texts:
This is more of an academic exercise than something practical. I've uploaded the image from a solution manual to a problem I was working on. I can't seem to agree with what they've done.

Also I can't seem to find a Euler path that works for both PUN and PDN.

Anyways about their solution, the PDN doesn't make sense to me. Why is the a/b shared region connected to Gnd? How are e/d/c connected? And how is b connected to g? Only e could be connected to g in the PDN according to their circuit diagram.
Also I'm unsure if their Euler path (which looks like c,d,e,a,b) works for the PUN.

Anyways if someone wants to offer their own solution instead of trying to explain this one to me that would be fine as well.

EDIT - No longer interested in trying to understand/fix the given solution, it seems to have too many bugs. I am interested in seeing someone's worked-out solution (xtor schematic and stick diagram layout) to the given function: g = NOT((a+b)(c+d)e)


texts: RMS value of fundamental harmonic vs RMS of third harmonic

texts:
If we have a periodic signal (square wave) with amplitude of 100V. Then what would the RMS value of the fundamental harmonic be compared to the RMS value of the third harmonic?

After some suggestion in the comments my solution was this:

Am I correct?


texts: What is the purpose of the anti-parallel diodes in this Wien Bridge oscilator circuit?

texts:
In the following op-amp circuit:

Rf here is replaced by the following:

What do the anti-parallel diodes here serve? This is a Wien Bridge oscillator circuit and I am showing only the negative terminal of the op-amp. Once the diodes are removed the output is very unstable and I am not sure why. Maybe explaining what they do will help me.
Edit: Another question I should ask is: why are the diodes necessary when there is a parallel resistance with Rf but not when it's on its own in series?


texts: Why add resistors to a Transistor Vin and GND

texts:
I am following a tutorial where the author uses an infrared sensor  (L-51ROPT1D1 on the left) as an input to an arduino GPIO. I am not using the emittor on the right, I am only using the receiver to count infrared light pulses.

I understand that here a transistor (2SC1815 with 1.Emittor 2.Collector 3.Base) is used so that when infrared light is received, arduino receives a signal with the full 5V. Here are my questions:

Why use a 1k resistor between the sensor and the transistor input ?
Why use a 10k resistor between the emittor and GPIO/GND ?


texts: Is there a risk of 18650 li-ion battery explosion in a low current application?

texts:
I have several used 18650 batteries from my old laptop battery. They all look OK, I have charged them and discharged. The capacity is around 1700 mAh, nominal capacity was 2500 mAh when new.

I'm thinking about how to use them.

There is wall clock in kids bedroom. I'm about to add some LEDs to it so the clock is slightly illuminated during night. Just a little bit so it is not too bright to disturb sleeping but it is just bright enough to barely see clock hands. The current consumption will be around 1 mA.

But I am pretty worried about safety, which is priority #1 for me. The last thing I want is to put a "incendiary bomb" in kids bedroom. Is there a risk that 18650 battery can explode or catch fire in this situation? Or is it better to use 4 NiMH batteries instead? (and dispose my old 18650 batteries).

This is schematic of my circuit:

(values of some resistors/trimmers are not entered yet but I will use as high values as possible)


texts: Why the current transformer behaves like this?

texts: Can someone explain to me why the voltage is rising in a current transformer when the "burden" resistor is removed and the leads open circuit ? I saw some current transformers in flame because of this.


texts:
I am trying to calculate the current required to energize and hold a 24 VAC relay coil while switching no load. I did the same for a 24 VDC relay coil using ohms law which is very simple and matched my measured current. But my calculation for the AC coil did not match my measured current value from my ammeter.

Measured values of AC relay coil:

DC coil resistance: 13.5 ohms
Coil inductance (while manually latched/energized): 168 mH
Operating voltage: 26.2 VAC RMS
Operating current: 262 mA

I created a series RL equivalent circuit of the relay coil by first working out the inductive reactance of the coil at 50 Hz to be 52.78j ohms, giving an overall impedance of 54.48 < 75.65 degrees (in polar form). Then simply V/Z, 26.2/54.48 = 480 mA.

This is considerably more than what I physically measured!

I think the reason for this is because I have measured the DC coil resistance instead of the AC resistance. If I work my calculation back from my known measured values, my coil resistance should be 85.94 ohms (this is assuming my inductance measurement is accurate as I used an inductance meter).

If anyone thinks there is something else I'm doing wrong, please let me know. If you agree I need to measure the AC resistance, can I do this accurately without an oscilloscope?


texts: Comparing industrial vs. off-the-shelf analog input

texts:
Industrial controls are expensive and my company current spends a great deal of money installing them to monitor some rudimentary signals on equipment.

For instance, we're trying to monitor:

temperature from some thermocouples (https://cache.industry.siemens.com/dl/files/991/25545991/att_70599/v1/et200s_2ai_i_4wire_st_manual_en-US.pdf)
vibration (https://cache.industry.siemens.com/dl/files/033/25546033/att_105646/v1/et200s_2ai_tc_hf_manual_en-US.pdf)

Temperature we're monitoring to about the nearest degree (not much precision required) whereas vibration (inches/second) needs more precision (standard value may be something like 0.0048 ips with alarms triggered at 0.400ips).

My question is this: would off-the-shelf hardware like the Arduino/rPI/etc. have the precision to measure these same sorts of signals for a radically lower price point?


texts: Efficiency of FIR filter in verilog language

texts:
Implementing a 4-tap FIR unity coefficients, is this code efficient in power and area ?

always@(posedge Clk)
begin
  //unit delays using flip flops
  xn0<=Xin; //x[n]
  xn1<=xn0; //x[n-1]
  xn2<=xn1; //x[n-2]
  xn3<=xn2; //x[n-3]
  add0<=xn0+xn1;
  add1<=xn2+xn3;
  add_all<=add01+add23
  Yout<=add_all;
end//aways


texts: Bulk power markets hour ending convention why?

texts:
Is there an engineering explanation for the hour ending (HE) convention common to  US Independent System Operators (ISO)? For example, hover over any MISO real time market data and they will show the HE. See link below:

MISO


texts: How to sync time between two devices (<30m apart) with a sub milisecond accuracy? (think PTP)

texts:
So my task is to detect the source of banging in a metal tube (picture radiator pipe). The idea is to put two mics to the ends of the tube and measure time differences when they hear banging. The tube is about 30 meters long and I need accuracy of about 50cm, which reflects to about 0.1ms.
I suppose that for that accuracy I need to use PTP, unfortunately, raspberry pi doesn't seem to have native support. Any suggestions how I could pull off this task?


texts: I'm designing a mod-3 asynchronous counter. The circuit is expected to count from 0 to 2 and the flip flops are set as soon as q become 3

texts:
module mod3counter(
input clk,
output [1:0] q
);

wire rst ;
nand a1(rst,q[0],q[1]);

tff t1(clk, rst, q[0]);
tff t2(q[0],rst,q[1]);

endmodule

module tff(
input clk,rst,
output reg q
);

initial q = 0 ;

always @(negedge clk or negedge rst) begin
    if(~rst) q <= 0;
    else    q <= ~q ;
end
endmodule

Test bench is simply two lines of code that run the clock.


texts: Power supply module on breadboard giving too much voltage

texts:
I'm currently following the tutorial "Electronics Fun Kit" by ELEGOO. The goal is to connect the power supply module with the breadboard in order to provide a 3.3V / 5 V source.

After connecting the power supply module and powering it with a 12V adapt, the LED of the module is on.

Therefore I'm assuming that I've powered it correctly.

Now when setting the jumper of the power supply module to 3.3V, I am able to measure this voltage (3.30V) on the breadboard, by using my multimeter (set to 20V DC.) So far so good.

But when setting the jumper of the power supply module to 5V, I somehow measure 11.47V. How is this possible? Is it a typical "beginner" mistake or is the hardware not ok?

PS: I know that the probes are not correctly connected to the multimeter. I've already changed that, but I still have the same measurement results


texts:
When powering a simple LED circuit (DC power source, LED, resistor), does the supply voltage matter, as long as the correctly calculated current limiting resistor value is used?

In other words, is there / could there be something inherently wrong by powering an LED with 12V or 24V as long as I used the correct resistor, knew the forward voltage of the LED, knew the maximum current, and calculated it using something like this, when I could have powered the same LED with a 3.5V supply knowing the same variables and using the same website?

I'm assuming there is a limit to the maximum amount of voltage to use for the LED here... when I look at the electrical characteristics chart for the CREE XP-G for example, it shows current as a function of voltage, with voltage starting at around 2.5V @ 0ma, maxing out at around 3.25V @ 1500ma (the maximum current the LED is rated at, as described in the Characteristics table in the same document.

After 3.25V, the chart depicts current quite rapidly approaching infinity.

I'm assuming this relates to my question, I'm just curious how its all related. I'm sure its all basic Ohm's law stuff, I'd just appreciate a clarification of the math at work.


texts:
I need to understand the concept of bidirectional bus. What i want to do is connect a memory with ports din and dout to a inout port named data. So along with memory i use a tristate buffer as component. One  tristate buffer has rd signal as enable while the other will have (not read) as enable meaning write.so when i write (read=0) , value flows from data into din(at this time read =0 disables other tristate buffer) so there is no driving of multiple signals in this case. similarly when  read =1 the vice versa happens. value flows from memory to data line. So the read signal itself takes care of the direction.
1)During read can there be contention of value coming out of memory and input data ?
as the buffer that takes value from data to memory is disabled.
2) In testbench when i read the memory why is there a need to give data <= 'Z' ? Isnt it already taken care when i connect the components using port map ?


texts:
According to the standard, C13/C14 plugs don't have a set voltage (unlike something like a L6-20P), so it is up to the consumer/manufacturer to decide which voltages are appropriate.

I recently stumbled upon a C13/C14 cable that had "10A 125V~" imprinted on the C13/C14 connectors. The cable itself was rated for 300V and was 18AWG.

My question is, what exactly determines the voltage rating (in this case 125V) for the connector portion of the cable? Would it be considered "safe" to use this in a 208V circuit (many C13/C14 cables are commonly used in datacenters to supply 208V).


texts: Is this a good design for MOSFET H-Bridge?

texts:
I have been looking around trying to design a simple but working H-Bridge for an RC car motor (12V and 2~3A).

This bridge will be driven from a microcontroller and need to be fast to support PWM. So based on my readings, Power MOSFET are the best choice when it comes to fast switching and low resistance. So I am going to buy P and N channel power MOSFETs that are rated at 24V+ and 6A+, Logic Level, have low RDSon, and fast switching. Is there anything else that I should consider?

Ok so on to the H-bridge design: Since my MCU will be running at 5V, there will be a problem with turning the P-channel MOSFET off, since Vgs needs to be at 12V+ to totally turn off. I see that many websites are solving this problem by using an NPN transistor to drive the P-channel FET. I know this should work, however, the slow switching speed of the BJT will dominate my fast switching FET!

