on here.


texts: Can we connect two overload relays in parallel for the same motor?

texts: The motor peak starting current of 17.5 amps is too high. We have two overloads with range of 4 to 10 amps. If we install them in parallel, what are the consequences?


texts:
I'm making a prototype that uses, among other things, a bluetooth mcu connected to a 2.4GHz chip antenna. Its using a 4 layer PCB, and I'm thinking about what to do with the feedline, whether it should be buried on one of the middle layers, or left on the top layer.

I've been using this website (https://www.eeweb.com/tools/microstrip-impedance) to look at the various calculations. To get a 50 ohm line, it looks like the top layer would need to be 13 mil wide, and the buried one would need to be 7 mil. Both of these would be fine.

Is there an argument to be made for burying this feedline? Is that a standard thing done in industry (to reduce unwanted radiation, for example)?


texts:
I've been doing an experiment which involves measuring the voltage across the capacitor at different driving frequencies.
Consider the circuit below:

A sketch of the experimental curve \$(R_1<R_2<R_3)\$ with $(L,C)$ constant:
However I am still trying to understand why resonance takes place in the first place.
My logic is as follows:
\$V_L\$ and \$V_C\$ are in antiphase with each other (the inductor is in phase with the capacitor), so the voltage of the LC combination and hence the voltage of the circuit is:
$$V=V_L-V_C$$
\$V\$ is in phase with \$I_R\$.
The circuit current is
$$I=\sqrt{I_{LC}^2+I_R^2}$$
$$\frac{V}{Z}=\sqrt{\left(\frac{V}{Z_{LC}}\right)^2+\left(\frac{V}{R}\right)^2}$$.
Since \$V=V_{LC}=V_L-V-C\$, \$I_{LC}Z_{LC}=I_{LC}X_L-I_{LC}X_C\$,
$$Z_{LC}=X_L-X_{C}$$
$$\frac{1}{Z}=\sqrt{\frac{1}{(X_L-X_C)^2}+\frac{1}{R^2}} \to Z=\frac{|X_L-X_R|R}{R^2+(X_L-X_C)^2}$$
For resonance, \$X_L=X_C \to Z=0\$.
But \$Z=0\$ would lead to \$I \to \infty \$ so something isn't right with my derivation for \$Z\$ (circuit impedence)?
Also, I have been given the amplitude of the resonance peak:
$$A=\frac{k}{\sqrt{(\omega^2-\omega_0^2)^2+(\gamma \omega)^2}}$$
where \$k\$ is some normalisation factor, \$\omega=2\pi f\$ and \$\gamma\$ is the damping coefficient.
For \$A\$ to increase with \$R\$, am I correct to assume that \$\gamma \propto \frac{1}{R}\$? Is there a differential equation to describe the circuit?
EDIT: The internal reactance of the voltage source ~\$ 600 \Omega \$, \$(R_1,R_2,R_3)=(1\Omega, 2\Omega, 3\Omega)\$, /$L=1mH, C=100nF$/
I obtained the folliwing differential eq.:
$$\ddot{I}_{LC}(t)+\frac{1}{L}\frac{R_{output}R}{R+R_{output}}\dot{I}_{LC(t)}+\frac{I_{LC}(t)}{LC}=\frac{RV_0 \omega cos(\omega t)}{(R+R_{output})L}$$, where \$\omega\$ is the driving angular frequency and \$V_0\$ is the peak driving voltage. This means \$\gamma=\frac{R_{output}R}{L(R+R_{output})}\$ even if the output resistance is taken into account, but wouldn't higher R lead to higher \$\gamma\$ and hence lower amplitude?


texts: How can i find the current divider in the right resistor valued as "2 * R1"?

texts:
simulate this circuit – Schematic created using CircuitLab

My intention here is to find the current in the right resistor valued as "2*R1" using the current-divider formula. I don't know how to interpret the connections between these resistors.


texts: I currently use a DPDT 30 Amp relay to switch between a utility supplied 120 VAC and an inverter supplied 120 VAC. The relay has a 120 VAC coil. I use the inverter 120 VAC power source to energize the relay coil. So whenever the inverter is turned on, it energizes the relay and switches the supply power from utility to the inverter. The problem is, the efficiency of the inverter supplied power is diminished by the amount of current it takes to hold the energizing coil. So, if I could latch that energizing coil to the on position until the inverter is turned off, I could increase the efficiency of this switch. I am concerned about the failure mode though. The failure mode of a solid state solution to this is why I haven't pursued that route. Any thoughts on this would be appreciated. Does anyone have a solution?


texts: What physical factor affects the antenna's bandwidth?

texts:
Antenna's have a rated bandwidth of frequencies on which they operate. I understand that the antenna will still operate outside these frequencies, just that the signal will experience a greater attenuation at frequencies outside this range (like a filter's passband). Hence, my question is not a duplicate of this one.

What physical factor affects the bandwidth of an antenna? Is it the material? The image below shows two SMA compatible antennas. Both are almost the same length. The shape of the grey covering of the second antenna suggests that there is a similar inductor like structure inside it, which I know from practical experience is the "gain" of the antenna (correct me if I'm wrong).

The grey antenna is for 2.4 GHz WiFi while the black one is for sub 1 GHz GSM.

I can't seem to find out what physical factor affects the bandwidth. The only option left seems to be the material. Is it the case?

Also, since both have the same shape, is it safe to assume that both of them have the same polarization and radiation pattern? (I'm not good at Physics, avoid downvoting me on this). I don't know the model of any of these antennas however a Pulse W5017 antenna (not shown here) with the same shape has an Omnidirectional polarization and a Figure-8 radiation pattern according to it's datasheet (also shown below). Is it safe to assume that these antennas will have it likewise?

Radiation Pattern of identical Pulse W5017:


texts:
Contoller datasheet

Can anyone explain how the actual winding happens?. The transformer is a shell type transformer used in a flyback circuit. The circuit is not working, and I'm suspecting the transformer, but I don't have a method to test the transformer. If anyone could help, that would be awesome.

From my preliminary examination, I found that the VDD is fluctuating from 12 to 5v, My inference from the datasheet is that the High voltage current source is helping till it reaches VDD(start) and turns off to let the bias voltage take over, but that's not happening, so it resets, and reinitiates the startup sequence and is in a loop. I'm getting roughly around 300V at the bulk caps after Full bridge rectifier and zero volts at the secondary. Kindly note this is a TI generated schematic. The PWM signals will drive the power Mosfet only when VDD Is at 14.7v. The dot convention shown in the schematic is wrong. The transformer was done according to the report which I have attached.


texts: Can't identify HT74 Texas Instruments smd chip

texts:
I'm trying to find a replacement for this burned out chip, but I'm bit confused which one do I need. Thisi how it looks like:

According to this datasheet, there are several HT74 chips in SSOP and TSSOP, but which one do i need? And what does 66K G4 means?

