texts:
What happened:

Two of the blue wires touched while an 11.1v battery was hooked up and POP

What's in the photo:

Yellow is the heat shrink wrapper I cut open
the material with square impressions on it from the ICs is the heat sink
My fingers are holding apart the heat shrink so you can see the burn
The burn is from the damage of the two blue wires connecting.
the PCB is flipped upside down so you can see the spot where the burn came from

It looks like the lowest left IC is a little melty on top so I'm thinking something fried in there. How do I check if that's bad? I have a multimeter and I'm prepared to use it I'm just not sure what to do.

EXTRA

This is an Electric Speed Controller for a brushless motor. The motor was spinning when two uncovered bullet connectors (from the blue wire side) touched and made a spark. After that the motor wouldn't spin it would just spaz out, acting like only 2/3 wires were working (understandably so).


texts: Verilog :Range must be bounded by constant expression

texts:
I have one doubt.....  The error is came like Range must be bounded by constant expression when Compile the below line
X=in[i+2 : i] +1'b1;
In[i]=-1;
Please tell how to resolve it?


texts: Strange I2C behavior: sometime it works, some time it doesn't

texts:
I am using Arduino Ethernet with PoE and Arduino Uno boards. In recent days I implemented a working I2C bus by using the Wire library and all it seemed almost to work: the two boards was communicating correctly, except in some cases.

Until yesterday I2C bus was working, now it doesn't. I didn't changed the physical location of any wire or sketch code: I just started the PC in order to give power to boards, and the communication over the I2C bus just stop working. Then, after a bit and some "reset" / "sketch re-upload" (note: I didn't changed any sketch code), it started to work again.

It is not the first time that this situation happens, and I am in trouble to catch the exact problem.

What could be the problem?


texts: Circuit to discharge capacitor after opening the circuit

texts:
I apologize upfront for another dumb newbie question (I'm in the beginning of learning circuitry).

I have a schematic like this in mind (disregard the specific nominal values of the components for now, please).
It works okay in simulators.

But I suspect the capacitor is going to stay charged even after the circuit is open (the switch is 'off').

So that next time the circuit it closed again the LED's blink will be way shorter (if any).

I had an idea I could discharge the capacitor if I 'short circuit' it to the batter after the switch is off (using some kind of transistor trick).

Then I read the capacitor can only be discharged when it's 'shorted' to itself, so that the electric potential on it becomes 0.

Do you think you might suggest a solution for the capacitor discharge after the circuit is open?

P.S. I apologize again if the terminology used is not absolutely correct or something is unclear. I will try to clarify if you ask.


texts: How to select a proper crystal oscillator and load capacitor for BNO055 IMU?

texts:
I am using BNO055 chip for custom PCB module

I could not find a proper crystal oscillator for this ic for the given spec in the datasheet.

datasheet mention only 32.768Khz crystal oscillator with 22pF load capacitors


texts: How does oversampling improve the measurement precision?

texts:
Regarding improving the precision of a measurement, I have heard that a measurement precision can be improved by filtering or oversampling.

When I think of filtering I can make sense because filtering reduces outlier measurement points and noise amplitude so it is easy to see that it reduces the spread around the mean value of our measurement. Less fluctuation results as narrower standard deviation hence better precision.

But I couldn't come to a similar qualitative understanding regarding oversampling resulting better precision. How could this be explained?


texts: Does the Arduino have any specific cooling requirements?

texts: If I were to encase my Arduino in a sealed case with no ventilation, would this be an issue? What about if I were to pot the Arduino in epoxy, would that pose a cooling issue?


texts: How to get an output voltage of 16 Vpk on my preamplifier

texts: I'm trying to vary the resistors here in my preamplifier so that I would get a 16 Vpk output voltage, but as you can see here the output voltage is currently 0.209 V. Can someone please help me find the right resistor values to make an output voltage of 16 Vpk?


texts:
While learning about two stage CMOS operational amplifier it is mentioned that the there is a phase shift of about -90 degrees so is there always a phase shift between an input and output signal?
and when we make a oscillator why dont we take this phase shift in consideration as we want the the total phase shift to be 360 to meet barkhausen criteria?

For this configuration it is also mentioned that we should take second pole value beyond the bandwidth value in order to avoid get oscillations that is meeting barkhausen criteria how is it possible?


texts:
While studying I ended up finding this question.

Write the value (in hex) of the P1 after the execution of the code below.

unsigned char var;
P1 = 0xff;
var = P1;
var = ~var;
P1 = var;
P1_0 = 1;
P1_4 = 0;

Consider P1 as Open Drain with Weak Pullups.

I tried to answer the question, but I'm not sure of my answer. Can anyone help me?

My approach to solve the question.

First I analyzed the code and I saw that the P1 output would be 0x01.

And then I analyzed the hardware.

P1.0 is High.
P1.1 is Low.
P1.2 is High.
P1.3 is High.
P1.4 is Low
P1.5 is High
P1.6 is Low
P1.7 is Low.

It would lead to a output of  0x2D (0b0010 1101).

My doubt is.

In the code P1.0 is set to 1, and in the hardware is connect to 1 (High). I believe that P1.0 is going to be 1. Therefore the answer is 0x2D.

But what if we have something like, by code PX is set to 1 but it's hard-wired to GND. I learned that open-drain port configuration work as a di-directional port, working as an output and an input, but I didn't get what happens when he have a mismatch (trying to set a ouput, where would be a input).


texts:
I make a small solar energy harvester. I'm searching for the type of diode with lowest drop voltage. Any suggestion for the type of diode for me ?

Thank you


texts:
I am working on a project which requires a dozen VL53l0X I2C-TOF sensors to be polled by one master MCU over a few meters of cable.
Thus, I decided to accompany each TOF by an Atmega8 acting as a gateway between the TOF and a Modbus (using a MAX485), which is managed by an ESP32 (the master). Since I require fairly low latency (~10 reads / sensor / second) I am a bit disappointed by the Modbus RTU performance (mostly caused by the forced 1.75ms delay between frames).
My question: Is there any quicker, more suitable, Atmega-bearable bus protocol for long distances? Ethernet is sadly not an option due to the limited slaves computing power and cost...


texts: Not sure how to go from PID error to PWM duty

texts:
I am trying to learn the basics of PID. I have made a contraption to try to implement a PID controller.

I am not using carbon fiber, but rather a chopstick.

So I am controlling the speed of the propeller with a PWM signal through a mosfet from an STM32. I think 14Khz...Dont recall what frequency I set it to.
My counter control register which controls my duty cycle can vary from 0 to 1000.

I am reading the pot value through the an ADC channel.

In my attempt to implement one control method at a time. P then I then D
I never got past P because I dont know what to do with the value I get.

For example,  Let say my chopstick is level (parallel to floor) at an ADC value of 2000. and I currently read 1200 then my error is 800.
According to PID literature this gets multiplied by a gain. lets say the gain is .5 So now my P value is 400.
But what do i Do with that?
I cant set the PWM CCR to 400 that is too low a duty cycle and it will drop even more.

So that is my issue how do I translate the value to something useful.

All I am doing right now is that if my error is grater than zero then
PWM = PWM - 1;
and vice versa for error less than zero
Obviously it works really slow because I am using the value of 1 but this is NOT proportional control. At least i dont think it is.

EDit: I think has to do with my issue.

SO Like I said in the comments I can get it to work (sort of) so long as when i disturb it I dont make it go above a certain point, otherwise It will fly all the way vertical have a huge error and then drop have another huge error and just keep going and going. And god forbid I try to make a target point that is above 0 deg that stays put for a few seconds and then oscillates again. I just think the complexity of this system requires more then the simple PID tutorials you see everywhere involving speed control of a motor. I would follow the edx course on this but I dont understand the math and their notations. No real number examples or anything. I do not learn well just seeing  bunch of variables and no real world examples.


texts: Why is 50ohm sometimes used as a differential impedance?

texts:
I'm creating a design where I convert an RF single-ended signal to a differential signal with a 5400BL15B050E RF balun that is then fed to a ADL5802 RF mixer. The balun datasheet specifies the single ended characteristic impedance should be matched to \$50\,\Omega\$ and the differential balanced impedance should also be matched to \$50\,\Omega\$. Why would the balun choose a balanced differential impedance of \$50\,\Omega\$ and not \$100\,\Omega\$? Practically, this means that my differential microstrip traces need to be much wider than the single-ended traces (in my case almost 3x as wide). This makes routing trickier since (at least for my PCB stackup) the trace width is larger than the mixer pin spacing, and so I need to add tapering to make all the connections. Would it not have been more sensible to have the differential impedance be \$100\,\Omega\$ so that the balanced trace widths could be roughly the same as the single-ended ones?

Is there a reason why \$50\,\Omega\$ makes sense here?

Edit

Prompted by pericynthion's comment below, I'd also be interested to know why the mixer would use a \$50\,\Omega\$ differential impedance.


texts: Why isn't the signal from the electret microphone being transmitted properly to the speaker in this circuit (see picture)?

texts:
I'm a novice. I'm trying to communicate wirelessly between an electret microphone and a speaker using HC-12 modules. What I have set up in the picture below works in the sense that a signal is sent to the speaker when I blow hard enough on the electret microphone, seemingly indicating that everything may in fact be wired correctly. However, the speaker just makes a deep buzzing noise that doesn't at all resemble the sounds that go into the microphone.

You can see in the picture that I'm using two amplifier modules - one for the transmitter and one for the receiver. I'm powering the transmitter with a rechargeable 9V battery and the receiver with 3 rechargeable AA batteries (~3.8 V).

I've verified that the HC-12 modules being used work independently. I've also verified that the microphone, amplifiers, and speaker work (when connected via wires, audio signal is transmitted just fine from the microphone to the amplifier to the speaker).

Can someone help me to identify what I'm missing?


texts:
I have a battery operated device with an old B&W LCD in it. I'm tapping to the display bus and would like to input it into an FPGA for some processing.

The bus includes vertical and horizontal sync. pulses, some pixel data and a clock at about 4 MHz. I connected the bus ground of the portable device to the FPGA dev. board ground using what I think is a good quality connection (soldered) and reassured under 1 Ohm using my handheld DMM.

To make things further complicated the data comes out of the device in 5V and I scale it down to 3.3V using a voltage divider (10K-20K).

When viewing the signal using a scope I can the signal is actually 1.7 Vppk + it does not "start" at 0 V but at about -0.5 V. The voltage can be explained by loading the bus because it has the original LCD hooked up + the FPGA + scope is parallel. However what's up with the signal being negative in part?

I need to come up with a way to buffer the signal to give it better drive capability. What comes to mind is some form of logic gates like inverters (2 in series) or something similar.