So why not use an N-channel FET to drive the P-channel FET like what I have in this design?

Is this bad or wrong design? Is there any problem that I am not seeing?

Also, will the reversed diode built in these FET be enough to handle the noise which is caused by stopping (or maybe reversing) the inductive load of my motor? Or do I still need to have a real flyback diodes to protect the circuit?

To explain the schematic:

Q3 & Q6 are the low side N-channel transistors
Q1 & Q4 are the high side P-channel transistors, and Q2 & Q5 are the N-channel transistors that drive those P-channel (pull the voltage down to GND).
R2 & R4 are pull up resistors to keep the P-channel turned off.
R1 & R3 are current limiters to protect the MCU, (not sure if they are needed with MOSFETs, since they don't draw much current!)
PWM 1 & 2 are coming from a 5V MCU.
Vcc is 12V


texts: Sending audio signals to output device through relay

texts:
I've created a paper speaker through this tutorial, except instead of conductive thread I used copper tape for the coil. When I hook it up to a device that is known to give off lots of sound, the speaker works pretty well.

My problem is that when I hook up the speaker to my Arduino Uno and run the example tone Sketch provided in the arduino program, the sound comes out veeeery dim. I can barely hear it. I think this is because the arduino wasn't giving enough power to the speaker for it to be loud enough because when I used a 2.5v and 9v battery to power it, it was very loud. I also tested the power going to the speaker and, if I read it correctly on the multimeter, it's barely giving off any power at all.

I know I can use a relay attached to a large battery pack (like 9v) to give more power and get a louder sound. But I'm not sure how I would send the audio signals from the digital pin on the arduino to the speaker through the relay. Would it be appropriate to even use a relay in this case? Or would I have to use something else?

EDIT:
Here's a pic of what I think it would look like in the end. I'm a total n00b with this, I apologize if I didn't draw it with the right connections or anything. I've never had any type of EE training.

...Let me know if any of that doesn't make sense. Thanks!


texts: Laser diode to remove copper layer from PCB

texts:
I used a DIY kit and made a PCB milling machine. So far I am happy with it but it is slow and the minimum thickness of the lines is depends on the tip's size.

I want to replace the cutting bit with laser diode to ablate copper layer directly to ablate acid resistant paint so I would overcome the issues I mentioned.

  EDIT: As Spehro Pefhany explained removing copper layer
  with laser requires much powerful laser than a simple laser diode. At
  this point using a laser diode to ablate paint would be a better way
  to do this.

Here are my questions:

What type of laser diode I need to use to remove ~1 mm thick paint layer?
How can I calculate the minimum power I need to ablate the paint layer?

I read about laser diodes, driver circuits, protections (diode itself and human body) but I could not find a decent source about my questions.


texts: Electrically isolate bottom side of a PCB

texts:
I have a 4-layer board with no parts on the bottom side, the bottom-side solder mask fully covers all vias.
I want to stick the board with a double-side adhesive foil on the metal bottom side of a display. As I do not want to use the isolating double-side adhesive foil to cover the complete display area (you'll never would be able to separate the display from the PCB anymore in this case), I only use some stripes for sticking the PCB onto the display.
As the solder mask is not very thick I'm afraid of short circuits between the traces / vias of the PCB with the metal frame of the display.
So I would like to have something like an isolation foil (no high voltage isolation, only max. 30V) on the PCB's backside without having high costs and work. As far as know on flex-prints an isolation called coverlay can be used - could this be used for a rigid PCB as well? If yes: is this expensive? Or do you have any idea how to solve this isolation issue?


texts: Adding time dependence in xspice code models

texts:
I am looking for a way to define an xspice code models for a custom voltage source, in which the voltage can be varied as a function of time (for instance a time varying frequency sine wave). However I could not find anything which could help me achieve this.
Does someone know how this can be achieved ? thanks in advance for the help


texts: Solder won't stick to metal tab, no matter what I do

texts:
This is an insane problem that I have had for 10+ years and never solved it: When trying to get solder to stick to metal, it won't. Not hot enough? I scorch the piece in lava heat for what seems hours, no dice. The tip of the soldering iron is so hot that solder liquifies immediately when touching it. On the metal tab? Nope, it stays solid when I heat up the tab by putting the soldering iron on it for 5 mins. The solder DOESN'T WANT TO GO ON THE TAB, no matter what I do, push it, kick it, force it, nope... I can even encase the tab when I dump a ton of solder on the tip of the solder iron, it stays away from it like oil and water. All solder beads off like water off a layer of oil. I cleaned the tab, roughed it up, no dice, nothing. It is like the damn thing is bewitched. I don't have this everywhere, but some surfaces that are clearly metal and clearly electronic conductors meant to be soldered just don't want to have any.  What is going on here?
And how can it ever be that I heat up the metal tab to the same burning heat than the tip of the soldering iron, giving it tons of time to heat up, the solder won't liquefy ever on it when touching the tab with the solder?


texts:
Im working on a display project and have run into some I2C issues. The display is of 3.3V design, so I figured, no big deal, ill use a level shifter and be on my merry way. Well, sure enough the level shifter kind of worked, at least it looked good, until i put the scope on it. I am was running with a low voltage of about 1.6V during the slaves ACK. The devices worked, but this is not in spec and I can't rely on this working across multiple devices. So, I'm wondering if anyone knows of a way to sink the extra current during the ACK while not effecting the input waveform from the master.

The display can only sink 1mA, but for the level shifter to work appropriately I need to sink the current from the high side pull ups as well as the low side, so about 2.5mA in the current setup.

I have tried using a pnp transitor with the slave device connected to the base and the low side of the level shifter connected to the emtiter with the collector across a current limiting resistor to ground. I then tied the emitter to the slave with a resistor. This worked to pull the ACK to about .1V, but the series resistor in line from the emitter to the display distorts the waveform from the master too much to be comfortable.

So, if anyone has any other ideas I would be greatful. Perhaps there is a purpose made solution that I can't google my way into.


texts: Possible to insert capacitor between voltage source and output to delay the output?

texts:
I'm a newbie at this stuff but basically I have a 3.5v coin battery connected to a tiny switch that turns on a tiny buzzer.

What I want to do is delay the power going to the buzzer by about 30 seconds.

Would simply putting a micro capacitor between the voltage and buzzer be a way to do this? I need to keep the weight of this contraption as low as possible so that it doesn't weigh much more than the battery itself.

I tried messing around with various circuit designers but all I came up with was artistic doodles...


texts: We want to generate a spark suitable for igniting a potato cannon (alchohol class fuel) preferably without automobile-class coils

texts:
I assume we need about 1000v for a 1mm gap.  I have a coil about 2cm with an iron core, but no idea how big L is.  I have a lot of 330uF capacitors rated for 200v.

What would be a clean way of doing this?  Voltage multiplier with capacitors?
How would we trigger it with the Arduino?  We have been using IRF630 power transistors to turn on power circuits, but those are rated for 200v.

Can anyone suggest a simple circuit to generate a small spark without buying $15 parts from an auto parts store?  If no, tell me and we will buy one...


texts: What is the use of Vampire Power. Does it do any good?


texts:
I've been tasked with finding the pulse transfer function G(z) of the combination of the following equation
 \begin{equation}G_p(s) =  {10\over (s+1)(s+2)(s+3)} \end{equation}
and a zero order hold.

I started by combining the hold with the equation to obtain

\begin{equation} {10(1-e^{-sT})\over s(s+1)(s+2)(s+3)} \end{equation}

and then splitting this up to the equations

\begin{align} {1\over s(s+1)} \tag1\\
{1\over (s+2)(s+3)}\tag2 \\
{10(1-e^{-sT})}\tag3
\end{align}

finding the z transform of each one, and finally combining them together. I'm not sure if I've went about this in the right way, the answer I obtained seems very complicated and I can't find any similar examples. Can anyone who knows how to do this tell me if I'm going about this correctly and point me in the right direction?


texts: 9x 1W LED's parallel + series resistor calculation help needed

texts:
I am struggling with the calculations of the current limiting resistor for my circuit so I wanna ask you guys for help. I've tried doing this calculations on online calculators and by myself with math but the results i get are all different from different sources.
I have 9x 1W green LED's which I want to drive using 12V 2A switching power supply but by my lame beginner electronics calculations that's not enough it seems and this is why I need your help too.
This is the scheme I am trying to figure out:

Most of my calculations are suggesting that for R1 I need to use 3,9ohm 5W resistor.
As noted on the image each LED should be supplied with 3V 300mA. I read many different resistor calculations but I cant figure out the right way for my circuit since I don't really know many things in electronics.
I would appreciate if any of you could provide explanation how to calculate such circuit and help me out, or if you have any better idea of how I should build this thing. I will make a video about my build and post it on YouTube and I will make sure to mention all of you.


texts: Is it good to have a higher slew rate? What are some of the effects due to slew rate limitations?

texts:
This question is in relation to the working of an op-amp. I know what slew rate is, but I am not entirely sure whether is it good to have a high slew rate.

As far as my understanding goes, a higher slew rate should allow the op-amp to give the output as per the input without time delay. Is my understanding correct?

What are the effects due to slew rate limitations?


texts: Why does the thickness of a wire affect resistance?

texts:
A teacher explained why by using a highway analogy. The more lanes you have, the faster the cars go through, where the number of lanes obviously represent the wire thickness and the cars represent electrons. Easy enough.

But after a certain point shouldn't the wire get so thick, that any thickness after that doesn't affect resistance? For example, if you have a 100 cars going down a highway, a 4 lane highway is going to allow the cars to move a lot faster than a 1 lane one, because there are a fewer cars per lane. But a 1000 lane highway highway is going to be as efficient as a 10000 lane one, because on both highways every car has its own lane. After a 100 lanes, the number of lanes doesn't provide resistance.

So why does increasing wire thickness always decrease resistance?


texts: what is the purpose of __weak reference used on Keil MDK ARM?

texts:
Got a little messy with a function defined in two files and one with a __weak symbol.
I called the below function to load the settings of UART1 in STM32L476RG from my main file

 if(HAL_UART_Init(&UartHandle) != HAL_OK) and this function is defined at
  {
    Error_Handler();
  }

I found that this function calls another funciton named  HAL_UART_MspInit(huart);
This is defined at two places ,

 1. in stm32l4xx_hal_msp.c as void HAL_UART_MspInit(UART_HandleTypeDef
    *huart)
 2. in stm32l4xx_hal_uart.c as __weak void HAL_UART_MspInit(UART_HandleTypeDef *huart)

My problem is that the whenever I load the UART setting the __weak function is called. I did it by referring an example, UART_WakeUpFromStop given in the [STM32F476RG Product page]. where in the example the function in  nstm32l4xx_hal_msp.c , void HAL_UART_MspInit(UART_HandleTypeDef *huart) is called. What is going wrong in my code? what is the influence of __weak symbol?