Thank you!


texts: Low cost 1A-5V h-bridge ( MOSFET or BJT)

texts:
I like to build 8 dual direction PWM dc motor drive for dc motor with around 5V and 1A max current like shown below, and control it by Arduino with shift-register IC like 74HC595 :

So I googled and found h-bridge for this usage like L293D :

And also found some module like TB6612FNG dc motor driver, but I like to reduce the cost below the cost of this module.
So I have seen this question and I like to build the h-bridge drive for these 8 dc motor by myself like this:

In my opinion the Darlington transistors like TIP series are good but the cost for 4 of them is similar to TB6612FNG module and in this condition I prefer to use like this (connection to Arduino and add module ...).
But I'd like to know other's suggestion about minimum cost BJT ic in market (like BC161 PNP Transistor TO-39 1A) with around 1A max steady current-5v output for this goal.
Update:
I found this site and there is some good design like h bridge with BD140 (1.5 max) and BC327 ( with max 800mA current )


texts: What does a buck converter do with the energy that a linear regulator would otherwise waste as heat?

texts:
I've been reading for hours about how switching regulators work but I'm still unable to understand what it does to keep the power equity between the input and the output (ignoring internal losses).

Let's say you step down 5v to 2v with a buck converter. What happens with the 3v dropped? Are somehow "converted" to current?

Another simple example: Let's say I have a 3.7v battery and I want to feed an IC which has an input VDD range of 1.8 to 3v so I use a buck converter to step down the voltage. If I step down the voltage to 1.8v would the battery last longer than if I step down the voltage to 3v?


texts: How to reduce the speed of a single-phase induction motor

texts:
I have a 1 h.p. single phase induction motor driving a dust extraction blower. The air flow is about 600 cubic feet per minute. The device that the dust collection duct is attached to requires only 300 CFM. I don't want to waste energy; is there an inexpensive way to reduce the fan speed to 300 CFM?

Update; I measured the flow in the duct yesterday with a hot-wire anemometer - it's actually only 245 CFM. 600 CFM is what's printed on the blower, but I guess it's either an inflated number, or the conductance of the duct system is limiting the flow.

Thank you all for the informative replies.


texts: Suppressing interference in a pressure sensor circuit

texts:
I just looked over a circuit designed by my predecessor, which is used to interface with a pressure sensor. It works, but I have some doubts about the way the input filtering is done. The simplified schematic looks like this:

simulate this circuit – Schematic created using CircuitLab

The pressure sensor has a differential, low level and relatively high-impedance output (up to 25kOhm) which is scaled up into a larger differential signal by those amplifiers. A differential amplifier at the output (not shown) then turns this signal into a single-ended one. In other words, this is part of a normal three-amp instrumentation amplifier.

The gain setting resistor is part of the pressure sensor, and it is factory-calibrated (between 2.5kOhm and 12.5kOhm) so that it compensates the variation of the full-scale output in each individual sensor. This way, replacing the sensor will not change the output much even though each sensing element has a different full-scale output. In order for this to work, R1 and R2 need to be 100kOhm.

This is all according to an applicaiton note (TN-003 by ICSensors) which I unfortunately couldn't dig up on the internet just now. However, my predecessor added the capacitors C1 and C2, probably to suppress interference issues we saw in tests - the sensor is connected via an unshielded cable inside our device, and since the feedback line to the gain resistor has such a high resistance going to it, it looks like a good candidate for picking up noise.

The output does not need to be fast (~1Hz is fine), so rejecting high frequencies seems like a good idea. However, seeing a large capacitor between a pair of op amp inputs makes me uncomfortable. I plopped this circuit into LTSpice and saw that it is stable (even with much larger capacitors), but it rings a lot due to a resonance at ~4.2kHz.

Now I'm wondering, wouldn't it be better to put C1 and C2 parallel to R1 and R2 instead? That way, the resistance of the gain feedback line would be lowered at high frequencies, and the amplifiers would somewhat attenuate high frequencies, too. The simulation looks good, but since I'd still consider myself a novice I'd appreciate some confirmation whether this is a good solution or if I'm overlooking something.


texts:
Can some one help me on this??

We are using two different make PMDC motors with different gear ratios(motor to gear box to lead screw to load) in one of our application.Below are the details. Application:Solar Tracking systems. Load:Around 1 ton solar structure.

Motor 1:

No load:
current: 0.2A
speed:2100 rpm
input voltage: 24V
Gear Ratio:67

Loaded:
Gear working:smooth .
Max current rating of motor: 6A
Load current: 1.2 to 2.3A(max)

Motor 2:

No load:
current: 0.6A
speed:3515 rpm
input voltage: 24V
Gear Ratio:57.

Loaded:
Gear Working:smooth to hard.
Max current rating of motor: 12A
Load current: 2.5 to 7A(max).

We are using the both motors for same application.

We have used motor 1 and it's working fine.But we have chosen motor 2 by thinking it has high no load and full current rating so that it can produce high torque.is it correct??
For lifting the same load motor 2 taking high current.why? and How to reduce load current??
We need to reduce the load current around 3A when we are using motor2. How to achieve this for same load?
Is there any possibility to increase the load torque and reduce the load current when we are using motor 2??
And finally where we have done wrong?and what are the changes need to do to get same performance as motor 1 connected to load???

Thanks


texts: High voltage non-inverting operational amplifier for DC signal

texts:
I am currently using LT6090 with Vcc=140 and Vee=0 for DC signal amplification with gain of 31 in non-inverting mode. For an input signal of 0-4V from a DAC the output measured is 0-124V (step change is <20mV, calculated as per DAC resolution).

What I am trying to achieve is by using the same opamp above I want the output range from 100V to 224V with Vcc=240 and Vee=100 such that Vcc-Vee=140 as per the datasheet spec.
But the issue is now the input should be above Vee(100V).
How can I achieve the same step change for 100 to 240V range using 0-4V DAC range?


texts: How do electricians know where the line is down?

texts: I had a power outage and I thought about the utility poles near the street. How do electricians know which power line is down considering that there are many miles of them? For example, if there's a car that crashed into the pole and brought the power line down, how does the electrician (or power utility) know where the break is located?


texts: Battery indicator connected with bicolor led

texts:
Battery indicator connected with bi-colored LED.

I need to make a system that indicates when a 3.7V battery is connected to a 5V source or not. When the battery is NOT connected a red LED stays on, when the battery is connected the red LED turns off and the green LED is on. I do not want to show a low battery or something like that, I need to show through the LEDs if the battery is ON or not, just that. Below what should be the circuit, but do not know how to make the connections to make the system work as I want.

simulate this circuit – Schematic created using CircuitLab


texts: Rms value and average value for a periodic wave

texts: Why are we using RMS value over average value for a periodic wave?


texts: Blinking fishing lure, best way to save this design?

texts:
Background
I ordered 10 PCBs with a design for a blinking fishing lure (it's a hobby project.) I have discovered I made a mistake when I designed it and wanted to see if anyone has any ideas how to best save the situation.
These boards are intended for testing use for a few months to check what colors/flash intervals works etc. In the future the idea is to replace the battery with an energy harvester.