Does anyone has a better suggestion + an idea what is going on with the negative voltage?


texts:
I would like to use a MOSFET as a switch in a circuit but I can't find any with a threshold voltage of 10v or 12v. Why is this uncommon?

As information, There is less than 1mA needed to go through it. I just don't want it on if its less than 10V on the gate.

Almost everything I see has a Vgs(th) of 1-4 volts.

EDIT*** Here is my circuit

I'm trying to delay the voltage to the gate by 2ms or more so that the LED won't light for that amount of time.


texts: FreqMult in ADS with harmonic balance simulation

texts:
I need to know why the output of the FreqMult component is not correct in this simulation. As you can see the difference between my input frequencies is not (87Mhz) multiplied correctly( I can't see (X3) 261 or (X5)435 Mhz frequencies).
In addition: I have set G1=G2=G3=G5=-20 or different values (in the uploaded ADS files these values are not inserted)

here is my ADS simulation file:
enter link description here


texts: Distance between 2 objects (up to 75 cm), independent of angle

texts:
Which sensor type or measurement principle (magnetic, ultrasound, time of flight...) would best fit the following requirements (i.e. worth trying first)? I am asking because while reading I got confused about inherent physical/methodological vs. just model properties regarding resolution, beam width/angle etc. An answer would be e.g. a summary of sensor types (magnetic, ultrasound...) in terms of typical data regarding "beam" angles and meaningful working distance ranges for a precision of < 2 cm, or a creative idea that solves the problem.

The purpose is to measure the distance (range: about 0 - 75 cm, precision < 2 cm) between two objects (blue and purple circle), which are moving? Important:

it should not rely on direction/rotation (i.e. the objects can turn in 3D space, each up to about +/- 60°, curved gray angle in figure).
stability over time is much more important than absolute precision. I can live with a stable error of few centimeters, but there should be little drift.

(The initial offset and further difference caused by turning the surface-mounted sensor(s) does not matter.)

As an example, think of your hands moving around in 3D space, and I am intersted in the distance (not necessarily the exact x/y/z position), and whether the movements and the minimal distance become larger or smaller over time (minutes to hours).

Technical limitations: Sampling rate should be in the range of milliseconds (> 20/s if possible).
Ideally (but not as an absolute requirement), the measurement would not be affected by an optical barrier such as clothes.
It should all be wearable at least in a reserach context (i.e. few centimeters, wireless, data can be stored transferrd for analysis in the evening), e.g. operated by a small Arduino with SD card.

So far, I looked at magnetic, ultrasound and optic sensors, but I am afraidf that they would depend too much on the angle between objects. The only suggestion I found so far was to use multiple sensors in a circular shape as workaround (by A. Gosh) (which would make it more complicated), and to use some 3D rectangular sender/receiver coils (I don't even understand what I should google for to learn more or buy them - happy for recommendations). Maybe a magnetic sensor/Hall effect sensor would work, if a more or less circular homogemous magnetic field could be achieved by a small but strong magnet? I am happy for ideas.

I want to distinguish the following: green vs brown movement curves are from 2 subjects, one (brown) with constant fluctuations, one (green) with also fluctuating, but increasing distance):


texts:
entity hex_kp is
    Port (
      coloumn : in  STD_LOGIC_VECTOR (3 downto 0);
      sevenseg : out  STD_LOGIC_VECTOR (7 downto 0);
      ca : out  STD_LOGIC_VECTOR (3 downto 0)
    );
end hex_kp;

architecture Behavioral of hex_kp is
  signal row: std_logic_vector(3 downto 0);

  process(row, column)
  begin
    ca <="0111";
    if(row = "0111") then
      case coloumn is
        when "0111" =>
          sevenseg <= "00000110";
        when "1011" =>
          sevenseg <= "01011011";
        when "1101" =>
          sevenseg <= "01001111";
        when "1110" =>
          sevenseg <= "01110001";
        when others =>
          sevenseg <= (others => '0');
      end case;
    end if;

This is one part of my VHDL code to interface keypad with Basys2. However it gives error to process(row, coloumn) part. When I exclude it it gives error to if (row = "0111") part. First I wrote row as an output but then I changed it to signal. Same errors occur in the situation row as an output. I can't see my mistake. Can anyone help?


texts: Why are the ground and neutral bonded in my panel?

texts: I took a look inside my panel today and saw a big green wire connected to the neutral bus bar. Why are these two bonded together? Why not just send the neutral back where it came from? Where does the neutral line go once it leaves my house? Are the neutral and ground also bonded at the electric meter?


texts: Strange behaviour of a LED bulb via SSR Relay: it's EMI?

texts:
I've just discovered a strange behaviour of a LED bulb (E27, 220v/AC) that I'm currently turning on/off via an 8-channel SSR relay. Such a relay module is powered with a switching power-supply, powering both the relay-module and an Arduino MEGA 2560.
I also have a wall-push-button connected to an INPUT_PULLUP PIN of Arduino (one side) and to GND (the other side). Another OUTPUT PIN of Arduino is connected to the first channel of the SSR relay module (to handle the SSR connected to the LED bulb).

As for Arduino, I choose to power it trough the Vin.

As for GNDs, both Arduino and the relay module get the GND from the power-supply.

A very rough schema is reported below (please, don't blame me for missing details. As for the driller, please ignore it for a moment!):

Such infrasctructure worked flawlessy for weeks, being powered on and correctly responding to push-button clicks without any issues.

Recently I needed to make an hole to a wall, actually a couple of meters away from the LED bulb, and at least 5/7 meters away from Arduino (Arduino, the relay module and the power-supply are located close to each other, in a box, under a staircase).

To make the hole I used an AC-powered driller (not a battery-powered one). Actually, it's exactly the driller you can see in the image above).

What happened was that.... the LED bulb "flashed", with a real quick "turn_on"/"turn_off" cicle. A single quick cicle.

This phonomena seems to be related to the "start" of the driller engine, more or less when the brushes inside the driller fires up some sparks (BTW: I'm supposing my driller is using brushes, inside).

I've spent some time investigating EMI, as electrical motors are known to be source of EMIs.

What I learnt so far is that:

my problem is different from the (quite common, indeed) one that see a LED bulb "flashing" at a very fixed frequency (once every 20 seconds, for example) despite the fact that the SSR-relay is open. My BULB keeps staying OFF and... flash only when the drill is working (actually it flash with a random behaviour, but only when the driller is running);
my SSRs, as well as almost any SSR, include a "snubber circuit";
if I unplug the power-supply, turning off Arduino as well as the "control-plane" of the SSR relay module... the phenomena PERSIST.
if I unplug everything... the phenomena disappear (obviously?).
if I use the driller very close to the SSR relay module (and Arduino, and the power supply), phenomena is exactly the same.

There are lots of things that I still need to investigate (starting from using "shielded" cables, as for the connections between Arduino's PIN, push-buttons and relay modules) but... point 3) above makes me think that I'm missing some bigger problems: can the 10 meters long electrical wires between the LED bulb and the AC power source, acts like an antenna so to catch so much EMIs to "flash" the bulb?

Can someone help me in understanding what's happening or, eventually, which is the proper "troubleshooting process" that I should put in place to (try to) solve this problem?

A final note: should you want to check by yourself the "phenomena", feel free to give a look to this MP4 video (22 seconds for 5.6MB), where I asked my son to "shout" as soon as he saw the "flash" (that I cannot see, as I was close to equipments, slight far away from the room). The driller engine is, also, clearly audible.


texts: If I have drawn an IC. Are there any manufucters that you can go too tom implement it?

texts:
Possible Duplicate:
  How much does it cost to have a custom ASIC made?

I have drawn a IC for an RFID application. And I want the IC to be super small. I wonder if there are manufacturers I can go to make it supersmall?


texts:
Suppose we have a 2d Systemverilog array declared as:

logic x [0:3][7:0] ;

How can we use an attribute to get the width of the first dimension ?
How can we use an attribute to get the width of the second dimension ?
Is there an attribute equivalent to VHDL's "range" attribute ? I.E: one that'll return not the size but the actual range ( 0 to 3 ) or ( 7 down to 0 ) ?


texts: Saving Arduino sensor data to a text file

texts: How can I save data retrieved from a sensor to a text file on the computer?


texts:
I am using a laser source that can accept analog input (0-5 V) to set light intensity levels.  The input impedance of this driving voltage is 50 Ohms.  Typically this is connected to a function generator to create sinusoidal modulations of the light level.

I don't care about AC light signals; I just want to set a DC light signal by providing a level somewhere between 0 (off) and 5 Volts , and I want to be able to do this remotely.

I could use an Arduino or Labjack to drive this signal, but I was wondering if there was a component-free solution that could just use the laptop, analog circuit elements, and some programming.

A couple of ideas I daydreamed about were:

Program the speakers to play a tone that I could connect to the laser source via the headphone jack.  (Soft tone would be faint light, loud would be bright).  This would seem to involve a bit of work as the headphone jack voltage is too low (~0.3 V) and the output impedance is also about 10 Ohms.
Program the RS232 port in conjunction with a voltage divider.  This would involve a bit of work as I don't know how easy it is to program pins directly.
Program the USB output power.  After googling around for a bit, this seems tricky to do with Windows.

If anyone has a good idea how to generate an analog 0-5V output from a computer, or could comment on the ideas above, please advise.


texts: Can a DC brushless motor produce the same torque at different power levels?

texts:
I am looking these Neo Brushless motors for a project. Here are the links to the data sheet and also to stall testing from the company:

http://www.revrobotics.com/neo-brushless-motor-locked-rotor-testing/
http://www.revrobotics.com/content/docs/REV-21-1650-DS.pdf

So in the stall torque testing, on the last test with 80A limiting, they were able to achieve a torque of about 2.3 N-m.

You can see the current is about 25A and the voltage is about 10V. This gives a power of 250W at stall.

Now, looking at the data sheet, they list a stall torque of 2.6 N-m. They also give a voltage of 12V and current of 105A. This equates to power draw of 1260W. How is this same motor producing the same torque at wildly different power values? I assume this isn't gearing related since these are motor tests to figure out the limits of the motor itself. Does it have to do with current limiting?


texts:
I'm trying to analysis circuit with parallel circuit of diode and resistor.

the diode is ideal diode with forward voltage of 0.8V, and I'm trying to calculate voltage across D2 and R2 (V_out)

For positive V1, D2 should be act like open switch, so V_out is voltage drop across parallel circuit (R1, D1 in parallel) plus V1.

For 0V < V1 < 0.8V, current will flow only through R1 as D1 is open switch yet, so V_out should be V1 - voltage drop across R1, which is 0V. And for V1 > 0.8V, voltage across parallel circuit should be fixed to 0.8V, so V_out = V1-0.8. Then it gives me nice continuous V1-V_out graph.

