texts: Are BJTs suitable for level-shifters? It seems FETs are more common,how do they compare?

texts:
I'm a hobbyist, and never got past the datasheets/tutorials for FET transistors; I'm a BJT man. I never found discussions dealing with BJT vs. FET and specific applications best suited for each type. My projects are very simple switching and logic gate style circuits. So once I got BJTs to satisfy a project's requirements, I just stayed with what was working. I have spent the afternoon researching this on EE-SE and found lot's of good stuff. I found that FETs seemed to the more popular choice for level-shifters. I was hoping someone could provide a "for dummies" explanation regarding the strengths/weaknesses and trade-offs involved with FETs and BJTs in some common applications.

I chose this level-shifter for my project:
I want to drive a 5V relay using an ESP8266 which has 3.3V GPIOs. I measured the relay's coil current to be right about 100mA. I want to use an S8050 and a minimum of parts, requirements are not high. I'm just using the ESP8266 to read the pin on a PIR sensor and also read some toggle switches to control a light using a relay. Is the above circuit a good choice? I designed my own circuit, but am not going to use it. Still, it would help my understanding if someone would kindly provide an analysis of my design, which was based on some hunches, guesses, and perhaps a bit of voodoo.

Just briefly, I reasoned that my base-current (GPIO output 3.3V - 0.7V base of Q1) / 1K ohm of R2 = 2.6mA would not be affected much by the current in the voltage divider R1/R3 which I think is 5 / (100K +100K) = 25uA. I don't know how the junction of R1, R2, R3 and U1's base will work; I guessed that the base of U1 will pull the 2.5V of the divider down to 0.7V, but wasn't sure how it would affect the 2.6mA that the GPIO sources. That's why I went with the circuit I linked.


texts: Problem with Simulation Results VS Tested Results for a signal

texts:
For the circuit shown i am having some trouble wondering why my tested signal looks like this (i understand that it could be clipping) but when i measure my circuit in the simulation it is correct? What could be causing these issues. I have to make a signal play through a speaker and just dont get what the issue could be? The amps are 2 x lm6484 and 1 x lm386. The circuit works perfectly and plays the sound as it should (with the 50k resistor being the potentiometer) but i just dont get what coiuld cause this change to the signal?

Could it potentially be a faulty breadboard. Also on another note i have a problem that when a different recording is played, the gain of the amp isnt 20, why is this?


texts: Circuit with reversing polarity and two microswitches

texts:
I am building a time-lapse camera slider with the following components

2rpm DC gearbox motor
PWM with reversible DPDT switch to reverse motor
2 SPST Microswitches

I am trying to wire the microswitches at either end of the track to stop the motor from running. However when the cart reaches the end of the track, the circuit is open, and the reverse direction switch is thrown the microswitch is still open and doesn't allow the cart to move. Is there a way to disable one switch at a time and leave the other active. Here is an image of how its currently setup.


texts: Op amp phase shifter with unity constant gain - How does this circuit shift the phase between -180 and 0?

texts:
(Kindly if its possible to understand this circuit w/o \$j\$.. I haven't made peace with complex analysis yet... so I beg your pardon using
 nasty trig expressions... )

Below circuit is NOT a phase shifter.
As \$R_4\$ varies from \$0\Omega\$ to   \$100\Omega\$, the voltage gain varies from \$-1\$ to \$0\$. I pretty much understand how this circuit works.

simulate this circuit – Schematic created using CircuitLab

If we simply replace \$R_4\$ by a variable capacitor, this circuit suddenly becomes a phase shifter with constant gain = 1. I see that input becomes a \$RC\$ lag circuit with fundamental frequency  \$\omega_0 = \dfrac{1}{ R_3C}\$.

As we change the capacitor value, the phase angle \$\phi\$ across the capacitor voltage varies between \$-\pi/2\$ to \$0\$. So the noninverting input at the op amp is \$V_+ = \dfrac{1}{\sqrt{1+(\omega/\omega_0)^2}}\sin(\omega t + \phi) \$,

where \$\phi = -\arctan(\omega/\omega_0)\$.

Question1 : The input phase \$\phi\$ can only change between \$-\pi/2\$ and \$0\$. So intuitively I expect the output phase also to change with in that window; that is not more than \$\pi/2\$. But my textbook claims that the output phase changes between \$\color{red}{-\pi}\$ to \$0\$. Its almost like the opamp is amplifying the phase difference by a factor of \$2\$. How is this possible ?

Question2 : How can the voltage gain remain constant ? The input voltage \$V_+\$  is a function of \$C\$, it clearly decreases as the capacitor reactance  decreases. Shouldn't this disturb the output voltage ?


texts: Do I have other options but shorting out those diodes?

texts:
I've been trying to connect my LED stripe -> rgb amplifier -> Arduino Mega 2560 -> PC. After connecting it according to this guide, nothing happened.

Looking inside the amplifier I noticed the three 5.1V Zener diodes. Using a multimeter I discovered the 5V from my Arduino only carries ~3.8V to those diodes and it consequently stopped there. Shorting out either diodes made my lights glow (and it only took me a few hours to get to that point..).

Now it seems I have two options:

Sending it back and order another one which hopefully uses different diodes
Using a soldering iron and short them out myself

Is the later even an option? Are there any safety issues?

Is there something else I can do?


texts: I've noticed is that 555 ICs seem to be extremely common.  Why is the 555 so prevalent, or ubiquitous; what about it so useful?


texts:
(Note: this is not a "repair" question - I have already decided I need to replace either the battery or the whole UPS)
I am probably overlooking something really obvious here, but... here goes.
I have an UPS with an (almost) brand-new sealed lead-acid 12V battery, three months' service life, holding 7 Ah of charge. So, that would be ideally an energy of 84 Wh. Taking into account a 20% deep-discharge margin (I don't want to go below 20% charge), and a further 10% loss in DC-to-AC conversion, that would leave me with 60 Wh of useable AC energy.
The UPS reports a load of 15% of its 540W nominal value, and additionally reports a load of 82 W. This makes sense, as 15% of 540W is 81W and some reporting approximation can be expected.
Now, in my book, having 60Wh of energy and needing to supply 82W of power translates into an autonomy of about 44 minutes (60 / 82 is 0,73 hours).
The same UPS (and a crude testing, consisting in unplugging the AC cord while holding a stopwatch) reports an autonomy of about four minutes - exactly one tenth of what I would expect. This with what is reported as a full charge (100%), with battery voltage reading correct.
If it was under its advertised load (540W), draining six times more current, I expect it would die in about forty seconds. This cannot be the expected performance.
What could be the issue here? Running the calculations in reverse I conclude that it must be the battery that is defective, and only holds 0.7 Ah instead of the advertised 7 Ah.
What baffles me is how can the UPS know this (since the "4m" time left estimate is spot-on). I don't quite believe it integrates the charge current over time.
So, either the defect lies elsewhere, or the UPS does not behave like I thought. This kind of information was not detailed in the documentation, so I'd love to be enlightened.


texts: How to place a hole at an angle in Eagle

texts:
I am trying to create my own package in Eagle 6.6. I have to place holes at specific angle of 36 degrees.

I need to place 10 holes on the circle with an angle of 36 degree to each hole.

The package I am trying to create as shown below:

I have created a circle with 5 mm diameter. The first hole I placed at position (0 2.5) so its top and bottom hole also like (0 -2.5). I am confused about how to place next hole at an angle of 36 degrees. I had placed 10 holes on the circle but those are not at correct angle to each other.

The package I am creating as shown below:

Can someone help me with this?


texts: What impact, if any, does the solder mask color have on the electrical and mechanical properties of a PCB

texts:
At my place of work, we use soldermask colors as a sort of poke-yoke for manufacturing purposes E.g. Technicians know that green pcb goes with green, blue pcb with blue, etc. This has lead to some ... esoteric color choices including matte white, hot pink, blue/red sunburst, etc. for our soldermask. Our board fabs are usually happy to oblige, and we have had no reason thus far to question the dye choices.
However, during a discussion with a manufacturer about quality defects, their production engineer claimed that dye's used to make the soldermask color have a subtle impact on reflow, creepage, solderability, electrical conformance and dielectric effect. Specifically citing increased risk of soldermask voids and solder spreading under the soldermask layer for blue dye solder masks.
Is there any validity to this, or research to support this claim?. Moreover, are there any differences that could conceivable have an effect. For example, reflow temperature considerations  when using very different solder mask colors (e.g. gloss white vs matte black) but nearly identical PCB and components.
I assume any material differences are up to the PCB material supplier, and while I am sure in that domain there are different materials and dye's used, I have always assumed it to be equivalent if it is offered as an option by the fab.


texts: What processor registers are saved and recovered in a "context switch"

texts:
A fundamental component of any OS is multi-tasking. It must be able to switch between tasks/processes.

What registers are required to be saved and restored when performing a context switch? Where are their values saved to?


texts:
I am having a hard time understanding the MCP4162 Datasheet.

The application for the digi pot is have an Ardunio to control the wiper resistance so I can have a constant desired output voltage regardless of input signal. So depending on the input signal the digipot will find the ideal resistance to get close enough to the target output voltage of 1.98V.

Example: Set Output Voltage = 1.98V

Input = 1.414Vp

\$Digi pot = ((\frac{V_o}{V_in})-1)*R1\$

\$Digi pot = ((\frac{1.98}{1.414})-1)*1000\$

\$Digi pot = 400\Omega\$

Input = 0.5Vp

\$Digi pot = ((\frac{V_o}{V_in})-1)*R1\$

\$Digi pot = ((\frac{1.98}{0.5})-1)*1000\$

\$Digi pot = 2960\Omega\$

simulate this circuit – Schematic created using CircuitLab

I have read the datasheet multiple times and I still don't which register is the one I need to be changing.

The one I would assume is the 0x04 address where it's described below. The datasheet only tells you about 2 registers and what their bits do when you write into them.

and I dont understand the equation stated in the datahseet that tells you the output resistance.


texts: Is one big PCB cheaper than multiple smaller ones, if so how to do this in Eagle PCB?

texts:
I have heard/read somewhere that one bigger PCB is cheaper than multiple smaller PCBs, is this correct?

If so, then rather than order seperate PCBs for different parts of a project e.g main board with "daughter boards", is it possible that the PCB file of different PCBs be combined together such as to create one single PCB which can then be cut into its individual pieces once manufactured.

I am not talking about combining the schematics. I am talking about the actual files that give the details of how to manufacture the PCB and combine them such that it becomes one board.

If this is good idea and possible, how can this be done in Eagle PCB?


texts: Is there an affordable way to learn the details of IEC 60950?

texts:
I'd love to read the actual spec, but it costs more than $300.

