texts: Electronically connecting/disconnecting device from a CAN bus

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What I'm trying to do can be best described by the following circuit based on an electromechanical relay:

simulate this circuit – Schematic created using CircuitLab

However, is there a simpler solution not involving any mechanical/moving parts?  [[ edit: as pointed out by Lundin's answer, switch bouncing and EMI from the coil could mean that this approach is entirely unsuitable ]]

The "complication" is that CAN is a broadcast bus with open-collector-like connections (not sure whether they are implemented as true open-collector) to emulate a "wired-AND"  (any device can assert a logical 0).  However, I'm not sure how exactly the physical "driver" (on the device's connection to the bus) is implemented, since it is differential, with states being:  both lines at 2.5V for a differential voltage of 0V, and (CAN_H,CAN_L) = (5V,0V) for a differential voltage of 0V (not sure whether it is always like that, but this seems to be one common scheme).

Would a MOSFET transistor acting as a switch do the trick?  What about a solid-state relay?  Would the SSR be able to transmit the 1Mbps (Megabit per second) signal when in its "closed" state?

Reaction time (time it takes to connect or to disconnect the device) is not important. [[ edit: the intended notion was "disconnect latency";  as long as the actual disconnection happens fast, it does not matter that it takes 100ms from the time we decide that we want to disconnect to the time when we actually disconnect it ]]


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I don't understand the reasoning behind solving for the \$Z_{out,0}\$ term in the extra-element theorem (EET) in this textbook example. For clarity, the full EET is that any transfer function can be expressed as \$H(s)=H_0(s)\frac{1+Z_{out,0} / Z}{1+Z_{in,0} / Z}\$. The \$Z_{out,0}\$ term is found in the following way: in place of the extra element [here the capacitor], place a test voltage source without nulling the input source. Then solve for the ratio \$V_x/I_x\$ such that the output [here the drain voltage] is 0.
In the below example, solving for this ratio is in general not possible since the output can't be zero while \$V_x\$ is nonzero. The example says this requires an "infinite current" which I don't understand. The current \$I_x\$ seems to actually be forced to be equal to \$g_mV_{in}\$ since if the drain is at 0 then no current goes through the resistor. What's going on here?


texts: How can the design of CMOS Transmission gate or Pass Transistor be improved to get a response similar to the ideal VCS like in LTSpice?

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I was trying to implement a Voltage controlled switch. I tried to implement it using CMOS TG and pass transistor in Cadence Virtuoso and used the nmos_1v model in gpdk090 with the default W/L ratio. How can I alter the W/L ratio or body bias voltage to get the desired Ron, Roff, Vt, Vh where switch trips at (Vt − Vh) and (Vt + Vh).

I've tried implementing the parallel connection of multiple pass transistors with common connections and also parallel connected CMOS Transmission Gate.

P.S. - I'm a beginner at VLSI Design so extremely sorry if I have made some mistakes in implementation, and Thank you!


texts: 3-way thick wire connector (8-10awg wires)

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What is a reliable, easy-to-use, and inexpensive 3-way connector for 8-10 awg or 5.5-8.5mm2 wires?
Most 3-way connectors such as the one in the image below are too small to fit two 8-10awg wires in one side.

So far I have t-spliced 8-10awg wires using solder and heat shrink, but I am looking for a more reliable and durable solution.


texts: Connecting ADC ground to alive part of a power supply board for measurement

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Before start, this is going to be a long question. My apologies in advance!

At my company, we are trying to design an automated engineering validation test (Auto EVT) tool for power supply board (PSUs). To achieve that we are going to use these commercially available CPLD and FMC cards:

FMCDAQ2 from AD for data acquisition
UltraITX+ Baseboard + UltraSOM+ MPSoC Module with Zynq UltraScale+ for processing and connectivity

There are a few slight problems with this setup which are that we have to do DC coupled measurement in PSU EVT.

For example this one of the measurements on switching transistor in PSU. We need DC couple measurements to evaluate this.

And also we need 16 measurement points where FMC card only has 2 ADC input.
Moreover, lastly, we will measure alive part of the PSU also, therefore the measured voltage difference will go as high as 300Vs.

To overcome this problem we thought of designing an extra relay network to add to in front of the ADC and DAC outputs of the FMC card.

This relay network board will provide selection of a single probe (out of 16 probe) to selected input channel, selecting the voltage scale (if the measured voltage difference is 300V select 100x if 3V select 1x etc.). Also, it will provide galvanic isolated RS232 drivers to send commands to other test equipments. But nevermind that part, that part is easy actually. The hardest part is the floating ground of the PSU.

Measured PSUs are usually don't have Earth connection. Also other parts, relay network board and FMC+BaseBoard are also powered separately without earth connection, with isolated dc.

The biggest problem is, FMC card has a common ground for everything,

And since we are going to turn ac couple into dc couple by bypassing the ac components and making them short circuit as below:

when we close the relay that connects the channel to alive part of the PSU (maybe 400V above in reference to the GND of FMC card) we don't know whats going to happen and these are really expensive instruments. We want the secure them and take every action for safe operation before starting experiments.

In relay network card, I have to provide a differential amplifier with common voltage equal to 2.05V according to the datasheet of ADC in the FMC card(AD9680):

I wanted to build a simulation to see the effects. You can see and download ltspice files here.

If I have to briefly explain the simulation, I connected the GNDs of the relay network board and FMC board with 2m ohm resistors which is more than reasonable. SMA connectors will have at least 5 miliohms serial resistance.

I charged a 10 nF capacitor up to 200Vs, that refers to a floating ground reference in the alive part of PSU. I put a voltage source to provide differential voltage between the tips of the probe. And put the relay accordingly. Relays have the same Ron and Roff resistance that we are going to use in the Relay network board, TLP3107.

When I run the simulation, I expect that it will simulate the close of a relay that is connected to a high floating voltage in alive part of the PSU.

It didn't work. When the relay closes, even though there are only 2 mohms resistance between the grounds.

Diff opamp inputs go up to 30Vs,

Tried putting ferrite beads, TVS/ESD/Zener diodes between the grounds and it didn't work.

So my question is how can I overcome this problem? I believe the same problem must have been in oscilloscopes too. I want to know how do they overcome this problem?


texts: I was studying pn junctions and came across the concepts of diffusion currents. From what I understand is, when the junctions come together, since there is an excess of donors on the n side and an excess of a accdeptor impurities on the p side the concentration gradients force a cross junction diffusion phenomena. Now what I would like to know is that what are the particles that move to create the diffusion currents. The notes from where I'm learning says holes and electrons. Now the actual movement of electrons make sense, because atomic ionization is a pretty ordinary event, but what does it mean when they say that a "hole" crosses the junction from the p side to the n side? Does the entire acceptor atom separate itself from the crystal lattice of the semiconductor and cross the junction? It doesn't really make sense to me? Or is it some exotic effect which I'm unaware of?


texts: What could be this particular thermometer used for?

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I came across this rather strange looking thermometer. It seems to have two scales and some kind of wires inside it.

There are two terminals at the top. Is it a thermostat? But it seems to be too long for one. Should be at least an arm length.

It seems to be very old to as I was unable to find anything on google about it with its name or data on it.

Update:


texts: How to synchronize readings with the HIGH and LOW states of a PWM output?

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I would like to oscillate GPIO infrared LEDs at a high frequency and compare the infrared sensor readings when the LEDs are off and when they are on. To do this I would need to synchronize the readings with the PWM. Currently, I can use a pseudo-PWM by using digitalWrite to toggle them between HIGH and LOW with a delay to take readings, but this only give me 500Hz.