Main function
The board is about 15x10 mm. Battery is 3V lithium, 70 mAh, mounted on the backside. The PCB is molded into the fishing lure with only a small piece exposed to the water. When the water comes in contact with two pads (named Touch in the schematic,) the gate of a MOSFET is pulled high and the main circuit is powered. This is an ATtiny10 that blinks four LEDs for 2 ms, then sleeps for 2 seconds, repeating.
The problem

Everything works as expected, except that the GPIOs of the Attiny10 are high when its ground is floating. This means the gate of Q2 is always high and the LEDs are always on except when in contact with water, then they're blinking.
Looking back this wasn't the best way to solve it but sometimes you make mistakes.
The question
I would like to salvage this design and im not sure of the best way. I see three ways.

Ideal way would be to find a way which stops the GPIOs from going high when the MCU ground is floating. Possible?
Remove Q3 and solder the drain and source pins together. MCU is now always powered. Put device in power down between blinks and have it always on. Battery would last about 120 days. (A year would have been enough).
Remove Q3 and solder the drain and source pins together. Solder a wire between J2 and PB1. PB1 is now pulled low by R1 but will go high in contact with water. This triggers interupt which pulls up MCU from deep sleep. The battery life in this solution would last for many years but adding wires to the board isn't very nice.
Other solution you guys may have.


texts:
I am trying to understand if digital ASICs with tens of millions of silicon-germanium gates exist. A comment in another post states (emphasis mine) "SiGe can hit 5 GHz pretty easily even with half a billion gates"—I am trying to confirm or refute this statement.

Below is how I understand things. SiGe (for example, SiGe 9HP from Global Foundries) is a BiCMOS process which integrates two separate technologies. It contains a "cost-effective mature silicon base" which is the 90 nm Si process. On top of this base, it allows for the use of SiGe NPN transistors with "exceptional high-frequency performance".

Looking at the applications of the SiGe 9HP process, it seems these NPN transistors are used for analogue purposes, e.g. for LIDAR, RADAR, 5G, Ethernet, etc. I have not found applications using NPN transistors to build large scale digital logic. A leading SiGe researcher has a list of "selected SiGe circuits" (see right column) and none seems to be large scale digital circuits.

As a side note, I found SiGe used in the context of strained silicon, but as I understand strained silicon is just Si CMOS.

My questions regarding the SiGe process are:

Are SiGe NPN transistors used to build digital gates?
Can digital ASICs be built from tens of millions of SiGe gates?
If the answer to 2) is "yes", are there public examples?
If the answer of 2) is "no", why not (e.g. size, power, yield, ...)?


texts: Why don't the currents clash in a 3 phase delta connection?

texts:
Consider 3 windings, a, b and c. L1 is connected to A, L2 to B and L3 to C. The 3 windings are then connected in delta.
If we could freeze frame the voltage waveform where L1 and L2 are positive maximum and L3 is negative, what will the current direction through the windings look like? Particularly through the bridge which connects a1 to b2...

Will we at any point have the current from 2 different phases going towards each other?


texts:
here is the circuit. I want it to flash a LED when it's dark, and completely turn off when it's not dark. so a LED is connected to Q2, and R4 should be a very high value to save battery life.

My questions:
1, will this circuit work for my purpose?

2, how to improve it to suit my purpose?


texts: Proper Way to PWM (Voltage Control) Dim LED Strip

texts:
I have been asked to create a dimming system (Along with other features) that interfaces to the cheap LED strip lights. A lot of people seem to use standard N-FETs with PWM on the low side. My concern is with a long strip (3M) wouldn't this produce a large amount of EMC/EMI due to a hard edged voltage and current wave?

Should the design instead incorporate more of a buck style control with an LC filter to smooth the output waveform? And effectively make it analog dimming if EMC/EMI or radiated emissions is of concern to for instance pass FCC or CE tester? Note values in schematic are for reference only, not calculated.

If so, is there an easy way to do it without a high side switch, or an easy way to efficiently drive it from 0 to 100% PWM?

simulate this circuit – Schematic created using CircuitLab


texts: How to buy difficult-to-find electronic parts?

texts:
A RF receiver project I'm working on calls for a very specific SAW bandpass filter. I've checked all the usual sources here in the US (Jameco, Mouser, Digikey, Newark, etc) without success. What I'm finding is that the part I'm looking for is highly specialized and thus difficult to find anyone that sells them in low, hobbyist quantities.

What are some approaches for buying difficult-to-find parts in low quantities?


texts: Finding an input sequence given a generating polynomial and CRC

texts:
I am working on a circuit that inputs a 31-bit pseudo-random binary string into a CCITT CRC-16 block which generates a 16-bit CRC output.

I know that M(x)/G(x) = Q(x) + R(x) and the transmitted code will be R(x) appended to M(x). [Q(x) is discarded].

When I simulated the circuit, I got a CRC of 1 0 1 0 1 0 0 1 0 0 0 0 0 0 0 0. From the help file of the software (VisSim/Comm), I know that the generating polynomial is G(x) = 1 0 0 0 1 0 0 0 0 0 0 1 0 0 0 1.

How do I determine the 31-bit input sequence that generated the CRC result?

Since M(x)/G(x) = Q(x) + R(x), we can say that M(x) = [Q(x) + R(x)]G(x). But we don't know Q(x). Assuming the 16-bit CRC is equal to R(x) and the G(x) is given, how do I go about finding M(x) without knowing Q(x)?


texts: How can earth fault meter work through inactive IGBTs

texts:
I have a setup with a Bender IRDH375 connected to the DC bus of an IGBT based inverter. If I connect a 50kOhm resistor to earth while running the inverter, it detects it well. That part is reasonably ok to understand. However while not running it still detects about 200-400kOhms to ground. How is this possible?

Schematic of setup illustrated below. Only 1 of 3 phases are illustrated for brevety.

simulate this circuit – Schematic created using CircuitLab

Shouldn't the IGBT be almost fully blocking while "OFF"?

Update:
If I take off R2, the earth meter will show almost maximum insulation (10MOhms). Same if the inverter is running or not.


texts: Matching JFETs for differential amplifier application

texts: How to choose a properly matched pair of JFETs for differential amplifier? Is it enough to measure their Idss?


texts: Intercept pin headers, three way or the header?

texts:
Is there some kind of T-splitter 3-way-splitter etc for pin header blocks? Something that passes through the pins but also contacts them and exposes a set of right angle pins too? So you can use a regular female strip on top (just sitting a mm or so higher than usual) but access the pins from the side too?