Is there a good summary somewhere on the web, or maybe a good book about it? I will pay $300 if I have to but I can think of many things I'd rather do with that money.


texts:
I'm designing a circuit with this LCD display.
It will interface with STM32L0 MCU over SPI bus.
as you can see, in LCD's datasheet there are only 3 lines of SPI pins. SCL - Clock, SI - Serial Data and CS.

I've wondered, is it because the LCD only receives data from SPI Master and not sending back any data? Is it possible to use SPI bus like that with route only 3 pins?

thank you!


texts: Multisim issue with current in differential amplifier

texts:
I did simple differential amplifier simulation:

As you can see Q2 current is negative, it is not possible right?
Also, if input signals on both transistor base are equal, u1 (volt metter) should show 0V but instead shows some nV, I know it's not much but looks like multisim try to be smarter then it should.

PS: The amplification depends on transistor beta value right? So the output voltage will be B times bigger than input difference. Is that understanding correct?


texts: NodeMCU v.1 / WEMOS Mini - Fail to Wake up from deep sleep

texts:
I'm Trying to put to deepsleep a Wemos mini/ NodeMCU / ESP-01, and facing the same problem - fail to wake up.

Looking around - I've found some articles such this github issue, and this issuedescribing same behavior of not waking up as expected.

code as posted in first github issue, which is very simple:

void setup() {
  Serial.begin(74880);
  Serial.setTimeout(2000);
  while (!Serial) { }
  Serial.println("Started.");
  delay(5000);
  Serial.println("Going to sleep.");
  ESP.deepSleep(30e6);
}

void loop() { }

Hardware setup: pins connected: RST + D0

But at the end - I found no solution but saying that "some of chips/ boards fail to wake up".

Since all my boards at hand fail, I don't know if is if the formal answer for that phenomena.

Any assistance will be appreciated,


texts:
I am working on a simple FM radio receiver. Built the circuit and it works very well. Learned few new things, and got some questions, especially the output stage. The Op-amp 2822 is a dual op-amp, but the output is only mono. One of the op-amp output is connected to one side of the speaker and other output to other side. The speaker doesn't connect to the ground in this setup, Very strange. there is Also a 10u electrolytic capacitor connected to the inverting inputs of these 2 op-amp. will a normal 104 ceramic cap works? and also what are the purpose of C11, C12, C14 and R6?

Another thing is CF2 and CF1; Are they ceramic resonators? but one has 3 leads while other only 2. and do they have polarity?

last very interesting thing is from the input stage. There are 2 resistors connected to the collector of the 9018, and there is a biased resistor 150k connected in between. what is the benefit of this setup? (instead of using one collector resistor and connect the biased resistor to the collector directly. )


texts: Lattice Diamond Port 'direction' is unconnected

texts:
I am following the tutorial to turn on the LED on the embedded vision development kit found in:

C:\lscc\diamond\3.10_x64\docs\tutorial\Diamond_tutorial\Ledtest.v

and when translating the design I get the following error:

I can't figure out what I did wrong. Is this even an error?


texts: Battery capacity: Says 12V18Ah/20Hr - how do I interpret that?

texts:
I have two sealed lead-acid batteries in parallel that have that inscription on the sides.

They power multiple 10W (Actually, 7 on the meter) PIR lights all night long, as required.

That inscription has me confused.

The first part is obvious, 12 Volt, 18 Ah.  But why does it say 20 Hr?

My guess is that it is telling me I shouldn't take more than 18/20 of an amp hour, and it will last 20 hours.

So, assuming 5 of my lights turn on, at 7 Watts Each, that would be 35 Watts, divided by 12V would be about 3 Amps.

Going strictly by the 18Ah rating I would expect 6 hours at that rate.  (In reality, I never draw that much for that long.  It is for young'uns to go to the bathroom at night and things like that.

The 20 Hr thing makes me think that it is a warning that battery damage might occur if I try to use all of those 18 Ah in less than 20 hours.

But clearly my concern is peak power load times.  It is possible for all of the lights to be on for an hour or so if the girls get up and work in the kitchen at night.

I believe my best way to interpret this is to keep it on a 2 Amp AC-powered trickle charger at all times, instead of just running the trickle charger off the inverter during daytime when the sun is out.

Agree?  Disagree?  I haven't used sealed batteries before, so don't know if the constant trickling might exceed that limit, also.


texts: In 4 Layer PCB - which internal layer has to be consider to calculate Microstrip characteristic Independence for bottom layer

texts: 4-layer PCB stack-up as shown in attached figure - In case of bottom layer; which internal layer has to be considered to calculate characteristic impedance for microstrip line on that layer. Is it power plane or ground plane?


texts:
I recently completed an Advanced Diploma level course subject for PCB design that taught Autocad as the design software.
Whilst I am aware of the power of Autocad my subsequent surveying of engineering firms has shown that none of them used Autocad and the majority 60% used Altium.

So my question is:
Is anyone one involved in PCB engineering/design or repair in a professional capacity use Autocad?
Thankyou.


texts: Where do I find those AC mains connectors?

texts: I am currently designing a "smart" power strip for aquariums and cant find an PCB mounted wall outlet connector like the image shows, it would be used to connect the load and not for powering the board.


texts: How can I tell what type of capacitor to use with an electric motor, if any?

texts:
I understand capacitors are used to reduce electronic noise from motors. I bought a little 4-motor car chass off of ebay and I wanted to know

a) Does this motor already have a capacitor built in to reduce noise? (can I check that with a digital multimeter?)

b) If the motor does need a capacitor, what would be the formula(s) I need to study to find out how to match the right capacitor with the motor I'm using?

Thank you


texts:
I need to find a way to trigger this Hall Effect Sensor with a non-permanent magnet. Does anyone know if an inductor's magnetic field would be strong enough? Or am I going to have to build an electromagnet? If it helps to know I am trying to send data wirelessly by turning a magnetic field on and off and tripping the sensor on the other side to pulse out RS232 data.

EDIT:
Current: Needs to be no more than 30mA.
Distance: A 4mm air gap.
Minimum data rate: Around 256Bits/second.
Size: Needs to be as small as possible.(Must fit into 5x10x5mm spot)
Cost: Looking to keep it under $1.50

EDIT2:
It is Unidirectional -
30mA transmit -
for now I don't really care how much it costs. I just need to get it working

EDIT3:
Okay. I have decided to do it optically. Does anyone known where I can get an IR detector in the 1.5micron range?(Should I move this to a new question?)

Actual data sheet here


texts: How can I boost/limit a signal to TTL levels?

texts:
I am researching a data acquisition system to measure the amplitude and frequency of a 4,100Hz 5v-25v AC square wave signal. Actually this is version 2 for me, in the previous version I analyzed the captured data points and counted the rising edges to determine the frequency, this worked pretty good. On version 2 of my system I would like to use the 32bit counter that is present on the data acquisition card. This counter accepts a TTL level signal. The card has a maximum of 10v analog input for the amplitude measurement, I will use a voltage divider to divide down the signal to within acceptable ranges. R1 = 806Ω, R2 = 196Ω which will result in a vOut range of .98V - 4.89v

All this is fine, but now I run into the problem of the divided signal not be within the valid TTL input range of 2.0v - 5.0v. I had planned on using the divided signal as an input to the counter. I'm not an electronics engineer and this is a problem I know nothing about.

How can I condition the signal so that small positive voltages are boosted to TTL HIGH levels (i.e. 2V) and high positive voltages are limited to TTL HIGH voltages (i.e. 5v)? All of this with minimal effect on the signal being measured.

Any help or guidance greatly will be greatly appreciated.


texts: Simulating an automotive load dump with a bank of charged capacitors?

texts:
I've been working on a data logging device that will eventually go into my personal vehicle.  I've scoured the interwebs and built what, in theory, should be a fairly stout power supply capable to handle fast transients and undervoltage and the fabled load dump.  My problem is, though... I want to actually test the power supply.

In previous questions that I've asked related to the design of the power supply portion, I've been told that the "right way" to simulate a load dump is with a proper, preofessional testing device.  I'm curious, though... what's stopping me from rigging up something that is "close enough"?

My idea is simply this: get a low-voltage DC power source, such as an old PC power supply.  Get a DC-DC converter to step that 12V up to something in the 80V range.  Assemble a bank of capacitors to get me in the neighborhood of a theoretical 12V load dump..  which from what I can tell is in the hundreds of joules range.  Once charged, simply connect it to the battery input of the device - which wouldn't be connected to an actual power source lest I want to potentially screw that power source up - and see if explodes, and if not, see if it works normally afterwards.

Does this sound like the dumbest idea you've ever heard?  Is it a somewhat decent idea that simply needs a lot of planning and number checking to in order to work roughly as intended?


texts: How do these powerline networking adapters work?

texts: I have some powerline networking adapters which can transfer at a peak rate of 200 Mbps (I get around 60 Mbps typical, but I am sharing the network with many other devices and many pieces of equipment are running on the line.) How do they do it? I always thought that it was during the zero crossing, but packing so many bits into such a space must be very difficult, nigh impossible. HowStuffWorks has an article on it, but it's only relevant to adapters which go at 14 Mbps.


texts: Matching appropiate current value for components

texts: I was looking around the site and I encountered an intresting answer.The one who posted it said that:"If you supply too much current to a device,it will draw as much as it needs" and also that if you give a smaller amount,it is possible to damage it.Now I remember that I tested a LED with a higher current(a significant number of mili-amps past the operating spec) and it wasn't really affected in the way I expected it to be.It looked to be just a little dimmer than usual.Is it true that only less supplied current would damage a device/component and not a higher one?It sounds absurd to me,but I just wanted to be sure.


texts: Arduino overheating with 5V addressable LED strip

texts:
I've got one of those 1-meter addressable RGB LED strips from Sparkfun (link) connected to an Arduino. The Arduino is powered by the recommended 9V DC 650mA power supply through the barrel jack.

According to the Sparkfun website and product video I should be able to power these from the 5V pin (also 1 data pin, and a ground connected). But when I do, the board gets really hot (untouchable). Also, if I try to set all the LEDs to white - they just fade down after a few seconds.

I'm guessing the LEDs are trying to draw too much power from the board? If so, what is the correct way to power both the Arduino and the LED strip (preferably from a single power supply)?


texts: How to cut off power supply if Input voltage is greater than 12Vdc and less than 7.2 Vdc

texts:
I need help here is the diagram that I followed. In this diagram, the supply will cut off if the Vin is less than 6.5Vdc. Now I want to cut off if the supply voltage is less than 7.2V and greater than 12V. Is this possible?