How can I synchronize readings with a PWM output? Or should I just use another method of digital on/off?


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I am sending off a pcb for manufactering, but it would be nice to round off the corners for them to mill off.

How can I make nice rounded corners? I have used the three point arc thing before but I dont really like that...

In what layer should I specify what should be milled off?

EDIT:

I'm also intrested in how to specify a small rectangle (ca 20 x 10 mm) to be milled in the middle of the card?


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I have a DS2401 and an ATmega32.

I can read the its contents with my AVR micro-controller.

I want to know, Is it possible to simulate the DS2401 with my ATmega32? I mean is it possible to connect atmega32 to a third-party master instead of the DS2401? if yes, how?

I myself think I must connect the master [third-party] to a interrupt pin of micro-controller and wait for a initial signal from master, is that right? What next?

Can anybody give me guidance?

DS2401 Datasheet: http://pdfserv.maximintegrated.com/en/ds/DS2401.pdf
ATmega32 Datasheet: http://www.atmel.com/images/doc2503.pdf


texts: v(t) is the potential difference across which nodes?

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QUESTION:
The switch above the 12 V source in the circuit shown below has been closed since just after the wheel was invented. It is finally thrown open at t = 0.
(a) Compute the circuit time constant (in ms).
(b) Obtain an expression for v(t) valid for t > 0 (you can use 'exp' and ^ symbols)
(here X is a variable)
I have to compute v(t) as given in the circuit but I have doubt as I cant find out across which two nodes the potential difference is v(t).


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I studied various techniques to reduce the leakage power consumption in CMOS design. Leakage  currents can be static and active.
I understand the meaning of static (standby) leakage, but I am confused about the active leakage.
Does this occur during transition phase (like that of dynamic power)?  How to calculate this particular (active) leakage?


texts: So I am trying to make a raspberry pi control a servo but it also needs to have speakers attached. But whenever the servo is powered there is a horrible audio output through the speakers. This will happen even when the audio out put is set to hdmi or the PWM pin either way it comes out of the audio jack and changing the volume doesn't help either. But as soon as the servo powers off it stops. To program and wire the servo I used adafruits raspi lesson 8: using a servo. Any help?


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I have a fairly simple question that I can't find the answer to in the datasheet or reference manual for an STM32L073RZ. Put simply: is there a mechanism within the processor that prevents entering Standby mode with WKUP pins enabled when the voltage supplied to either of those pins is greater than or equal to logic high?

I ask because this is the behaviour I'm observing but, as previously stated, can't find mention of this in any documentation.

I currently have a board whereby the GPO of an NFC EEPROM (M24SR64-YMN6T/2) is attached to a WKUP pin. The GPO is active low and configured for SESSION OPENED mode. This means that the GPO line usually sits high, but, when an RF session is underway, will go low. When the RF session is finished the line pulls high again and would trigger a WKUP. This is the intended outcome, at least.

However, as I've already mentioned, I believe that the GPO line being high is preventing the processor from going into Standby mode. If this is the case it's a simple hardware fix, but I just want to make sure that I'm not missing anything.

I should mention that, if I disconnect the GPO line from the WKUP pin the processor goes into Standby mode as expected. I should also mention that, if I drive the WKUP line high from another source then it seems to prevent Standby mode. Lastly, if I have the GPO line connected to the WKUP pin but pulled low externally, then the processor goes into Standby mode.


texts: Transfer Function for a combination of filters

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simulate this circuit – Schematic created using CircuitLab

I am currently working on trying to determine the transfer function for the audio tone circuit pictured.

$$R_1 = t \times 20\text{k}\Omega$$
$$R_2 = (1-t)20\text{k}\Omega$$

where \$t\$ ranges between \$0\$ and \$1\$ and is the value for "tone";

I have what I believe to be the TF for the Low pass filter:

$$H_{\text{LP}}(j\omega) = R_1 \times \frac{1}{j\omega R_5C_1 +1}$$

However I am struggling with the TF for the high pass filter \$H_{\text{HP}}(j\omega)\$ as the addition of Resistance \$R_4\$ is throwing me off.

I had tried using:

$$H_{\text{HP}}(j\omega) = R_2 \times \frac{j\omega RC_2}{j\omega RC_2 +1}$$

where $$R = \frac{R_3}{R_4+R_3}$$

However when I used it in the transfer function for the entire circuit:

$$H_{\text{circuit}}(j\omega) = H_{\text{LP}}(j\omega) + H_{\text{HP}}(j\omega)$$
the results I obtained are wrong.

I have modeled the circuit in LT Spice and found that when \$t = 0\$ the circuit behaves as a low pass filter. However when \$t = 1\$ the circuit behaves as a sum of high pass and low pass filters.

Can someone advise me on how I would go about finding the transfer function for this entire circuit please?


texts: Why does voltage drop across resistance contradict Ohm's law?

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Very basic question here.
I have been learning a ton about Ohm's law, and I don’t seem to ever be able to completely understand it.
One of which I am getting particularly confused about is voltage drop and Ohm's law.
According to what I know about Ohm's law, if you increase the resistance, the current decreases, but the voltage stays the same. See below figures:

From: learn.sparkfun.com
Example:
Here is a graph of the voltages of my 5V battery with resistors in the circuit:

simulate this circuit – Schematic created using CircuitLab

The questions I have are:

What are the physics behind this?
Is there another law that covers this?
Why does this contradict Ohm's law, or is there something that makes this inline with Ohm's law?


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I have a darlington Transistor circuit. Like in the schematic i attached. When i power up the 3V3 from my raspberry, the led is not on. When Doing Danke same with 12v instead of 5v, it Works perfectly. the r3 is 82ohms for 5v And 470ohms for 12volts.

What is wrong With the circuit?
Thanks


texts: What are these programming terminals for a 2 kW power supply?

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Does anyone recognize the programming terminals on the real panel of this power supply? I would like to get the 50 amps out.

It is an ATE1 made by Redfern radio, it is an old army surplus.

Going in blind I have placed a 10k resistor from the +15 to the Vp and Ven allows me to get 44 amps max into a 0.5 ohm load. Vp seems to be clamped at 7.5V, even if I drop the resistance of 10k resistor connected to it.

thanks


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I have 5050 RGB LED Strip and an RGB controller (Something like this http://www.amazon.com/SUPERNIGHT%C2%AE-Waterproof-Flexible-300leds-Changing/dp/B00ASHQQKI/ref=pd_sim_MI_3?ie=UTF8&refRID=0KQRVAR859JNNWFDFDHG but bought from the Indian market at a much lesser price.)
I want to place this entire setup in my car and connect it to the Dome light switch. The connections are all easy as the dome light is already providing 12V. the strip has 300 LEDs all connected in parallel. And has 100 segments (3 LEDs each) where it can be cut without disturbing the strip

Now for convenience I have cut the strip into multiple sub strips (containing either 7 segments or 10 segments. to be placed at different places through out my car. The problem is with connecting them. The LEDs are already in parallel within each sub strip. Now I am worried that connecting each substrip in parallel to the RGB controller would require even higher current. The RGB controller is rated at 1.5A output. Should this parallel setup of substrips be fine? Or should I figure out a way to connect them serially to the RGB controller? so that it looks like an extended strip with wires connecting the sub strip.
Edit: One more thing, The controller comes with a 12V adaptor rated at 2A output. I am planning to connect the RGB controller directly with the dome light, Should I install some sort of protection there (to limit the current at 2A maybe?)


texts: Unrouted wires double after routing in eagle

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I almost finished routing a PCB but after trying to change the placement of a via to ground plane ripup and route the wire connected to it, I've got a weird airwire which is between a pad and nothing. and when I run run length I got . When I try to route it to the closest via to GND I got new unrouted wires like mentioned in the picture
How can I fix this ?


texts: Which part of a pnp-transistor is the buried layer connected to?