And to confirm my thought, I simulated with pspice and it turns out that V_out for V1 positive is V1, and voltage across parallel circuit is zero (not exactly zero, but I'll say zero for it is ideal). I can't understand this result. I also edited Vj of dbreak (forward voltage as far as i know) to 0.8V

Why the voltage across parallel circuit is zero?


texts: What kind of capacitor should I use in Buck topology if the load is a lead-acid battery?

texts:
I'm using BQ2031 to charge lead-acid batteries. BQ2031 takes battery voltage as feed back and controls the switching element according to it. Now the load is not a passive element, instead it is a battery with a very low internal impedance. The battery itself will behave as a huge capacitance. In this case, what kind of capacitor should I use, or should I use one?

Specifications
Maximum charge current: 30A
Maximum ripple current: 2A peak-to-peak
Battery type: Generic, not a specific one


texts: How to drop voltage to 4 volt from 5 volt source voltage with resistors?

texts:
A SIM800L module needs voltage between 3.7V to 4.2V. The Arduino power source output is 5 volts which will damage the module.
Is 220ohm enough? I was testing with a multimeter. Its drops to 4 volt with parallel circuit like this:

What is different with a series circuit? Which is better? Series or parallel to drop the voltage?


texts:
I'm building a programmable current load.
The big picture is : A microcontroler (stm32f303) drives (through its dac) some n-mos
(tested with PSMN034 and IRL2203) that drawn current. The microcontroler
also measure current and adjust the gate voltage until the current reach the target.

My problem is I have some strange behaviour while controling the mos' gate with
the DAC.

For this test, I only output a fix value on the DAC. With nothing connected to DAC, the output is stable. When connecting the gate to the DAC, I measure voltage oscillations on the DAC output. I supposed that the DAC was not able to
provide enough  current, so I added a AOP but the result is the same.
With a fix DAC output, the oscillations' frequency is slowing down while the current is raising. The speed is "exponential". Current is growing from 20mA up to 1A, when I stop the experience.

I expected everything to be stable : DAC voltage and current drawn in mos.

Do you know what it can be ?

Thanks.

Here's a schematic:

Power is connected to a +8V power supply. The microcontoller is powered by a 3v regulator connected to my computer's usb port. AOP is powered by USB.

Here's a screenshot of the measures. The top curve is the DAC output. The bottom curve is the output of the AOP (tied to mos' gate).

and a video to see the frequency changing:
Video


texts: Alternative LEDs Blinking circuit(Analog) Help

texts:
Can someone explain the operation of this circuit, I understand the basics of the BJT and its modes, but most of my confusion arises when there is some-sort of feedback loop in the circuit, my thought process breaks down, could someone help me understand things better.

I don't understand the exact operation of the capacitors in this circuit, I know they charge and discharge causing the transistors to turn on and off, but not sure how the capacitors go about doing this.

The LEDs light up alternatively, D1 and D2, the speed of alternating is adjusted through the potentiometer R3

Adjusting R3 causes the LEDs to alternatively light up faster or slower

simulate this circuit – Schematic created using CircuitLab


texts: Can a power supply be too powerful for a device assuming that the power supply is at operating voltage of the device?

texts:
Let’s say a device’s operating voltage is 5V and maximum current that it can draw is 5A.

Is it possible for a 5V power supply to have very low internal resistance such that a device that operates at 5V turns down its resistance in attempt to draw 5A from the power supply , but instead accidentally draws greater than > 5A due to the power supply having very low internal resistance or being “too powerful” ?

Of course this is assuming that the way a basic electronic device draws current is first, it assumes that it is being supplied the correct voltage, and 2nd, it lowers down its resistance at some constant number base on the current it needs to draw

Is this how regular devices such as servo motors draw current? Or can they actually monitor how much current a power supply can give and lowers its resistance base on that?

I know that it is possible to be at operating voltage and still not supply enough current, but could it be possible to be at operating voltage, and supply too much current for a load?

Wait Unless of course, as long as the voltage across the load is less than or equal to the operating voltage, it can never accidentally draw too much current. ( I think I answered my own question, not sure if this is right )


texts: How is a battery's capacity (mAh) compared to a fuel cell capacity?

texts:
Batteries (Li-ion, Li-po, Ni-mh etc.) are all rated in mAh, which gives their capacity (C). But what about hydrogen fuel cells? How can we rate their capacity? I have done some research, but fuel cells do not have mAh ratings. I read some tutorials for fuel cells but they don't give a good explanation (rather no explanation) on this matter.

In a few words to make it more clear: if I want to find a fuel cell that is equivalent of a li-po battery rated for 3.7v @ 1000mAh capacity how do I search for it?


texts: For which purpose are those resistors on the ANT output?

texts:
I've bought a cheap FM transmitter and installed it in my car, but sadly, it gives me too much interference (Too weak signal), even in a totally static signal, so I decided to disassemble the transmitter and look for the antenna.
I found that the antenna goes through a bunch of resistors, but why? For what are those? Are they limiting the signal strength, so that it doesn't break laws of some countries, or are those there, because they are needed?

Is there any chance to remove (some) of them and increase the signal, at least a bit?

Below is the image of the "main" transmitter unit:

And here the image of the bottom unit, which goes to the car's 12V port:

Any suggestion is also greatly appreciated.


texts: voltage-controlled frequency tuning of an antenna

texts: I am looking for an antenna whose frequency could be changed by an applied voltage signal, I am not sure what is the name of this kind of antenna or whether it exists or not. By searching on google using this question's title and other variations of it all I could find was a paper on research gate .


texts: Programming binary values [0000 to 1111] to port pins in C?

texts:
I'm using PIC 89v51 microcontroller, and i have to generate voltages from port pins of a particular port [i have used R2R ladder ckt in hardware] but the thing is i need to generate it from the microcontroller only i.e. i have taken four port pins say P2.0=V1, P2.1=V2, P2.2=V3, P2.0=V4;

So if V1=0; V2=0; V3=0; V4=1 it should display the voltage say 1v and similarly for all binary values from 0010 to 1111 it should display 2v to 15v,kindly help me in resolving this..

MEANWHILE I'll make clear that I have constructed R2R ladder circuit, but while checking the output i'm not using this circuit... I'm testing from microcontroller only..


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I am working on a project about data transmission with lasers. The project is very young so I can modify my current planned setup if necessary.

This is the actual planned setup:

Every raspberryPi can control a laser (probably via a dedicated driver) and a phototransistor. After a "syncing" phase the devices can communicate turning on and off their own laser to send a one or a zero respectively. To help receive the laser beam I am planning to add some kind of lens.

My goal is to archive enough bandwidth to make a voice call (see below for more detaild) between the two devices, about 5 KBps.

The expected working distance is at least 4 meters, up to 20 meters if possible.

I thought about infrared laser to avoid some disturbs from artificial ligth, sun, etc.

What kind of (possibly low cost) laser and photransistor can I use in this setup? I have searched online for some lasers but I am concerned about the speed at which the laser can turn on and off.

Clarification: I have not been very clear about what i wanted to archive with the project. Sorry. My  goal is to be able to transmit arbitrary data (bytes) over this channel. With this first prototype the goal is transmitting fast enougth to carry a phone call. The voice is first received by a microphone connected to a sound card, converted to binary data, compressed, sent through the laser channel, received by the other end, decompressed and played through a speaker. In future prototypes with more bandwith i'd like to transmit other kind of data such as small files or video streaming.


texts: MOSFET instead of a contactor in Battery Management Systems (BMS)

texts: For relatively high current systems (>50 A) with Lithium based batteries, I've seen that usually BMS controls the output with contactors for both main supply and precharge. Why not use a high current rating MOSFET(s) to do this instead?


texts: Does using only 2 phases (400V) in a 3 phase transformer affect anything?

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I just witnessed a 3 phase control transformer in the mcc that steps down 400V to 230V connected only with 2 phases on the 3 400V terminals, and on the other side (secondary) are your live and neutral wires.
Does only using 2 of 3 wires affect the transformer or secondary circuit in any way?

Any information would be appreciated


texts: Transmission from atmega32 to PC using max232 not working. When I checked the data from the Tx pin (in the realterm software) of atmega32 it was fine. But there was no output data from max232, when I was trying to read data in the realterm software. I have attached the circuit that I used.Where am I going wrong?


texts: Transistor IRF520N not working as expected

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Please be gentle as I am a total newbie with electronics.

I recently bought an Arduino beginners kit. In that kit was a 9V motor with the proper transistor (I think these are also called MOSFET?). The printing  on the transistor reads IRF520N IOR P533B D5A2 (see picture left). I have started my own little project and bought a 12V pump and hooked it up just as I previously did with the motor from the kit and it worked perfectly (see picture). Since then I decided I wanted to buy more transistors of the same type and I found one which I thought was the same. It is labeled IRF520N IOR P702D AP9Q (see picture right) but when I use that transistor the pump doesn't start pumping.

Apparently the two transistors are not completely identical. I found the datasheet to the newly acquired transistor (listed on the page of the online store I bought it from) but I don't really understand anything it's trying to tell me. Also I couldn't find the datasheet for the one delivered with the Arduino.

So my questions are:

Why is that transistor not working?
Could you point out which values in the datasheet are important to me so I can pay attention to those when I look for another transistor?
What does the transistor actually do which I bought and can I still use it for something (I actually bought quite a lot of them..)?

If I missed any important information please ask in the comments and I will include it in my post. I included a schematic at the bottom.

Edit #1:

As joren vaes suggested I used the new transistors with the old motor and a 9V power supply. To my surprise that actually made the motor spin. So it looks like the new transistor can't handle the 12V?

Edit #2:

I did some experimentation with pump, 9V and older/newer transistor.
Using the 9V batterie with the 12V pump works fine but only with the old transistor. With the new transistor the pump moves super slow and the transistor got worryingly hot. The old transistor doesn't heat up noticeably. As suggested by joren vaes i made another photo of the setup which shows the wiring properly and photos (first page, second page) of the instructions which came along in the kit. There isn't really any more valuable information about the transistors which came along if you were hoping for that.
Also the Arduino supplies 5V and the code I uploaded just sets the transistor pin HIGH when the button is pressed. I know that I wouldn't need an Arduino for that ;)

Edit 3: Included schematic. I hope I didn't do anything wrong..

simulate this circuit – Schematic created using CircuitLab


texts: Power dissipated or generated through an element

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We know that if a current is entered through the positive polarity of an element and exit through the negative polarity, then the power is positive which means that the power is consumed through the element. On the other hand, if the current is entered through the negative terminal then the power is negative which means that the element has generated power to any external element connected to it. My question is that I need to understand the physics behind this "rule" in an easy way. Thanks in advance.

Edit: I need to understand the physical reason behind this convention. For example, why specifically if the current enters the + terminal then the power is dissipating in the element why this is not the case if the current enters from the -ve terminal?