I found this on https://www.electroschematics.com/78xx-voltage-regulator
Any help would gladly be appreciated. Thanks


texts: Transformers and phasors question please?

texts:
We have the circuit in the figure.I have to find n for which RN has the maximum power.What is the power?We have that J=2A,R1=1 Ohm,R2=75 Ohm,RN=100 Ohm

I find the Thevenin equivalent for the left part of the circuit,where V=J*R1=2V

The reflected load impedance is \$ZL’ = \frac{ZL}{n^2}=\frac{175}{n^2}\$

For maximum power transfer,I have to equal this to ZL' but is ZL'=R1?

After I learn how to find n there,its easy to find the power...but how do I find n?


texts: Optimizing regulator power circuit for low noise?

texts: I am trying to understand the attached circuit. It's an ADP3333ARMZ-3.3-R7 regulator to provide 3.3V to an analog system. My goals is to have a very low noise regulator and power circuitry for a 16 bit resolution Analog Circuit that is attached to it, but am concerned this design is not optimal for low noise. Does the inductor indicate that it is a noisy regulator? Next to the inductor there is a surge resistor which also sounds like it is expecting noise, is there are better regulator to use for low noise applications? Also, can I replace the polarized capacitor with a non-polarized capacitor? The data sheet for the ADP3333 regulator suggests it can have a capacitor as low as 1uF - why is the capacitor at the input 10UF? Love any insights on how to optimize this circuit.


texts: Adding Low Bandwidth 3G Internet Access to Embedded Device

texts:
Do any companies offer devices to allow limited cellular internet connectivity for low bandwidth data transmission.

I'm imagining an embedded device that typically does not have (nor need) internet access but could access the internet via cellular networks to transmit error reports back to home base. Do any companies offer such systems without the need of a full blown data contract?


texts: Dual smart battery design and PCB layout

texts:
I have a system that is powered by a 7.4V Lithium-Ion battery. The system, which is a combination of processor module and sensors, draws a varying amount of current at varying voltages (5V, 12V, -12V, 6V...) but pulls about 10 watts. The battery I chose is quite a hefty 10 amp-hour one.

This started off with a simple off-line charger which is no problem. Then feature creep set in (sigh) and now I'm tasked with a dual battery + charger with gas gauges. That means there are up to 3 DC sources to be managed - two batteries and a charging port. And I've two months.

One way to do this is use a fully featured chip like the LTC1760. This has support for dual smart batteries and a power path architecture, all managed from SMBUS. It's in TSSOP-48. That creates another issue - you have to come up with the smart batteries but they can be bought off the shelf (example). I don't believe it's reasonable to make smart batteries from scratch in this case!

The question is:

Is this adding complexity where it isn't warranted? If I have to put in a gas gauge type system, the smart battery has that but really requires a smart battery charger chip.
I can't see how to (simply) support two batteries, multiplexed with on-line charging, except by using the LTC1760. Is this really a common scenario?
The LTC will switch-mode large currents. This easily leads to RFI issues and supply noise. Is it a requirement for a TSSOP-48 chip like this that I should go to a 4-layer board? Or could I get by with 2-layer? I haven't done 4 layer before but there's some good information on stackexchange!


texts: Nodal Analysis of a circuit with a dependent source

texts:
simulate this circuit – Schematic created using CircuitLab

Hi,

So the trouble I am having with this problem is that I don't know how to do nodal analysis with the dependent source. I would normally just do a source transformation and change the current source to a voltage source and then just do KVL's. But since the dependent source is reliant on Vo, I don't know how to solve it using Nodal Analysis. Vo is the voltage across R2.

Thanks


texts: How to improve load transient response of an LM317 voltage-regulator powering an audio amplifier?

texts:
I am building a voltage regulator circuit for powering a pair of mini-speakers (about 3-5W) with built in amplifier and an old mp3-player/FM radio. The power source is an old mobile phone charger (switching PSU) with a no-load DC voltage of 7.3V, which is regulated to 4.2V by the LM317. I use the standard circuit exactly as recommended by the TI datasheet:

Besides the 2 resistors there are three capacitors, Cadj = 10uF, Co = 1uF electrolytic, Ci = 0.1uF ceramic.
The circuit works OK, noise levels are low. However, using an oscilloscope in AC coupling mode and testing the regulated  voltage output by actually playing back music on the system, I see a significant variation in voltage that follows the audio signal’s transients. A kickdrum can drop the voltage by around 0.5V (i.e. about 12% of Vs) and I'm measuring peak-to-peak voltages of around 1V (24% of Vs). Adding a 1000uF electrolytic cap on the input side in parallel with Ci reduces peak-to-peak voltage swings drastically, to about 200 mV. Subjectively, the basses also sound fuller and deeper if I add this large capacitor.
My questions are the following:

Is it correct to assume that an ideal (theoretical) PSU for audio applications should produce a constant voltage regardless of load variations (i.e. it is a voltage source)?

In practice, what are acceptable levels of supply voltage variation due to transients in an audio application (in percentage of Vs or mV)?

What is the correct approach to improve load transient response? Should I place a capacitor on the INPUT or OUTPUT of the regulator? Is there a rule of thumb/calculation for the required capacitance? Are electrolytic capacitors OK, or should I use polyester or tantalum caps (i.e. something with a lower ESR)?

UPDATE:
Regarding the input and output capacitors I found the following info on some hi-fi audio blogs and forums:

Large caps are recommended on the input for amplifier voltage regulators, i've seen LM317 schematics with around 2000uF and upwards. Cadj could also be somewhat larger for extra noise suppression (someone recommended 20uF or even 100uF).

The output capacitor should not be overly large, as this can cause stability issues with the LM317, however it could be higher than the 1uF in the datasheet (I've seen 100uF, someone stated that he uses 1000uF, however with a 0.33ohm series resistor for increasing ESR, see below).

The output and adjust caps should have a high ESR (i.e. they should be electrolytic caps, not polypropylene or tantalum ones), because low ESR caps introduce ringing, possibly in the audible range. Larger caps have lower ESR, so this consideration limits the size of the output cap. A possible solution to this problem is adding a small (0.2-0.3ohm) resistor in series with the caps to compensate for the lower ESR of larger caps.

If using higher Cadj and Cout caps, protection diodes D1 and D2 are strongly recommended to discharge the caps when powering off.

The issue described in my question (large transient voltage drops) was in part caused by transient voltage drops on the PSU, rather than the regulator circuit as pointed out by Peter Bennett. The regulator's input voltage fell a few hundred mV below the necessary input of the LM317 (Vout + 2.5V). These transient drops did not show up on the multimeter, but a scope revealed them:

Replacing the PSU with another unit that stays well above Vout + 3V still results in some transients on the regulated output, however the voltage drops are much smaller (60-90mV compared to 200-700mV). Replacing the 1000 uF input cap with 2x 2200 uF did reduce the transients further, but only by a fraction (to about 70 mV from 90 mV). Subjectively this 2% voltage fluctuation is not very noticable on this small amplifier so I consider this problem solved.


texts: How can I plot histogram for Monte Carlo simulation results using Synopsys HSpice?

texts: I am using Synopsys HSpice version 2013 to run Monte Carlo simulation. I can succussfully output the family plots. However I cannot find any tool to plot the histogram. Anyone familiar with HSpice can advise? Thanks.


texts:
I am designing a circuit using a CD4011 Nand Gate 5 volt Vcc and a CD4555 using a 15 volt vcc. Will the Nand gate High output have enough voltage to drive the input of the CD4555 to a High Output?  <>  Nand Gate High Output = 5 volts
Due to circuit configuration and board space I need to use this circuit.
But I need more drive voltage for another circuit. I will have to build a new board to make this work and I would like to know before I start.
I have tested it using 8 volts on the CD4555 Vcc on another circuit design and it works.


texts: High speed signal return path in a stack-up with multiple ground planes

texts:
Consider the following 6-layer stack-up for a mixed signal board.

 1: Top --- analog signals, components ---------------
    ================================================== (0.20 mm)
 2: GND --- return path for analog signals -----------
    ================================================== (0.36 mm)
 3: Pwr --- supply 1, supply 2, supply 3 -------------
    ================================================== (0.28 mm)
 4: Sig --- high-speed digital signals ---------------
    ================================================== (0.36 mm)
 5: GND --- return path for high-speed signals ??? ---
    ================================================== (0.20 mm)
 6: Bot --- control signals --------------------------

Layer 2 and 5 are solid ground planes, without splits in the copper.
Layer 3, the power plane is split up into several regions (AVDD, DVDD, VCLK).

What I am trying to achieve, is to keep the layer 2 GND "clean".

My guess is that the high-speed return current should flow trough layer 5.
Since this plane is directly underneath the high-speed signal trace, it should offer the lowest impedance return path.
Am I right? Does this stack-up make sense at all?


texts: DC-DC step up and step down converter for a solar panel

texts:
I have a 1W solar panel that will output about from 0 to 7V (7V in full sun). I want to power up a small USB gadget with it. I need a device that is a step up converter when panel's voltage is under 5V and step down converter when the voltage is over 5V. Does it exist?

For now I only have this step up converter.
Maybe I can use it with a 5.1V zener diode so I won't care about when the voltage is over 5V?


texts: 60Hz transformers are smaller than 50Hz transformers for the same power rating. Transformers designed for operation in the kHz range are even smaller. Why does transformer size decrease with frequency?


texts: I'm going to use 4 NEMA 17 stepper motors to build a quadcopter. I need to find the maximum upthrust that a single motor can give with a propeller of length 6cm (end to end). The holding torque of the motor is 53 N/cm.


texts: Does an increase in frequency affect a capacitors value?

texts:
When looking at an open circuited microstrip line, when the frequency is increased the value of the capacitance is changed.
When looking at an ideal capacitor the value does not change with increased frequency.
If it wasn't an ideal capacitor would the value change?


texts:
I'm trying to calculate the Forward converter's efficiency. For that I calculate the losses, trying to include as much factors as possible. To calculate the loss on the input capacitor's ESR, I have to calculate the RMS current in the capacitor. For that I have to know the input current of the converter, which i suppose to be constant (so all the ripple currents are supplied by the input capacitor, which should be the ideal case). The easy way would be calculating the input current from the input voltage, the output power and the efficiency, but the problem is, that it would make it an implicit equation system, because for calculating the efficiency I already have to use the efficiency in the calculations.

My other idea is calculating the capacitor's amp-second balance. With that, I get \$I_{in}=I_{out}n_sD + \frac{I_{m}}{2}D(1-n_r)\$ , where \$n_s\$ is the primary to secondary turns ratio, \$I_{m}\$ is the peak magnetizing current and \$n_r \$ is the primary to reset winding turns ratio.