For a project I'm working on I have a 40 pin header (typical GPIO, SPI etc block on an rPI) and a board that stacks on top. The top board has a female block pre-soldered on and it's not feasible to de-solder it. I need to access some of the pins in the rPi's GPIO block for another purpose but have very little vertical space to work with. I can't add another full height stacking layer and a breakout board or some kind.

I expected to find sets of pin header taps or similar that formed a collar around the headers and projected at 90 degrees. But can't find anything of the sort.

I'd rather not solder a PCB straight onto the base of the headers and break it out that way. Fiddly access, sensitive components and too easy to melt the base of the pin headers.

There is presumably some "everybody knows" answer I don't know the words for . Help?


texts: Does it matter what the input voltage is to a DC/DC step-up converter?

texts: I have a converter that outputs 5v and 1 amp. The input voltage can be 2.5-6 volts. Does it matter as long as it is in the range? Also, will the current draw from the batteries differ if I change the input voltage? Here is the link to the usb converter: http://www.ebay.com/itm/261097668334?euid=cbb7b0f1c6c84804827dc94d84ad2d39&cp=1.


texts: Need for inverter chain to decrease rise and fall time in a comparator

texts:
I was designing a MOS comparator for my laboratory and I could not understand how an inverter chain helps in increases the slew rate across the load capacitor. And why an inverter chain ? why cant a single big inverter(High W/L ratio) serve the purpose ?

The overall system looks like the following with the comparator followed by the inverter

The inverter stage looks like this with inverter having an increases W/L in each stage by a factor close to 2.5


texts: Duration of inrush current for high pressure sodium lamp with electronic balast

texts:
I'm trying to find reliable information regarding the duration of inrush current for high pressure sodium lamps with electronic ballasts.
This document  states that:
"In reality, due to the wiring impedances, the inrush current for an assembly of lamps is much  lower than these values, in the order of 5 to 10In for less than 5 ms."
However it is not specific to high pressure sodium lamps.
The lamp I wanted to install have inrush current rating <30A, but there is no duration indicated. The retailer of the contactors I intend to use needs the duration (in microseconds) in order to recommend a specific contactor.
How do I get the duration?


texts:
I am trying to supply my circuit from this part. I have two different supplies which are VUSB_5V and VORG_5V. My aim is when one of two comes to circuit, this supply does not go to other one or effect it to prevent a dangerous situation. If both supplies are available, the bigger one should become to VCC_5V. For this reason, i put tho didodes. However, when i supply one of these only with 5V, i am measuring approximately 5V at the other's while there is a diode before it.

For example, if there is only VUSB_5V is supplying, i measure voltage of C17 is 4.9V. I observed another interesting thing that when i am measuring voltage with multimeter, voltage is increasing at TP9 until 4.9V. Voltage on D1 is approximately 0.2V.

I am thinking to change diodes and adding pull down before didodes. What can be the reason of this situation and how can i solve this?


texts: Can a rectified sine wave still induce voltage?

texts:
I would like to learn more about the behaviour of a transformer when the primary coil current is not the standard AC sine wave.
What happens if the current supplied to the primary coil takes the waveform of a rectified sine, like as shown below?

I feel like there is still a changing level of current in the primary, and therefore a changing magnetic field in the core - am I correct in thinking this?
Will the transformer still induce a voltage in the secondary coil? Would the induced voltage be less than with a standard AC sine wave?


texts: Use Ibutton to wake MCU and fire an interrupt

texts:
I'm working on  a battery powered device which takes tree inputs, two buttons and one ibutton. Each input must be able to wake the MCU(Atmega1284p with arduino bootloader) from sleep. With the two buttons i have used an interrupt and it goes well. Then the MCU wakes I can tell the difference of which button was pressed by setting a variable in the ISR function.
However now I want to be able to wake the MCU by either the two buttons or the ibutton. Unfortunately the ibutton only creates a very short pull down on the signal line for approximate 40us. This means that the MCU will wake but the interrupt will not be fired. From page 30 in the datasheet of the MCU(http://www.atmel.com/images/doc8059.pdf) I can see that i need to keep my signal down for 65ms+14ck. This behavior is described on page 65 at the bottom of section 11.1.

My initial solution was to check if any of the other interrupts was fired, if not then assume the mcu was woken up by the ibutton. The drawback is that if the sleep time ended i would not be able to tell the difference.

My second solution was to use an ibutton port with tactile feedback. Then use the tactile feedback to wake the MCU. But this will increase the hardware cost.

The question is now, is there a smarter way to do this?

EDIT:
It has turned out that I only see these pull downs when i'm not hitting it perfectly clean hence short the signal line to gnd. This means that i'm anyway not able to relie on this event happening. Back to rethink how to wake the MCU with an ibutton.


texts: Can more than one device read data from GPS?

texts:
I have an OSD(atmega88p inside), which is reading data from GPS through serial connection as I understand and I would like to connect second device (FEZ Cerb40) to read GPS data, wondering if that will cause any problems, may be serial device can be read only by one device at the time?
Could FEZ Cerb40 work as a proxy (I mean read data from GPS for it self and then pass same data further)?


texts: Interpretation of the graph of excitation current for magnetic circuit

texts:
(From Electric Machinery, Fitzgerald)

Why does the current waveform here have such a sharp peak like that?


texts: Why is this reed switch / solenoid circuit not working?

texts:
The (normally open) reed switch should close by waving a magnet across it, completing the circuit. The 6v solenoid lock should pull inwards allowing the door to be opened. When the magnet is removed the reed switch should open.

So my issue is the solenoid pin isn't being pulled in when 9 Volts is applied. It only pulls in when pressed three-quarters of the way in. This made me suspect the voltage wasn't right but tested showing 9V. I tried two others batteries with the same results. I also tried putting two 9V batteries in series to make 18V, but the solenoid would only operate if pin was pushed in half way. ($%£!!!) I also noticed on both the 9V and 18V that the reed switch would get stuck in the closed position.

Any ideas would be greatly and deeply appreciated.


texts:
I have an STM32F4-Discovery Board with an attached STM32F4DIS-BB Base Board attached, giving me access to a Serial Port to use for the Discovery board.  I am trying to program the board to read data sent to the serial port from the PC.  I am having trouble finding information online on how to do this, so I am posting here trying to get some help.