Edit 2: Ok Guys I think I have an explanation but I am not sure of it. When the current enters from a positive terminal and exits from the negative terminal, this means that the charges did enter from a point of high energy (high volt) and exit from a point of low energy (low volt) this means that the charges while they have passed through the element they have lost some energy and therefore this lost energy is absorbed by the element according to the law of conservation of energy. The opposite can be said if the element where generating energy. So is this explanation is right?


texts:
I'm designing a power supply for hybrid amplifier (tube + discrete semiconductor power amplifier). I need 30V for power amp and 60V for tube. Also I need 6.3V for the filament (6DJ8 dual triode doesn't allow series connection of filaments so I can't use 12V power supply).

Let assume I have a transformer with two secondaries rated to 15V each. I can connect windings in series and get 30V directly and 60V using voltage doubler.

To obtain 6.3V for the filament I can utilize transformer's midpoint and use a linear regulator. In this case all filaments' current will pass through single winding. Can I spread this load to both windings? Filament power supply may float.

Edit: I think something like this may work. Values are nominal, regulation is omitted.


texts:
To my understanding both pipelining and caching make use of memory to reduce the amount of idle hardware.

I am considdering a project that has multiple input data streams with a slow clock rate, which are transmitted to data processors at a higher clock rate using an asynchronous FIFO IP core.

Each data processor is assigned to multiple data streams, but it does not have access to the data streams from other data processors.

Is this called caching or pipelining? (I'm for caching, but I would like to be sure)...


texts: General rules to define a part for BOM and Assembly files.

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I would like to know if there are some standards or rules to describe parts when generating the BOM or assembly files for manufacturing.

For example, I would describe an SMD capacitor with format 0805 as:

Cap 0.1 µF, X7R, 50 V, ± 10%, SMD 0805

but could be also defined as:

Capacitor 100nF, 50V, X7R, MLCC 0805, ± 10%

or just..

100nF, 50V, 0805

The same apply for Resistances and all other stuff.

Which is the best way to define it?


texts:
1)I need to design hardware for SPI communication with 2 different slaves. Slaves chip select pin is being pulled from high to low by the GPIO pin(port output)of the Master. But on the hardware design, I have only one port pin left. Can the same port pin be used to enable/disable the chip select pin of both the slaves? Response from both slave are obtained at different timing. Both slaves are not identical. Clock for both the slaves are derived from the system clock.The connection is as shown below (Fig1). Can this design possible for SPI communication?
Also can anyone tell which design (shown below) is recommended. Fig 2 or Fig3
Is it necessary that different slave should have its own SPI unit?
2) Which factor decide if daisy chain type SPI communication possible or not? Because in datasheet of both slaves it specifies, daisy chain type SPI communication is not supported. Does slave decides about the possibility of daisy chain type SPI communication?Can someone please explain how daisy chain communication happens?

Thanks


texts:
We are using a MAX9926 IC to filter 2 VR signals (from a HONDAS2000 Crank and Cam VR sensors) One being 24 tooth, and one being 3 tooth (per cycle of the Engine). At RPMs below approx 5000-6000 the signal comes through the 9926 fine, and triggers the MCU correctly such that it decodes it fine. At around this RPM we start to get extra/missing teeth on the IRQ lines to the MCU. Note we can 'push through' this noise and get to 9k RPM - just seems to be a 5-6K RPM issue...

We also used a scope to capture the signals at the entrance of the ECU to rule out electrical noise. The signals are smooth and clear at both idle, AND when hitting the point the ECU loses sync due to the 'phantom' teeth. The scope doesen't show these phantom teeth so I am assuming it is a 9926 issue, or the parts R1, R2, C1, R3, R4, C26. The only difference between perfect idle signal and higher speed 'issue' signal is the frequency of the wave, and its amplitude, as shown in the plots. We have 50v P-P at high speed and around 20v P-P at low speed.

1) Maybe I should and how could I attenuate both signals say by half? (Adding what, where)
2) Should I reduce the value of C1/C26 as they might be acting as a filter?

With regard to (2) if I keep the throttle down and 'push through' the noise the engine will regain sync and run all the way to 9k RPM without issue, so that is also odd!

Low speed, IRQs passed via 9926 perfectly

6K RPM, phantom events passed out of the 9926: (Note the signal shows no issues at all, just different voltages and frequency.

Schematic of the input system:
[![Schematic][5]][5]


texts: Determine transfer function from circuit with different currents

texts:
Just started on the topic Circuit Analysis, and am supposed to find the transfer function of the following circuit:

So I know I am supposed to use KVL to solve this problem.
I can first transform the circuit to:

From the circuit, I can see that because u*Vc is in parallel with the output:

$$V_o(s) = uV_c(s)$$
$$V_c(s)= \frac{V_o(s)}{u}$$

Using KVL,

$$V_i(s) = (I_1*R)+(I_3*R)+V_c(s)$$

where: $$V_c(s) = \frac{V_o(s)}{u}$$

Now the problem is, how do I exactly get I1 and I2 from the circuit?

New to this, thanks :)

EDIT: I crafted another KVL equation, as well as being able to determine I3.
$$V_i(s) = (I_1*R)+(I_2*1/sc)+V_0(s)$$
$$I_3(s) = \frac {V_c(s)}{1/sc}$$


texts: Voltage regulator from first principles - why is power dumped in the transistor?

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I'm trying to further my understanding of electronics, so I decided to try to design a fixed voltage regulator capable of supplying an amp or so. I put this together from first principles without referring to any kind of reference on how voltage regulators are usually designed.

My thoughts were:

Zener and resistor to provide a fixed voltage reference.
Comparator to detect when the output voltage was above the target threshold.
Transistor to switch the supply on and off.
Capacitor to act as a reservoir.

With that in mind, I designed this fixed 5V regulator, which appears to work:

What I did notice, however, is that it has certain limitations which I can't quite derive the cause of:

The current from V1 (input) roughly equals the current at R2 (output), despite differing voltages. This seems to match the behaviour of linear voltage regulators (is that what I just created?) but I'm not sure why it happens. Why is so much power dissipated from Q2 considering it's just switching on and off?
When V1 is less than about 7.5V, the output voltage never hits the 5V threshold, but instead hovers around 4V. I have tried this with varying loads but it simply does not function below that input voltage. What is the cause of this?


texts: Exact mechanical location of pin1 on J8 of raspberry pi 3

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Designing HAT for Rpi3.

I am looking for precise dimensions of Pin1 of J8 on Raspberry pi 3 board, relative to the mounting holes.
No luck finding this after hours ..........

Any help is much appreciated !!
rob


texts:
I know this is an extremely simple question, but I haven't been able to figure this out on my own. I'm trying to get an LED to get brighter as ambient sound rises. What I've come up with: use a transistor, attach the base to the electret microphone (that's the part I'm not sure how to do), then have the circuit for the LED pass through the collector and emitter. Would this work? Would the LED brighten continuously? Most importantly, is there a better way to do it?

The goal of this is to visualize the interference pattern created by two speakers. I'll have a camera set up using a long exposure, move the circuit around the lab area, and hopefully the bright spots in the picture correspond to points of constructive interference.


texts:
I'm trying to choose a voltage regulator, and considering I will have a relay on my PCB it seems a switching regulator is the better choice for the coil noise.  Example Reference

I found a lot of schematic examples over the internet, and a lots use a switching regulator when have relays. I don't know if it is coincidence, or it is really better for the coil noises.

Is it really true?
How can I choose a good switching regulator to help with the noises? A higher switching frequency will be better?
My PCB operates in 3.3V, and I'm considering use this regulator MCP16311. If I use a Vin 12V or 5V it will make any diference with the noises handle?

Edited: By noise, I'm referring electrical noise caused by the relay coil operation, which can makes the microcontroller reset


texts: What happens to the output (S) in an NTE74C4067 multiplexor if multiple channels are active?

texts:
I found the data sheet for this multiplexer/demultiplexer, and as I understand it, when channel 5, for example, is active (I5), S0 and S2 would be active, making the S nibble 0101.

The question is, if there were multiple channels active, say 5 and 6, what would S be?


texts: Switch 12v solenoid from 3v3 control signal

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I am going in circles on the web and appreciate your help with this novice question, operate a solenoid with a mosfet (original idea, I know). I bought a Gravity DFR0457 to switch a 12V solenoid on from a camera remote (Pocketwizard) that outputs 3v3. I can't get it to work (apparently common with logic level needing more voltage), so i am guessing i have to bump up the output remote 3v3 somehow?. Is this even the correct route to go? I was hoping that I could use existing boards so i wouldn't have to solder together different components.
Schematic for the DFR0457 MOSFET switch module:

Connection diagram

My schematic


texts:
How to transform a set of analog voltages from V to ppm/K?
I have to use this to calculate the temperature coefficient of a bandgap.

Is the derivative the same as the temperature coefficient calculated in ppm/K?

The derivative of the function:


texts: Understanding how a tristate buffer works (74LS241)

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I'm trying to understand how the 74LS241 works. From what I read, if two input are high on a buffer, then the output will be high. For some reason, this isn't working on my circuit.

So here is what I did:
I have put a led on the 3 output pin, in order to test the output. Then i wired the 19 and 17 pin with 3.5v, but my led isn't showing any high input.

(red where the input are at 3.5v, green where the expected output should be high)

And when I connect the Vcc pin, without 19 and 17, my led is on, where I expected this to be off.

I have the feeling that I have understood the schematic, but the fact is this is not working. So I clearly don't understand at all.

My question is: did i break the chip not protecting the input ? (I didn't put any resistors on the input). But I thought gate like those didn't need to be protected.

update
Here is my actual scheme:


texts: How to prevent noninsulated wires close together during manual wiring a PCB?

texts:
Actually I have two problems, but this one is most annoying:

I have like 10 wires I want to solder to the pins of a pin header (2.54 mm distance apart).

Initially I kept like 5 mm of the end of each wire noninsulated, to be able to solder it to the pin. However, I found out it's quite a lot, since two adjecent wires may touch each other eventually.

Now I keep the noninsulated distance just a few mm, but I prefer not to redo the wires I already did (some of them are not on pin wires, but on components directly and it would get messy removing the solder).

How can I 'fix' this. What I could come up with:

Of course making the non insulated ends very small.
Putting heat shrink tube around the wire before soldering and slide it as much as possible to the end and heat it. Quite some extra work though. Never tried heat shrink tubing, so maybe even the solder might get ruined?
Sticking tape in between/over it, but the tape might get off later.

I wonder if there are better solutions.

Another problem I have, is that I didn't make the most beautiful soldering joints from some wires to some components (Hi Link AC/DC converters). They have short pins only and I'm a bit weary to remove the solder. However, I had already twice that when I put 220-250V on it, the wire broke lose from the component. Probably a cold solder connection? And what to do (probably redo the soldering?)