Is this correct?


texts:
I'm newbie and would like to know about LED strips.

In this schematic can I use the flow from Diagram B? I understand that Diagram A is the correct +12V Input supply and I can measure the end of the led with the same voltage and can also continue to link another led strip. With Diagram B to supply +12v supply it will still turn ON the LED but the end of the LED is 0v. I hope I'm making any sense. I already installed the LED strip underwater with Diagram B. I want to know will my mistake break my PSU and can cause issue on both LED and PSU? although its working.


texts: dspic33E series ADC Buffer size and Sampling count confusion

texts:
I am using dspic33E series microcontroller. The most using peripheral is ADC. So, I go through the ADC Reference manual for dspic33E family microcontrollers from Microchip.
In the FRM, they said that, this controller has 4 ADC channels, 16 ADC buffers for storing the converted ADC results each of 16 bit size.
There are some configuration registers which should be correctly configured in order to use ADC accurately in time-critical applications.
One main bit is SMPI<4:0> bit in the ADCxCON2 register. This bit<4:0> determines how many samples need to be generated per single ADC interrupt.This samples will be read from ADC buffers after interrupt is genenrated.
Total number of ADC buffers are 16. If I set the value in that 5 bit sized SMPI as 7, I will get 8 samples per interrupt of ADC and each sample is stored in each adc buffer after ADC conversion done. I will get those 8 converted values from ADC buffers,after interrupt is generated.
So theoretically, maximum I can get 16 samples per ADC interrupt.
But, in datasheet, the 5 bit sized SMPI section has an option to set the sample count up to 32. But only 16 results can be stored in ADC buffer since that is the maximum count of ADC buffer in the peripheral.
I have searched in FRM to know the reason for setting SMPI value to 32 samples/interrupt, but couldn't find it.
I am not using DMA feature for ADC. I am only using ADC peripheral. Since the maximum capacity is only for 16 conversion results, why the SMPI bit is allowed to get 32 samples per interrupt. How those all 32 values are stored in 16 buffers?
Link for ADC FRM: https://ww1.microchip.com/downloads/en/DeviceDoc/70621c.pdf
Image 1: ADC Buffer peripheral image

Image 2: SMPI bit value selection ranges.


texts: Best way to power Christmas lights without nearby outlet

texts:
I want to power Christmas lights (without a nearby power outlet) for at least 2 hours and was wondering how to go about it. The lights run on 120V AC and draw .34A per strip (about 40 watts) and I want to use 5 strips. I could buy a 12V battery and power inverter to supply 120VAC, but I would like to see if there's a cheaper or easier way.

I could rig up some AA batteries in series and parallel to supply 12V to a power inverter, but since batteries lose voltage as they drain, would I need to buy some sort of "voltage booster" to maintain the 12V? Could I even use a single portable phone charger battery (3.6V) and a voltage booster instead? Or is there some other easier way to do all of this?


texts: A voltage source placed in the output of a DC-converter?

texts:
simulate this circuit – Schematic created using CircuitLab

I have a voltage source(V1) connected to a boost-converter, the components aren't rated(more focused into the theory than actual build). And there is a a voltage source(V2) that is in the output of the boost-converter, what would happen too the circuit? Would the voltages add-up since they are in series?

The output voltage will be higher than 50V(if they do add-up).

Edit (Circuit II):

simulate this circuit

Edit(2) Motor circuit:

simulate this circuit


texts: how the CPU start by execution stored in motherboards flash memory chip

texts:
I had read that at start, the CPU program counter register is fill with F000.

I though that:

PC registers contain the next instruction address.
This address is send to the address bus and value return to the data bus

Does the address bus only deal with RAM? Obviously the bios isn't store in ram.

So HOW F000 target the ROM to start BIOS execution


texts: Over what frequency range can the microphone of smartphone receive the sound?

texts:
I have a project in which I am considering using the microphone from a smartphone for the reception of inaudible signals (> 15khz).

What is the frequency range that such a microphone of receive sound?
And what is the maximum frequency ?


texts: How to rebuild Ni-Cad battery pack for power tools

texts:
I have some cordless power tools which all require a certain 12V nickel-cadmium battery pack.
My battery packs are dead, but the good news is they're held together with screws, so I took them apart to have a look. The bad news is the cells inside are all shot; they have the little crystals on the outside telling me they're done.

So, the dead cells are going to the official hazardous waste drop-off site.

What should I replace them with?
I've wired up battery packs for RC cars and stuff before, and I'm confident I can put it back together properly. The problem is I'm having a hard time finding the nicad cells now. did they stop making them? I see a few for sale and they're like $3-5 per cell now (I need like 50 of them).
Is it possible to salvage the good cells from several different dead ni-cad packs to create one working battery?


texts: What are values of fundamental frequency and the harmonics for the below signal g(t)?

texts:
We  know that a Fourier series formula for any signal $s(t)$ is given as
$$\frac {a_0} 2 + \sum \limits _{m=1} ^\infty (a_m \cos \frac {2 \pi m t} T + b_m \sin \frac {2 \pi m t} T)$$
Here,as we see from the formula ,except the DC component and fundamental frequency components there are all harmonics present at right side of the Fourier series formula.
Let us consider 4 sinusoidal periodic signal $$x(t),y(t),z(t) and g(t)$$ such that
$$x(t)=\cos \frac {1.2*2 \pi t} 8$$
$$y(t)=\cos \frac {1.4*2 \pi t} 8$$
$$z(t)= \cos \frac {1.6 \pi t} 8$$
and
$$g(t)=x(t)+y(t)+z(t)$$
Then,

How would you apply Fourier series formula for a signal $$g(t)$$ which is nonharmonic?

If there are fundamental frequency and harmonics present ,can anybody tell me what are they and their values?


texts: Tri-state push-pull configuration GPIO protection

texts:
I am designing a sort of "driver" for a high voltage Charlieplexed LED array, since normal GPIOS can't handle 12V. For that, I need to be able to use tri-state logic, which means LOW, HIGH, and HIGH-Z.
The schematic below shows two arrangements of PMOS and NMOS similar to a push-pull configuration using two of these ICs plus two not yet defined NMOS. The first -U1 and U4- define the behavior that can be represented as push and pull, and the second -U3 and U6- are the output enable. (HIGH means enable and LOW means HIGH-Z)
So far, the simulation is running well, however, In the last question I asked someone made me a heads-up about the ideal behavior of the GPIOs and that I should be careful with the 12V present in the gate of the PMOS. To solve that I included these two NMOS -U5 and U2- keeping the voltage of the GPIOS under safe values.
Is this fix correct? can someone note me if I might be overseeing something, I'm still a noob at this.
Also, I'm simulating with NI Multisim 14.2
Note1: I'm aware of the body effect difference that U1 and U4 will have with respect to U3 and U6 since the body/bulk terminal is kept shorted to the source terminal and not Vcc/Vss. However, I think that for this application it will not have a noticeable effect.
Note2: S1, 2, 3, and 4 are spst placed there only for the simplicity of the simulation, and they are not considered for the final design.


texts: How to use the Free Starter Edition of Sigasi's VHDL IDE

texts:
I downloaded sigasis ide for vhdl lastnight and i opened up the tutorial vhdl folder and tried to hit the run button (the green play button im assuming) and i got some menus and i just put some stuff in and now when i hit the play button i get this message.

"Exception occurred executing command line.
Cannot run program "C:\Users\Cameron\workspaceSigasi\test\workbench.vhd": CreateProcess error=193, %1 is not a valid Win32 application"

Im new to VHDL so if you would be so kind as to run me through what software I need to just simulate the code that would be great. Im learning VHDL because we never really learned it in the class i took on logic desgin and id love to say to a prospective employer that i know something about VHDL design.


texts:
My understanding is that standard electrical soldering fluxes will not be effective on aluminum or stainless steels.  Is that correct?

But are all rosin fluxes adequate for the other metals encountered in electrical work -- namely:

Copper
Lead
Tin
Bronze (copper-tin alloy)
Brass (copper-zinc alloy)
Silver
Gold
Iron and non-stainless steels?

And what about the flux and solder I use to join copper water pipes: Are those equally good for electrical soldering (assuming I can work with the diameter of the solder wire)?


texts: How does a charger know when to stop charging a BAD battery?

texts:
I have a straight forward question that I was thinking about earlier. So I've read that battery chargers will usually periodically measure voltage and decide based off that when to stop charging the battery. Let's say for a car battery this is 13.8V.
If you had a car battery that was damaged somehow and only able to output 13.6V, what would happen if you connected it to one of these chargers that only stop supplying when it reaches the 13.8V mark?


texts: Industrial standard communication between multiple micro controllers on same pcb

texts: I'm just wondering what would be considered industry practice of communicating between multiple micro controllers on the same pcb for instance when the digital i/o's or analog ins have been used.


texts:
How would I design a circuit made of rising edge triggered flip flops and inverters to make its output 1/6 of the clock frequency.

Cheers


texts: Can you convert two wire 220 (no neutral) to normal 110?

texts:
We have a water pump way out in the field (500+ long wire run) that is wired for 220 with two wires - no neutral.

It would be very, very convenient to have a power outlet at this site for tools, etc.  However, my electrician said there is no way to add a normal 110 outlet because there is no neutral.

One option is to run a neutral (or maybe run a standalone 110 circuit) in a new conduit, but 500 feet of new underground conduit is a very big job.

Is there any way to (safely, code compliant) get a 110v outlet at this site without running new wires ?

Thank you.


texts: Cheap Step-Down converter as Solar Charge controller

texts:
Instead of buying in an expensive MTTP-Charger I want to buy a cheap module only.
You get these small 2A/40V Buck-converters at eBay for 2-3 USD or the bigger 10-12A /40V from 9-11 USD.

Setup:   Solarmodul 18V - Step-Down-Modul -(Skotty-diode)+(Fuse) - Battery.

Fuse is a should have, I know.

But I wonder if you need the Skotty-diode?
What happends to the Step-Down Buck-converter-

when there is no SolarInput?   Then you have the 12.6V from the
battery at the moduls OUTPUT.
when the Buck-input(Solar) is short-circut, what will happen to the
modul? Take all ampers from the battery to do the shortcircuit?
Will it burn?

Perhaps the easy answer would bee to test it out in real, it iss only 2 USD.


texts:
I've finally come up with what looks to be a manageable design for this circuit where an Arduino is controlling 9 solenoid valves through solid state relays. I've attached both the schematic and photo for the setup for what it would look like for two solenoid valves. The setup will be exactly the same for the additional 7 valves.