I am trying to use the Discovery Board's USART1 connection, and have been initializing it with the following code:

void Init_USART() {
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1);
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1);
  GPIO_InitStruct.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10;
  GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP;
  GPIO_InitStruct.GPIO_Speed = GPIO_Speed_100MHz;
  GPIO_Init(GPIOA, &GPIO_InitStruct);

  RCC_AHB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
  USART_InitStruct.USART_BaudRate = 115200;
  USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
  USART_InitStruct.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;
  USART_InitStruct.USART_Parity = USART_Parity_No;
  USART_InitStruct.USART_StopBits = USART_StopBits_1;
  USART_InitStruct.USART_WordLength = USART_WordLength_8b;
  USART_Init(USART1, &USART_InitStruct);
  USART_Cmd(USART1, ENABLE);
}

I am trying to use an interrupt handler, and have initialized it with the following code:

void Init_Interrupt() {
  USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
  NVIC_InitStruct.NVIC_IRQChannel = USART1_IRQn;
  NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
  NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0;
  NVIC_Init(&NVIC_InitStruct);
}

Now I am trying to see if the interrupt handler is even working, by just putting a printf() statement within the handler's code like so:

void USART1_IRQHandler(void) {
  printf("test\n");
}

When I run my program however, I am getting nothing coming through the console window, which to me is indicating there is a problem somewhere with what I am trying to do, however I am not sure exactly what it is that is wrong.  If anyone could help it would be greatly appreciated.


texts: home automation with arduino, raspberry using externally powered relay board

texts:
I have a plan to put together small home automation system.

For now I was just playing with smaller parts like single type of sensors at once etc...
I would like to ask for opinion & check of my scheme if basic idea is ok, before I plug everything together.
I saw many variants of externally powered Relay Board, so I am little confused and I am not sure if its ok.

Basic idea is to see data & control everything from website
DHT sensors (read and display data on website graphs)

only DHT22 nr1 will trigger PC-FANs 1 & 2, when temperature or humidity is too high
PC-FAN (1 & 2): they run ON all the time (set time from ... to ...)
LED strip (1 & 2): they run ON all the time (set time from ... to ...)
(LED strip has to be on separate power line since current A is to high for single relay)
Soil sensors (1-4) (read and display data on website graphs)
Water pump (1-4) each separately triggered for period of time when humidity in soil is to low (from Soil sensor 1-4)

Is my plan ok?
Any suggestions are welcome, thank you.


texts: Arduino Pro Mini (3.3V) ATMEGA328P: Measure 0-5V/0-10V and 0-20mA analog inputs

texts:
I'm looking on how to design circuitry in order to safely measure 0-5V and 0-10V analog inputs from my bare bones "pro mini alike arduino" (ATMEGA328P) powered from 3.3V external power source.
This is my base schematic:

I was thinking to use a simple voltage divider for the voltage measurement, but I'm not sure. I mean, the board will be used in a industrial environment and a voltage divider seems to be a bad choice.
Also for the current loop (0-20mA and 4-20mA), inspired from this DFRobots breakout (SEN0262), this current measurement solution looks quite good and safe:

It is a good way to go this current measurement method?
About the voltage measurement, does anyone is able to give me some advice on measuring those voltages in a "safe way" (e.g., protecting the microcontroller from high voltages and low voltages wiring errors)?


texts:
I've got some code i'd like to use in multiple projects so i'd like to put it into a library

The library will use no special features of the chip and whichever two pins it uses to do its job only have to be general I/O

As I plan to use this for multiple projects, these projects will have to specify which pins these two pins are on a project-by-project basis

My question is how I can set up my library and code in each project so that I can define which pins I want to use within each project - independent of the library.

Using XC8 compiler for PIC10s and 16s

Any guidance appreciated


texts: FRAM : excessive erase of one memory cell can damage another memory cell?

texts:
Erroneously , we made excessive erase of FRAM first 1024 bytes multiple times (millions and more erases).

Afterwards we observed that memory upper half is damaged (part of it).

Can it be that excessive erase of one memory cell damage another memory cell ?


texts: Wiring 18 gauge 2 wire into type C or DC?

texts:
I have a Garmin fish finder that requires 12V-18V with 0.5A draw. Since I'm in a kayak I would like to use a light power bank (laptop lithium bank). Bank has 25000 mAh and operates with 2x USB (5V), 1x type C PD2.0 (5V, 9V, 12V, 15V, 18V), 1x DC (12V-18V).
I'd love to figure out how to wire 18 gauge positive and negative from Garmin unit into either the Type C port or the DC port. Is either one possible?
Bank is 5A max output but that's well within everything I need.


texts: Finding number of pole pairs in a BLDC motor

texts:
I have a 3phase CDROM BLDC motor for which I don't have any datasheet. How can I find out the number of pole pair in the motor?

Hint:-With a magnet, I could check that there are some N and S poles in the rotor inner layer but how can I know the exact number of pole pairs.?

Thanks, Charles Cowie. But I have another bldc motor which has 3 windings at 120 degrees apart. But its datasheet says is a 4 pole pair motor. Can you explain how it is possible.?


texts:
I'm struck in calculating the I(switch,rms) in boost converter. Average current through diode = average o/p current , also average current through the inductor = average current through the source. From this I drew the following waveform. So,

EDIT
This was the part of the following question.

  A DC-DC boost converter, as shown in the figure below, is used to
  boost 360V to 400 V, at a power of 4 kW. All devices are ideal.
  Considering continuous inductor current, the rms current in the solid
  state switch (S), in ampere, is _________.


texts: What is the Voltage on a tablet's battery when it is turned off

texts:
Basically I tried to find out what's wrong with my broken tablet, so I used a multimeter to measure the voltage at the battery pins on the tablet's board and it was 0.1 roughly, and the transistors had some voltage on them, but the device was not booting. So the obvious reaction was to cut out the old 2x3.7V in series battery and try to use a normal 9v battery(through the battery protection). The screen what reacting this time but the OS was not, and the voltage on ports was half of that of the battery.

So the question is why there was only 0.1V at the beginning. Maybe the 2x3.7V battery was not charged enough?

Also if the battery used was 9v,it could activate the screen but not some other components?


texts: How does this circuit multiplex an antenna between a transmitter and receiver?

texts:
I've built a Softrock RXTX kit (full schematic: pdf gif, see lower-left corner). It has one connector for one antenna used for both receive and transmit, but I don't fully understand (likely due to my inexperience with RF design) what all the parts do. The full schematic is a mess, so I've done my best to transcribe the most relevant parts:

(source: circuitlab.com)
So, I understand that when \$\overline{PTT}\$ is low, then Q10 is off, which isolates the receiver. Q11 is on: why?
When \$\overline{PTT}\$ is high, Q11 is off, which is good, since I don't suppose we want to ground the receiver's input. How do we know that Q10 will be on, given that its source is floating?
What does C27 accomplish?
Say I had an RF amplifier and I wanted to add a similar circuit to bypass it when receiving. Would I have to worry about disturbing the impedance matching?
What should I consider when selecting the transistors to use? I intend to cover HF at least up to 30 MHz.


texts:
From all my browsing, it has become clear that as drain-source voltage increases, we eventually reach saturation. Mathematically, Vds>Vgs-Vt is the condition we look at.
But when I try to understand it logically, we need a reverse bias at Vgs to attract minority carriers from substrate to form a channel. So now that the channel is formed, a drain source voltage gives rise to a current flow due to electrons.
It also makes sense that Vds should produce a depletion region at one of source/drain and reduce depletion region.