(sorry for not having pictures, the 'project' is not next to me now).


texts: How to use a Raspberry Pi Pin(3.3V) to reset a ATMEGA328(5V)

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I have a ATMEGA328(AVR) connected to a Raspberry Pi(RPI) via serial using a level shifter.

The AVR has the Arduino Bootloader installed and I would like to program it via serial.

What would be the best way to connect the AVR reset pin to the RPI GPIO pin 4?

(Keep in mind that the AVR reset pin has a 5V pull-up resistor connected to it.)


texts: Bolting a steel ring terminal to a steel tab on IGBT?

texts:
This is a similar question to one answered here: what are the best practices for bolting a ring terminal to a steel panel?

However, the main difference is that I am not attaching a ring terminal to a chassis. I am attaching it to the steel tab on an IGBT.

Should I still use a serrated washer? What is the best bolt material? Steel as well?

Should it be brazed to ensure the highest conductivity? (Serviceability is not much of an issue)

I just want to make sure this is done correctly. Thank you!

Datasheet for CM600DY-12NF IGBT http://www.pwrx.com/pwrx/docs/cm600dy_12nf.pdf


texts: FPGA HDMI graphics, higher level flow for basic desktop

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I am interested in using an FPGA which has HDMI output and mouse and keyboard input to do a primitive GUI/desktop. The FPGA will have some processing happening in the background, and I basically want to create a graphical plot of this. I also want a window the user can click to change some system settings related to that background processing.

So far, most of the FPGA HDMI tutorials are very low level: delivering pixel information/HSYNC/VSYNC... just the lowest level interface. I think I can intuit that there is some RAM/sequencer block attached to this low level interface that provides the sequencing to draw pixels in the correct order.

What types of blocks exist for the rest of the flow: What fills out the RAM? Is it as simple as having a MicroBlaze handling every single pixel, or something more sophisticated?


texts: Calculating Rotor Inertia or Mechanical Time Constant for BLDC Motor from Published Specs Only

texts:
TLDR - Is there any way of calculating the Mechancial Time Constant and/or Rotor Inertia and/or Run-Up Time based soley on the specs provided on this motor

My end goal in asking this question is to correctly size an onboard fuse for a product that I am designing. My caveat: I am not any type of engineer and I am very new to figuring out electronics.

To be as thorough as possible, I am trying to ensure that not only do I size the fuse correctly for normal operation, but to take the I^2T ratings and the Pulse Cycle Withstand ratings into account.

My specific problem at the moment is trying to calculate the duration of the inrush current. The product will need to deal with varying amounts of "Additional Load" at startup.

Amongst other sources, I am trying to use the formulas on Page four (4) this Maxon guide

The results I am trying to calculate are for the Mechanical Time Constant, and from there, the Maximum Angular Acceleration and Run-Up Time. I believe these results will allow me to simulate the inrush current duration.

Until something better comes along, I am considering using a Mabuchi RS-555VC-3754
Unfortunately, they don't provide all of the specifications that other (more expensive) manufacturers do - or at least I haven't been able to find them.

So my main question is;

Is there any way of calculating any or all of these amounts based on the specs provided by Mabuchi?

Follow up questions:

-Is there another way to calculate the inrush current duration in order to calculate the I^2T value?

-Do you know if Mabuchi publish full specs such as a company like Faulhaber does (example here

Apologies in advance if I have rambled/asked something ignorant/not been clear.

Thanks for the help!


texts: OpAmp clamping circuit not working for a Pulse voltage reference in PSpice

texts:
So, we had an analog electronics lab exam today where we had to generate a waveform:

I wrote the PSpice code, using a clamper circuit (in hindsight a summer was the best option, but whatever). The code is as:

VSP 7 0 DC 50
VSN 8 0 DC -50
VNO 2 6 DC 0
R1 2 3 4.7k
C1 2 1 0.1u
VI 1 0 SIN(0 -8 10)
D1 5 6 D1N4002
VREF 4 0 PULSE(-48 -8 0 0 0 100M 200M)
XA 4 3 7 8 5 UA741
.lib nom.lib
.TRAN 10u 500m 100M
.probe
.end

The problem is that code is not working an I can't figure out why.
If I give replace VREF from a pulse to:

VREF 4 0 DC -48
or
VREF 4 0 DC -8

the sine wave gets clamped to -48V or -8V. But when I give a pulse it doesn't. I am getting an output waveform as

Can someone please help me figure out the issue?


texts: Using Arduino, how can I dynamically change signal input from one pin to another?

texts:
Background
I am building a multirotor project similar to this one I built a few months ago.  This particular multirotor will be geared for flying FPV (First Person View) which means that I will transmit a 5.8Ghz video feed from my aircraft to a ground station where I can pilot from the view point of the aircraft.
I am going to have three small cameras: one at the nose, one topside and at the rear of the aircraft, and one in the belly facing down.
What I would like to do is assign a switch on my transmitter that will allow me to toggle between the three cameras.
I already know how to read a signal value from the receiver on my aircraft to the Arduino and I can get three nice, clean values (1000, 1500, 2000) depending on the state of a three position switch on my transmitter.
Question

Given that I can read three distinct values from my radio control on one pin, and
Given that I have three different video signals coming in on three separate pins, and
Given that I have one pin that will output the video signal to the 5.8Ghz video transmitter

How do I dynamically switch which video input is sent to the video output pin?


texts:
Does anyone is able to demonstrate this formula?

Where Co is the output capacitance, Rc is the ESR associated to the capacitors, Io is the output current of the particular output, fs is the switching frequency, Dmax is the maximum duty cycle.
Where Vro is the reflected output voltage, idspeak is the primary peak current and KL(n) is defined as follow:

Suppose a 1:1 transformer with 1 output then the expression is:
$$
\mathrm{
DeltaV_{o(n)} = \frac{I_{o}*D_{max}}{C_{o}*f_{s}} + (Isec_{peak})*R_{c}
}
$$
i.e
$$
\mathrm{
DeltaV_{o} = \frac{I_{o}*D_{max}}{C_{o}*f_{s}} + (I_{o}+Icap_{peak})*R_{c}
}
$$
Nevertheless, I do not understand why in the second terme there is the output current Io which appears as it does not flow through the ESR resistor. And for the first term, I am not sure about the charging time of the capacitor.
Does anyone is able to demonstrate this formula?
Here is the AN which gives the formula for determining the output capacitor :
https://www.onsemi.com/pub/Collateral/AN-4137.pdf.pdf
Here is the schematic :


texts: misunderstanding of a Computer Architecture

texts: I have the following architecture , and the timing diagram below . my question is , it's seem that no 'relation' or dependency between control logic and Extender , but at timing diagram , the time of starting execution of the Extender , is dependent on the control logic , can anyone explain this misunderstanding ?


texts:
I want to design a notch filter for eliminating 100Hz waveform. I am using the below schematic. I tried the circuit with bandwidth 300Hz but this will affect the frequency of 20Hz to 200Hz signal also. As well I am getting the -13dB at 100Hz( Vout(peak-peak) = 200mV and Vin(peak-peak) = 1V ) but I want the output signal as low as 10mV.

For reducing the effect of the filter on other frequency I decrease filter bandwidth(4Hz) by using below calculator and then change the R4 and R5 resistor value(mention in the schematic). But it is now giving the worst result. Now it is giving the output of -2.5dB(750mV(peak-peak)) at 100Hz. Or I can say there is negligible effect at 100hZ or other frequency.

Need to ask how to improve this circuit for deeper notch and approx (peak-peak) 10mV(or less) signal at the output for 100Hz frequency.
Thank you in advance.


texts: How would adjusting the bias on an op amp effect the signal?

texts: I am using an op amp to boost an audio signal. The bias, it appears, is typically half of the input voltage. What kind of effect would it create if the bias was to be adjusted up or down? Would adjusting the voltage up cause it to clip sooner? What if it was adjusted downward?


texts:
I need help on a 12v-220v Boost converter design. the converter is to have a feedback system that keeps the output voltage steady even when the input voltage drops. I have done a lot of reading and designs using a NE555 as the control system but it seems all my calculations are wrong. I am able to get a 250v output but if I add a load to it the output voltage drops drastically. I'm really confused. I need to use it for an inverter project in an exhibition next month. So please I need help.

I will attach the screen shot of the simulation on proteus 8.


texts:
I am trying to get an lcd 16x2 with PCF8574 I2C working with my arduino due. If i connect my lcd with 3.3v (backlight doesn't work, led from the PCF8574 lights up) and upload the i2c scanner sketch from arduino.cc the following address "0x27" is found which is good.
The problem now is the lcd needs 5v so i use a level converter (I2C Logic Level Converter Bi-Directional Module 5V to 3.3V) and than nothing works anymore. When i start the i2c scanner sketch it returns me only once the following two address "0x02","0x03" and than it says "no i2c devices found". I think the problem is the level converter. Anybody an idea how to fix that problem?

Schematics:
http://s28.postimg.org/pc9kdhgzx/Arduino_DUELogic_Level_Converter_LCD16x25_V001.png

Level Converter:
http://www.aliexpress.com/item/5PCS-IIC-I2C-Logic-Level-Converter-Bi-Directional-Module-5V-to-3-3V-For-Arduino/1972789974.html


texts:
I'm working with an ATMega128 micro working with a joystick (pot in the schematic below) that's a .25-4.75V output with a 2ohm output impedance (Joystick Part Number is: ch products ts-2-r-1-u-05-a).  When the line between the pot and the 33kohm resistor gets removed while the board is on however, the voltage will float ~.5V for a period of time (20-30 minutes maybe) before pulling down completely.  I was thinking that the 499kohm resistor should pull it down effectively, but something doesn't seem quite right on this.

simulate this circuit – Schematic created using CircuitLab

Anyone have ideas as to why it wouldn't pull down completely and immediately? I've watched it on a scope and it hovers for quite a while around that .5V mark. Also to note, I'm currently piggybacking the 499kohm resistor onto the .01uF cap for testing.


texts: Avoiding battery charge interception with high-current devices

texts:
I could use some help to certify an assessment of an ongoing automotive issue. The vehicle is equipped with a high-performance electrical fan (40 amp draw/10 AWG), and I suspect that existing wiring is intercepting the charge from the battery.
Here is the current wiring diagram:

There is an AGM automotive battery under the rear seat, and it's grounded to the chassis.
There is an electrical junction box located under the hood where the battery and alternator connect.
The positive battery wire runs there and connects with alternator output (+). Basically, this is where the alternator flow meets and charges the battery.
The aftermarket electrical fan is also connected to the electrical junction and pulls the power from it on demand when the vehicle reaches operating temperature.