My question is whether or not I'll have any issues with this grounding setup. Is there any problem putting the ground from the SSRs to the 24V power supply (positive input is from digital pins on Arduino).

For a little more info: in the photo those two wire molex plugs will have the lines to the solenoid valves hence the blue "S". The black "+" is the positive input from the 24V power supply, the black "-" is the ground for the solenoid valves to the power supply, and the red "-" is the ground for the SSRs also to the same power supply.


texts: Manually removing bulk components from cut tape?

texts:
I ordered a bulk quantity of components for experimentation and they were shipped in a cut tape format.

I've been removing components individually from the tape but it requires a large amount of labor, removal of tape residue from the leads, etc.

Is there a better method?


texts:
I'm trying to make a logical NOR-gate using a 74HCT02 IC (datasheet), but I cannot figure out how to wire it. Below is a schematic of what I tried.

simulate this circuit – Schematic created using CircuitLab

The power source (V1) is coming from a transformer connected to the power net, it gives a 4.5 VDC output at 3.6VA maximum.

What I observe is that the led is always on, with little intensity difference when I press or release either button.

I do not have much experience regarding circuits with IC's, so I might be making some beginners mistakes here.


texts: How does a (halogen) wound transformer dimmer work?

texts:
I'm replacing a broken halogen dimmer and I noticed that it has inside a wound transformer, but it is connected only to two leads: "input" and dimmed "output".

It also has some more electronic components, but I haven't checked exactly.

I thought that the dimmer required some neutral connection too, to have a reference point for the phase control, so that the TRIAC can cut the waveform when the threshold is reached.

What is the equivalent circuit of a wound transformer dimmer that has only two leads?


texts: Shift Register Output tidied up by capacitor over a length of Cat5. What is happening?

texts:
I was hoping someone could explain to me what is happening to my project. Initially I had an HD44780 Driven LCD positioned close to the 74HC595 Shift Register controlling it, but in the most recent iteration of my project I've deemed it necessary to move the LCD to another location. Im testing at the moment by having the two IC's conneceted over a 1m (approx) stretch of Cat5 cable.

In my code the LCD initialises, then prints 0123. Waits 2 seconds then prints "Hello World!" character by character. When the LCD was close to the Shift Register this worked no problem, but when on the other end of the Cat 5 cable. 0123 are printed fine but "Hello World!" is typed with different characters all together (Japanese Symbols, "V" and whitespace).

I later added a 100nF capacitor to each "bit" close to the LCD and the printout is now fine.

So my question to you is, how and why has adding the caps allowed the Data High and Low's to "clean up" and represent themeselves to the LCD correctly? Is there something I could do better (apart from  a redesign).

simulate this circuit – Schematic created using CircuitLab


texts: SAMD20/21 development on Ubuntu without IDE

texts:
As someone who is trying to break away from high-level APIs for embedded development, I wanted to try out programming Atmel's (or  Microchip's) SAMD20 or 21 mcus directly without any IDEs or tools that spoon-feed you pre-made APIs for convenience.While I appreciate how much faster it makes things flow, as someone who wants to learn more embedded dev,I would like to learn how to program microcontrollers at the register level.
Now my question is the following:
Even though I am trying to move away from Atmel Studio and MPLAB, I still want to have the peripheral register definitions header file for the SAMD21 and 20. Does anyone know where I could get these files so that I can include them in my Ubuntu projects?


texts: Why can the offset voltage of the comparator let the transition time be longer or shorter?

texts:
When\$ V_{FB}>V_{REF}\$,then the battery enter the CV mode,otherwise,battery enter CC mode,and  because inherent offset voltage of the comparator, the transition from the CC stage to the CV stage may be too early or too late.

My question is why can the offset voltage of the comparator let the transition from the CC stage to the CV stage may be too early or too late?


texts: Making a Tachometer using LED and Laser?

texts:
I am making a tachometer to measure speed of a wheel using a LED and Laser.

The phenomena is that when Ray of Laser is shown on LED , 0.5 V are produced. I will connect a Schmitt trigger (made using LM741). The output of the trigger will be read using the interrupt pin of Uno. And using some calculation i will measure the rpm.

The problem is that when i connect the Led in Pull up configuration as shown in figure. The LED voltage does not change with laser. I am using Arduino Uno to Read Analog Values.

    ////           + GROUND                                 +5 V   DC
    ////           |                                        |
    ////           <                                        <
    ////           > 220 ohm resistor                       > 100K ohm resistor
    ////           <                                        <
    ////           |                                        |
    ////           |                                        |------Analog Read
    ////         -----                                    -----
    ////          / \    >>Laser >>>>>>>>>>>>>>>>>>>>>>>>  / \   LED
    ////         -----                                    -----
    ////           |                                        |
    ////           |                                        |
    ////           + +5V DC                                  +  Ground

I think that this method of LEd and laser is non-practical. Is their any other way that can help me to make tachometer?


texts: Is there a preferred order VHDL case/when and rising/falling_edge statements in processes?

texts:
What pitfalls are there in putting my rising_edge check within a case/when block?

I have VHDL that uses code similar to the first example below and simulates correctly and is synthesizable. However, it is not behaving in accordance with the simulation.

process ( clk_in, rx0_busy, reset_n, spi_cs_n, spi_sclk, tx_state )

begin
    case tx_state is
        when ( RESET )=>
            if ( rising_edge( clk_in ) ) then
...

Is it better form to write VHDL more like below, with the clock edge driving the case/when? If so, why?

process ( clk_in, rx0_busy, reset_n, spi_cs_n, spi_sclk, tx_state )

begin
    if ( rising_edge( clk_in ) ) then
        case tx_state is
             when ( RESET )=>
...


texts: Need help with identify device and its possible functions

texts:
My boss found some device at his office. My task is to find out what the device is, what is its function and everything i can find about it. It may be some kind of test that expose that I can handle problems or give up with nothing. I'm not an electronic type of man :( Device is broken so i can't guess just by using it.
I guess it can be a part of playing postcard or some box that activate sound when opened but need to be 100% sure if my guess are right.
Searching in Internet using search by picture i found on electronics.stackexchange device looks 100% the same as mine. Link below
What is the black thing on the circuit
Need help and best option is just ask user about his device(author of question i found) but how?
Here is pic of my device


texts: Simple circuit to detect ac power loss and use dc backup?

texts:
I want to make a simple circuit like those used in commercial emergency lights.

I would have a "walmart" AC to DC  adapter powering say a DC light or two. I would like it so when the AC powering the adapter goes out the DC battery backup in the light goes on.

Is this at all possible without complicated circuits and components? I want to try and use what little parts I have.


texts: switched capacitor voltage doubler for strobe circuit

texts:
I am interested in making an LED blink fast with a low duty cycle. To make the LED bright again (despite the low duty cycle), I thought I'd try to use some sort of charge pump to overdrive the LED. I'm hoping I can charge the capacitor while the LED is off, and place it in series with my voltage source when the LED is on.

Here's an example that doesn't work at all:

simulate this circuit – Schematic created using CircuitLab

(ignore the LED model, ignore the capacitor rating)

The circuit correctly charges the capacitor when the LED is off. However the capacitor needs to be reversed during the "on" part. Is there some way to accomplish this with minimal additional transistors/diodes? One way I can guess is to have a sort-of H-bridge around the capacitor, but I'm hoping for something simpler.


texts: Setting number format for PCB fabrication in Altium

texts:
I 'm very new in PCB designer CAD. I have a simple PCB design in Altium which I need to create gerber and drill files before sending it to a milling machine. When I go to:

Files-->Fabrication Outputs-->Gerber Files

Here I need to select one of the formats from 2:3, 2:4, 2:5 as below:

But I cannot decide which format to chose. How can I figure out what my resolution is and how can I associate it with these formats?

Edit: I found only this info:

  If you are using one of the higher resolutions, check that the PCB
  manufacturer supports that format. The 2:4 and 2:5 formats only need
  to be chosen if there are holes on a grid finer than 1 mil.

What does it mean "finer than 1 mil" ? I use mm. I have holes on the PCB but when I double click on them it shows hole size and location in mm not the resolution. How can I figure out the resolution?


texts: Finite State Machine not initializing in planned initial state

texts:
I have an assignment where where I have to design a FSM which outputs the following Hex number in binary, one digit at a time: 12498A3B. The FSM must use a clock signal and D flip-flops to do so.

I firstly made the state diagram, then I made the current/next state table, next I created 4 Karnaugh maps to determine the next state bit output for each DFF. I used the 4 Boolean expressions derived from these K-maps to create my FSM in the "Logisim" program.

My circuit cycles through each digit as it should in the correct order, however the initial output by my FSM isn't the initial digit of the Hex number, but rather one of the digits in the centre of the number. How is this possible? I am new to designing FSMs but I had the impression that when implementing the Boolean expressions obtained from the K-maps would produce the expected initial state?

I can provide screenshots of all my work if further clarity is needed.


texts:
Why would I prefer to use a buck converter over a voltage divider, and vice-versa?

I know that voltage dividers are less complex and cheaper than buck converters, given that voltage dividers are simply two resistors.

What are other pros and cons of using a buck converter?


texts: Board to board communication (Backplane) in possible noisy environment- UART, RS232, RS422, RS485?

texts:
I've seen alot of references for RS422 and RS485 using cables and twisted pair wiring, but how well do they do over short distances and with just a PCB layout (no cables at all) ? Do people do that ? Is it recommended ?

If I'm looking to create a bus to communicate with 5+ more boards all connected to a backplane, what would be the suggested protocol ?


texts:
in a project I am developing I have a matrix of cells, each cell containing 3 buttons (it will be more eventually, around 10). The schematic is like this:

I want to read each one of the cells, and in each cell I want to read each one of the buttons. To do it, I want to multiplex each cell, and read the first button on the MuxBTN1 pin, the second on the MuxBTN2 pin, etc. I also want it to be expandable, the matrix will be NxM sizewise (the number of cells will be around 30-40).
Each button is a bit, each cell is an 10 bit number, I want to map all the cells numbers to a bi dimensional matrix in code. Speed is not very important.

What would be a good approach to this problem? Everything I have found on the internet was about multiplexing an led matrix, which is not the same. Thank you!


texts: Manually control smartphone power current drawing during charge?

texts:
How can I manually control, how much power the smartphone does draw?

Sometimes, a smartphone does accidentally consider a charger as much weaker than it actually is. Sometimes, a boost converter/transformer does not help due to clusmy chargers that supply a temporary voltage drop that fools the smartphone into thinking that the charger is weak.

But what is a way for the phone to be manually controlled by the user, how much power to draw?