But how would all this relate to channel widths, saturation and everything else that gives rise to saturation?


texts:
Hello, I have a question above from random material and tried to solve it.

Here, I assume signal power to be S1(dB) and noise power to be N1(dB) at input, and S2(dB) and N2(dB) at output.

So below is what I started from "S1-N1=S2-N2"

Step 1 :

S1-N1=S2-(2*N1)

N2 becomes (2*N1) because question said noise power at output is twice as much as input.

Step 2 :

S1-N1=(S1-10)-(2*N1)

S2 now becomes (S1-10) because question also said there is attenuation of the channel which is 10dB, and it also says "The channel does not attenuate the noise", which means that it only attenuate signal power instead. So I subtract  10 from S1 and set it to S2.

Step 3 :

Then I get N1=-10, then we know N2=-20 (because Question said N2 is twice as N1)

Step 4 :

Now, question want me to determine SNR in DB at output.
So, here I used SNR(dB) formula, which is "SNR(dB)=10log(SNR) where base is 10".

10log(-20) = 13.01 dB

And I guess I am done.

So my question is, is this even correct way to solve this question? And did I get the answer correct?


texts: If my battery charger says 160mA on the back, what does that mean to my 1800mAh batteries?

texts:
I'm sorry if this is a horrible place to ask such a question. I just stumbled upon here from google.

So I have this battery charger that DOES NOT indicate when a battery is fully charged (stupid right?)

It simply says:

  input: d.c.5v
  output d.c.1.4v
  aa  2 160mA
  aaa 2 160mA

Additionally, I see that my batteries say Voltage: 1.2V. Does that mean using a charger that says 1.4v is BAD, or totally fine?

I figure someone here would know.


texts: Can I determine the rough frequency of an ac current by measuring the frequency of the electromagnetic radiation predominantly emitting from it? - if so, are there any other variable I need to consider, also how would I go about doing this?


texts:
The question is:

Two signals have to be subtracted from each other. You want to have a very high input resistance and an overall transfer functiON of Uout=2*(U1-U2).
Draw a suitable circuit diagram. The resistors of your circuit have tolerance of +-10%, futhermore U2=0, U1=5V. Calculate and plot the output signals.

Answer: I got the diagram from my friend.

That's the diagram that he senT me, But I don't understand. I got why he used the first opamp but what is it with the second? Can somebody explain me?


texts: How do I fix pin assignments on a Quartus Prime Lite project?

texts:
I am using Quartus Prime Lite Edition 16.02 and am trying to fix messed-up pin assignments for a simple project with a single verilog file:

module mux4( input  a, b, c, d,
             input [1:0] sel,
             output out );
  wire t0, t1;
  assign out = ~( (t0 | sel[0]) & (t1 | ~sel[0]) );
  assign t1  = ~( (sel[1] & d) | (~sel[1] & b) );
  assign t0  = ~( (sel[1] & c) | (~sel[1] & a) );
endmodule

In the past, I've assigned nodes a, b, c, d, sel[1], and sel[0] to SW[0], SW[1], SW[2], SW[3], SW[4], and SW[5], respectively, and I've assigned node out to LEDR[0]. Since changing the verilog file, however, I've been unable to get pin assignments to work.

I tried the following:

I deleted the .qsf file from the project directory (through the
file system).
I selected Assignments > Import Assignments and imported
DE1_SoC.qsf.
When I open the assignment editor, the pins to which I had assigned nodes show up with question marks in their status column:
In the bottom of the assignment editor, I see my earlier pin assignments:
I start a compile.

I get these messages:

Info (171003): Fitter is performing an Auto Fit compilation, which may decrease Fitter effort to reduce compilation time
Warning (292013): Feature LogicLock is only available with a valid subscription license. You can purchase a software subscription to gain full access to this feature.
Error (171016): Can't place node "c" -- illegal location assignment PIN_AF9
Error (171016): Can't place node "b" -- illegal location assignment PIN_AC12
Error (171016): Can't place node "d" -- illegal location assignment PIN_AF10
Error (171016): Can't place node "sel[1]" -- illegal location assignment PIN_AD12
Error (171016): Can't place node "sel[0]" -- illegal location assignment PIN_AD11
Info (11798): Fitter preparation operations ending: elapsed time is 00:00:00
Warning (171167): Found invalid Fitter assignments. See the Ignored Assignments panel in the Fitter Compilation Report for more information.
Error (11802): Can't fit design in device. Modify your design to reduce resources, or choose a larger device. The Altera Knowledge Database contains many articles with specific details on how to resolve this error. Visit the Knowledge Database at https://www.altera.com/support/support-resources/knowledge-base/search.html and search for this specific error message number.
Error: Quartus Prime Fitter was unsuccessful. 6 errors, 3 warnings

I was able to simulate this design in the past. What do I need to do to get it working again?


texts: I was wondering if its possible to convert the high frequency PWM output from a Beaglebone Green's PRU into an analog audio signal. I was looking at building a low pass filter and I was wondering if that is the right direction to go?


texts: Why can RLC resonance be dangerous for electronics

texts:
There is a lot of information about RLC circuits and resonance, and many times it is mentioned that when a series (parallel) circuit resonates, a really high voltage (current) can be found across the inductor and the capacitor and this can lead to faults of components.

But why?
I mean, it's clear that if I take a component and put it under 1kV, it's going to break (unless designed for sustaining high voltages...), but I see the case of resonance a bit different: while it's true that there is a high voltage/current across the components, the net voltage/current is zero if you consider both the capacitor and the inductor.
Let's take an RLC series: the voltage across the series of the capacitor and the inductor is zero, at the resonance. The power supply or the load are not interested in whatever high voltage is there across the capacitor or the inductor. So why should it lead to problems?

Please let's assume that the capacitor and the inductor have no problem in sustaining the voltage across themselves and they don't break because of it. The issue is how this can lead to problems for other components in the circuit.


texts:
I have faced that problem:
9-15V Vin (12V accu) and 5kV, 0.001A out (5W)
and dont know how to solve that, i tried to use push-pull SG3525 but efficiency is very poor, about 20-30%. Can someone suggest me what IC/topology to use? I even tried capacitor charger but with no luck too:(
What i did more was sepic step-up with voltage multiplier (mc34063 :) ) but Ton/Toff is too big i think and i can reach only 1.6kV...
Please give me, if you can, any piece of advice...

best regards


texts: Need for edge triggered versions other than master slave

texts: I am studying synchronous digital circuits and I have come to the conclusion that master slave flip flops are edge triggered? Is my study correct? If master slave versions ARE edge triggered, why do we need separate edge triggered flip flop versions like the edge triggered D flip flop (the non- master slave configuration)?


texts:
I know that the roll-off of a transfer function gain is given by:

$$20\log_{10}\left(\left|\text{H}\left(\omega_2\right)\right|\right)-20\log_{10}\left(\left|\text{H}\left(\omega_1\right)\right|\right)\tag1$$

And when I have a three pole transfer function, that the roll-off tends to \$-60\space\text{dB}/\text{decade}\$ when \$f\to\infty\$.