All three positive leads for (battery, alternator, and electrical fan) are connected at that junction. The positive wire running the electrical fan is also shorter than the battery wire that runs all the way to the back in the car.
Is it scientifically correct that the fan, at full operation (40 A), will intercept the alternator charge from the battery? If so, how significant would the interception be, and would it actually impact the charging of battery during normal operation? Please note that the alternator on the vehicle is rated at 140 A.
If there is an interception, would re-routing the positive wire from an electrical fan directly to the positive battery terminal remedy this issue?
Thank you!


texts:
I have a 5V voltage source with 2.5A current as input. I want to have this source in the output. I use a microcontroller. I can't use a relay because it takes up a lot of space.
I first used this circuit for this, but this wasn't suitable for me because I had a voltage drop which wasn't manageable.

How can I switch input voltage as output?


texts:
I used uart receive using polling method. But same I want to use in ISR. How can I write a ISR function. For example if I am using CC2541. In the manual I have seen that Vector Table for Port 1(where UART is connected) is P1INT_VECTOR. But I don't know how to write a function. After some search I found many people used a function like below.

#pragma vector = P1INT_VECTOR
__interrupt void p0_ISR(void)
{
    /*Some statement*/
}

But I don't know what is p0_ISR. I didn't see this in the manual or datasheet. This interrupt function has any prototype?. Can some one help me to understand this. So that I can implement to every microcontroller not only CC2541


texts:
I'm building an IC programmer (for the AS5043 sensor) that requires two voltage levels; 5V and 7.5V. I decided to control those with two PNP transistors. I'm controlling them from a 5V microcontroller.
The programming scheme requires a 2us pulse for each bit.
For the 7.5V line, I made an NPN driver based on the circuit here. Here's the schematic of the switcher:

The C3 capacitor is explicitly required by the manufacturer for the OTP programming process. For development purposes, I have a small (<100R) resistor at PROG to simulate a load and discharge C3 after each pulse.
The circuit works, but exhibits strange, to me, behavior:

Magenta: control signal
Yellow: output
Blue: voltage after resistor R3, just at the Q3 base.

It seems that there's a delay to the transistor turning off. This delay is constant and doesn't change if I make the impulse longer.
For reference, the IC I'm trying to program is described here; the datasheet contains programming information as well as the simplified schematic of the reference programming board.
I'm not very well-versed at analog electronics, so I might need a good basics refresher and/or might be making a fundamental error.


texts: It is possible to use audio jack output to give power to a microcontroller? How many milliAmperes it feeds?


texts:
The CAN bus has CAN-High and CAN-Low lines. Normally, in the recessive state the voltages are each 2.5 V and in the dominant state the CAN-High line goes to 3.5 V and the CAN-Low line goes to 1.5 V.

How are these voltages actually achieved in the transceiver? What would be the circuit for the sake of understanding (using FETs or transistors or something else)?
In dominant, is that 1 V drop and rise happening in the CAN-High and CAN-Low lines?


texts:
I have a question regarding white noise generated by an arbitrary waveform generator (AWG). I'm working with one (AWG5014C) that has a sampling rate of 1.2 GSamples, with which I want to produce white noise that is relatively flat over some range, for example up to 300 MHz.

However, when I have it produce a white noise signal, it is not flat up to these kinds of frequencies at all, as shown in this figure

Here I show the PSD as measured with a spectrum analyzer; a clear dropoff is visible starting at relatively low frequencies compared to the sampling rate (or maybe not?) and I am wondering what the cause of this is.

I should note that I am not so much looking for a 'fix' for this; I assume that this is just a consequence of how the machine operates. My question is of what it is a consequence, so that I can understand it better. One clue that I have is that I can for example use the spectrum analyzer to extract a filter that will offset the dropoff; treating the AWG as some sort of black box that applies a filter |H(omega)| to my time series, applying |H(omega)| gives me a flat spectrum.

As a short aside, you can ignore the first points that are way off. Although I don't understand where they come from (another question?), they seem to be artifacts of the spectrum analyzer.


texts: memory for the simplest possible computer (Pi0K)

texts:
I'd like to build the simplest possible computer.   I don't care about speed or storage, indeed having slow speed and low storage is a huge advantage as I want to build it out of transistors (ideally relays!) and I want an LED for each state.   It'll be programmed via a Raspberry Pi which will host a camera so that you can see each clock cycle executing (yes, it's going to run at Hz not GHz).  It'll be an open design with the intention that schools can buy the parts, understand and improve on the design.  So the total budget must be well under £400, preferably about £100.

I have researched this over many years and have good ideas for the CPU (minimal registers, microcode in DIP switches and bit serial logic/arithmetic operations to reduce the transistor count).   What I can't figure out is how to get the memory, I'd like 1024 to 8096 bits.

The best I can come up with is two 6 bit one-of-n decoders giving access to 64 x 64  grid of capacitors.  Either they have a charge in them or they don't, and reading would reinforce that state.   There would be no LEDs on the capacitors as the refresh of this 'DRAM' would be in the order or minutes (which is a shame as this would be the only part not to show state).

Other ideas include some form of tape drive (compact cassette mechanism: great storage, too complex, no seek), drum memory (tape around a bean can: too hard to get the mechanics working), mechanical memory (bike wheel and ball bearings: too many bit errors), core memory (large hard ferrite cores: still very tricky to get right at the scale required), tape/card (can we still buy the tape readers), rotating disk with punched holes in binary order and some magnetic memory for storage (too complex to build).

Ultimately the aim is to publish a design that can be build in a school year where all parts of a CPU and memory are 'visible' and so you can see the instruction fetch, decode to microcode, and address decoding/register access/logic all happening over the course of minutes.

If anyone has ideas for really cheap memory (<<£100) where it's clear exactly how it works then please do let me know.

Tony

P.S. current state of play is at http://www.blinkingcomputer.org/


texts: LED Driver Output - Current Adjustment Range

texts:
I bought this Led Driver(HLG-480H-48A) for my Strips that use around 43V 9A. I've never used a LED driver before and have got a few questions about them:

The output current adjustment range (according to datasheet) is from 5-10A. Does that mean that the driver "pushes" 5A minimum through the circuit?
If I connect a LED strip that uses same voltage but only 3A what will happen?
I want to connect 3 strips(total I=9A), all in parallel to the same driver. What will happen if one of them has a short-circuit/fault? Will the other ones get damaged as well or should I independently fuse them with a fast acting 3A fuse?

Thank you for your time.


texts: AC transmission just requires live wire, why is neutral present

texts: If I touch a live wire and stand on the ground I will die because a circuit is completed, so for any load if I connect one end to live and other to ground it should work right, then why is neutral required in the first place?


texts:
First time poster here on electronics, so please excuse any big mistakes.
I'm working on a project that uses the NRF24L01+ chip for radio communication between an arduino uno and a raspberry pi. It sends a simple ascii char array which is interpreted by the pi as a string. The radios are being supplied with 3.3v from the boards.
I'm having a serious range issue, though. Everyone I've spoken to has said that they have had little problem having them work up to 100 meters apart. My units, while they work in the same room, loose connectivity immediately after walking around a corner, even if I'm less then 15 feet away. It seems to be a line-of-sight issue, but it's odd to me that the drop off is so fast.
I'm currently using the "naked" chips, which look like this:

I've seen them with "rubber-ducky" antennas before, though:

(source: wikispaces.com)
My question: Would adding an antenna on top of the flat antenna help with my propogation issues? If so, how would I go about attaching the antenna? Would standard leaded solder do the trick?
Thanks in advance for any answers.
Resources:
Data Sheet
Schematic


texts: ROM initialization in VHDL for waveform generator

texts:
I have to create a waveform generator and i used matlab to generate the sine wave. Now my TA told me to store the points from the wave in a ".mem" file then initialize the ROM by i guess importing them.

I don't really know how to initialize it and can't seem to find any references to
.mem files being used in vhdl.

I have the wave but i need help with creating the ROM and initializing it by using the values from matlab.


texts: How can I calculate the hysteresis of Reed sensor?

texts: As question says, I want to calculate the hysteresis of Reed sensor and I don't know how. As I seen in Reed sensor's documentation, hysteresis may be x/y, or the difference between x and y, and I'm not sure which is true.


texts: Accelerometer and/or Gyroscope for gesture sensing

texts:
I want to sense 3D motion (gesture). I have 3 axis accelerometer. But I am confused if I need a gyroscope or not for orientation and rotation sensing.

Isn't it possible to measure them from accelerometer alone? Because when the sensor rotates along one axis (say z-axis), there will be change in y-axis and x-axis output in accelerometer.
Is gyroscope really necessary or is it just easier if I have one?


texts: Pin as both input (for a switch) and output (for LED) with ATmega32U4?

texts:
There are several questions close to this topic already, but they are either for another µC family, or target reading analog voltages or other special cases.

So here goes: I would like to read a button and drive a LED from the same I/O pin on the ATmega32U4. Is there anything wrong with:

Pin => 22K resistor => button => GND
Pin => LED resistor => LED => GND

Then of course the pin would be put into input mode (with internal pullup) ever so often, and be in output mode most of the time.

As far as I can tell, the internal pullup is 50-100K on that µC, so the 22K with the button should be able to sufficiently sink that.

In output mode, when the button is not pressed, all is as normal; if the button is pressed, this will add a path through 22K to GND, which might or might not make the LED slightly  darker; anyhow, in my application it would not matter at all how the LED looks while that button is pressed.

Any chance to damage anything? Any pitfall that is not obvious?


texts: Design a tuned BJT common emitter amplifier with some specifications

texts:
I've been 2 days trying to design such amplifier with the help of a book of Boylestad (Electronic Devices and Circuit Theory), but the best I came with was an amplifier that amplifies what it's supposed to, but it's in cutoff, so I think it's not being well done (unless even being in cutoff, if it amplifies it's good enough? It's not, right?). The question is the following:

  Project a tuned amplifier stage of intermeditate frequency using an
  adequate transistor with f0 = 455 kHz [f0 -> central frequency] and a
  bandwidth of 10.7 kHz. The amplifier must have a voltage gain of 34 dB
  to hold a load of 600 Ohm. Use a DC voltage source of 20 V.

I think the problem with what I'm doing might be the calculation of R_E and I_C. I'm very confused on how to calculate those 2. Though, as I've been trying for 2 days, I can't be sure the rest I did is correct or not (I also have already 4 versions of the things - and not more because I thought various on my head instead of writing not to take infinity resolving this). Could anyone point me in the right direction please? If any more information is needed just tell me and I'll try to provide it.

PS: I've tried to use the 2N2222 and the 2N3904, by the way. If a better one would be recommended, I'm all ears (or eyes, in this case haha).

Thanks in advance!