STM32L476RG Reference manual


texts: How significant are hysteresis losses in iron wires with RF currents?

texts: I understand that iron isn't a great choice of conductor for RF currents, as a wire dipole antenna for example. I understand there are several reasons, but I'm wondering specifically about one: hysteresis losses. How significant are hysteresis losses when an iron wire is a conductor, not part of a magnetic circuit? Can they be calculated? Are there any empirical data?


texts: Switching another circuit that has high current

texts:
I'm trying to use a Raspberry Pi to switch on and off another circuit. This other circuit draws a LOT of current, so I'm using a power supply dedicated to that load.

I tried to do a simple op-amp comparator (1.65V coming from a resistor divider off the Pi into the V-, 0 or 3.3V coming from the GPIO pin on the Pi to the V+, and then 0 and 9V from external battery to the VS- and VS+ pins), with the output then connected to my load and to the external battery ground.

However, I then realized that op-amps can apparently only have up to 25mA passing through them when there's no feedback. (Just a figure I found, it might not be exact.) My load can take up to 1A or higher.

I was thinking of doing a CMOS switch, but as far as I can tell I would need to have some sort of negative voltage source as well as positive to be able to make the switch. I'm not sure how to do that with just batteries, though.

Is there any way to do the CMOS switch, or just have another switch mechanic in general?


texts: PCB RF Layout Critique: Input on my radio-telescope PCB

texts:
I'm attempting to do the board layout for a radio-telescope we're building at one of my jobs.

Here is the overall system topology:

QRFH is for "Quad Ridged Feed Horn". It's a rather esoteric antenna type.

Basically, the intention is to allow extremely high-precision measurements, with in-situ calibration and drift tracking. There is a built-in system for measuring antenna SWR to calibrate out drift due to physical changes from temperature changes, calibration for the SWR calibrator via the ability to feed the SWR oscillator directly in to the analyzer, a optional pilot tone to allow for tracking oscillator drift in the spectrum analyzer, a noise diode, termination, and a small dipole for measuring local RFI.

Complete PDF of everything here

Anyways, here is my current layout:

Updated Layout:

Original layout:

Stackup:

Top layer:

Ground 1:

Power and interconnects:

Ground 2:

Overall view:

All transmission lines should be within ~1Ω of 50Ω, taking the dielectric of the FR4 from the board house I intend to use into consideration.

Right now, this is intended to operate in the 50-300 Mhz band, so more esoteric dielectrics aren't really warranted, but I have them under consideration.

LNA Amplifiers are mini-circuits CMA-5042 with TCBT-14 bias-tees.
ESD protectors on I/O is via CLM-83-2W+.
RF Switches are JSW6-33DR+ (the 6P switch has better performance then the 2P switches, so I'm using a 6P switch in the 2P switch position as well. The price difference is negligable).
Variable attenuators are all DAT-31R5-SP.

Basically, I'm seeking a few things.

Does my layout at least look mostly sane?
I have switch and attenuator control traces running under RF traces, albeit with a ground plane in-between. I don't think this is an issue, but RF is weird.

I've kept the soldermask back from all RF transmission lines as much as possible, with just little barriers around the SMT parts to prevent the solder from running down the traces.

Mostly, I have just not done RF layout before, so I appreciate any input.


texts: Multimeter showing negative voltage on servo connection

texts:
I am trying too get my first (ever) servo sweeping back and forth and for some reason am having enormous difficulty with the wiring.

In the Fritzing pic below, I have the circuit connected (both + and - terminals) to a 5V power source (Arduino). The orange "signal" (or "pulse") line is connected to an output pin on the Arduino. Because, for reasons you'll see next, I'm convinced this is a wiring issue and not and Arduino/code issue, I've omitted the Arduino from the diagram/pic for simplicity's sake.

When I power this on, nothing happens. At first I thought it was a code issue, but then I busted out my multimeter, setting it to its 6V setting. In the pic above, you'll see two contact points in purple; these are the board connections to the Arduino's 5V and GND connectors respectively. When I test them with the multimeter, they do in fact read about 5V. So far so good.

However, when I test the green connections in the pic above (the power connections between the breadboard and the servo), the multimeter tells me that there is -20V (that's negative 20V) passing through the servo!?!?

I may very well have a code issue, but this is certainly not correct either. Am I wiring this up wrong, if so, how? If everything looks OK, what are my next steps for debugging/troubleshooting here?


texts:
I am having a problem here can't make this code compile. It is a 4x4 keypad scanner with a 20ms debouncer. It gives error "Error: 'col' has not been declared"
Any suggestion?

module keyboardScanner (input clk, input wait20, ,input [3:0] col,output reg [3:0] row, output reg [7:0] keyCode);
reg [1:0]state=2'b00;
reg [1:0]nextState=2'b00;
reg start = 0;
//state register
always@(posedge clk) begin
    state <= nextState;
end

//output CL
always@(posedge clk) begin
    if(start == 0)begin
        case (state)
            2'b00: row <= 4'b0001;
            2'b01: row <= 4'b0010;
            2'b10: row <= 4'b0100;
            2'b11: row <= 4'b1000;
            default: row <= 4'b0001;
        endcase
    end
    if (col != 4'b0000)
        start = 1;
    if ((col != 4'b0000) && (wait20 == 1) && (start == 0)) begin
        keyCode <= {row[1],row[2],row[3],row[0], col[0],col[1],col[2],col[3]};
        start = 0;
    end
end

//next state CL
always @(posedge clk) begin
    if(start == 0)begin
        case (state)
            2'b00: nextState <= 2'b01;
            2'b01: nextState <= 2'b10;
            2'b10: nextState <= 2'b11;
            2'b11: nextState <= 2'b00;
            default: nextState <= 2'b00;
        endcase
    end
end

endmodule


texts: A circuit with a non-inverting op-amp and comparator for amplifying the output of a piezo transducer. Am I missing anything?

texts:
I'm a total noob when it comes to electronics so was hoping some people might be able to take a look at my circuit and see if it makes sense.

I'm trying to create a circuit which amplifies the puny 50-100mV output (Vin) signal of a piezo transducer (with a gain of ~20), then feeds it into a comparator with a fairly low reference voltage on the inverting input, ~450mV (Vref), which has an output voltage (V2out) of 5V. This signal is then plugged into a digital pin on an Arduino.

Here's the schematic (sorry if the design is terrible - I'm still learning these things!):

Does that look okay? Have there been any egregious oversights?

One thing I've learned is that modelling piezo transducers is somewhat difficult, and that an AC voltage source (as above) is not ideal. Any tips on improving that would also be really appreciated.

Thanks!


texts: Why Ferrites are used as a cores for inductors

texts: Why specifically we use the ferrites as a core for the inductors? For example a NiZn toroid as a core for an inductor?


texts:
In the  given circuit I want to compute the current going through R3 given the current of Rs (Rs is a shunt resistor.)

simulate this circuit – Schematic created using CircuitLab

What is Iout in terms of Isense ?


texts:
Is there an IC that will "record" a digital signal received (highs and lows) record or buffer that input, and finally send to another IC thru I2C interface.

The problem is that I have two different clocks and the receiving IC is not able to get signal because it is too fast.

UPDATE:
Thanks for the answers.

Chip sending data works at speed at least 256Mhz, chip receiving data - 48Mhz.
Communication protocol looks like that:

http://i39.tinypic.com/2gv7ts3.png


texts: using a NOR gate output to a mosfet switch, improper high level output voltage

texts:
I am using a hex 2input NOR gate IC (TI SN74AS805BN). NOR Datasheet with a 5V regulated supply

I want this to control a power mosfet switch Vishay FB180SA10B MOSFET Datasheet. The problem is that the NOR gate high level (i.e. logic '1') Voltage output is apparently as low as 2V, and for the MOSFET to act in its saturation region, a Vth of up to 4V must be exceeded. I am constrained for board space and don't just want to amplify the signal.

So was thinking of using another MOSFET with its gate controlled by the logic output, to switch the bigger power Mosfet, by just connecting my 5V supply to the drain of the first MOSFET and the source connected to the gate of the power MOSFET, but get the feeling that this is bad practice. 1: Is this so?

Alternatively I was thinking of having the MOSFET pulling down the output when conducting in series with a resistor (ie a resistor pulling up) as in the simplest MOSFET switch. In the Logic stage I could possibly deal with the inversion to the power MOSFET gate that this would cause, but, 2: I was wondering what the recommendations would be for the most elegant solution.

Or 3: Am I just reading the NOR IC datasheet wrong?

Thank you so much!


texts: stop mask error remains after deleting offending text in eagle

texts:
I ran the DRC for dirty pcbs, and it's giving me these stop mask errors for values assigned.

In this particular example, It's D1 with a 4148 label. In the first image, you can see the 4148 value that is causing the stop mask error with the 5v pad. I remove the '4148' value for D1, and you can see that for some reason the '4' and part of the '1' from '4148' still remains.

How do I get the remaining 41 removed from the pad to get rid of the error? I tried to remove the diode and the 5v pad from the schematic, but when it's added back, the 41 remains.

Before:

After:


texts:
I want to test the analog inputs of a CD4051BE multiplexer, so I created four voltage dividers in order to measure four different values of analog input. I connected them to the I/O0 - I/O3 ports of the IC and connected the output port of the IC to the analog input of an arduino board.

After that I read the values of each one voltage divider using the select lines, and it worked as expected.

I have five pieces of CD4051BE in my possession (bought from the same shop), so I decided to try them all. I was surprised by the fact that every each one was delivering different values, about 5-10% of maximum value.

Mt guess is that it happens due to a slightly different internal resistor for each one IC. If this is the case, how can a multiplexer be used for manupulation of several analog sensors, since accuracy errors occur?


texts: Is it possible to convert the audio signal from a smartphone's headphone jack into radiowaves?

texts:
I was watching a video of someone using his smartphone and a custom designed coil to make a metal detector.

The smartphone was connected to the coil via headphone jack.

I couldn't understand how he managed to convert audio signals into radio waves using the app on his phone.

Is this even possible or practical?

PS: Link below to the video

https://youtu.be/xkkI8Qhvf8Y


texts: how to determine the probability the two signals are equivalent

texts:
I am new to electronic engineering and DSP.
I have this orignal signal matrix
[X1,Y1]
.
.
.
.
[Xn,Yn]

and then it goes through series of transformation. It can be rotation/shift_bit/or whatever transformation through a transformation Matrix. so suppose  through this operation I will have A1....Am matrix from the original signal

and I have another signal. but go through different transformation not necessarily the same as above. let say B1...Bm

now if I mix the two bags A1...An and B1...Bm together.
And then draw from these combine bag randomly of the two matrix How can I determine
the two matrix Ai = Bj

I am thinking using spectral analysis but not sure if it is the right path
and also if any R/Matlab/python package can help this work ??