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I am preparing for exam and one of the questions is this: "Which part of a pnp-transistor is the Buried  Layer normally connected to?"

According to the lecture notes handed out, the correct answer is: base
According to the IEEE (the title being "p-n-p heterojunction bipolar transistors with buried subcollector layers"), the correct answer is: collector

Which answer is correct?


texts:
I have been working with a device that uses RS232 communication to a PC. There has been some confusion as they have defined their TX and RX pins relative to the device. In their definitions they use to mean TX being the pin that sends data from the device. In my mind this should be labeled RX because it is the pin the computer receives on.

How should the pins be defined? Are they relative to each device or relative to the "controller"?


texts: Is the RS485 common mode output voltage supposed to be only 3v

texts: I am designing an RS485 driver to connect to an ESP32 using SP3485 from Max Linear. I understand that the differential output is 3v and not +7v and -5v like the RS485 spec stipulates. Are there some drivers that achieve +7v and -5v output from a single 3.3v supply, or do they require dedicated power supply eg +12v,-12v to achieve this?


texts: What can be microcontroller resets causes?

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I'm using a ATSAM4S device and I've encountered some problems. I've assembled two boards that are very similar(same pinout, same devices, just a change in LED GPIOs and MCU position on board). First one works very well, second one created me problems from start, like wrong ID, security bit set when it wasn't ecc. I've not used it for a while but now I need to use this board. Programming now working well(don't ask me how, I've switched to JTAG from SWD and this solved all problems also for switching back to SWD) but now, if I load the same code that is on the first, well working, board to this MCU, it goes random to HardFault in debug mode. Also when running simply code as LED blink, MCU resets at random after some seconds. Main cause of this problems is related to faulty MCU or PCB board(as after a lot of test I can't say that is a code error). So, since it's more probably that it's a PCB error, what can be the main problems that cause a MCU to reset randoms after some seconds?

p.s. I've tried same code on either MCU, changed to more stable power supply, tried simply codes, still have problems on this MCU.


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This question is in the context of a production environment where part numbers and change notices are strictly controlled, and any alternate manufacturer parts under an internal part number must be equivalent components.

For Class 2 Dielectrics, the rating codes are well defined. When requesting a new part number X5R and X7R are not equivalent are are given different internal part numbers (even if they are valid substitutes in a given design).

For Class 1 Dielectrics the picture to me is a little fuzzy. I recognize that there are a few different dielectric codes associated with Class 1 parts.However,  C0G and NP0 specifically are used by some manufacturers interchangeably. Also, some distributor search engines (e.g. Digikey) will give option as NP0/C0G when filtering capacitors.

As an example there are two equivalent parts from TDK, an 0603 1000pF Capacitor. One is sold under NP0 designation the other under C0G, their spec sheets are identical...

C1608NP01H102J080AA

C1608C0G1H102J080AA

My question is, when applying the most stringent view of production Change Control and Controlled Part Numbers, Could NP0 and C0G be considered equivalent or synonymous?


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I am wanting to measure the pitch of a single guitar string and convert into MIDI within 10ms.

FFT takes too much time, I was wondering what other options are worth looking at? The main issue is latency.

Can this be done using an analogue method? I.E Frequency to voltage converter?


texts: Current coupling in self-monitoring laser diodes

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I always wondered why the most common pinout for laser diodes with a monitoring photodiode was so strange. It wasn't sure how it was intended to be used until I ran into this circuit here:

https://www.youtube.com/watch?v=MUdro-6u2Zg

In my mind, it seems a bit strange that the current source is shared by both the laser diode and the photodiode since it seems that this coupling would cause the laser diode and photodiode to distort each other's output.

The only reason I can think for this is to reduce component count by using the laser diode's own forward voltage voltage drop to reverse bias the phtoodiode to eliminate the need for  a bias supply, and that the tiny photodiode current is considered negligible relative to the full laser diode current.

Is my reasoning correct? Or is there a useful purpose to this coupling?


texts: Filttering noise out from high frequency 1MHz oscilator (Teslacoil driver)

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I have a 74HCT14N based ''RC'' square-wave oscillator.
The produced signal then goes to PMIC gate-driver and finally to a mosfet which drives the primary coil at resonant frequency. (about 930-1000kHz)
It is a hobby project, and I'm learning new every day.

I'm having problems with the stability of the oscillator/power supply. I'm powering the entire thing from ATX PSU with 5V, 12V voltages and ground from molex adapter.

In the schematic below all GND pins are eventually connected to single wire. This includes the secondary coil ground wire. However without that connection the circuit didn't work. Also U3 and U4 PMICs are powered from same +12V PSU rail as the primary coil.

Observations:
The circuit draws about 3-5Amps from 12V when there are sparks and few 10mA from 5V rail. When I probed the mosfet gate the signal looked okayish.. when drawing an arc there is sinusoidial ringing on top of the square wave. Also the oscilator may eventually glitch out if I pull big enough sparks or move objects near it. (like a finger)

So the question is how do I isolate the oscillator and PMICs enough that the primary coil+secondary coil doesn't interfere with them?
I was thinking that maybe adding LM317T + capacitance multipler to supply U2 with clean +5V would help?


texts:
I was experimenting with my laptop's audio jack port (the headphones one) and something that blew my mind happened. I took an AUX to AUX cable and connected it my laptop (so I could easily have access to cable's pins (or something like that)) and with some wires I connected the right and the left channel with some self-powered speakers. As expected it worked ok.

Then I disconnected the left channel but I realized that if I was holding the one end of the left channel cable cable with my one hand and touching the other end with my other hand the sound would play normally! So the sound could pass through my body. Then I called my sister to repeat this process but instead she was holding one end with her hand and when I was touching her the sound would play again! This is my question: How is this possible? How can the sound signal go through 2 human bodies?


texts: 10 MHz reference distribution (daisy chaining vs. BNC tees vs something else)

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10 MHz is the quasi-standard for reference clock in measurement equipment. Most boxes have "REF in" and "REF out" or "10 MHz in"/"10 MHz out".

In my case, I have a measurement setup consisting of an FSW, SMW200A and SMF100A (all top notch boxes from Rohde & Schwarz) as well as a Tektronix signal generator.

What is the best way to distribute the 10 MHz reference clock along >2 devices?

Daisy-chaining
Use BNC Tees (for 3 devices one tee, for 4 devices 2)
A combination: E.g. take the FSW as master, use a BNC tee to connect to the SMW and SMW via RefIn. Then take RefOut from the SMW and use it for the Tektronix signal generator


texts:
In the book, Power Electronics, by Need Mohan at the end of chapter 7, it is this image:

Relating the output power and the power that the transistor is handling, I want to reproduce this plot for the buck, boost and the buck-boost converters, but I don't quite understand how to write down the equations.

I understand the boundary values at D = 0, D = 1 for the buck and the boost since the transistor is either on or off during the whole period, But I'm not sure why the relations is completely  linear.

In the book, fundamentals of power electronics by Robert Erickson there is table regarding this subject

In this case, there are no plots, and obviously, the plots of this equations will be different that the ones in the above image.

Both, the images and the table give some kind of intuition that if possible it's better to use the buck or the boost converter instead the buck-boost.