EDIT: I forgot to say, but it's a single tuned amplifier. In this case, it must have a resistor, a capacitor and a coil in the collector in paralell.

As per Andy aka request, this is schematic I've been using - though, any better alternatives on emitter or anywhere else are welcome. This is one of the versions that bias it correctly (one of the problems before was when I connected C3 and L, it would go on cutoff, but no more):

And the best I come up with is this (now correctly biased, but the bandwidth is still totally wrong):

After biasing this thing, I used 2 equations the professor talked about to find the capacitance of C3 and then to find the inductance of L:

\$BW = \frac{1}{{2\pi  \times {R_C} \times C}} \Leftrightarrow 10700 = \frac{1}{{2\pi  \times 600 \times C}} \Leftrightarrow C = 24.8{\rm{ }}nF\$

\${w_0} = 2\pi {f_0} = 2\pi  \times 455 \times {10^3} = 2858.85 \times {10^3}{\rm{ }}{s^{ - 1}}\$

\${w_0} = \frac{1}{{\sqrt {LC} }} = 2858.85 \times {10^3} = \frac{1}{{\sqrt {L \times 28.8 \times {{10}^{ - 9}}} }} \Leftrightarrow L = 4.9 \times {10^{ - 9}} = 4.9{\rm{ }}\mu H\$

Though, I'm unsure about the \$2\pi\$ on the bandwidth formula. But I think it's without that, but with or without, it as a start, doesn't put the peek in 455 and then the final bandwidth is completely wrong. But I think it's without (any correction is welcomed). How can I put the transistor having the bandwidth I want? Was it not by putting the right values on the C1 and C3 capacitors with the \${f_{L/H}} = \frac{1}{{2\pi RC}}\$? If it's that, I've tried and I get nowhere...


texts: ATX Power Supply Pin Material? (gold or tin)

texts:
I'm planning to use an ATX power supply to power a small set of 12v devices.  I've read plenty of guides about adapting ATX -> bench supply, but I can't seem to find any mention of the connector material for the pins themselves.
I'm primarily interested in the ATX12V 8-pin connector, but the same question also applies to the ATX 24-pin.  I'd like to connect directly from the 8-pin connector to a device without going through a board first, so just wire-to-wire.
I've found the appropriate housing parts from Molex:
(8-pin and 24-pin).
The documentation for both of those housings lists the compatible connector pin types (it's the same pins for both).  The problem is that I have no idea which pin material to choose.  Broadly, the options fall under tin or gold, and within each of those two categories, there are several sub-choices.  For example, there are many choices for 16 awg pins.
My understanding is that gold coating is better for many reasons, but more expensive.  However, gold/tin matings are the worst.  This is a small scale project, so I'm not worried about the cost.  I don't want to buy gold if the PSU pins are tin and vice versa.  I've been unable to find any documentation to suggest which of these materials is used (either mandated by spec or just typically in practice).
TL;DR:

Does the connector pin material matter (tin vs. gold)?
If so, which should I get for interfacing with a standard mid-to-high-end ATX power supply?


texts: How do electricians calculate the maximum allowed on circuit breakers if the current is measured in AC?

texts: Correct me if I’m wrong but the majority of electronics circuit operate of a 3V3 constant DC voltage, which the current would be reasonably stable draw apart from charging up capacitors, chips loading up, so adding up current is relatively simple ie. i1 + i2 ... etc. =iTotal  but most of appliances are powered from mains drawing an AC current which means a sin waveform, so the equation becomes more difficult i1sin + i2sin .... etc. , so to answer my own question would I be right in saying that circuit breakers are rated for total AC current?


texts: How can I use mbed TLS library in my ARM project in Keil IDE?

texts:
I want to do an RSA encryption/decryption using my AT91SAM7S256  ARM MCU. After googling I found mbed TLS library. I download it on my Windows and extracted it in the directory of my project.

I was created the project using Keil IDE as below:

Project >> New mVision Project
Assigning a name to the project
Choosing "AT91SAM7S256" under Atmel MCUs
Accepting the following suggestion:

After that, in the following tab, I added the path of mbed TLS extracted directory to the Include Path of Keil(Path of header files, I think):

Project >> Option for Target "MyProjectName" >> C\C++

As the last step I did a right click on the project name in the right sidebar and using Add files to group AGroupName I added rsa.h and rsa.c of mbed TLS files to my project. I added a file named main.c that I myself was created it already with the simplest content:

#include "rsa.h"

int main(){
    return 0;
}

Here are the pictures of above steps:

Finally I tried to build this project from Project >> Build all target files, but I faced the following error :

Build target 'Target 1'
assembling SAM7.s...
compiling rsa.c...
mbedtls-2.0.0\library\rsa.c(30): error:  #5: cannot open source input file "mbedtls/config.h": No such file or directory compiling main.c...
main.c(1): error:  #5: cannot open source input file "rsa.h": No such file or directory Target not created
<</quote>>

Well, I added config.h to the group just like rsa.c and rsa.h and replaced "mbedtls/config.h" with "config.h" in the rsa.c file and that error removed. but another similar error appeared. Well I added about 10 files and edit the content as described but I still faced similar error.

I want to ask if is this the correct way? Am I should manually add all the files one by one? Or there is a better and efficient way?
As the contents of mbed TLS library shows(make, makeinstall and so on) and as the extension of downloaded file shows(".tgz"), it is written for linux platform. Does that mean I can't use it in windows?
As a starter, witch one is better for the above described project? Keil vs IAR IDE? Windows vs Linux platforms?

Note that this is the first step of project, I think I must add other algorithms also.

Thanks in advance.


texts: Ethernet controller ENC28J60 not working with Arduino Nano nor Mega

texts:
I have a problem with running  ENC28J60 with Arduino with EtherCard.h.
This is the device I use: http://img20.allegroimg.pl/photos/oryginal/36/70/08/91/3670089168
This is the library and examples:  https://github.com/jcw/ethercard
I use Arduino IDE  1.5.4 on Windows. The library and skeches compiled without any errors.
I tried connecting ENC28J60 to Arduino MEGA 2560 this way:
GND   GND
VCC   3.3V
SO   Pin50
SI   Pin51
SCK   Pin52
CS   Pin53

The LEDs on the RJ45 were active (green on, yellow blinking), but example DHCP or static IP failed or showed IP 0.0.0.0. Router detected the new device but the device did not responded to pings.
I tried the modified example with modified line:

if (ether.begin(sizeof Ethernet::buffer, mymac, 53) == 0)
    Serial.println( "Failed to access Ethernet controller");

Where pin 53 is specified in ether.begin() function - with the same result.
Then I tried connecting ENC28J60 to Arduino Nano this way:

VCC   3.3v
GND   GND
SCK   Pin 13
SO   Pin 12
SI   Pin 11
CS   Pin 8

But then the LEDs on RJ45 blinked during connecting ethernet wire, and went dark.
The red LED on ENC28J60 was on during above experiments.

I would apprieciate any help. I found many projects with google were people use  ENC28J60 + Arduino Mega/Nano without a problem. I think that the EtherCard library version may not work with the latest Arduino IDE I have but then I don't know what version should I use, or maybe should I use some other library.

I need the ethernet controller for serving simple web page allowing changing the state of relay ON/OFF.

Some update:

After some debugging I can see that the code hangs in this line:

while (!readOp(ENC28J60_READ_CTRL_REG, ESTAT) & ESTAT_CLKRDY)
    ;

in enc28j60.cpp file.
I suspect that I have faulty enc28j60 module.


texts: I need to modify the option bytes at compile time for STM32L0xx controller and generate the binaries i.e. .hex, .bin. could you please suggest a solution for the same. I amusing STM32Cube IDE for development in C


texts: thyratrons or vacuum tubes for relay control

texts:
I am trying to build a tube amp without using any semiconductors (just for the fun of it, trying to make it using the technology that was available when tube amps were mainstream). I may need to control some relays in it, however, I cannot figure out how, or rather, how to do it properly.

I have some thyratrons (both hot and cold cathode) and obviously some vacuum tubes.
I may have to:

turn a relay on or off with a pulse (like a push button)
Switch between two relays (one off one on)
have a relay turn on for some time then turn off (shorting the output of the amp for a few seonds to avoid a pop when switching inputs etc).

How do I do it without semiconductors? I currently do not have a specific application in mind, just looking to learn more.


texts: Program an ATtiny13 as an audio oscillator with variable frequency and pulse-width

texts:
I want to create a simple square wave oscillator similar to what one would do with a 555, but I want to use interrupt based PWM support to control pulse width and frequency.

I have been studying the datasheet, AVR APIs and whatever PWM examples I can find, but I haven't quite been able to put it all together.

Is it possible to create such an oscillator with the built in AVR PWM functionality and, if so, how? I friend of mine did something similar with an 8 pin PIC.

My reasoning is that I will get interesting sounds by changing the pulse-width and therefore the wave form at a given frequency. Similar to how the Atari Punk Console works but hopefully in a more stable way, i.e. changing the pulse width, but leaving the frequency constant or vise versa.


texts: Resistor network explanation and calculations

texts:
First question - What is this resistor network doing? Answered that it's linearizing the thermistor but this isn't what I was looking for. I'm looking for an explanation that describes the relationship between the resistors and the output

Edit (June 23 2015) for Question #2:

I'm doing calculations on the beginning resistor circuit and something's not making sense. I need help calculating or an equation which will give me the voltage for Vout.

Here are the numbers I've been using.

V+ = 12V
RA, RB, RC, Rd = 15kohm for simplicity I'm using all the same amount
Rth (multiple data) = 15k, 9.6k, 2k, 39k

I took measurements from the RA,RB,Rth node (#1) and RB,RC,RD node (#2) and the Rth,RD (Vout #3) node.

For:
•

Rth = 15k -> #1 = 7.5, #2 = 4.5 and #3 = 6V.
Rthh = 9.6k -> #1 = 7.4, #2 = 4.6 and #3 = 6.3V.
Rth = 2k -> #1 = 7.2, #2 = 4.8 and #3 = 6.9V.
Rth = 39k -> #1 = 7.64, #2 = 4.36 and #3 = 5.24V.

I understand #1 + #2 = V+. But if I do voltage division for #3, it doesn't give me the correct voltage. I'm assuming because Rc is coming into play with Rd (parallel?) but I'm not 100% sure. I've been told the only reason #1+#2 = V+ is because Ra = Rc. I came to that conclusion because I'm trying to find the relationship between all of the resistors.

What am I missing?