-Thx sincerely.


texts: Choosing the right (flyback) diode to stop contacts (points) arcing (sparking) on solenoid (relay)

texts:
Clock with a simple electric remontoire, consisting of a solenoid, with an arm, that kicks back the main spring, rewinding it.

Solenoid coil data:

operating voltage: 12V-15V
measured resistance: 3ohm
theoretical operating current: 4-5A

(unable to measure current since the coil is energised just for a fraction of a second. Weirdly enough... a lot of current for a small clock).

What would be a good flyback diode to use for this application?
What are the rules/formulas helpful for chosing a flyback diode for
other characteristics of solenoids (relays).

simulate this circuit – Schematic created using CircuitLab

THANK YOU!


texts: DC Motor Control - h-bridge pulsing strategy?

texts:
Question is with regards to a DC motor controller built around an Allegro A4940 and four discrete FETs.

There are at least four possible strategies for driving the FETs, and I'm struggling to understand if any one of them is the accepted "right" way or if the best choice depends on circumstances. The options I can see are:

Turn on the low-side FET to select direction, and PWM the corresponding high-side FET to set speed. Opposite pair are off.
Similar to #1, but PWMing both, instead of the low-side just being held on.
Similar to #2, but with the low-side and high-side FETs taking turns switching off, instead of both doing so (so, PWM out of phase).
PWM back and forth between opposite pairs, varying the ratio depending on the commanded speed (so, like a class-D amplifier).

Option #1 seems like the simplest. Are there efficiency or heat dissipation reasons to go with #2 or #3.

Option #4 seems wasteful and unnecessary if you don't need the precise control for audio.

Thoughts, or pointers to resources on this?


texts: How to pass a square wave through transfer function in MATLAB?

texts: I am currently trying to create a band stop filter which attenuates frequencies between 2000Hz and 8000Hz. I have got the transfer function but now I am struggling to find the documentation on how to pass a square wave of 6000Hz and another sqaure wave of 20 000Hz to test the filter. I am doing this on MATLAB or Octave so any help will be appreciated. Should I be using the step function to get the frequency response graph?


texts:
This may be a stupid question, so please bear with me.

I have a fuse block with #8-32 and #10-32 screw terminals. What size loop connectors would I order for those, for proper fit? The loop connectors are usually listed in fractions of inch. How do you convert #8 and #10 to loop connector sizes?


texts: What is the reasoning behind Arduino choosing 9v?

texts:
I've always was wondering why they chose 9v, well really 9-12v.. Why not 5v or 3.3v or 12v?

Surely there was some good thought put into this. Does anyone know or have sources?


texts: What are the advantages of using a transistor as a diode after interconnecting its collector and base?


texts: Specify Xilinx FPGA DSP placement with Vivado

texts:
How can I, either in the RTL or in a constraint file, map specific DSP blocks to certain locations? I see that DSPs are labeled by site, with names like DSP48_X5Y30 and I'd like to be able to map a particular DSP instantiation to that site.

I have a design a tiled design where, without constraints, Vivado places things reasonably within columns but arranges the columns in what seems like a random order, creating very long routing delays. It's basically a systolic array, so the data flow is simple; manually mapping an instantiation to the correct DSP site should be easy. However, when I trace Vivado's automatic placement, it's not uncommon for two columns that are logically adjacent to be on opposite ends of the chip, with the next column being back near where the first column is, requiring an entire round trip across the chip to traverse three stages.

When I look online, I see manuals on how to do this with ISE, but everything I've seen related to Vivado involves pblocks, which seems like an extra layer of indirection which is pointless for something this simple?


texts: P-Channel MOSFET reverse polarity protection on NMOS array chip

texts:
I'm trying to achieve reverse polarity protection for the TPL7404LADR chip which is basically an updated version of the ULN2003 darling transistor array. To do this I want to use a P Channel MOSFET but I'm worried about the effects this will have for fly back current protection. If an inductive load (say a solenoid) is switched from ON to OFF will the P Channel MOSFET effectively allow the chip's internal free-wheeling diode to carry the fly back current through to the +24V source?

Thanks


texts: MSP430G2553 with MAX30100 library compiling errors

texts: I am trying to work on MSP430G2553 with MAX30100 pulse oximeter sensor but the energia max30100-master library is not working. These errors are I am trying to fix. How can I get these components to work with energia? I tried different libraries but it always says multiple libraries found. I deleted all and tried again and again but I am still getting same the errors.


texts: Difference between a lock in amplifier and an oscilloscope

texts:
I'm a physics student and in my lab we are currently dealing with lock-in amplifiers.
So far the thing that I found out is that an oscilloscope displays a signal in the time domain and a lock-in amplifier displays it in the frequency domain (as the sum of many sine waves with differing amplitudes, frequencies and phases.)
I didn't have too much luck finding any more explanations than this so I've wanted to try and ask here if anyone could give me some insights in this and in which use-cases you would chooses either the one or the other.
One guess from me would be that I use the lock-in amplifier when I want to extract a small signal from a rleative broad noise. (That's my only guess because that is what we use the lock-in in our laboratory for.)


texts: Design of a single cell low voltage reverse battery protection circuit

texts:
I have a design that will run off of a single cell 1.5V AA battery and I wanted to provide some reverse battery protection to it while also maximizing my run time.  The classic way to do this is just with a FET.

But then I was reading a TI app note where they note that when a battery is drained to 0.8V the voltage is not sufficient to fully turn on the FET and it will operate in the linear region.  Therefor the RDSon is much higher and the voltage drop will not allow the regulator (which is placed after the protection) to turn on.

Their solution in the app note is a regulator they have with a Vaux output that charges up to 2.5V before turning on the main output.  This Vaux pin is used to pull up the gate of the FET thus turning it on.  The part they use is a little too small for me and I was trying to figure out a way to get just this feature discretely or with some additional IC.

Has anyone run into an application like this before or have any advice?

I looked for some charge pumps but they stopped around 0.9V input where I want to get down to 0.7V (their circuit can do 0.5).  I looked for some other regulators and I've considered using their regulator just for it's vaux capability :)  Finally one AA battery is a hard requirement, I don't have a choice here.

Here's the TI circuit for reference:


texts:
I have a 10W AC/DC converter that works in the range of 80~265Vac and I was using it with an input of 220Vac, but now I need to supply with 220Vac or 380Vac.

I was thinking about using a step down transformer to divide by two the input voltage and use the same AC/DC converter. I am looking forward a transformer to do this but I am newbie and I don't know where to start. Could you give me some advice?

Thanks


texts:
I took apart an RC car recently and found 2 sets of motors.  The rear wheels (left) seem to run off an electric DC motor which is understandable.

The front wheels (right) I expected to be controlled by a servo motor because it can only make the front wheels face 3 directions (front, steer left, steer right) and no angles in between.

However, looking at the insides I can see that there are only 2 wires instead of 3.  And the servo's that I've worked with before needed 3 wires for Vcc, ground and a control wire.

Could somebody confirm whether or not this is a servo?  If not, what's the next best type of motor it could be? And how would I control it (PWM?, etc)


texts: Difficulty of implementation of this Rayleigh variate generator on simpler FPGA

texts:
For a university module we have been tasked with a 'research project' whereby we need to implement an FPGA non-uniform variate generator. I've identified one possible choice for the specific distribution I was assigned - the Rayleigh distribution. I'm now trying to deduce if this design from literature will be possible for me to implement as a 16 bit version. I will be using a Terasic P0082 Cyclone IV De0-Nano which is a much simpler board than the one the authors used.

I have very limited exposure to FPGA and VHDL and so it is difficult for me to judge the complexity of implementing this design. On the surface it looks tame but the specifics of implementing the State Memory, Addressing Unit and Coefficient Memory in VHDL are unknown to me.

My question to more experienced FPGA designers is what they think of the complexity of this design. Is this something that would be easily implementable on the FPGA mentioned above for an undergraduate student or will this be a significant challenge?

The implementation from literature is based on the Box-Muller method and was implemented on a Xilinx Virtex-55VFX200TFF1738 FPGA. The design comes from A.  Alimohammad,  S.  F.  Fard,  and  B.  F.  Cockburn and their paper titled "Hardware Implementation of Rayleigh and Ricean Variate Generators". In the paper they give the design as:


texts: Does anyone knows the name of the part that connects with this power adapters cable?


texts: Altium Designer 19.1.5: very dark 3D preview, black footprints

texts: Anyone facing the same issue? How this could be fixed? Tried to do a clean install, but it doesn't help. I'm on Windows 10 with all the recent updates.


texts: finding the current in a branch with resistor, capactor and a voltage source

texts: I'm solving a question in Linear circuit analysis 2 class. the question is to analyze a switching circuit with inductors and capacitors. this is the circuit in the time interval  drawn in S-domain using laplace tranform with initial conditions for the inductor and capacitor already considered. if I want to find , what will the current passing in the second branch from the left be?? and what would the node equation look like?


texts:
I am trying to build a robot with the Arduino Uno and the H-Bridge SN75441.
The robot has 2 1.5V rated motors. I set it up with this tuto: http://www.mlbelanger.com/arduino/ard-bot/
So the circuit is like this (I have just not plugged the Arduino Vin pin in the pin 8 of the chip):

(source: mlbelanger.com)
As you can see, the H-Bridge only supports down to 4.5V for the motors. That is why I had to use a 5V power input (adapter 5v @ 1A) to power the motors, with PWM (80/255, giving a 1.5V normally) for regulating the power to 1.5V.
So here goes my problem. I have two cases:

one where the motors have no load, which means that the robot is in the air. The motors run at 1.5V @ 0.26A normally.

the second one which I have trouble with: it runs at 0.5V @ 0.145A. So the voltage dropped as the load increased. The robot doesnt advance and makes a kinda high-frequency noise. If I use 1.5V AA batteries connected directly to the motor, it runs well so the load is not the problem, but rather the PWM setup somehow.


texts: Efficiently turning electric to kinetic energy

texts:
What are the most efficient electric  mechanisms for creating kinetic energy?
Purely from a coulomb-volt to foot-pound perspective.


texts:
I designed the bridge rectifier circuit.
I wnat to make a full-wave rectification. so, I made a CMOS circuit.
I refered to other papers. Figure2.
"An ultra-low-voltage self-powered energy harvesting rectifier with digital switch control"
Link:

I think this circuit is full-wave rectification. But the result is a half-wave rectifier circuit. Is the result of this graph correct?