I believe that both, buck and boost converters are more efficient than the buck-boost  but is still hard for me to made that claim without more information. There is other book or article which covers this subject more in-depth?


texts: Use AC-DC adapter instead of AC-AC adapter

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I'm building an O2 amp, which according to the designer requires an AC-AC adapter (Triad WAU 12-200) to convert regular wall power to 12VAC. By looking at the schematic for the amp however, it seems that I might be able to use a regular AC-DC converter (also 12V) instead.

According to this site, an AC-DC adapter uses a transformer to stop down the voltage, rectifier diodes to make the current DC, and caps/regulators to smoothen it. Now, the datasheet for the WAU 12-200 shows the following as the adapter's schematic:

(Credit: Triad)

It would seem that the WAU 12-200 merely acts as a simple transformer. Meanwhile, the following equipment is present inside the O2 amp:

(Credit: NwAvGuy)

After entering the O2, the AC power goes through a set of diodes and caps/regulators just like what would happen in a AC-DC adapter. Not that I don't plan to use batteries in the amp at all (strictly wall powered) so the "battery power" section of the amp in the schematic should be omitted.

I've got a 12V AC-DC adapter that delivers 200mA (same as the WAU 12-200). Is it possible for me to omit the diodes and caps on the O2 board and feed it 12VDC power instead?


texts:
I have a specific question regarding test and verification of circuits on PCBs such as the following one:

Since I am not from the electronics industry and never been in such a place I thought someone might have an answer to my question here.

Such a circuit on the above photo includes various components which are soldered on the PCB board above.

I am very curious how are each components or subsystems on such a a complex PCB are tested before assembling. Let's say such a circuit includes diodes and ADCs and voltage regulators ect.

Are these components tested one by one before being assembled/manufactured on the PCB?
And secondly if they are tested on by one are there specific boards or probes for the tiny components which have extremely small pins?


texts: Calculate Thevenin voltage in a Common Emitter Circuit

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I am confused on how to proceed with the above problem. I have solved many problems on thevenin voltage but never faced one involving BJT. Please help me with this problem.

EDIT: I have 2 approaches in my mind.

1st Approach is short ckt a and b and get Isc. Calculate Voc for open circuit case and divide Voc by Isc to get Rth.

2nd Approach is to calculate re using DC Analysis. Then draw small signal model short circuiting DC and use this circuit to get Rth.

Both approaches look perfectly fine. Which one is correct and why?


texts: Use of very large bulk capacitor for microcontroller power stability

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I have a PIC32 microcontroller (MCU) system that experienced intermittent (though regularly) resets, most likely due to ground bounce caused by the switching of inductive loads (solenoids). All the decoupling capacitors and bulk capacitor are present as per the datasheet's recommendation. The MCU is contained on a breakout board that plugs in to the rest of the circuitry. For modularity and ease of replacement if necessary.

One solution that nearly eliminated the resets was to put a very large value capacitor across the main MCU power pins of the breakout board. The MCU is powered by 3.3 V. In this particular case, it was a 1000 uF electrolytic capacitor with a 25 V rating (which is a rather large capacitor). However, the odd intermittent resets still occurs now and then, but not nearly as much as it did without the electrolytic capacitor. I did some testing with a power supply and LED where I removed the power to the breakout board, and the LED still remained powered on for a couple of seconds, as expected. However, it seems that there is a saturation point at which more capacitance doesn't help the situation anymore.

Herewith follows a few questions:

Is there a saturation point at which any larger capacitors will not help the situation (i.e. that remains charged for longer)?
Does the fact that the capacitor is rated for 25 V make it a bad choice for such a bulk capacitor for use at only 3.3 V?
Is there a minimum voltage at which a particular capacitor will reliably provide adequate stability as a temporary power supply in the event of a ground bounce occurrence?
Would a super capacitor be a better choice in this case (particularly the ones with low rated voltage and high capacitance in the Farad-range)?
Taking all the above questions into consideration, what is the best way to provide an MCU with a reliable, stable power supply to eliminate susceptibility to ground bounce (other than using external power supplies like switch mode supplies).


texts:
I am trying to interface a circuit with an FPGA. There is an H-bridge in the circuit that is driving me crazy. The inverted RED and IR signals are coming from FPGA. The light intensity signals are coming from a DAC to control LED intensity.

Can someone explain how this part works? Specially why there is this FDS56892 N channel MOSFET in the design. Is't H bridge on the circuit enough to alternate the LEDs?**


texts:
I am trying to build a curcuit to convert 0 - 2  VDC to 4-20mA using two OP07.. I have designed the circuit in multisim as in the attached file. I have also developed the circuit on the general purpose pcb. In physical circuit at 0 VDC it gives me some milli Amps out put which i can adjust to 4 mA using 1k trim port. In multisim the output at 0 volts is stuck at 6.086mA it doesn't change even though i change 1k trim port value. Any idea where i am going wrong. I have chosen to simulate circuit because this is my trial and error process, so to save time i have switched on to multisim simulator. At 2 VDC the output changes and that i can trim to 20mA using  R8 1k trim port. I am able to adjust the span output but fail to adjust the zero output.

Any idea what i am doing wrong.

Is it possible to simulate this circuit in simulink ?

In my physical circuit it gives me output from 4-20mA but in between the output is not linear, so i need to play with the values of resistors and this is the reason i wanted to simulate the circuit and fine tune if possible.


texts: Electronic device that is open for 6V and passes current once it reaches 12v?

texts:
Please excuse the way I am this question as I do not have much of an electronics background...

I am trying to upgrade the headlights in my car to HID projectors. One of the issues I'm running into is that the daytime running lights circuit runs the low beam bulb at 6V when the system is active, and then 12V when the full power low beams are needed. I am trying to find a device that I can put between the power supply and HID ballast/ bulb so that it only turns on when 12V are available on the circuit. Does such a thing exist?

Thanks in advance!


texts: Commercial SRAM with separate power supply for the core and peripheral?

texts:
Are there commercial SRAMs available with a separate power supply for the core transistors (6T) and a separate supply for the remaining circuitry such as the sense amps, write drivers, etc?

I believe the voltages are usually tied together but wanted to know if there are ICs with a separate pin for each. Just to be clear, this is NOT a dual rail sram. A dual-rail sram would have two different power supplies but it uses an internal level shifter and both are delivered through the same external pin.


texts: Compiling a simple 2-input multiplexer with GHDL fails

texts:
I started reading "The Designer's Guide to VHDL" by P. J. Ashenden, but I'm already stuck after exercise 9, here is my code:

entity mul2 is
port ( a, b, sel : in bit;
       z : out bit );
end entity mul2;

architecture behav of mul2 is
begin

multiplex : process is
begin
    if sel then
        z <= a;
    else
        z <= b;
    end if;
end process multiplex;

end architecture behav;

When I invoke GHDL with

ghdl -a mul2.vhdl

I get the following error:

mul2.vhdl:11:19: can't match port "sel" with type boolean
mul2.vhdl:2:21: (location of port "sel")

I'm kind of confused, because in the book there is a example that shows a in bit port being used in a if-statement the same way I do in my code - but that example won't compile as well(example 1.2, if you have the book on hand).