Example: From an 12W USB charger, I would like to draw out 5V 2A instead of 0.6A.

And yes, I know: Everything at my own risk.


texts: Strange measurements for Vrms in LTspice

texts:
For my experimental methods class (basically an intro to electronics) in university we had to simulate a circuit, which was nothing out of the ordinary, it just produces different sine waves of 2 volts peak to peak. However, what was interesting to me was the fact that, when reading the measurements that the software produced for the Vrms, it seemed to depend on the frequency, contrary to the theory.

Of course, I expected the measurement to be different to the theory, given that simulating it with a computer probably introduced limitations. What I didn't expect was for it to behave so weirdly, having these peaks where it would rapidly decrease and increase again, and ultimately converging to around 702.42 mV, which doesn't make any intuitive sense to me.

I thought that the measured voltage would just stray arbitrarily far from the ideal one, but was surprised when that wasn't the case.

So, why does this happen? It might be a stupid question but when I saw this I got curious and couldn't come up with an explanation by myself (I'm not too far into my studies, so that might be a reason).

Thanks in advance!


texts:
I make custom clocks, some of these with electromechanical control circuits.  An example would be a cuckoo clock that has a small dc motor / drive circuit used to actuate a bird/door mechanism.  Although not explictly forbidden by the manufacturer, I've had customers substitute the normal 'AA" sized alkalines with a rechargeable variety and now have had a couple of issues come up that may / may not be related to this configuration.

A couple of observations about these mechanisms when driven with the rechargeables - The magnetically driven pendulum has a noticeable difference in amplitude ie much larger swing arc.
- the bird drive mechanism appears to actuate more "crisply", the drive motor appears to have an increased rpm as it drives the  worm gear actuator.

One of these cuckoo units have failed, and it is something in the drive circuitry that has apparently died a bit at a time - eg. the cuckoo would drive in one direction and not the other. Pulling the batteries and resetting the unit and it would start up again - but ultimately exhibited the same failure and died altogether.
Is there an operational issue with the voltages / current profile with rechargeables that might explain this failure mode?  Customers resist the idea that the batteries might be causing the issue as the are the same "voltage" and sold on the idea of "plug compatibility".  Any thoughts would be appreciated.
Thanks.

I appreciate the quick replies - with limited knowledge on the subject I can't fill in the technical questions in too much more details - assuming that the operational cycle has repeatable power draw, woud the device require more current if the available voltage is lower in the rechargeables?  And if so, would the driving circuit take a hit?


texts: How to make 7-segment display count up ?

texts:
I've connect 7447 decoder and 74193 counter as shown in the picture but I have not used 555 timer yet.

Is there any way to test the circuit before using 555 ?
I've connected the pins (up and down) of the counter to the positive terminal, and then disconnected them several times. ( I just wanted to do the function of 555 manually ). but the display did not count up... why ?? I want to test the circuit before putting 555 ?

one more thing, what are the pins A,B,C and D of the counter ? why do we connect them to the ground ?
and also what Bo,Co and load are?

this is the datasheet of the counter :
http://www.ti.com/lit/ds/symlink/sn74ls193.pdf


texts: Weird interference when controlling piezoelectric humidifier

texts:
I am trying to build an Arduino controlled piezoelectric humidifier. I am using two humidifier modules which have 5V dc operating voltage(they have usb connectors). When I connect one module to my cicuit it works fine, but with two weird things happen. If I try to switch on both modules simultaneously the cicuit works, but if only one is turned off the one that is supposed be on also turns off and an intergrated indicator led(in the module) only glows dimly. If replace one of the modules with another load(it doesn't matter which one) the circuit works fine so the modules must be producing some sort of interference. Is there any way filter out the inteference for example adding a capasitor somewhere or is the circuit somehow incorrect?I have measured that the gate voltage on fet that is supposed be on is 5 V.  Circuit diagram is below. R1 and R3 have arduino digital outputpins connected to them and S1 and S2 represent the humidifier modules.
After further measurements I have found out that module that is supposed be on receives 5 V but only draws few mA of current. The issue must be within the modules themselves, but I still need a way to filter out the interference.


texts:
I need a logic gate to check if A or B or C is negative voltage (referenced to the ground).
It does not matter if the output is positive or negative logic (as long as it is in positive voltages)

Does this circuit work?

Do you see other solutions or improvements?

One problem I see is that out goes negative if "True".

simulate this circuit – Schematic created using CircuitLab

EDIT

I thought about this one too:

easier to compensate the voltage drop of the diodes by tuning the resistances.
and I can invert the logic easily.

simulate this circuit

EDIT

What I finally did, it works well:

The comparator has built-in reference, just tune the voltage divider to match it. I didn't use hysteresis, the comparator has a built-in hysteresis too, but only few mV.

simulate this circuit


texts: Routing impedance controlled signal with a power plane as reference

texts:
Assuming i chose to route an impedance controlled signal with a power plane as a reference plane instead of ground (microstrip or stripline), and assuming i'll make sure the signal won't cross power planes.

Does it matter if the reference power plane is the VCC of the driver driving the signal or it can be any VCC i have on my PCB?


texts:
I'm interested in getting into experimenting with wire wrapping for some small microcontroller projects using some Arduino Nanos.

I've watched a bunch of videos online, but something that is not explained is - how do you handle power and ground when wire wrapping?

Do you chain all your pins that use power or ground point-to-point?  Or do you create some sort of bus that runs near certain components that you tie into?

I found this image:  in a Hack-a-Day post by Bil Herd which shows some designs he wrapped.  I noticed the thick black wires that run along the board, which I believe are for power.  On the opposite side of the board, he appears to have a bare-wire ground wire:

This looks handy - but I'm not sure how you tie into those wires since you can't wrap onto them.  It's not clear to me from the picture as to how they connect to the wire wrap pins.  I believe the T-bits that go from the ground on top of the board to the bottom are soldered.

I had a thought of taking some male headers that have wire-wrap length pins on both sides of the plastic bit in the middle and just wrapping all of the pins on one side together to make a ground or power strip.

Any suggestions?


texts: USB charging in place 3 Li-Ion batteries spaced evenly in parallel on LED string

texts:
I am a total noob in electronics, and so some other answers to this question are already over my head. I am working off the inspiration of this design of an LED hoop: https://philihp.com/blog/2011/diy-led-hula-hoop/, but I don't understand the wiring diagram at the bottom of the page:

I am wiring through hole 5mm LEDs + resistors to 22 gauge stereo wire in parallel, with the batteries interspersed in parallel. I don't want to make a battery pack, since this is a hula hoop I want to space the batteries evenly in the LED string inside the tubing, otherwise the hoop is off-balance and hard to use. In fact I already made a hoop with one battery and that experience made me want a design with balanced weight.

My focus right now is understanding how to have a built-in USB charger so that the batteries can stay in the hoop and be charged, and therefore be spaced evenly inside the polypro tubing to balance the hoop's weight. But it seems like I'm setting myself up to light myself on fire.

This page at Adafruit says it's not safe to be a hobbyist
and string/charge batteries in parallel, is that true? What if on each
battery I put a Protection Circuit?
Does each battery need a Protection Circuit?
Adafruit says to only use its MICRO LIPO - USB LIION/LIPOLY CHARGER with their battery packs, which won't fit inside a hoop. Is there a different small charger I should/could use, like the one in this post?
If I have 3 batteries does that change the charger I can use (voltage, current?) or will it just charge more slowly as long as it's rated for 3.7V batteries?

Sorry if a lot of this is obvious, I'm having trouble piecing the information together.


texts: Low voltage cutoff circuit with Zener and BJT

texts:
I have a circuit that's supposed to cut off at <4V. It instead caps the voltage at 3.3-ish and reduces the voltage linearly below that.
Zener - 3.3v
Source - 5V +-5V


texts:
Let's say I had a very large static dataset that I'd like to distribute via solid state memory to a lot of people. Let's say it's on the order of terabytes. What would be the densest type of storage I could use?

I read somewhere that in Intel's 14nm process they can fit ~37 million transistors on a square millimeter which would mean that about 400 MB could be stored on a square centimeter. This assumes one transistor per bit, which I assume is as good as you can get for ROM. (is this a good assumption?)

But then I notice that you can buy a 256 GB microSD card which is smaller than my hypothetical ROM. How the hell is the flash so dense and would it be possible to make a ROM that dense (or denser)?


texts: If I want to build a railgun, how do I calculate the length of the rails?

texts:
I want to build a railgun, but I find it difficult to calculate the length of the rails, since the acceleration is not uniform, due to the voltage's decreasing when the capacitors discharges. Neither do I know the way to calculate the curve of the capacitor's discharging. I plan to use 6 fully charged 1000uf 450v capacitors as the energy source, giving 1215 Joules of energy.
The projectile will be a 7mm steel ball weighting around 1.4g.
The rails will be copper cylinders, 10mm in diameter. The current in the rails will also create the magnetic field.
How long should the rails be?


texts:
I'm playing around with an Atmel 89C microcontroller. The datasheet indicates a port can sink 20 mA in total. As an output with a load connected to the pin, when a 1 is written to it, the load is connected to the pull-up resistor.

I've seen the value of 10k as the effective resistance of the pull-up. But this would be 0.5 mA (@ 5V), which is very low.

Is the effective value of the pull-up much lower than this or am I misunderstanding something?


texts:
Left  one - "no plumbum/lead"
Right one - "triangular invert color no picking by hand"
(found on BeagleBone Green)


texts:
I´m implementing a floppy disk to USB adapter as a freetime project. I´m using the WD37C64C as controller IC and the PIC32MX230F256D as microcontroller to translate the signals to USB.

Would you recommend programming the PIC32 on an external board? Or build the whole thing on one PCB?