And my theme is Energy Harvesting. So input in mV units. I had input 0.3V but Simulations output is 1V. Why does this result?

Thank you for reading.


texts: GPIO input connected to garage door button

texts:
I know there are other GPIO / Garage door related questions, but this is not a duplicate- I need to read the status of the garage door button, not a garage door sensor.

I would like to connect the garage door's button to a GPIO input on my Pi. I want to be able to trigger actions when someone pushes the button. I am able to read the status of a basic switch using this circuit I found. My concern is that when I connect a volt meter across the garage door button I see over 16 volts (presumably to drive the LED in the button?). I am concerned that if I connect my switch reading GPIO input circuit to the button, that 16 volts could fry my Pi. How can I read whether the button is open or closed, but protect my Pi from the voltage on the line?

I do also have a garage door magnetic switch sensor that I can read fine with my GPIO circuit, but my requirements include knowing when the button is pushed- not just whether the door is open or closed.


texts: What is this symbol that looks like a 3/4 circle connected to wires?

texts:
I am reading an application guide related to high-voltage DC and have come across a symbol that I do not recognize:

The source of the schematic is this document from Siemens.

Based on the context, my guess is that it might be either some sort of adjustable or controllable element, like a contactor or adjustable reactor, but I am not sure.


texts: In a negative feedback loop, why does increase in v_out lead to increase in v-?

texts:
I hope this is the right place to ask this question. (Please let me know if there's a better place to ask this.)
Basically, I'm quite confused about how we check if we have a negative feedback loop.

During lecture, when checking whether this was negative feedback, my instructor said that if the v_out increases, then v- increases as well, which would lead to the next v_out decreasing because v_out = A(v+ - v-), where A is the gain of the op-amp. I get how if v- increases the next v_out would decrease and that'd give a negative feedback, but the problem is, I don't understand how v_out increasing (initially) also leads to the v- increasing.
Actually, there was a similar question we went over just before:

For this one as well, my instructor said the same thing; if the v_out increased, then v- also increases, leading to smaller v_out the next time. Here, I thought I understood why: there's a voltage divider from V_s to v_out, where (v- - v_out) = R2 * V_s /(R1+R2). Since none of the resistances nor the voltage source V_s change, if v_out increases, v- would have to increase as well, or that was my understanding. (Is my understanding right?)
However, going back to the circuit for Inverting Summing Amplifier, we don't exactly have a voltage divider, do we? Because the two voltage sources V1 and V2 are in parallel, I don't see how I could combine them (I think you can only combine voltage sources in series). So assuming I'm right in not seeing any voltage dividers in Inverting Summing Amplifier, what makes v- go up as v_out goes up?


texts: Powering micro controller using n-channel mosfet and tpl5111

texts:
I am trying to create home made battery saver circuit to powering on my microcontroller (nodemcu v2),

I am following http://www.ti.com/product/TPL5111/datasheet/detailed_description, and created the connection on breadboard,

TPL is connected as follows

Pin  -1 V+      - to power rail (5v or normal Li-Ion battery 4.2v)
Pin  -2 GND     - common GND
Pin  -3 DELAY   - 20Kohm to Ground (~20 sec of up time)
Pin  -4 EN      - GND (Since i want this to be one shot and not as timer)via push button and other leg of push button to V+.
Pin  -5 DRV     - Gate to my MOSFET (FQP30N06 N-Channel enhancement)
Pin  -6 DONE    - Done pin to MicroController D2/2 (depends on esp8266 type)

On MOSFET side

GATE is connected to Pin 5 above, so every time i push the button TPL asserts DRV pin high which should enable the mosfet
MC USB pin connected to V+
MC Ground is connected Drain of Mosfet
Source of Mosfet is connected to Common GND
GATE and DRAIN are connected using 5K ohm resistor

Following are my doubts

Even when TPL DRV is low my external LED to MC on pin 13 is lit and voltage is < 0.5 volts, should microcontroller be OFF completely?
My intention is to attach Reed Switch instead of push button to TPL so every time i open the door it should turn on mosfet via tpl and microcontroller should do the job and send the DONE to turn off
Sending DONE via microcontroller doesnt turn off the TPL, but thats not something bothering me at this stage but still would like to know

I will upload my circuit from breadboard but i need to put labels on it.

Below is simple code which turn on LED on Pin 13/D7

    #include "AdafruitIO_WiFi.h"
    #define HUZZAH
    #ifdef HUZZAH
      #define DONEPIN   2 // TPL5100 Done signal
      #define LEDPIN    13
    #else
      #define DONEPIN   D2 // TPL5100 Done signal
      #define LEDPIN    D7
    #endif
    #define DEBUG true
    #define BAUD_RATE    115200

    const char* ssid = "wifi";
    const char* password = "password";
    #define AIO_KEY  "mykey"

    AdafruitIO_WiFi io("userId", AIO_KEY, ssid, password);

    void logMessage(String message, boolean noCRLF=false){
      #ifdef DEBUG
      if (Serial){
        if (noCRLF){
          Serial.print(message);
        }else{
          Serial.println(message);
        }
      }
      #endif
    }

    void connectAdaIo(){
      bool sendData = false;
      logMessage("Connecting to Adafruit.io");
      // connect to io.adafruit.com
      io.connect();
      int retry = 0;
      // wait for a connection
      while(io.status() < AIO_CONNECTED || retry < 10) {
        logMessage(".");
        retry++;
        delay(500);
      }
      if (io.status() < AIO_CONNECTED){
        sendData = false;
      }
      // we are connected
      logMessage("Adafruit connected:" + sendData ? "true" : "false");
      logMessage(io.statusText());
    }

    /*
     * send DONE signla to TPL5100 to shut the power off
     */
    void sendDone(){
      digitalWrite(DONEPIN, HIGH);
      delay(1);
      digitalWrite(DONEPIN, LOW);
      delay(1);
    }

    void setup() {
      delay(10);
      Serial.begin(BAUD_RATE);
      Serial.println("Measuring Temp on DS18B20 \n");
      delay(10);
      pinMode(DONEPIN, OUTPUT);
      pinMode(LEDPIN, OUTPUT);
      digitalWrite(DONEPIN, LOW);
      connectAdaIo();
    }

    void loop() {
      io.run();
      digitalWrite(LEDPIN, HIGH);
      logMessage("I was here", true);
      delay(3000);
      digitalWrite(LEDPIN, LOW);
      while(true){
        sendDone();
      }
    }

simulate this circuit – Schematic created using CircuitLab


texts: How to choose an op-amp used as a buffer

texts:
I am having difficulty choosing an op-amp for essentially a one-off design.  All I am trying to do is buffer inputs to a +/- 10V 16 bit ADC.  Super high precision is not necessary, but I would like to be within 100mV of the actual value.

I have several voltages that I will be monitoring all within the +/- 10V range.  I want an op-amp to buffer these voltages before sending to a 16 bit ADC.  I already have a 12V regulator, so I would like to power it with that.  When searching for these parameters, I still get hundreds of results.  How do I pick an op-amp?  LM741 should be able to do this, but so should a LMP7702.  Which one should I use?  How do you decide?

Here is an example of what I'm trying to do.  I've put a bunch of catch-all caps on the input to filter.  Not sure if that is the best approach, but that is what I have for now.

EDIT:

I've decided to go with an AD822 op amp.  It basically came down to what is available to me within the +/- 12V range and that had a readily available model.  Follow-up question:

The datasheet for the AD822 shows a unity gain circuit that has no input resistors and no feedback resistors.  I was under the impression that you had to balance the inputs.  Also that you may need some sort of feedback resistor with a small cap across it to prevent oscillations. Maybe because the bias current is so low for this amp, it doesn't matter?  If I were using a large gain, I could see it becoming an issue.  Thoughts?


texts: I am replacing a 4.7 uF 35v electrolytic axial leads capacitor near the cpu on an atari 2600. Can get away with using a 4.7 uF 50v capacitor?


texts: Trying to follow schematic for the first time, getting weird result

texts:
So I am trying to follow this circuit diagram to implement V-USB for my ATmega8:

I was trying to attach C4, like this (I left out all the other connections just to keep it simple):

Now, the problem is the wire connecting the VCC pin of the AVR to the ground rail. Judging by the circuit schematic, it looks like that is what I have to do. But the circuit doesn't work right this way. The power just seems to fade away (I have an LED connected to the voltage and ground rail of the breadboard, and it just fades out every time I connect the power source).

But, when I take out the ground wire, everything works just great. So I think that's the way to do it, and I found it very weird to be connecting the ground wire in the same line as the power anyways. I want to know why it doesn't work the way depicted above, and what the schematic actually intended for me to do.

Thanks.


texts: Voltage Sucked Down on OPA541 (amplifier) Circuit Output

texts:
I am currently working on a design to generate a 5VAC (rms) @ 400Hz supply capable of 5A continuous. The design contains a non-inverting amplifier that takes a 213mV (rms) @ 400Hz voltage waveform (generated by a COTS board) and boosts it up to 5VAC (rms) @ 400Hz. The circuit is shown below:

This circuit works just fine, effectively generating the 5VAC output that I desire... that is... until I put it under load... When I connect this thing to our expected load (special incandescent aircraft light-bulb design, the voltage on the output waveform gets sucked down to 3.2VAC (rms) and draws 1.039 Amps AC (rms), and stays at 3.2VAC until I remove the load. When I remove the load, the amplifier output returns to 5VAC @ 400Hz. What could be causing the voltage to get sucked down like this?

Some additional information (not sure whether it will help anyone looking at this, but figured I'd share as much information as I actually understand/know). I've tried a specialized industrial supply capable of 5VAC @ 400Hz (at very high current) and the voltage does not get sucked down at all. Under normal circumstances the bulb draws 1.15 Amps AC (rms) from the industrial supply when 5VAC 400Hz is applied, not impacting the voltage whatsoever. I am convinced there is something wrong with my amplifier circuit...

Let me know if there are any other details that would help if I provided, or am missing something.


texts: Correct Polarization of Common Source Amplifiers

texts:
I was reading a book about amplifiers and I have read the following sentence about the following picture:

  The idea-guide is that we must access simultaneously to the Gate terminal and to the Source terminal of a transistor so that we can command it to produce a controlled current, as shown in the previous picture.

  But from a practical point of view, access to those two points requires some caution in order, for example, not to alter the polarization of the transistor: in fact we could not directly connect two ideal voltage generators referred to ground to the two terminals of the transistors shown above. We should necessarily think of a coupling in AC, at least for one of the two inputs (though this is not always possible, in particular in an integrated circuit where the realization of high value capacitors is practically impossible).

First question: can you explain me the highlighted sentences? I do not understand which is the problem: I have always seen Common - Source configurations with only a voltage source with its positive terminal connected to the Gate and its negative terminal (often GND) connected to the Source. I have never seen two voltage sources connected as it says; but also if I decide to do this, I do not see any problem).