I think this is a problem with GHDL not implementing the standard properly. Has anyone an idea what's wrong here?


texts: Raspberry Pi relay on GPIO does not toggle, but does on +3V power

texts:
I am trying to toggle an SRD-03VDC-SL-C (3V rated) relay with a Raspberry Pi GPIO.
When I put a wire to the Raspberry Pi 2B ground pin and the other to a 3.3V power pin the relay works (it clicks). I measured 3.28V with my multimeter.
Now, as the relay is confirmed to be working I want to toggle it via software by switching a GPIO pin. I confirmed that the GPIO switching is working with my multimeter: It shows 3.28 V when high and 0 V when low.
But when I connect the wire with the GPIO in high state it does not toggle the relay. How is this possible when both pins have the same voltage and how can I fix this?
Experimenting with the Raspberry I also observed the situation that I could set the voltage to 0 but disconnecting then made a difference. I would assume that in this case disconnecting would not make a difference.


texts: How can I modify this working circuit to reach 1V peak to peak voltage?

texts: It's a 100 kHz sine wave generator. But I want to reach 1V peak to peak voltage.


texts: Make the led work only if a certain voltage exceeded

texts:
How could I make the led work only if a certain voltage exceeded?

I have four voltage regulators in my project to supply my ICs, and i want to put 2 leds on the box so i know if my regulators giving +15V and +5V.
 I need to down it for 4 led, so it need to be simple .
I try to make a comparator with op amp but i cold not.


texts: How to prevent a voltage drop when a motor turns on?

texts:
I have two motors (looking like this one) connected in parallel and attached to a 9 V battery; initially motor A is switched on and Motor B is switched off. When I turn on motor B, motor A's speed slows down - and when I turn motor B off, motor A speed is back to previous value.

How do I prevent this behaviour, i.e. what should I do to keep motors running at same speed no matter if the other motor is on or off?


texts:
My only requirement is time triggered cooperative scheduler. I heard they are more reliable and predictable.

If I want to use only the 'cooperative scheduler' of FreeRTOS for STM32F103 then is it possible to disable its:

Semaphores
Mutexes
Task-preemption logic

I want to strip down FreeRTOS to a simple cooperative scheduler that uses:

Single stack for all tasks
Global variables for inter-task communication.


texts: What does 32 mean in QFN 32? Term is related to IC chip specification

texts:
ESP8285 IC QFN32 is a chip.
https://robu.in/product/esp8285-ic-qfn32-original/
What does 32 mean in QFN 32?
If I have a part/ footprint having the name as QFN50P500X500X90-33N-D. Will it be different than QFN 32 ?


texts: P MOSFET turning on before gate threshold

texts:
I was simulating a P MOSFET, and for turning a P MOSFET on we need gate to Source voltage less then its threshold voltage. as per below simulation circuit at start VGS= 0, then there is no way mosfet get turn on,because it need at least -2V as per datasheet gate thershold to turn it on. but simulation i am getting 4V arroud, whats wrong here.

Some Might say i applied voltage VDS=5V but for P MOSFET it should be negative, but i saw some circuit where they used this type of connection where R1 is just replaced by a supercap.


texts:
I have the following circuit which is used for DSB-SC modulation but, I can't understand

Why we use High Pass Filter(I expect to be High pass filter , I'm not sure with that ) at the carrier ?
Why we used Dc Biasing at Both input and carrier input ?


texts: I am making a motor and was wondering if it is necessary to use insulated copper wire instead of any regular copper wire.


texts: For a given power, which will be larger, a motor or a generator? Is there a certain relationship between motor/generator size and power?


texts: I know that .data will be in the RAM, but I came across article that says during boot of an micro-controller the initial value of variables is stored in the ROM and then the boot-loader copy the initial values of variables from ROM to RAM, Is this true!?


texts: Is Adafruit's recommendation for led strip driver MOSFET incorrect?

texts: Adafruit's article ( https://learn.adafruit.com/rgb-led-strips/usage ) states that transistor IRLB8721 can be used with 3.3V or 5V gate voltage to drive LED strip. However, in  IRLB8721 datasheet ( https://cdn-shop.adafruit.com/datasheets/irlb8721pbf.pdf ) On-Resistance vs. Gate Voltage diagram shows no data for resistance for 3.3V (most likely resistance is to high to show it in used scale). So when driving the transistor with 3.3V voltage, wouldn't it heat too much? Is it a mistake in their article or maybe I'm missing something?


texts: Clock domain crossing timing constraints for Altera

texts:
I have a slight problem with my clock domain crossing timing constraints.

I have two clock groups

set_clock_groups -asynchronous -group {clk_A} -group {clk_B}

As I understand it this will cause all signals from clk_A to clk_B to be treated as false paths.

However I would like to constrain a few of these paths as

set_max_delay -to [get_registers {*|*|some_reg}] 8

But if I understood the Altera documentation correctly. The implicit false paths created from the asynchronous clock groups will cause the later constrain to be ignored.

For now it beats my why a more specific constrain has less priority then the more general one.

Has anyone solved this in a practical fashion, or do I need to stop using clock groups and constrain all relevant paths manually?


texts:
I've built this circuit to charge 3 large, .47F capacitors:

The capacitors are really big, and they charge up slowly. The addition of R2 and D is for D to light up in increasing power as the capacitors charge, and when they are fully charged, D should light up in full power.

However, I didn't manage to get it working correctly. D lights up in seamingly full power when the capacitors are not even half full.

How can I create a V(t), I(t) and finally a R(t) functions for the capacitors? (It isn't an ohmic resistance but you get my point). Using these I'll be able to find proper values for R2 and D, and anyway I'm just intrested in how the voltage is built up.


texts: Holding register in microcontroller for Modbus RTU

texts:
I'm very noob in microcntroller modbus.
I want to do Modbus RTU slave device using RS232. I read modbus documentation from modbus.org site. But still I'm not clear about few things.

How to define the holding registers in Atmega32? Or is any new storage element need to be interfaced with mcu? Or does the internal memory of MCU need to be used?
Please provide some examples.


texts: I'm planning on building my first robot using an Arduino. It's going to be a small obstacle avoiding robot powered with a 9V battery. What should the voltage of the DC motor used in the robot be? Also, if you you've done this before please give some tips, or refer me to some link.Thanks.


texts: Measuring high voltage with low power op amp

texts:
I want to use AD623 instrumentation op amp to measure current at high side of the circuit:

simulate this circuit – Schematic created using CircuitLab

I was thinking to use a voltage divider like above diagram to drop the voltage to AD623 input limit range. but then I came across this article which describes how one can measure high voltages with low power op amps:

  Won’t 150V input burn up the op amp? Not if the V1 voltage is used to
  generate the positive powersupply (Vcc_H) for the first op amp, OP_A.

And then talks about return path about bias current, but honestly I don't get it.

Why it wont burn the op amp?
What if we use a regulator to generate positive supply for the op amp?
What about negative supply for the negative rail of the op amp?
What specification should the mosfet have? do we need a logic level mosfet?

Appreciate it if someone please expand and explain the whole concept of this method in simple terms.


texts: Does doubling conductors double the ampacity?

texts:
If I have a 4Awg copper conductor being used as a bus bar for a lithium ion battery pack, the chart at https://www.powerstream.com/Wire_Size.htm seems to imply that I can run 135 amps through that bus-bar.  If I take two 4Awg wires and twist them together, is it correct to assume that bus bar can now conduct 270 amps?
Do these values continue to scale in a linear fashion?


texts: Determining Voltage and DC/AC from Wiring Diagram for Spark Door Buzzer

texts:
I'm looking to use my Spark Core to control my door buzzer in my apartment. I'd like to identify the correct parts I need to build the required circuit, but this seems to be dependent on the voltage and current type that the buzzer system uses. I have been referencing this question:  to try and identify the proper relay and transistor needed. Here is the schematic for my buzzer system (My apartment unit has model 3404 inside it with LISTEN, TALK, and DOOR buttons):

http://www.leedan.com/Pacific_AF-1000_Diagram.jpg

According to this similar example, I need to find a relay with a coil voltage equal to that of the door buzzer system. Also, as the Spark core provides 3.3 VDC, I believe I would need to amplify this using a transistor. From the schematic, can you help me identify what the voltage and type the system uses, and also what types of relay and transistor I would need for the circuit?