Another thing that bothers me is the OSC crystal. Also I couldn´t find the capacitor size needed for the crystals. From the datasheet I deduced that I can dimension the part between 4 and 10 MHz. Do I need two crystals (SOSCI and OSC1) or is the one for SOSCI sufficient? And if I´m using the PMP ports (PMD & PMA), how do I program the microcontroller? I do know I need 5 to 3.3 V level shifter.


texts: Multiple SPST relays in parallel for high switching power

texts:
I have a Pulse PLA900 AB amplifier and I would like to use a non-latching relay switch to switch it on/off from a digital platform. Unfortunately, the technical data sheet of the amplifier lacks crucial information for my project, such as standby power (i.e. when there is no input signal to be amplified) or power consumption on full load, or peak power when the amplifier is switched on, therefore I can just guess them. The RMS is 760 W so with the assumption the efficiency of the amplifier as well as of the transformer is 80% then the maximum power consumption of the amplifier from mains is 10/8 * 10/8 * 760 W * buffer = 1187.5 W * buffer = 1500 W. I have no equipment to measure the peak power that the amplifier picks up when it is switched on but it has a 10 A fuse on the mains - which means nothing but this is what I have.
This is my simplified diagram, the starting point - I do apologise for its simplicity and imperfect nature, hope it is good enough for visualisation:

simulate this circuit – Schematic created using CircuitLab
I have tried a switching relay with no load on the amplifier, that was certified for AC 250V 10A, and the guess based on similar types its maximum switching power was around 200W, but it probably got welded because I was just able to switch it on/off like three times then it never switched off again.

simulate this circuit
Someone then suggested to use two relays in parallel with a small power resistor (10 ohm 5 W) in series of the first, then for switching ON follow the below steps:

switch ON the first with the power resistor
wait 0.5 sec
switch ON the second without resistor

and for switching OFF follow the same steps in reversed order:

switch OFF the second without resistor
wait 0.5 sec
switch OFF the first with resistor

simulate this circuit
My questions as follow:

Is this proposed method standard and safe?
If this is standard and safe, then

What would be the best way to calculate R and W of the resistor with the limited available of information?
Which type of power resistor would suit best for this problem: cement or wire wound (aluminium case)?
Would a relay with max switching power 2770VA 210W be sufficient? I have a 2 relay module handy, that data sheet could be this but unfortunately not sure https://www.generationrobots.com/media/JQC-3FF-v1.pdf


texts: How to connect to 30 awg Nichrome wire to 28 awg wire?

texts:
I'm looking for a quick way to connect my 30 awg Nichrome wire to some 28 awg stranded wire and have tried an inline splice and crimped-on receptacles.

For my project I'll potentially be making lots of these joints and want to make sure I've looked at all my design options. The length of the Nichrome wire is some what critical, and so far the crimped connections make the length a little easier to control.

Are there any other ways to do this that would be better or make the results more repeatable?


texts: Does FFT (fast fourier transform) give RMS or peak to peak amplitude vs frequency?

texts: I am using periodic triangular wave (Vp-p=3V, freq= 2kHz), as an input to my oscilloscope to do FFT. My question is that does the magnitude(y axis) of in FFT plot represent the peak to peak contribution or the RMS value of each sinusoids? Is there a difference between the y axis representation of FFT and simply a fourier transform? I am having hard time understanding the y-axis in both FFT and fourier transform representation plots. Help!


texts: Determining Z1 for voltage divider of RF Matching Circuit

texts:
I have a problem where I was given an RF circuit with a series RL load. I am tasked in finding a matching L circuit and determining the values of the components. I used a smith chart to determine that a shunt capacitor and series inductor is a suitable L network topology and determined their values.

The second part of the problem was to find the frequency response of the voltage across the load resistor. It comes down to two voltage dividers to derive the transfer function. I calculated the first voltage divider for the voltage at the shunt capacitor, straight forward. I then used a second application of a voltage divider to get Vout. My problem is I don't know what Z1 should be the second voltage divider, and I am asking for help on that.


texts: TP4056 Output-Voltage too low when connected to Load

texts:
I am designing a battery powered Esp32 board for the Institute I am working at. I recently got my hands on the board and the battery charging circuit has an issue. The TP4056 that I used should deliver 4.2V on its output when no battery is connected. However when I connect it to the HT7333 3.3V Linear regulator which supplies the ESP, I get around 3.6V delivered to the Input of the Linear Regulator and both STDBY and CHRG LEDs of the TP4056 light up. I tried it with those popular tp4056 modules as well they show the same problem. However everything works fine when I supply the regulator with 4.2V from an external LAB-Bench power supply. What could could cause this? I sadly am not allowed to share the entire Schematic of the board, due to it being technically Institute property. But here are the parts concerning the problem.

Any help or experience sharing would be much appriciated.


texts: SMD soldering: tiny components stick to tweezer point

texts:
When soldering SMD components, the 2-pinned ones (like resistors, capacitors, ...) are the hardest in my opinion.

I started long time ago with the 1206 format. Then scaled down to 0804, 0603 and finally I'm working with the 0402 ones.

I'm facing a new challenge right now. Once I get some flux on my tweezer points (it happens all the time), they get really sticky. This leads to numerous problems.

If I'm really lucky, I grab the part first time right. This means that I grab the part by its middle, and I can move it to the pads for soldering:

Misery starts when I grab it wrong first time. "Wrong" can be many things: I grab it by the side, it's not aligned well to the eventual target, ... Anyway, the moment I want to release, I open my tweezers and the part keeps sticking to either side of the tweezer points.

Has anyone experienced the same problem? What was your solution?

EDIT

Here are some ideas that might inspire you..

Tweezer material or coating

I've found a pair of tweezers online like this:

These tweezers features a "Stainless Steel Body" and "Carbon Fibre Tip". Will this tip material help to prevent the stickiness?

Perhaps you're using tweezers with some special coating?
Super hydrophobic coating

Maybe this is a bit strange, but did anyone experiment with a "super hydrophobic coating" on its tweezers? I believe this should help to avoid any liquid/flux from sticking to the tweezer points. I've discovered some sprays online (http://www.neverwet.com/) but haven't bought any of them yet. Would they work on a pair of tweezers?
Tweezer form

To avoid stickiness, would you recommend a very fine tip? Curved or not? If curved, curved inwards or sideways?
Tweezer tip roughness

Some tweezers have polished points, others are more rough. What is best?
Demagnetization

Some tweezers claim to be "antimagnetic". Does this feature really help?


texts: RMS OR DC value of the waveform is measured by DC voltmeter for the below input?

texts:
The DC voltmeter measures the average value of the waveform right?

I have read that ac voltmeters (high end)  measure the RMS value based on heating effect while DC voltmeters measure the average value of the waveform.

My question is :

When i calculate the average value of the waveform i get 3.33V  (10/3) assuming its a nonperiodic input signal,but the actual answer is 10V WHY???


texts: Even vs Uneven Magnetic Field Cancellation in Toroidal Transformers

texts:
If the secondary winding of the 230v-115v Step Down Toroidal Transformers have multiple separate ends and you are only tapping a portion, would there be uneven magnetic field cancellation? See for a version with dual primary and dual secondary:

Schematic of which are:

Compare it with a single primary and secondary where the entire windings are used at once.

Do you agree the version where the entire windings were used at once have even magnetic field cancellation than the first one just using a portion of the secondary winding?


texts: shift registers: differences between the standard parallel-in serial-out ICs

texts:
I must be blind... I'm trying to decide which of the '165, '166, and '597 shift registers is appropriate/inappropriate for a SPI input shift register. All are 8-bit parallel in.

HC165: http://www.nxp.com/documents/data_sheet/74HC_HCT165.pdf
HC166: http://www.nxp.com/documents/data_sheet/74HC_HCT166pdf
HC597: http://www.nxp.com/documents/data_sheet/74HC_HCT597_CNV.pdf

It looks like the HC165 has a latching asynchronous load input (parallel load triggered by a pulse), the HC166 has a clocked synchronous load input (parallel load triggered by the same clock edge as the serial shift, when load enable is asserted), and the 597 has a separate set of load registers.

Can anyone add anything to the differences, or suggest which might be the most appropriate for SPI? (my gut call is the HC165, with the parallel load triggered by the inverted SPI CS line, and I'd have to add a 1-gate tristate driver for the MOSI signal)


texts: Confusion in grounding shield wires of transducers

texts:
There is a 6-wire Wheatstone bridge type load-cell and one of the wire is called shield and it is electrically connected to the metallic case of the load cell as below(I marked that with yellow indicators):

Two identical load-cells are wired to two amplifier units and the amplifiers are powered with an isolated SMPS supply. All is shown below with my primitive drawing below:

LC1 and LC2 gray parts represents the metallic part of the load-cell and the yellow wire is the built in shied wire attached to it. 5 orange wires are the other wires between the load cell and the amplifier unit. The outputs go to a single-ended data acquisition board.

I was not using the shield wire before(yellow wire in the above illustration). I mean the shield wire was not wired to to the earth. We were sometimes having interference problems and I was suggested to earth the frame.

Is my way of earth grounding the shield in this case i.e. earthing the shields at a single point to the mains earth correct?

I really couldn't find an clear information on this.


texts: Loop bandwith and open-, closed- loop gain in ADIsimPLL

texts:
I'm want to use ADIsimPll to calculate the loop filter properties for a PLL I want to build. I read some things in the programs help topics which I find somehow strange. Maybe you guys can help me out with those.

They define the loop bandwith as the frequency of unity gain for the open loop gain. Wouldn't it make more sense to use the closed loop gain instead?
The open loop gain is defined as \$G(s) = \frac{K_d K_v F(s)}{N s}\$, where F(s) denotes the loop filter transfer function. Why is N in there? Normally, the open-loop-gain is defined as VCO-output/phase-error (or \$\frac{\Theta_O}{\Theta_{REF}}\$ in the diagram below) which is just \$\frac{K_d K_v F(s)}{s}\$. If this N is in there or not changes the loop bandwith drastically. Also the closed loop gain is influenced by this.

Here is a block diagram of the (type of) PLL I'm talking about.


texts: Encoder PCB design - grounding, noise and decoupling

texts:
Hi first time posting here. There always seems to be helpful answers and tips.

Okay my question is simply are there any glaring mistakes in my approach to the PCB layout (see image links below), I'm referring to grounding, noise and decoupling more than anything. Which always seem to be a tricky subject with varying opinions on the 'best' solution, I've read just about everything I can find.

The first bit that I'm a little unsure on is what happens to the return path on a differential signal? As I presume it must run back through 'ground' at some point?

How close do you really need to get all the ground points in a DC-DC Buck converter (bottom left of the board). Is it worth adding a 100nF capacitor beside the large electrolytic's on the 24v in-feed side of the LM2575, to help reduce high frequency switching noise on the 24v rail?

The analogue section has been through SIMetrix and looks to be doing what I'm expecting.

Eagle:


texts:
I'm using both STM32F103 and STM32F407 with a SEPS525 SPI driven OLED display (160x128). I want to store images to display in internal flash, but BMP uncompressed images with 16bit colors are huge (about 40kB each). Is it possible to transfer jpeg images in the internal flash and use them with TJpegDec http://elm-chan.org/fsw/tjpgd/00index.html to save some flash space? (I'm using IAR Ide and ST-Link v2)

Many thanks


texts: What determines the discharge time of Dual slope ADC?

texts:
I were watching a video about dual slope ADC's here on youtube

simulate this circuit – Schematic created using CircuitLab

I understand that the charging equation is $$ \frac{{V_{in}}\times{t_1}}{{R1}\times{C1}} $$

But bout discharging, the woman puts out something like this:

I do not understand how discharging equation is $$\frac{{V_{ref}}\times{t_2}}{{R1}\times{C1}}$$

The way I see it, at time t1, Vref is positive and Vo1 is positive, and inverting input is GND, so when we switch off S1 and switch ON S2, another current will flow through C1 and charge the capacitor more. I don't see how this will discharge the capacitor.