Overall circuit task: I am trying to put 12V into the circuit and get 1-5V out of the opamp depending on the amount of light the Thermopile picks up for an outside application. So the temperature could be 30F to 110F (0C-43C).


texts: Why is my voltage controlled current source circuit not reaching above 1A?

texts:
I was given a circuit that converts 0-10V to 0-1A using an op amp and a mosfet. The current is driving a solenoid. However, I needed to alter the circuit to provide 0-1.5A using the same voltage range. The circuit has a voltage divider built in before the op amp to scale the voltage from 0-10V to 0-1V. I know that whatever the input voltage is supposed to be in the op amp, it will drive its output and the mosfet to match this. However, when I implemented the voltage divider to produce a 0-1.5V input in order to cause a 0-1.5A output, it will not reach above 1A. I have tried looking up why this occurs and I cannot find anything on the internet about this. Does anyone have any idea why the voltage/current will not reach above 1.5?
Circuit schematic:


texts: How to measure current in a DC series parallel circuit using a DMM?

texts:
Today in class I was given the task of building a circuit in a simulator, then building it on a breadboard to measure the current/voltage/resistance etc. This was my first time working with a series-parallel circuit, and I just couldn't get the right measurements for current.

I understand that the ammeter must be in series with the circuit, but it seemed as though no way of breaking the circuits would give me the expected current.

Ex:

How could I break the circuit to measure the resistance through R4 in this diagram?


texts: Switch multiple contacts in parallel from a single 24V DDC output

texts:
I have a DDC (direct digital control) with a 24V digital output and I need to control around 100 external circuits, each having their own input.

The switching distance between DDC and remote panel will be anywhere from 25 meters to 100 meters, they would share the same building ground.

There are two types of output available on the DDC (and ideally would like to use both types to increase the utilization, ratings below are per output):

Digital output dry contact (relay contact, SPST NO, 48VA at 24VAC)- pilot drive @ 24VDC 0.5A, or direct drive @ 24VDC 0.5A.
Universal output configured as digital output. Open Collector Output, Max Sinking Current Rating: 200mA @ 24VDC.

I would like to connect them in parallel and switch all at the same time (near, timing isn't key).

I don't want to have to provide 100 DDC I/O to do this, and would like to do it via as few as possible outputs (ideally one DDC output to 100 external circuits) - even if one DDC output could control 10 external dry contact circuits that is ok.

Questions please:

Is the switching of multiple external circuits in parallel possible in this manner (intermediate higher power relay is OK), if so what calculations would need to be looked at to ensure we are well within head room of what current the DDC can source (if any is required)?
This input type of the remote systems can be specified at this time as the remote devices are yet to be built, if it is advantageous to use opto-isolated inputs then we can specify this.
The manual states on page 11 of the digital output wiring connection It does not output voltage or current. It is a dry relay contact - is it right to say that the meaning 'dry' for the digital output (as opposed to the universal output which is open collector) is that it is not sourcing its own current and we need to provide the 24V externally, and it is just the switch that is closed in the output within the DDC electronics? What is the difference in meaning between pilot drive and direct drive?
I see one question in comments as what voltage is present on the dry contact inputs, how much current flows when you complete the circuit? I guess the current depends on the input if it is opto-isolated or a dry contact relay (we are free to specify) - any benchmark current ratings between opto-isolators and dry contact current required @ 24V?


texts:
My Components:
ESP32 Dev Kit C from Az - Delivery
Power Adapter 5V - 5A
Level Shifter
RGB - STRIP
I'm using the Adafruit_neoPixel library. My programs are working fine with the LED-Strip, but every time i clear the strip some random LEDS are lightning in different colors and with different brightness.
On my ESP8266 it worked without problems.
The assembly
https://drive.google.com/file/d/116THKp5w-OJPHqCHTN398WxaH3-hWZXn/view?usp=sharing
My Test-Code:
#include <Adafruit_NeoPixel.h>
#define LED_PIN3 17
#define LED_COUNT3 150
Adafruit_NeoPixel strip3(LED_COUNT3, LED_PIN3, NEO_RGB + NEO_KHZ800);
void setup()
{
  // Initialsierung Strip 3
  strip3.begin();
  strip3.clear();
  strip3.show();
}
void loop()
{
  uint32_t green3 = strip3.Color(255,0,0,0);
  uint32_t blue3 = strip3.Color(0,0,255,0);
  uint32_t red3 = strip3.Color(0,255,0,0);

  //strip.setBrightness(25);
  //strip2.setBrightness(25);
  strip3.setBrightness(125);

  strip3.fill(green3, 0, 150);
  strip3.show();
  delay(5000);
  strip3.clear();
  strip3.show();
  delay(5000);
}

The Random LED`s:
https://drive.google.com/file/d/1Fl7ZuFU_VvzgoixMGkxw5vANh4sGxeNN/view?usp=sharing


texts: Is over charging the phone while using headset risky

texts:
I recently came across a post in social network which was claiming to be a news about a girl getting electrocuted during her sleep with her headsets connected to the mobile and the mobile being connected to a charger.

Leaving aside the authenticity of the news, I was wondering whether there is any possibility of such an incident, considering even the rarest of the rarest scenarios.


texts: Testing a power supply without hooking up its intended load

texts:
I have a PSU that I would like to verify and see if it is outputting all of the correct voltages.

It's an old computer PSU from 1990 with a specific form factor that cannot be easily replaced with a new one.

The PSU will only switch on with a certain load attached to it. Usually it is sufficient to hook up a hard drive or an old floppy drive in order to get a computer PSU to start properly. Without load it will either not start, or try to switch on but make a clicking noise. Without load it is also not possible to measure any output voltages.

I am always a bit reluctant to hook up the actual intented load on to it (in this case a mainboard + hard drive + floppy drive), in fear of risking to damage the mainboard should there still be an issue with the PSU.

What is the best way to simulate such a load ? I was thinking about hooking up some resistors on certain power lines (The PSU also exposes -12V) but I am a bit unsure on how to calculate the resistor values (actual resistance but also wattage)

What would be a safe / meaningful way to simulate some load and make the PSU think it is hooked up to the mainboard, so I can verify that the voltages are OK before hooking up the PSU to the mainboard.


texts: Two Five-foot Ground Rods vs. One Ten-foot Ground Rod

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I am thinking about installing two five-foot ground rods in place of one ten-foot ground rod. What would be the relevant comparison(s) and contrast(s)?

Let me know if you need further information. Thanks in advance.

PS: My reason for the replacement strategy is because I would dig two five-foot holes rather than one ten-foot hole. My main concern is whether I would be losing total resistance by doing so.

PSS: I am using enhanced/chemical ground rods. I am sorry for the confusion led by my omission of this information regarding digging holes for ground rods.


texts: Do we analyze real poles the same way you analyze complex conjugate poles?

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So I am analyzing a filter and I came up with the following expression for the transfer function in its canonical form:
$$\frac{987654 + 4666.67 s + 1. s^2}{2.48519 \times10^8 + 52316.2 s + s^2}$$
which of course is of the type
$$\frac{\omega_z^2 + \frac{\omega_z}{Q_z} s + s^2}{\omega_p^2 + \frac{\omega_p}{Q_p} s + s^2}$$
Now I went on to calculate the poles and the zeros and came up with real poles and real zeros.
$$z_1=-222.222$$
$$z_2=-4444.44$$
$$p_1=-5284$$
$$p_2=-47032.2$$
Now if these were complex conjugate poles and/or zero I would proceed to check for the natural oscillation frequency (\$\omega\$) and quality factor (Q).
Now I feel that talking about the quality factor actually as, since it is below 0.5 it will match the fact that we have real poles and or zeros. But does it make sense to calculate the frequency. Because since the poles/zeros have different real parts, they oscillate in different frequencies.
I actually checked for the Bode plots on this site http://www.onmyphd.com/?p=bode.plot.online.generator and it indeed shows, in the asymptotic one, that we have 4 different frequencies affecting the slopes. So what should be my correct interpretation? I feel there are some underlying concepts here that I'm missing? Can someone help me organize my thoughts on this?


texts: Connecting capacity modules to Weidmueller power supplies

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In weidmueller power supply catalogue, There is a "Capacity Module" as an expansion module for the power supply to  ensure a secure power supply even at peak loads (for example when the motor starts) and the specific triggering of circuit breakers(as the catalogue says). But I cant understand what exactly capacity modules are? are they a solution for bridging short-term power supply failures? How can they be used in  triggering specific circuit breaker?

this is the link to the weidmueller capacity module for power supply catalogue.
http://catalog.weidmueller.com/procat/Product.jsp;jsessionid=86A7E09EBD413FB06A36C80BE6551A5C?productId=(%5b1222240010%5d)&page=Product


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My input source is 3x1.5V alkaline batteries.

The input power supply is then connected directly to a 12V voltage boost regulator. I used my multimeter to measure the current draw of my load and it reads 200mAH. (The multimeter is connected series after the regulator and before the load)

Question:
How long will my batteries last assuming they have a total capacity of 900mAH? And will the current draw be the same if I used a 12V power supply non boosted? (Assuming the voltage booster has an efficiency of 100%)

My thinking is that since the voltage is boosted, in order to maintain the same power rating, the current draw will increase, which makes the actual current draw 533mAH in this case. Please advise!!


texts: Danger to laptop due to fan malfunction even with cooling pad?

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My laptop fan makes noises that indicate to me that it is failing -- if I accident nudge it abruptly, it can become very noisy and even make a loud buzzing noise before it seems to shut off although the laptop itself continues to run.
The cooling pad I bought seems to increase the length of time before the internal fan turns on but the fan continues to run even though the laptop feels cooler than without the cooling pad.
Can I just ignore the malfunctioning internal fan or can a broken fan damage the laptop either due to heat damage (even though the laptop with the cooling pad feels ok) or some kind of mechanical damage from the fan blades?
I would like to simply disable the internal fan but there seems to be no way to do so and maybe that is a bad idea; but if it is a bad idea, eventually the fan will fail entirely I would guess and then I wonder if the laptop will no longer work, even with the cooling pad?


texts: LC circuit + diode problem ! (without resistors)

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What will be steady state capacitor voltage?

My hit at the solution:

The static resistance of the diodes come into action causing a large current to flow across the diodes ( assuming diode isnt damaged) the voltage initailly at the input of LC circuit is 6v which appears across the inductor causing the current to increase ,eventually charging the capacitor to 6v. Also,when the current in LC goes negative,the Diode D2 does provide a path which would mean current in LC ciruit should be sinusoidal!

My doubts:

1) What happens after the cap reaches 6v ,the inductor current is still non-zero right?
which would mean the cap should continue charging?

2) How is steady state achieved in the circuit?

3)Why does cap stop charging at 6 volts?

4)Will the current oscillate in the LC part?


texts: Basic circuit analysis?Which are parallel?

texts: I think there are 6 nodes(as I've labelled in the picture),8 branches and 6 loops in the circuit.But which resistors are parallel to each other?R7||R4,R2||R5||R3 + R6 ?I'm really not sure.Can someone give an answer an explain?