Then it continues in this way

  Note that the two inputs have different DC voltage and different impedance shown on signal. Both of these situations are uncomfortable in application practice.

Second question: why?

Then it says:

  To overcome these obstacles we could think of accessing one of the two terminals of the transistor via a follower stage. The following circuit has the beneficial effect, as it is easy to verify, to bring the two inputs, Va and Vb, of the new system to the same DC value.
  The solution of adding a follower to the simple initial transistor is actually correct and effective. This configuration of transistors is typical of the input stage of operational amplifiers (OpAmp) and is usually called "differential stage". In fact, the input impedances of the two terminals have been matched to a high value (in the case of even infinite MOSFETs), making this stage ideal when both voltage signals are to be read. Note how in this case, thanks to symmetry, the follower is lost and who is the signal transistor.

Third question: can you explain me how does it work in simple words?


texts: I have a pretty good concept of Encoders and Decoders, but I can't get insight on the "Active High" keyword, and there are two enable lines which confuses me. I encountered the problem while working with a microprocessor address decoding circuit. I have an image here:


texts: How to remove this board to board connector? (Home Theater Amp)

texts:
I am trying to revive a months-dead home theater amp/audio unit (Panasonic SA-XR50) that a family member cooked after a move and was not sure what "OVERLOAD" on the front panel meant before it went off totally (he let some of the speaker leads short).

I've already spotted a few bad caps, but want to isolate the boards and see if I can get it to power up with some of them disconnected.

I've come across this lovely connector below and quite to be honest, embarrassed that I can't figure out how to remove these (properly).

I am not sure if this whole section just lifts off, I've tried moderate pulling and pushing from underneath, but no movement.

There is a sort of "cover" that I un-clipped on another similar connector, but not sure if this is part of the process...

If anybody could shed some light/advice on how to properly remove these connectors before I end up botching it up, it is greatly appreciated.

EDIT:  As per the suggetions of passerby and WhatRoughBeast I used a fine tipped screwdriver to wedge into the wire/pin... after working all pins, the wire pulled right out.


texts:
I want to replace my cargo van's lead-acid battery with a LifePO4 battery. Never used any li-ion type battery for high amp burst.
The current lead-acid is NAPA The Legend Premium Battery BCI No. 75 690 A Wet, which is 850 Cranking Amp and 690 Cold Cranking Amp. I see some 50Ah LifePO4 battery has 100-amps 30-seconds continuous output. Theoretically, it is enough to replace that lead-acid.
The other thing that puzzles me is if I need to attach a battery charger for the lifepo4 or the car's alternator is appreciated as a charger.
Has anyone had experience with it? Which capacity should I go for?


texts: Current mirrors as active loads in BJT differential amplifier, what does that mean?

texts:
I have seen current mirrors being used as current source in differential stage of an amplifier design.

The reason given is that the current mirror has a very high output impedance and behaves like an active load. I am not sure what this means.

Why do we need to use a current mirror in differential stage of an op-amp? I understand that it is to provide the same current for collectors of both transistors in the differential stage. However, I do not understand why we do this in the first place, why does current mirror have a high output impedance and what does the current mirror being used as an "active load" means here?


texts: PWM to analog RC based filter with minimum analog voltage level

texts:
I am trying to design a circuit to accomplish the following:

1) 5 V PWM signal is converted to 0 - 2.5 V analog voltage

2) The analog voltage should never drop below a certain minimum voltage level when PWM is 0 or filtered PWM signal results in a voltage level less than this minimum.

I know I can do this with a microcontroller and other ICs but I am looking for a simple solution. I've come up with the following. A voltage regulator produces 2.5 V. An n-channel FET switched by the PWM signal produces a 2.5 V PWM signal. This 2.5 V PWM signal is converted via RC filter to 0 - 2.5 V analog voltage. I also have a voltage divider to feed the minimum voltage level to the capacitor through a diode. I am aware I will need to compensate for the voltage drop over the diode.

Will this work? Any advice?


texts: Can I make a VCO full audio range with only one capacitor?

texts:
I'm trying to make a VCO with a low voltage setup (3.3V), and i 'm using a mcp6002 op-amp. I'm controlling the frequency with an MCP4822 (dac). The problem is that i get a limited range of frequencies.

I'm willing to make it full audio range (20-20000Hz) but till now I am only able to add an offset to the base frequency by using different values for the capacitor or changing resistor values. Is it possible to make it full range and my control signal to modulate the oscillator frequency to a wider range?

I have tried using this circuit but my op-amp does not oscillate with this configuration. How should I proceed to adapt this configuration for my low-voltage op-amps?


texts:
I am trying to understand hardware Caches. I have some understanding, and I would like to ask if my understanding is correct.

I understand that there are three types of cache mapping; direct, full associative and set associative.

I would like to know, is the type of mapping implemented with logic gates in hardware and specific to say some computer system and in order to change the mapping, one would be required to changed the electrical connections?

My current understanding is that in RAM, there exists a memory address to refer to each block of memory. Within a block contains words, each words contain a number of bytes. We can represent the number of options with number of bits. So for example, 4096 memory locations, each memory location contains 16 bytes. If we were to refer to each byte then 2^12*2^4 = 2^16 16 bit memory address would be required to refer to each byte.

The cache also has a memory address, valid bit, tag, and some data capable of storing a block of main memory of n words and thus m bytes. Where m = n*i (bytes per word)

For an example, direct mapping 1 block of main memory can only be at one particular memory location in cache. When the CPU requests for some data using a 16bit memory location of RAM, it checks for cache first. How does it know that this particular 16bit memory address can only be in a few places?

My thoughts are, there could be some electrical connection between every RAM address to a cache address. The 16bit address could then be split into parts, for example only compare the left 8bits with every cache memory address, then if match compare the byte bits, then tag bits then valid bit

Is my understanding correct? Thank you! Really do appreciate if someone read this long post


texts: Voltage Comparator Circuit Output 0V or 5V

texts:
I'd like to build a very simple voltage comparator circuit with the following properties:

Vs = 5V
V- = Ground
Vout = 5V if V+ >= 200mV
Vout = 0V if V+ < 200mV

I'm using this comparator: NTE943M
http://www.nteinc.com/specs/900to999/pdf/nte943.pdf

Any help is greatly appreciated.


texts:
Working with the FPGA section of the Zynq chip of the Zedboard. I want to use an external signal as clock  (in any case, the tool infers that it is a clock since I have @(posedge sclk_loopback) in the HDL).

From the forums, I see that I need to use "clock capable pins", and the JA4 and JA10 are the two available "clock capable" pins in the PMOD connectors.  However, I get this error:

[Place 30-876] Port 'sclk_loopback'  is assigned to
PACKAGE_PIN 'AA8'  which can only be used as the N
side of a differential clock input.

I can't seem to find the necessary information to follow through.  It looks like JA4 would be the positive input and JA10 the negative --- if so, do they have to be complementary signals?  or would it work if I tie JA10 to GND and then feed a clock signal through JA4?

Any pointers will be much appreciated.

Note:  the circuit does work if I override the DRC check as suggested at the end of the error message  (set_property CLOCK_DEDICATED_ROUTE FALSE...).
But it does not work reliably at the speed that I need it to work, so I suspect my next step is to fix this external clock issue.

Thanks!


texts: How to convert ( 11011.0101 ) from binary to decimal?

texts: How do we convert this binary number to decimal? I am confused about the decimal point, the one before the decimal I got (27), how about the part after the decimal point?


texts: Combining voltages sources to increase current

texts:
So I know when current is divided among parallel wires, you can combine them to one current at the ends. My question is can I combine a circuit with 3 sources in parallel to get an increase current?

I have googled, and I am hearing conflicting answers saying "yes if you add sources" but also "no, because charge does not accumulate." Can anybody give any insight.

Example of circuit I am asking about:

Does my logic follow?


texts: Exporting fabrication files (gerber) in Altium leads to wrong connections

texts:
I'm going to print my first PCB wich is a small controller, nothing complicated. I know that I need to output GERBER or GERBER-X2 files. I prefer GERBERX2 because it comes with the board outline for the manufacturer.

My problem is the following:

Here is the CAMtastic file altium produces:

But when I export that file to a Gerber file and I open it in Altium, it produces that:

I followed instruction on youtube videos for the settings. Here they are:

Then I export the CAMtastic file as gerber with those settings:

Every layer is wrong! I don't understand. Is altium corrupted?


texts: Input impedance butterworth filter with multiple feedback

texts:
I have a problem finding the input impedance of a Butterworth filter. The circuit is shown in the figure below:

I have calculated the transfer function between input and output; but now I have to find the symbolic expression of the input impedance seen from the \$V_{\text{in}}\$ generator.
I've tried a \$V_{\text{in}}/I_{\text{in}}\$ approach.
Since

$$I_{\text{in}} = \frac{(V_{\text{in}} - V_{\text{x}})}{R_1} $$

and $$ V_{\text{x}} = -V_{\text{o}}(sC_2R_2) $$

I find that
$$
Z_{\text{in}} =  \frac{R_1}{1+ W(s) sC_2R_2}
$$
Where \$W(s)\$ is the transfer function
$$
W(s) = \frac{V_{\text{o}}}{V_{\text{in}}}
$$
This sounds wrong to me, because the input impedance should decrease at high frequency, and in my case it's increasing.
Where am I wrong?
Thank for the precious help!

EDIT : I've checked it with SAPWIN, and it looks like the expression above is correct.

In the Picture there is the 1/Zin function.

Thanks to all for your help in solving the question!


texts: What is capacity in the context of scheduling algorithms in Real Time Systems?

texts:
In Real Time Systems, scheduling algorithms often speak about Capacity of a Task.

For example: In Polling Server Algorithm, the Capacity of the Server Task is lost when there are no aperiodic Tasks. Or, in Sporadic Server Algorithm, the Capacity of the Server Task is replenished only after it has been consumed.

Now the basic understanding is that Capacity is the amount of CPU that can be used by a particular task. It looks quite simple.

But, in case of Polling Server Algorithm, if there are no aperiodic tasks present when server is active, why is the Capacity of the Server Task lost? And once its lost, even if an aperiodic task does arrive in that period and there is CPU resource available, the Server Task cannot execute the aperiodic task because "It simply does not have the capacity".

In the above example, at time instance 1, the Server loses capacity. At time instance 2, an Aperiodic Task arrives. Since the Server has no capacity, it cannot execute the aperiodic task. And also, at time instance 3, CPU is idle which is a waste of resource. We can see that in time period 0-5, the Server could not execute the aperiodic task arriving at time instance 2 because it lost its Capacity at time instance 1.

So in the period 0-5 the Server executes nothing even though it earlier had a capacity of 2.