Many thanks!


texts:
I've bought a bunch of film type capacitor as they were pretty cheap and I thought it was a good idea to get some and test them. (set here)

So I'm trying to figure out what's the specific application for these but for now I've only found them more usefull than other types when working with high frequency.

So, can I just use them as replacement for ceramic/electrolytic capacitors ? For example as decoupling capacitor for IC or on voltage regulators ?

(I'll confess that I really love their looks so as I'm just a hobbyist and most of the time space is not a problem, if I can use these cool looking little parts :) )


texts: Inrush current limiter 230V AC 16A (~325V DC 3,6kW ) - low power losses - safe

texts: I need an Inrush-Current limiter and struggling with a good starting point. Basically I was thinking about using a NTC which then get short-circuited by a relais after a short period of time to minimize losses. Any helpful thoughts on this? What is best used as a trigger for the relais? Voltage drop across something? Current itself? Just time? Pros/Cons?


texts: What is this yellow component in my Samsung mains charger and what is its purpose?

texts:
What is this yellow component in my Samsung mains charger? On the top is written "DT0506C" and on the side is written "ETAOU81EBE BE 1218".
Similar looking components I've found were transformers. In my opinion it is way too far away from the rectifier and the mains connection. Its traces point me nearer to the USB port.
In the third picture is the bottom perspective with the component (yellow), mains connection (red), and probably rectifier (green).


texts: Problem with the pulses given by the motor encoder

texts:
I'm experimenting with differential encoder and I have some questions now. First specs: motor reduction is 14:1 on official page, encoder count 512 pulses per revolution so that mean that on one full rotation I got 512 * 14 * 4 = 28672 pulses. x4 because count rising and falling edges of both channels (A and B). Analog comparator in IC form is used to deal with differential signal (AM26LS32AC).
I assume that I need to got exactly 28672 pulses per revolution but for some reason I don't get that value. It is especially expressed when I rotate encoder 50 revolution and on 50 revolutions error is huge. I try different MCU and always got some results. I catch that error is ~0.00405% or ~116.53 pulses. My conclusion is next: error is deterministic and I "solve" problem with changing expected pulses per revolution to 28672 + 116.53. What can cause this problem? I calculate that motor reduction isn't 14 it's more 14.0567. So why encoder give wrong number of pulses? Any idea is welcome


texts: Tekpower TP-3003D Switch Between Constant Current and Constant Voltage

texts:
I understand that the Tekpower TP-3003D power supply has two modes: constant current and constant voltage.  There is no switch or button or anything obvious to select one mode over the other.  How is this done?

It appears to be stuck in constant current mode.  With no load on the supply, I set the voltage to 12 volts.  Once a load is put on, the voltage drops to around 9 volts and the current is around .47 amps.  Adjusting the voltage while there is a load on the supply does nothing; the voltage remains unchanged.


texts: how to switch off multiple power source (+5/+12/3.3) in the same pcb

texts:
I'm designing a PCB that receives 3 power inputs 3.3v, 5v and 12v.
I need simple way to switch all of them of in one go.

Here is a schematic of my PCB

I looked into using a relay but all the types I found are either to big or don't have the correct specification i'm pretty sure i'm missing something about the correct usage .
I looked for a regular switch but I cant seem to find one that fits my needs.

My 12V line is for running a led strip and may go up to 10A.
The 5V line is just for the level shifter.
The 3.3V is for running a NodeMCU ESP-12E board.

I'm using this to drive everything  EVGA SuperNOVA 650 G1+.
I can switch the outside power source but it should run a couple of this boards and I want to be able to Independently shut them off.
I need to run a lot of those and I'm already running 7A on the 12v line so I can't just keep drawing power form only the 12v line there is the matter of the cable and how much amp it can run.
I can use what ever components I want I just need to keep it small.
On the matter of transposing the connectors the board is going to sit in a casing that is labeled and right know it's for a private project so there is no problem.


texts: Aluminum project box: should BNC conenctors touch it?

texts:
I want to make a aluminum shield box (this is my first time!), I made some holes to host some female BNC connectors. Now my question is, should I isolate the BNC connectors from the box? Or should the outer shield of the coaxial cables touch the shield box?

Update

What I am trying to do is making a test fixture to measure leakage current of a diode. I found the picture below on the net:

If I have 2 female BNC connectors and an aluminium box, what will the representation of that metal shield connected to the LO of both ammeter and source in the picture above in my case? does it mean bnc's should betouching shield box ??


texts: If ROM has no data inputs, how is it able to produce data outputs?

texts:
I've been reading CODE by Charles Petzold, and he mentions that ROM has no data inputs, only data outputs.

How does ROM know what address signals to recieve then, if there is factually no data inputs whatsoever?  I never found any explanation in the book.


texts: Switched-mode constant current supply with Schmitt Trigger

texts:
I'm planning on building a small constant current power supply for charging lithium-ion batteries on the go. While they normally use constant current AND constant voltage, I've elected not to include the latter for design concerns - it's not necessary since I won't need to fully charge the battery, and constant-current will suffice for about 70% capacity depending on charge rate.

Looking at normal CC-CV chargers (such as one for the LTC1541, seen here: http://cds.linear.com/docs/en/design-note/dn188f.pdf), it seems this may be achievable with a Schmitt trigger combined with a current-sense resistor and voltage reference, as well as an inductor for filtering and MOSFET for switching. I envisage a system whereby the current sense (resistance would be <0.1ohm) is connected as close to ground as possible, and the voltage drop across the current sense compared with a voltage reference; the hysteretic output should yield a small current ripple but hopefully should keep it relatively constant.

I imagine a voltage drop across the current sense of about 0.05V, driven by a current of 2A. Since the ripple needs to be fairly low - say, plus/minus 0.02A, which corresponds to a very low fluctuation in voltage - would the comparator-driven schmitt trigger be able to detect this change and switch the MOSFET effectively?

While I understand the circuit theory I'm afraid I don't have much experience building these sorts of circuits (I normally buy micro power supplies), so I'm not sure what sort of values to use, nor the feasibility of something like this. I'm aiming for high-efficiency of the circuit, so a linear regulator is out of the question.


texts: Crystal oscillator circuit not reaching full voltage

texts: I want to generate a clock for a z80 CPU using a crystal oscillator but somewhere between 8 and 13.5mhz the  voltage drops and with 20mhz it's about 1 volt peak to peak. I have tried numerous circuits including the one below using a 74hc14 and a 74hcu04 with the same results , what could I be doing wrong?


texts: Wiring an automatic solar light for a tiny library

texts:
I want to add a light that comes on when you open the door to my tiny library that's powered by a small solar panel. I'm no electrical expert but I do know basics enough to make simple circuits.
My original idea was to cannibalize one of those cheap garden solar lights that come on when it's dark out and then run it through a normally open switch attached to the door. My problem is that the lights I want to use run off 12v and the output of the little circuit board is around 1.5. I tried running a voltage booster circuit off the output of where the LED from the garden light was, but for some reason it won't register anything on the output side of the booster.
Does anyone know an easy (and more importantly cheap) way to make this work?
Thanks


texts: Why is carry on for an adder that is simply on?

texts:
I've understood that the behaviour is correct when I make a simple adder:

But why does carry on light up just because I switch on the + operation for my 4-bit system?

http://www.ict.kth.se/courses/IS1500/2012/dicom/index.html

The spec I try to follow has all the details but I can't really understand why the system in effect is like:

1 + 0 = 1

2 + 0 = 1 carry 1 (carry in lights up)


texts:
I want to try making an 230 VAC bulb that automatically turns on/off using

a relay
a transistor
an LDR

I have collected the following components:

a 9 V battery
a 9 VDC relay
an LDR
a BC457 transistor

I want to connect a resistor to the LDR, but don't know what value of resistor to buy. I tested that relay, it needs a minimum of 6-7 VDC to turn it on.