Question: In order to calculate the roll-off accurately I must choose \$\omega_2\$ and \$\omega_1\$ much larger than the cut-off frequency. But how much larger?


texts: Thin wire overheats, thick wire allows too much current to flow

texts:
I'm currently building a mini lathe to turn wood. I am using a 12v motor and I was experiencing some initial problems with the thin wires I was using; they overheated instantly.
I then changed to 14 AWG (thicker wire), and the motor was so strong this time that it hurled the wood straight out. I'm guessing this is due to it having less electrical resistance?
I was wondering if there was a solution to alleviate both issues. If the wire is too thin it overheats, while if it's too thick it overclocks the motor. Do I just have to keep buying wires until I find the sweet spot, or is there a better way?
Thanks! (I hope this was informative enough, I don't have much of an electrical background)


texts: Resistor values calculation: how to arrive at these values? (Make: Electronics example 10)

texts:
I'm finally trying to learn basic electronics and working through Make: Electronics. Excellent book so far, but I often wonder how exactly the author calculated the necessary resistor values and I feel that I absolutely have to understand this before diving into more complex topics. Let's look at example 10:

+12VDC o--+-----R1--Q--R3--D--o 0VDC
          |         |
          +--S--R2--+

R1 = 180Ω
R2 = 10kΩ
R3 = 680Ω
Q = NPN transistor 2N2222
S = switch
D = LED

(R1 is connected to collector of transistor, R2 to base, R3 to emitter)

In an earlier part of the book, the author assumed that the LED requires 2.5V/20mA. I assume that as soon as S is pressed and the transistor is conducting, the current can flow through collector/emitter to the LED and all that matters for the LED part are R1+R3.

So since we've got 12V and only need 2.5V/20mA for the LED, I've calculated R = 9.5V/0.02A = 475Ω, but R1 + R3 = 860Ω. I've tried to insert different values and struggled with this for an hour but I don't get why specifically 180Ω and 680Ω were chosen.

Edit: Updated the drawing with respect to the power supply.


texts:
I'm facing with a problem regarding continuous acquisition of ADC channel in STM32F103.

I use the interrupt at the end of conversion to call a callback function to store the acquired value.

The problem regards the callback that is called only the first time.

I configured my project using STM32CubeMx for continuous acquisition and interrupt generation.

This is the ADC configuration:

hadc1.Instance = ADC1;
hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;
hadc1.Init.ContinuousConvMode = ENABLE;
hadc1.Init.DiscontinuousConvMode = DISABLE;
hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc1.Init.NbrOfConversion = 1;
if (HAL_ADC_Init(&hadc1) != HAL_OK)
{
    Error_Handler();
}

/**Configure Regular Channel
*/
sConfig.Channel = ADC_CHANNEL_11;
sConfig.Rank = 1;
sConfig.SamplingTime = ADC_SAMPLETIME_71CYCLES_5;
if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
{
    Error_Handler();
}

This is my acquisition function:

ea_ADC_Err_Code_t ea_ADC_n_data_read(Adc_Channel_t channel, adc_eoc_callback adc_cb)
{
    ea_ADC_Err_Code_t err_code = ADC_ERR;
    ADC_ChannelConfTypeDef sConfig;

    adc_read_value    = 0;
    adc_eoc_cb        = adc_cb;
    n_adc_acquisition = ADC_MAX_CONS_ACQ;

    /* Deinit ADC */
    //while(HAL_ADC_DeInit(&adc_handler) != HAL_OK);

    /* Initialize ADC */
    //HAL_ADC_Init(&adc_handler);

    /* Configure ADC Channel */
    sConfig.Channel = channel;
    sConfig.Rank = 1;
    sConfig.SamplingTime = ADC_SAMPLETIME_71CYCLES_5;
    HAL_ADC_ConfigChannel(&adc_handler, &sConfig);

    /* Set ADC callback */
    HAL_ADC_ConvCpltCallback(&adc_handler);

    /* ADC Calibration */
    //HAL_ADCEx_Calibration_Start(&adc_handler);

    /* Start conversion with interrupt*/
    if (HAL_ADC_Start_IT(&adc_handler) == HAL_OK)
    {
      err_code = ADC_OK;
    }

    return err_code;
}

And finally my callback:

void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
{
    if (n_adc_acquisition)
    {
        adc_read_value += HAL_ADC_GetValue(&adc_handler);
        n_adc_acquisition--;
        edi_Print_L1("ADC Callback %d\n", n_adc_acquisition);
    }
    else
    {
        HAL_ADC_Stop_IT(&adc_handler);
        adc_read_value = adc_read_value >> ADC_DIVIDE_BY_EIGTH;
        adc_eoc_cb(adc_read_value);
    }
}

Did I forget something in the callback?


texts:
Could anyone help me identify what component this is, it's value and explain how they could tell. I would like to be able to do this myself but turned a blank on Google.

What ever it is, it appears to be a short and has burnt the trace in the picture.


texts:
How do I design the pwm circuit to produce the output voltage I desire?

Full explanation:

So I know enough general knowledge about electronic circuits to get by, but I'm building a NAS from an old laptop and need a power supply that can power a laptop (19v) and two 3.5" HDDs. Because I want this to be fairly small form factor, I'd prefer to only have one power supply and just use several buck converters to get lower voltages from a 25v DC power supply I plan on buying.

In the past I've used voltage regulators to get the voltage I need, but they dissipate excess voltage as heat and I've had bad experiences with them in the past (I managed to make one explode by connecting it wrong lol.)

From Google I've found plenty of circuits that all rely on a pwm clock, but I've found almost no documentation on how to create a clock for the voltage I want.

TL;DR:

How can I design a circuit that can take 24V and output 19V@4A, 12V@2A, 5V@4A and (maybe) 3.3V (if SATA needs it I haven't done too much research into that part yet.)

How much heat could this produce?
Would it be safe in a 3D printed enclosure?
Would it need vents and/or a fan?
Would it be better to just take apart an old desktop power supply for this?


texts: In VHDL, what is the difference between "downto" and "to"?

texts:
Are there differences between

 (x downto y) and (y to x)?

Where should we use (x downto y)? Same question is for (y to x).