Is this Capaciy just a concept used in scheduling algorithms?

If not, how can "Losing Capacity" be explained?

And, how is Capacity implemented (in hardware/software), that is, who keeps a record of Capacity.

All terms as used in the book Hard Real-Time Computing Systems - Giorgio C. Buttazzo


texts: How do I limit the current supplied to a boost converter

texts:
I have a power supply that can supply up to 20 amps at 12 volts,  I want to give a boost converter a maximum of 4 amps.  I tried using a 3 ohm resistor but the resistor burned up.  I want to use the power from the boost converter to do anything I need include being able to short the leads without the fuse on the boost converter frying.

DROK® 150W DC Boost Converter Power Transformer Module Voltage Regulator Board


texts: How do I find the transfer function of this op amp circuit?

texts:
This is a phase detector circuit used in PLL, the inverting input is a sinewave and there is a reference signal which is a square wave.
How would the output look like if the inputs are in phase and out of phase?


texts: Long term voltage change - analog voltmeter, op-amps and logarithmic scale

texts:
I want to display one minute voltage change on analog voltmeter.

Voltage change: from -0.5V/min to +0.5V/min.

My analog voltmeter has 0-10V scale (I will replace it with homemade printed scale).

I don't want to use any microcontroller, PWM etc.

I want to learn how to do it by using op-amps and single supply.

In future - I want to scale it logarithmically (-0.5, -0.05, -0.005, 0, +0.005, +0.05, +0.5), but for now - let's assume that I need just linear delta-V read.

WHAT I KNOW FOR NOW

I know that I need active differentiator block. I can use formula from Wikipedia, find resistor and capacitor value. After that block I can use some non-inverting block to amplify voltage to desired range and add 5V with summing amplifier block to have 0V/min at the center of my voltmeter scale.

WHAT IS MY PROBLEM

My problem is single supply. When voltage change will be negative - I guess single supply op-amp will not work properly.

How can I deal with that?

BACKGROUND

Long time ago I was bored and I built custom thermometer that measures water temperature at the output pipe of old central heating furnace. It is supposed to inform me about temperature and temperature change. I can see how fast temperature is rising or dropping, and I can estimate when I should go to basement and put some logs or coal into furnace.

There is analog LM35 temperature to voltage converter (linear, 10mV/°C), microcontroller with 10-bit ADC with high oversampling and low pass filter at input.

Display looks like this:

I realize that 0.01°C resolution for temperature read is huge overkill and my thermometer acurracy is about +/- 1°C, so please don't comment that.

Now I want to build analog version of this and use two analog voltmeters similar to this:

One will show temperature, another temperature change.


texts: voltage of input(+5V) is greater than the supply(+3.3V) provided for 74HC245 buffer

texts:
In my design I am using 74HC245 buffers between a input signal of +5v and controller pins of +3.3V. What is the supply value I have to use for buffer (74HC245). I want to use +3.3V as the supply, but in data sheet it is mentioned that maximum VIH is Vcc. Please suggest me what happens if I provide +3.3V as supply voltage and feed input pins +5V?.
I am providing the link for buffer data sheet below.

http://www.nxp.com/documents/data_sheet/74HC_HCT245.pdf

Thanks in advance


texts: How to find the state-variable equations from the signal flow graph of the system?

texts: How to find the state-variable equations, i.e, the state equation & the output equation for the system described by the signal flow graph below?


texts: How to provide a 5 volt rail from 24 volt source

texts:
Edit: Added practical observations at bottom.

I need to provide power to an ESP8266 12E NodeMCU board, and my "raw" power is a 24 volt "wall-wart" PSU. My first thought was just to use a 7805 with a heatsink, but I have doubts about the suitability of this.

The current drain for the ESP device has been measured as about 80 mA under "normal" conditions, but with a peak during startup of 350 mA. It's not clear to me how long this startup current persists, but the "boot time" of a typical program from power up is less than a second.

So, the peak power dissipation seems to be (24-5)*0.35 or close to 6.5 Watts. If I read the data sheet correctly a 10C/W heatsink will support this (continuously) up to an ambient closing in on 50C (I live in Colorado, so in the Summer that's "good enough" but not plenty). I have, on hand, some no-brand extruded aluminum heatsinks that are just a little wider and taller than the TO-220 package, and have four fins on them that are perhaps 1/4" deep. They look similar to things that actually do claim to be 10C/W.

As a side note, I need the 24 volts for other things in this particular project, so getting a lower input voltage isn't an option in this case.
ed
So I have three questions:

Am I missing something obvious that might be a better way of doing this?

Is my interpretation of the data sheet close enough to correct?

Does my heatsink seem adequate?

Edit:

Well, given that I had the parts to proceed with a 7805 on hand, and the buck-converter (I admit I'd never heard that term before, but it seems to be what I have called a "switch-mode", yes?) won't show up for a day or two, plus the observation that sometimes these switch-mode devices might not always be totally happy/stable at very low output current, I went ahead and constructed the proposed configuration.

With the heatsink in place, with no insulating layer, but also with no thermal grease, and the CPU doing some very minor ticking over, the heatsink warmed up fairly substantially, in a few minutes, it was running around 110~120F based on an infrared thermometer. Of course, that's the "outside" temperature, so I have to assume the silicon inside is running quite a bit hotter.

From this, I conclude a few things, first that the heatsink I have probably isn't as good as I'd hoped (though it's also not nothing). Second, that for this much drop, the proposal to use one of these buck converters is clearly far more satisfactory. I built my (strip/vero) board layout so that I can jumper the 24v supply off the 7805, and instead put the new converter between the two. That way, I'll still have the low-current-stable linear regulator, but be feeding it with perhaps 7.5v instead of 24.

Bottom line, not such a good plan to try to drop this much voltage, even at very low current over a 7805 (nor, presumably, it's siblings).

Appreciate all the input.


texts: Can the same address lines be used for multiple multiplexers?

texts:
I am connecting three demuxs and one mux to an arduino to be able to communicate with multiple ADCs. As there are many signals that need to go from the arduino to these 6 ADCs, I was thinking of using multiplexers and demultiplexers to get the work done but I wanted to know if setting the same digital outputs (D4,D5,D6 as per the image) of the arduino to be set as the selector inputs (S0,S1,S2) for all the mux/demuxes would be OK.

The arrangement would look like this:

Consider START/RESET/CS/DRDY all as digital IO pins of the arduino. It seems like in theory this should work but I just wanted to confirm.


texts: I want to create a strobe light with an LED strip, so I can use a DSLR with a longer shutter time to measure the speed of a plastic bb accurately (distance between the 2 images divided by the frequency). I was thinking of using an LED strip and a MOSFET to drive it, using a microcontroller to control the frequency and on/off times. The thing I was wondering about is if I need a special kind of power supply to handle the fast on-off switching (I'm thinking of on-times in the order of 20-40 μs to get accurate enough measurements) or if I will be fine with one of those multi-purpose 12V 2A DC supplies.


texts:
I am driving dc motor with drv8848. I send pwm pulse to the drv8848 and then ı read encoder value. My pwm frequency is 500 Hz. So here is my problem, pulse count is same but encoder value is different. I don't expect to be same. But difference is very big. For example one time I send same pulse count, encoder value is 4 um but in other same pulse count encoder value is 15 um. So can you help me about this problem ?
thanks


texts: I am trying to find an example of BJT current mirror with high power consumption. Any advice concerning the setup , or an example design will be appreciated.


texts: Calculation of 3-phase power in Electric Vehicle Charging

texts:
I have a doubt regarding calculation of 3-phase power in EV charging. On the last page of the pdf in the link given below, the power calculation is done as 3 x 230V x 16A = 22kW.

http://www3.fronius.com/cps/rde/xbcr/SID-673FE905-375C8296/fronius_australia/Why_three_phase____An_overview_of_the_benefits_of_a_three_phase_network_1195856_snapshot.pdf

However, I don't understand why is it not √3 x 230V x 16A or 400V x 16A instead. Can somebody explain the calculations with the reason for the same?


texts: Oscilloscope: trigger and multiple periods of the signal

texts:
I am trying to understands the basics of an analog oscilloscope trigger. As stated here,

Instead of collecting a single snapshot of the input signal, an
oscilloscope repeatedly updates the display with newly collected
snapshots. Each snapshot is called a trace.

The trigger is used to not overlap the successive traces of the signal on the screen.
Each trace begins when a trigger event occurs: that is, when the signal has a specific slope (positive or negative) and a specific voltage level. If I understood correctly, the trace begins each time a trigger event occurs. However, this would imply that the oscilloscope can show in its display just one period of the signal. Instead, there is plenty of images of oscilloscope displays, using the trigger, with multiple periods of the signal.
For example, from this page:

It seems that in all these examples the trigger is ignored for an arbitrary number of periods after the trigger event.
How is it possible? Isn't this a contradiction?

Edit:

The trigger is used to not overlap the successive traces of the signal
on the screen.

Sorry, I was meaning exactly the opposite. One of the answers points this out.


texts: How to check PIC system clock speed MCU?

texts:
The entire project depends on this, so I just want to make sure I have it right.  I'm using a 20MHz external resonator and putting that through the PLL in hopes of getting an F_SYS = 120MHz.  Without having to get into the math on a timer, I thought the simplest way to check the system frequency would be to toggle a GPIO pin every 1000 iterations or so but the frequency of the toggle on an o-scope makes no sense.  I see 175Hz for two toggles every ~10000 instructions (or 7MHz?).  What is the real way to validate what comes out of the PLL?:

int16_t main(void) {
  uint32_t i = 0;
  ConfigureOscillator();
  _TRISB5 = 0; _RB5 = 0;

  while (1) {
    i++;
    if (i > 10000) {
      i = 0;
      _RB5 ^= 1;
    }
  }

  return 0;
}

void ConfigureOscillator(void) {
  // Disable the Watch Dog Timer
  RCONbits.SWDTEN = 0;

  // Assume the internal oscillator has come up

  // Configure PLL factors
  PLLFBDbits.PLLDIV = 70;
  CLKDIVbits.PLLPRE = 4;
  CLKDIVbits.PLLPOST = 0;

  // Initiate Clock Switch to Primary Oscillator with PLL
  __builtin_write_OSCCONH(0x03);  // Set OSCCONH for clock switch
  __builtin_write_OSCCONL(OSCCON | 0x01);  // Start clock switching

  // Block until the clock switch has completed
  while (0b011 != OSCCONbits.COSC);

  // Block until the PLL has locked
  while (1 != OSCCONbits.LOCK);
}

Generated configuration bits if you care to look:

// FICD
#pragma config ICS = PGD1               // ICD Communication Channel Select bits (Communicate on PGEC1 and PGED1)
#pragma config JTAGEN = OFF             // JTAG Enable bit (JTAG is disabled)