Please explain how to calculate the resistor value needed.


texts:
I have some confusion regarding the difference between half-bridge and buck converters. I thought they were inherently different structures (H-Bridge having a transformer) however in some places, I've seen the term 'half-bridge buck converter' used.
Can someone clarify to me the difference?


texts: Connectors that protect wires from breaking when it is resonating alot

texts:
I am building a robot vehicle, that is resonating alot when it is in rough areas. Cause of this the wires in the robot will resonate a bit too. When this happens every now and then a 'vein' (tiny copper wire in the wire) of the wire will break off. After a certain time the wire will break off from the connector.

Are there connectors that will prevent this? Or is there another solution to prevent this? I am currently using normal screw terminal blocks from TE connectivity. The connector should be able to handle atleast 5A.


texts: Computer Power supply not powering when connecting power pin to the ground

texts:
I have an old power supply which hasn't a power button to turn on/off.It is made by Enlight corporation.The model is: ATX-1123B 230W.

I found an image with the ATX power supply pinouts.Here it is:

As you can see, the green pin(PS_ON#) is for turning on the power supply. You connect the green pin to a ground pin (COM pins) and the power supply should turn on. But in my case ,it wont! But it will turn on if i connect the yellow pin(+12VCD) to the purple pin(+5VSB). Why does this happen. Can it damage my power supply??I can't get any power if i turn it on by connecting the purple pin to the yellow pin. The purple pin is "+5 VDC Standby Voltage" and the yellow pin "+12 VDC". I think that this is wrong and can damage the supply


texts:
I noticed that the rotating plate of many microwave ovens usually rotates with a specific direction, even if sometimes this changes. What makes the plate rotating clockwise/counterclockwise?

I know that in many two-phase AC synchronous motors a capacitor is added to create an initial phase shift which (I imagine) determines the rotating direction. However, can it be that this direction reverses e.g. depending on the initial position of the rotor? Or is it that in some case this capacitor is not added?


texts:
I still don't seem to understand the basics of MOSFETs, I was looking over this slide from a lecture but I don't understand how the gain was solved for.

Can someone explain to me how the gain was found?


texts: How to implement ion acceleration and deceleration in stepper motor?

texts: Actually, I am using pic microcontroller and software uses for programming is microC. One more thing I use a controller unit (DH542-D)for controlling bipolar stepper motor. I did read several articles and notes regarding this acc/deac. I tried to implement it but I did not get proper output on my servo motor. I did work on equation but the resultant output didn't affect that much. Pls, share me the equation to implement this motion in my motor.


texts: What is the name of this connector on the end of a serial cable (not DB9)?

texts:
I just found that a piece of hardware I would like to connect via a serial port uses a non-standard hardware connection.

One end is a female DB9 the other is what I think is an "old" telephone connector, but I can't seem to find the name of it. Here is the pinout of both the connectors from the manual for the device

What is the name of this 4-wire/4-pin connector?


texts:
So there are several ways to transmit a bitstream but where is the actual info when my carrier is a sinewave?

My basic understanding is we have symbols (phase,amplitude or frequency), we assign bits to these symbols and by modulating or changing those parameters (APSK,BPSK,FSK..) the receiver knows (or tries to decide) what got sent from the transmitter.

So the symbols can be seen as graphical representations of the associated bits?


texts:
An old AM radio that passed down to me from my grandparents finally ceased to function after I accidentally dropped it and old parts inside got damaged. I ripped all damaged parts out and replaced them with modern equivalents. There is one thing I am having trouble replacing: the detector diode.

The original diode is 2AP9 (Chinese part, was THE detector diode in Chinese radio designs, similar to 1N34A,) a germanium detector diode that got shattered. I don't have any germanium parts any more (the germanium PNP transistors was replaced with silicon ones, but the amplifier is adjusted accordingly to make them work correctly after a few resistors get replaced)

However I do have a few Schottky rectifiers 1N5819. Are those good enough as detector diodes in AM radio? Do I need to adjust some caps and resistors to compensate the 110pF junction capacitance? (2AP9 have 1pF)


texts:
EDIT: I have added the drawn circuit. The LED (here) is 1W @ 3.4V so pulls about 300mA. I was hoping I could get somewhere close to that.
Thanks.
I am following an online course and struggling to get my head around transistors. Just when I think I have it something like this confuses me!
The PNP in my circuit is only allowing around 40mA to the LED and I am unsure why. The image shows the 4.2v battery connected to a TP4056 charging IC. One side is connected to a 6V solar panel and the other side is a 3V LED.
The idea is that when there is no light on the solar panel the PNP is closed, allowing the current from the battery to the LED. When there is light on solar panel the base current forces the PNP to open, cutting the power to the LED. Hopefully I have this part correct.
The problem is, like I say, that the LED is not too bright and when I put it through the meter I get ~40mA. Is there anyway to allow more current flow through this transistor or do I need different parts. The LED directly to the battery hits over 200mA.
Also, sorry about the photo instead of the circuit diagram, I can't figure out how to add ICs to them which would have made it very confusing.


texts: How to prevent capacitive discharge on my load after MOSFET off state

texts: I built a button on off latch circuit using nand Gates then connected latched output to Nmosfet's gate with a resistor. My load is a smps circuit drives the power Led and this circuit has emc filter stage that contains capacitors and inductors. My load takes place between Vcc and MOSFET drain and source connected to ground. My Led must work stabil between 18-36 volts. While low voltages below the 24volts Led working well but as the voltage increase when i turned off button, Led opens instantaneously after it close. At low voltages my smps Led circuit draws little bit more currents and no discarge happens. But as the voltages increase current dicrease and instant on state happens. CAN u help me to prevent this problem guys.Here is my circuit that i draw pmosfet to see are there any diffrence or not with pmos. But same thing happend. Let me inform photo is clear or not.


texts: Cause of difference in theoretical and experimental values of RC time constants

texts:
What accounts for the slight difference in the theoretical and experimental values of the time constant in a simple RC filter?

The slight difference was just (.5*10^-4) seconds


texts: Where does the power absorbed of this capacitor come from?

texts:
In my circuits book, the voltage across a capacitor is given as \$v(t)=100\cos({2\pi60t})\$.  Because \$i_{ab}=C\frac{d}{dt}v_{ab}\$, we naturally compute the current as \$i(t)=-120\pi\sin({2\pi60t})\$.  The book concurs.  It is easy to understand that for any given two-terminal component, \$p=vi\$, or in this case, \$p(t)=v(t)i(t)\$.  However, the book gives the answer to \$p(t)\$ as \$-18,850\sin({2\pi120t})\$.  However, WolframAlpha gives the link as \$-6000\pi^2sin(240\pi t)\$.

I have no idea where \$\pi\$ dissapears off to.  I have no idea where \$18,850\$ comes from.  I would be most grateful to anyone who could get me out of this jam.


texts: How can so many memory cells fit on MicroSd card?

texts:
I just wondered, when I saw my new MicroSd memory card , how the hell can 32GB fit in that space?

Simple math:

it's around \$\frac{1}{2}cm^2\$ (my estimate, most of it is controllers anyway)
and it contains 32GB cells. So \$\frac{5*10^{-5}}{2^{(5+30)}} = 1.45*10^{-15} m^2\$ space for one cell. Since atoms are in area about \$10^{-12} m^2\$ , how come the memory cells are smaller than atoms?