Am I missing something here? Would you please help me to understand this?


texts:
I'm trying to import a step down voltage regulator from texas instrument into orcad capture.

  LM22670-ADJ Unencrypted PSpice Transient Model

  Pspice model available at texas instruments (was unavailable to have more than 2 links)

I have tried to follow a guide, but after completing all the steps, I'm not available to place the hole component, only parts of it (see image).

It seems like orcad doesn't look at the imported "lib" file, like one component, instead it exports it as "LM22670" is a library itself, with the other SUBCKT and Diode as the part of a library called "LM22670".
Maybe the guide i'm using isn't applicable on these kinds of components, how ever I would gladly receive any help, which helps me successfully import this model. Thank you.


texts: Tektronix MSO4104B oscilloscope SCPI command to add a measurement

texts:
I have searched the programmer's manual in vain.

I can configure measurements if already on-screen but cannot figure how to add measurements if not present.

Does anyone know the correct command?


texts:
I've been working on a project with Atmega328PB microcontroller using both the UARTs for communication. The controller runs fine for a long time but all of a sudden it does not respond at all. It happened two times in a span of one week. The weird issue is, it does not even respond to hardware reset, i.e., connecting RESET pin to ground. But it works normally if it is powered off by removing the supply and connecting it again. It is supplied with a 4V source with a 100nF capacitor to the Vcc pin of the controller and RESET pin is pulled up through a 10K resistor. Below is the schematic of the circuit.

My questions are :

Is it a hardware or a software problem?
FYI, it has extensive use of pointers for string manipulation. Does memory leaks cause the issue?
It has WDT (Watch dog timer) implemented. Does it affect the Hardware reset?
What could be cause of this problem? Did any body face this kind of issue?


texts: Initialize array with variable length in vhdl

texts:
I want to initialize an array with length dependent on a signal I set earlier (as can be seen in the code below), unfortunately I can't quite get the datatypes to line up and am having a hard time finding documentation on this.
signal count : unsigned(31 downto 0) := 4;

type my_array is array (0 to count) of std_logic_vector(255 downto 0);
signal my_signals : my_array;

I've tried switching unsigned to integer and natural, yet I keep getting the error only scalar types may be constrained by range
. How would you resolve this?


texts: Does a transistor work by connecting the collector to emitter? If so, why do transistor regulators work?

texts:
I am wondering why a transistor, such as one used in this Zener diode + Transistor regulator , has the output controlled by the base voltage rather than the collector. My textbook (which has this image) says that the constant voltage being produced with the Zener diode (that is, its reverse breakdown voltage) is applied to the base of the transistor, and as a result, the Vo (voltage out) is the Zener voltage minus the transistor conducting voltage of 0.7V.

This largely makes sense, but wouldn't the transistor bridge the collector with the emitter once the base-emitter voltage exceeds 0.7V? And assuming the Vin (input voltage) is something like 10V, while the Zener voltage would still be something like 5.6V, why would the voltage at the emitter be (5.6V - 0.7V = 4.9V) and not 10V?

Many thanks for your help.


texts: SR Latch: Why reverse S and R in NAND and NOR if it reverses the outputs too?

texts:
Here is a NOR based SR latch:

And here is a NAND based SR latch:

So, basically first we flipped the orientation of R and S and then declare that in our NAND latch, the output would be flipped i.e. 0 for set and 1 for reset which defies the meaning of set and reset.

Why in the first place did we change the names of the input corresponding to Q only to find out it reverses our output ?
Had we kept the RS naming in both the latches, we would be getting a sensical output that would be 1 for Set regardless of NAND or NOR gates used.

PS: I don't know if this question belongs to this stackexchange as it focuses on why a decision was made. Please move to proper site if required.


texts: STM32L442 programming in production phase

texts:
I am working on a project using the STM32L442 32 pin version.
I am using all pins, pins for external oscillator as GPIO input and pins for STLINK programming as GPIO output.
I am planning to program the MCU by setting BOOT0 pin to 3.3V in programming phase and using UART.
Will i have any problem not using external oscillator and programming the board with the internal bootloader?
I could use the larger version of the MCU but I would like to keep it smallest possible.


texts:
I read the documentation of NGSpice, voltage source is mentioned in Chapter 4 with N+ N-, I tried LTspice, I only found voltage source with two terminals.

How would a single terminal voltage source get simulated in NGSpice?


texts:
I did a circuit to test it using the application everycircuit (https://play.google.com/store/apps/details?id=com.everycircuit.free). But when I did the following circuit I've got the following error message: Voltage source Is shorted

Could someone explain it to me?


texts:
I believe the right most antenna is a mono-pole helical "rubber ducky" (please correct if wrong).

But what type of antenna is on the left? It is terminated with a U.FL connector (not shown) and the center pin connects to a thin copper braid covered in a transparent insulator. The metal spiral connects to the shield and is conductive but I'm not sure what type of metal it is.

Both antennas have had their rubber moldings removed. They are both made by Wellshow but I can't find details of the left one. I do know they are both made for 900/1800MHz.


texts: DC-DC Regulator/Converter to Power Robot and Laptop

texts: I have a small form factor Lenovo IdeaCentre PC that I would like to use as the primary controller for a large scale tanked robot. I've ironed out the accessory connections using usb->server controllers and usb->motor controllers. However I am not certain how best to power the actual PC using LIPO batteries. The power supply/brick that shipped with the PC is a standard AC->DC 19v 3.42amp power supply. I'd like to power the robot and pc using ThunderPower lipo's, what type of regulator/converter is available for purchase? Or am I completely wrong in what I need? Any help would be greatly appreciated. Thanks!


texts: Attenuating mid-supply biased audio signal before AC coupled audio amplifier

texts:
The context here is simple volume control of a DAC generated audio signal with a potentiometer before an audio amplifier stage in a single supply, battery powered system.

Is there any advantage to attenuating only the AC component of a mid-supply biased audio signal, before buffering and feeding it into an AC coupled audio amplifier:

As opposed to attenuating both AC and DC components, before buffering and feeding it into the AC coupled audio amplifier:

Assuming the buffering op-amp is rail to rail, it seems that the two approaches should be theoretically equivalent.

The former approach seems like it might be more linear, avoiding the rails of the buffering op amp. The latter approach requires less parts, but there could be clipping near the rails  due to non-idealities (albeit small) like input offset voltage in the buffering op-amp. Is one approach preferred over the other in practice?


texts: MC34063 Step Up regulator output voltage too high

texts:
I have a wall wart which is rated for 12V-2A, but I noticed that the voltage drops to 9V when I put a load of 500mA. To get a steady 12V on output I am trying to build a regulator using MC34063. I am using the chip in step up mode and calculated the values of components required using Vmin as 9V, Vf as 0.4V and Vsat as 0.45.
Now the problem is that the output I am getting is around 21V steady. When I put load the voltage starts fluctuating between 21V and 18V.
Following are the component values:
Rsc = 0.5ohm
R1 = 59kohm
R2 = 540kohm
CT = 100pF
Co = 100uF
Cin = 100uF
L = 47uH

I have checked the circuit multiple times and evryting looks good. The voltage at pin 5 between the voltage divider is around 3V which I feel is strange for inverting input but follows the output.
Any pointers or help is appreciated.


texts:
Disclaimer: I have little to no background in electronics / electrical engineering.

I believe this circuit is to provide a steady and accurate current source, which can be altered with a potentiometer. I would like to know why 4 op amps have been used, and what the benefit of this configuration is?

Unfortunately, I don't have the exact spec of the chip at this moment in time, merely the hand drawn diagram attached.


texts: How equate capacitor's voltage for mixed series paralell RLC circuit

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I need to find the voltage's equation across the capacitor in the schematic below using differential equations.

My professor said that it's a simple matter of finding the natural and step responses and adding the results together, but I cannot see how this problem can be that easy.

There is no need to solve the differential equation, just a demonstration on how to get it will be accepted as an answer.

Important: Vg is actually a Square Wave, I could not find the symbol in the schematic provided.

simulate this circuit – Schematic created using CircuitLab


texts: Build a circuit so that you can determine the I-V curve of a diode

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The question I have is: how can I design a circuit so that I can determine the I-V curve of a diode.

I've found this one:

But is that a smart circuit or can I find a better one? Thanks for any advice.


texts: Multiplying the voltage of an output pin on an Arduino board

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I am in hold of an Arduino board and 12V DC motor.
I need to be able to control the motor speed gradually, my intention is to output a PWM current in range of between 0 and the maximum 5V of the board to the motor.

My question is what do I need to have in order to multiply the output from the range of 0 - 5V to 0 - 12V to fit the motor?


texts: Is it possible to recover from this un-soldering mistake?

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I did a real mistake when un-soldering this PCB :

The metal part of the PCB was accidentally removed. Now it is impossible to solder anything at this place again: the solder material (what's the name again in english?) doesn't "glue" to the PCB anymore.

Is it possible to solve this problem?


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I'm wondering why the node voltage of C will equal to

Vc = Vd + 770

I've done research but have no clue. Any help will be appreciated.


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How can I measure the impulse response function of a single coil - like an electromagnetic shaker?

The construction of a second winding would be difficult. I was thinking about a T/R switch but there will be better ideas - I hope...

Image source: Schematic view of an electromagnetic shaker


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I am using the Bosch BMP280 pressure sensor and the FGPMMOPA6H GPS chip together on a PCB. I am using the reference designs from Adafruit's breakout boards for each chip (found via the product links: BMP280, Ultimate GPS). Both breakout boards use the MIC5225-3.3V regulator, but have slightly different support circuitry.

Here's the regulator circuit for the BMP280:

and here it is for the GPS chip:

Since these are going on the same board, I only need to use one voltage regulator for my 3.3V rail. From what I gather from Adafruit's documentation, the enable pin for the BMP280 is always high to keep that sensor on, while the enable pin for the GPS can be switched off to conserve power when the sensor is not needed. Is this correct? Why does the GPS also need a ferrite bead but the pressure sensor does not? Can I keep the ferrite bead in place without it affecting my other loads on the 3.3V rail (such as my ESP32)?