// FPOR
#pragma config ALTI2C1 = OFF            // Alternate I2C1 pins (I2C1 mapped to SDA1/SCL1 pins)
#pragma config ALTI2C2 = OFF            // Alternate I2C2 pins (I2C2 mapped to SDA2/SCL2 pins)
#pragma config WDTWIN = WIN25           // Watchdog Window Select bits (WDT Window is 25% of WDT period)

// FWDT
#pragma config WDTPOST = PS32768        // Watchdog Timer Postscaler bits (1:32,768)
#pragma config WDTPRE = PR128           // Watchdog Timer Prescaler bit (1:128)
#pragma config PLLKEN = OFF             // PLL Lock Enable bit (Clock switch will not wait for the PLL lock signal.)
#pragma config WINDIS = OFF             // Watchdog Timer Window Enable bit (Watchdog Timer in Non-Window mode)
#pragma config FWDTEN = OFF             // Watchdog Timer Enable bit (Watchdog timer enabled/disabled by user software)

// FOSC
#pragma config POSCMD = HS              // Primary Oscillator Mode Select bits (HS Crystal Oscillator Mode)
#pragma config OSCIOFNC = OFF           // OSC2 Pin Function bit (OSC2 is clock output)
#pragma config IOL1WAY = OFF            // Peripheral pin select configuration (Allow multiple reconfigurations)
#pragma config FCKSM = CSECMD           // Clock Switching Mode bits (Clock switching is enabled,Fail-safe Clock Monitor is disabled)

// FOSCSEL
#pragma config FNOSC = PRIPLL           // Oscillator Source Selection (Primary Oscillator with PLL module (XT + PLL, HS + PLL, EC + PLL))
#pragma config PWMLOCK = ON             // PWM Lock Enable bit (Certain PWM registers may only be written after key sequence)
#pragma config IESO = ON                // Two-speed Oscillator Start-up Enable bit (Start up device with FRC, then switch to user-selected oscillator source)

// FGS
#pragma config GWRP = OFF               // General Segment Write-Protect bit (General Segment may be written)
#pragma config GCP = OFF                // General Segment Code-Protect bit (General Segment Code protect is Disabled)


texts:
I am putting a 50W 3.4A max 12V solar panel on my camper van. I want the option of removing it from my roof racks & mounting it remotely (so I can park in shade, but still have the panel in the sun).

I am planning on just putting a replacement extension cord socket on the two MC4 leads, and then cutting the socket off of an extension cord (16 gauge) & wiring that to the charge controller, then running 2 wires (16 gauge) to the battery.

My question is since usually the total wire length will be around 6-7' can I use 16 gauge wire and then use a 14 gauge extension cord for when I want the panel remote or do I need everything to be 14 gauge (planning on 25-30' extension cord)?


texts: NPN Transistor Parameter Determination Gain Question

texts:
In the interest of making an oscillator, I made the above circuit after reading about gain, current flow, active region, and how an NPN transistor works.

I then put the circuit in LTSpice and note the input and output voltages.

The input is in blue, the output is in green.

I see that there is gain.  For the oscillator, where all I think I need is some amout of positive gain, this should probably work.  I then started thinking about microphoens and speakers and how to dial in an exact amount of gain given a mic.

So, my question is this, lets say I have a signal that oscillates += .005 volts and I want it amplified to swing between +9 volts and 0 volts, what equations would get me the appropriate resistor values.  I would set the middle of the active region to be Vcc/2 as a Vce reference.  This would be 4.5 volts.  How do I best determine the resistors to get to this level?

Lets say, I then change the input swing between += .2, how do I reset the resistors to get to the appropriate swings in the output region?

When I say swing, I mean above and below a DC bias voltage on the base.

I feel I should be able to adjust this to exactly to whats needed by choosing the appropriate values of resistors.  Thanks, Jeff


texts: Transistor analysis, how can I find the currents?

texts:
I am struggling with the currents and their directions.

Here you can see the simple circuit part.

Since Vth(EBJ)= 0.7, Vth(CBJ)= 0.7

I could calculate the VCE by V(CBJ)-V(EBJ)= Vc-Vb - (Ve-Vb) = Vc-Ve = V(CE)= 0.2.

The thing I cannot understand is emitter current value of Q1 (Ie1) and base current of Q2 (Ib2).

We know the +10Volts, V(CE)=0.2 but I cannot still find the currents properly (especially when the base current of Q2 and collector current of Q1 meet.) Can you please help me to understand the logic?


texts: controller circuit for charging 12V 7AH Lead Acid battery from main source and Solar source

texts:
I need to have a controller for charging a 12V 7AH battery and provide uninterrupted supply.

The source for charging would be 12VDC from a PSU or if there is a failure in that from a solar panel.  I am confused , I found a few such solutions for lipo batteries but cannot find for lead acid batteries. I want to have auto charging and cutoff on full charge.

There are some ICs that provide solution for solar but they have no support for the other source.


texts: Maximum Allowed Radiated Continous Wave Power in 61.25GHz ISM Band

texts:
I am looking into a possibility for 60GHz energy harvesting for low power sensor nodes and I am little confused about the differences I have found between the US and European regulations related to 60GHz RF output power. FCC states in II/4.  that 40dBm average EIRP is allowed. On the other hand ETSI makes difference between indoor and outdoor values, and also specifies the maximum power density. These lead to very different rules for two big markets, which I find confusing.
ETSI allows the same 40dBm for indoor communication, but allows only 13, and -2 dBm/MHz spectral power density for indoors and outdoors respectively. This is equivalent to 27dB and 42dB lower power for a continuous wave, and makes energy transfer infeasible in Europe. Here of course I've assumed that the ETSI standard is applied across Europe.
A third value - without reference - was 20dBm EIRP, stated in this paper, which increased my confusion further.
One question is whether my understanding above is correct, and such difference exists in the regulations, or I did not found some other regulation which extends or overwrites those above. And the related other one is: What is the allowed maximal output power, or EIRP in the US and in the EU for a continuous wave?
The references:

Revision of Part 15 of the Commission’s Rules Regarding Operation in the 57-64 GHz Band, Federal Communications Commission (FCC) Std., Aug. 2013.

Broadband Radio Access Networks (BRAN);60 GHz Multiple-Gigabit WAS/RLAN Systems; Harmonized EN covering the essential requirements of article 3.2 of the R&TTE Directive, European Telecommunications Standards Institute (ETSI) Std. EN 302 567, Rev. 1.1.0, 2009.

C. Bredendiek, D. A. Funke, J. Schopfel, V. Kloubert, B. Welp, K. Aufinger, and N. Pohl, “A 61-GHz SiGe Transceiver Frontend for Energy and Data Transmission of Passive RFID Single-Chip Tags With Integrated Antennas,” IEEE J. Solid-State Circuits, vol. 53, no. 9, pp. 2441–2453, 2018.


texts: two-port networks with voltage sources connected on ends

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Suppose we have a two-port network. Then, we connect voltage sources V1 and V2 to the left and right end. For the transmission parameters, t11=V1/V2, then could one use the voltages given by the voltages sources and not care about the network? That doesn't make sense to me, and one should use the actual network to determine t11 (and all the other parameters), however I am not sure. Could someone shed light on this confusion?
Thanks


texts: What is the correct way to block current going into a solar panel from battery

texts: I have a 6v 750mA solar cell that I am using to charge a couple of panasonic 18650 3400mAh 3.7v batteries.  I have the positive from the solar going through a 1N4007 diode (cathode side toward the battery) then to the positive side of the batteries.  I have the negative side going to the negative side of the batteries.  I do not want any of the current from the batteries to go back to the solar panel from the batteries at night so I installed the 1N4007.  However I just read the 1N4007 is only good for about 1A.  Is this an ok diode to use of should I use something else.


texts: I need to use some sort of component to boil water inside of a container that will be triggered by an arduino signal. How?

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I'm trying to build a prototype for my own coffee machine. It'll have a container of water that will need to be boiled when a signal is sent by my arduino. The question is, what component should I use to handle this?

This is for a hackathon this upcoming weekend, so I don't mind it looking incredibly terrible. Some have recommended that I simply run a kettle through a relay controlled by an arduino, but my problem with that is I need the water to be inside a container that I'll be making, as it will need to be connected to some sort of stand. I was thinking I could take the kettle apart and isolate its heating element. Would this be ideal, or is there some component out there that will handle this?

Any suggestions and/or advice would be very much appreciated.

EDIT: An idea - What if I just connected a fully assembled kettle to a fuse, and used some sort of "pump" to retrieve the water in it? rather than creating my own container with a heating element that I would be able to drain with by opening a flap at the bottom.


texts: How to fix noise from resetting my micro

texts:
I'm working on a project that has a micro-controller controlling a servo(it's battery powered so its not an issue with it's local power supply), it's connected to a control panel about 3m away with 3 long wires. The wires are open signal, close signal and ground. The panel simply has two relays that switch open or close between 5v and GND. Everything works nicely but when a large linear power supply in the control box is switched on it causes the controller to do strange things like close and then open the servo. We figured that the 3 wires are acting as an antenna and picking up the inductive spike from turning the psu on(we even ran the signal 5v and ground from a battery in the control panel to isolate the circuit so it's definitely the wires that are picking up the noise)

Originally I was not sure if it was a spike on the close line that was causing the weirdness so we disconnected the open and close wires and just left the ground wire connected, same problem. I also confirmed this on my 'scope and during switching there are no spikes on the open or close lines during switching. Thus I have come to the conclusion that it is common mode noise on the lines that is causing the problem, as even when it is only the GND wire connected the spike causes GND to float up momentarily and reset/mess with the micro?

My solution that I'm going to try next is to add some opto-couplers on the inputs so that the two electrical systems can be completely isolated. I also want to add a common mode choke on the three wires as this should damp the noise? Can anyone suggest how I would go about choosing a choke and/or any other suggestions on how to noise proof this micro?


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I am trying to create a polygon in my pcb in altium. At first I thought it didn't create a polygon at all, but now I realized it is creating it, but only outside of the board. The polygon inside of the board does not exist. I tried to define a keep out layer to circumvent this, but it did not work. Any ideas?
Thank you


texts: How is the internal pullup resistor in a microcontroller wired?

texts:
I am constructing a circuit where 2 microcontrollers will communicate with a high or low state on their IO pin. Basicly a state pin for Bluetooth connected, or not. One microcontroller will have an IO pin as an output and the other an IO pin as an input. I know my microcontroller has an internal pull up (also pull down) resistor, but how does this circuit look like? Below is how I want to connect it, for sure I shouldn't need to have resistors when there are internal ones, right?

simulate this circuit – Schematic created using CircuitLab

So my real question is how does the internal pull up/down resistors look in the microcontroller? Is it like this?

simulate this circuit