Notation :  x and y are integer


texts: So, ?nobody? makes a high(er) current tri state driver chip?

texts:
I'm wanting to charlieplex some 100ma LEDs, and I can hardly believe no one makes a higher output tri state driver.

I know how to do it with discretes, but Prove me wrong, please.


texts: Is there a need for reference plane for differential traces

texts: Is there a need for a reference plane for differential traces. I have seen cases wherein people use unshielded FFC cable like ones from Wurth Electronik for a board to board connection of differential signals like MIPI CSI2. Is this practice correct?


texts: What is the triangle components in this diagram?

texts:
I am reading through datasheet of a voltage translator for I2C (FXMA2102) and I cannot understand the triangle components in the block diagram:

Are they diodes to make current flow in one direction? NOT gate? Are they op amps? If so, what are they for?

Background

I have an I2C sensor module that uses this voltage translator to convert 5V to 2.8V for the sensor. I realized that when I connect 2 of these modules, the low voltage of I2C increases by a little. When I connect 3 modules, the low voltage again increases by a little. With 3 modules, the low voltage is already around 0.4V which is the maximum allowed by I2C. Communication becomes unstable at 3 modules so I am speculating that this is the issue.

Increasing the pull-up resistor on the 5V side of I2C bus did not decrease the low voltage (which should happen on a basic I2C setup) so I am guessing that something in this voltage translator might be causing the low voltage to increase when connected in parallel.

I figured that the part that says "Dynamic Driver" on the above diagram is a push-pull driver so the output would be inverted. But when OE is high, A and B are shorted via the two N-MOSFETs at the center of the diagram so it doesn't really make sense.

I'd like to hear any opinions from whoever might have experience with this type of thing before I make a custom board that uses only one voltage translator connecting to 3 sensors rather than a setup that uses 3 translator-sensor pairs.


texts: How is this OLED cable being soldered to PCB?

texts:
In this video, from around 4:18 onwards, you see the cable of an OLED display being soldered.

How is this soldering happening; i.e., how does the solder "flow" to the PCB pads given that the contacts on the cable present a physical barrier?
Also, what is this type of cable called? I've seen it on many LCDs, such as TFTs and OLEDs. Can this type of cable be soldered the other way, i.e., upside down to what it is in the video (since that allows me to re-orient the display as I need)?


texts: Thevenin equivalent with independent source

texts:
I'm struggling with analyzing this circuit:

simulate this circuit – Schematic created using CircuitLab

\$R_1 = 5\Omega\$

\$R_2 = 5\Omega\$

\$R_3 = 2.5\Omega\$

\$R_4 = 5\Omega\$

Voltage source = 5 V

The task is to determine the Thevenin equivalent (Vth and Rth) between a and b respectively (black boxes). I'm not sure how to approach this question. Could anyone help me to get started?


texts: How to draw the JK flip flop waveform for Q

texts: The task is to draw a signal for the Q output. I know that the x is the one and the only one of inputs, but I have no idea what to do if I have this AND gate. How this signal will looks like in this situation? And what is the method to know how to draw it?


texts:
I am looking into taking the power supply 12V output of my PrintrBot and plugging a very simple parallel circuit with some LEDs.

I know I can connect a parallel circuit similar to this Splitting a power supply between two circuits. And it would be particularly easy if they use the same voltage.

I also know that I could put 4 3V LEDs in series without a resistor (or add a resistor if the LEDs are rated for less voltage), and they should work properly with a 12V input... and I believe my power supply has enough juice for this (it is a 6A power supply).

My question is:

How to minimize the risks to my printrbot circuit? (I guess there is always a risk that an issue in my LED circuit would affect my printrbot circuit).

While a 4 LEDs in series circuit sounds like the most simple circuit in the world, I know little about electronics (and my experience is very limited). For instance, I am concerned that things like a short in my LED circuit would ruin my PrintrBot circuit or that a LED getting burnt while the printrbot is printing would cause an issue.

Note: I know some people powers the LEDs out of the BED port in the board, but that's too risky for me.

UPDATE after getting answers (2014-09-28).

As explained in the 3 answers so far, some of the asumptions related to the LEDs made by me in the question above are plain wrong. Please read the answers below and do not let my asumptions mislead you.


texts: Understanding Flip Flops/Registers in Low Level

texts:
So I'm reading "Elements of Computing Systems" trying to really understand how everything works underneath (Any other book/article suggestions that would help would be amazing) Since eventually I want to implement this basic stuff on a breadboard and maybe someday get a 4-bit computer or something similar going (but that's a while away).

Anyways I'm looking at the Section on Sequential Logic, and I guess I'm getting mixed up in the "time" or clock when it comes to registers and flip flops. When I think of flip flops I think of the Schematic such as this:

So I'm a bit confused when it says out(t) = in(t-1). For that matter, how exactly is a 0 represented in this case. I know 1 is a voltage being sent, but how would something like a Register holding 1 or 0 know how to differentiate the time difference in the signal being sent?

I'm also a bit confused by the 1-bit Register part, Is it saying that if there is a load that is being "sent down the line" that the output is the same as that load (I'm assuming load is equal to 1 or a current being sent)

as you can tell im a bit confused, I'm sorry if I'm all over the place, but I think it's the "clock" that's throwing me off.


texts: BJT transistor max switching frequency vs FET in high frequency computer architecture

texts:
Why arent BJTs used with RISC architectures to produce very high speed relatively sparse CPUs? My understanding is that BJTs don't have the forward bias gate capacitance requirements of FETs which is a key consideration in clock and voltage settings on modern CPUs.
Power consumption and thermals aside is this possible? Please let me know if I am mistaken in any of my premise.


texts:
I'll start by saying I'm a bit new to electronics.  I found a wall to usb charger at a surplus store.  It is rated to put out 5.0V and 0.7A.  I'm using it right now to power something else which is working fine but I wanted to learn more about how this supply works.

Here are some pictures of it.  I already removed the usb connector to use for another project.

I think its a flyback converter?  I can see that it first goes through a full wave rectifier and then into some unidentified chip.  I assume the chip does the pwm because it goes right into the transformer.  Am I way off?  Is there anything else I'm missing that I should read up on?


texts: How do I visualise the variables in OpenSTM32? Is it like in Open STM Studio?

texts:
I am programming a standard STM32F407 board under Linux. And I'm looking for a way to visualize the variables on a graph in an OpenSTM32 environment.

How do I visualize the variables in OpenSTM32. Is it like in Open STM Studio?


texts:
I have four 200AH batteries connected in a series-parallel form. These batteries are charged using an alternator mounted on a running engine. The purpose of these batteries is for lighting.

There are about 25 lamps each containing 60 watt bulbs. Distance between the loads and the batteries is about 20 metres. The issue that I'm having is that: whenever I switch more than one light on, voltage drops immediately. I cant seem to figure out what's the cause of this.