Here is an image of what a microSD card looks like:


texts: Help learning from a mistake connecting an oscilloscope

texts:
I have built this circuit to dim a lamp with a PWM signal. It had an issue where the MOSFET was getting really hot. So I wanted to know what was happening on the gate of the MOSFET.

I turned the PWM signal off and with my multimeter I measured \$V_{GS}\$ as  12V. Now confident that I can look at the waveform with my little USB-oscilloscope (rated to 20V) I connected it. Bammm, the lights go out and I'm left with a bricked oscilloscope and PC that was connected to it.

I'm quite sad about breaking my PC. However I have to know what went wrong so I'm here.

About the problem with the hot MOSFET: It turns out there was a bug in the code making the PWM frequency very high. Making sure it was 200Hz fixed the overheating and the dimmer appears to be working as intended now.

edit:

MOSFET: IXTQ40N50L2

Opto-coupler: ILQ2


texts: CMOS Gates, I can't understand when we use those negation bubbles

texts:
I began to study CMOS gates, that are in my teacher's book, and I have 2 questions, because there is no explanation.

If we use NAND or NOR , it means we have F = ~(A*B) and F = ~(A+B) and is normal to have that little bubble (negation) at gates A and B right?
What if we have function F = A(B+C) + D . Since is not ~(A(B+C) + D) , then why we have that negation bubble at A, B, C gates? Can someone explain please?


texts: verilog: why do same references show different values?

texts:
I have this line in my verilog code:
tcam_cell tcell0(cell_data[0], data, cell_wr[0], clk);

tcam_cell module:
module tcam_cell(out, in, wr, clk);

parameter length = 4;

output [length - 1 : 0] out;
input [length - 1 : 0] in;
input wr, clk;
endmodule

So basically, cell_wr[0] refers to tcam_cell module's wr input, which essentially means tcell0.wr = cell_wr[0].
Further down, I have these lines:
always @(posedge clk)
begin
cell_wr[0] = 1'b0;
$display(cell_wr[0]);
$display(tcell0.wr);
end

This is what I expect to see after simulation:
# 0
# 0
# 0
# 0
# 0
# 0

But instead, this is what I see:
# 0
# x
# 0
# 1
# 0
# 0

What might be the problem?


texts: Capacitor matching by capacitance multiplier

texts: I am developing an analog fully differential circuit that needs a tight capacitor matching to reach high performances. Because discrete capacitors are difficult (and expensive) to match for production I was thinking about using a calibration method based on a linear capacitance multiplier, using an operational amplifier with a digital potentiometer or a sample and hold circuit to store the multiplication factor. What are the drawbacks of such a method? I am thinking about the amplifier bandwidth (which is not a problem in this circuit), power consumption and, of course, the hardware overhead for both the calibration and the multiplier itself.


texts: What is the purpose of metal layer on the bottom of a ceramic patch antenna for GPS

texts:
In a ceramic patch antenna for GPS if we remove the double sided adhesive tape completely from the bottom we get a metal layer on bottom. What is the purpose of this metal layer ?

If we mount ceramic patch on a double sided PCB (top layer having ground plane for patch antenna and bottom layer having feed line) feed point goes through the PCB to the bottom layer and soldered there. Bottom of the ceramic patch is fixed to ground plane on the top of PCB through adhesive. So there is not contact of metal layer (which is there at the bottom of ceramic patch) to ground plane on PCB. So what is the purpose of that metal layer ?


texts: Signal strength on Freetronics 100% Arduino Compatible Board

texts:
I have been using a Freetronics 100% Arduino Compatible board to run switches that trigger sound file players in MaxMSP.

The only sketch and patch I could use to get the board and Max communicating was Arduino2Max. I am able to get 1's and 0's out of the board using the Arduino2Max patch to trigger the sound file players on and off but the signal is extremely ambiguous. When the switch is open it should be sending a 0, when it is closed a 1 but it is flickering between the two. It also can take up to 4 secs to switch back to a 0 to close the switch. When the sample rate is slowed it just means that the signal flickers at a slower rate.

I have tried using a prototyping board as well as plugging directly into the digital pins. Can someone please give me any advice? Could this be a signal issue to do with the quality of the wires I am using or could there be a problem with the board or the way the signal is converted through usb?

Thanks!!


texts: How do I know if the serial cable is plugged in the right way?

texts:
I recently got a LeddarTech Leddar One rangefinder, which has a UART serial connector. I'm used to boards denoting the pinout directly next to the pins, but the only distinguishing mark on this board's serial connector is a small triangle pointed at the last pin (or the first pin, if you turn the board around.) Does this triangle mean the ground pin? I don't know a lot about PCB markings, and there isn't very much documentation on this product.

As you probably can figure, I don't quite want to find out firsthand what happens if I plug the cable in the wrong way.

Any help would be very much appreciated.


texts: I've read a lot about people cleaning keyboards in the dishwasher. But how does the water damage electronics? Does it cause shorts on the ICs on the internal circuitry or physically get in the IC(which I can't see happening). So what actually happens?


texts: Unwanted "memory effect" on a bus with optocouplers

texts:
I'm working on a microcontroller driver for an equipment which can have up to 64 optically isolated digital inputs. The hardware was designed with an 8-bit bus in mind, so we have up to eight rows of 8 optocouplers arranged like this (TCMD4000 is a quad optocoupler chip with darlington transistor outputs):

Figure 1:

simulate this circuit – Schematic created using CircuitLab

The idea was to sequentially assert the control lines L1 to L8 low so the bus (bits or columns B1 to B8) can be read as a whole byte. While a Lx line is asserted low all the others should be held high so we guarantee no other opto row will interfere with the bus, for their transistors would theoretically be cut (Vc=Ve or Vc < Ve). That way a logic one on an outside input would turn the corresponding LED on and drive the bit on the bus low for the current selected row, with the bus logic level being inverted again by a 74LV240 between the resistors and the microcontroller (that way a logic "one" on the LEDs side is also perceived as a logic "one" at the microcontroller data port reading from the bus).

To make it easier to follow, consider just 1 bit; it is enough for the problem to show up:

Figure 2:

simulate this circuit

Using a frequency of 1kHz to change the asserted lines low (L1 to L8) we would reread the state of the same row at 125Hz. Initially I was asserting L1 low, read the row state and right away would assert L1 high again (this takes up only a few usec), so on the next 1kHz timer interrupt L2 would be asserted low and so on, but I was surprised to see that, when either opto on the same column is turned on, the voltage on B1 goes to 0.6V while the LED is on (low level, as expected) but instead of coming back to high (3.3V) it gets stuck forever at 1V when the LED is turned off and a Lx line is driven low (for simplicity I was using just two lines on my tests, L1 and L2). Note I said "forever" because the voltage at B1 never comes back high, even though no LED is ever turned on again, like a flip-flop that changed state (see figure below, where the yellow trace is the voltage at B1 and the green is the L1 line; the waveform underneath is the same but zoomed to show detail of B1 voltage waveform):

Figure 3:

Figure 4:

The only solution for that bit to go back high is to disconnect one of the involved transistors' collectors from the bus, which then restores the voltage B1 to 3.3V, with a time constant dictated by the 10K resistor, like shown below:

Figure 5:

Note however that while we switch the Lx lines high and low the time constant is many times greater than if L1 line is always held low (~320ms vs. 5ms):

Figure 6: opto response time with LED on and then off, with L1 always low:

That behaviour suggested me that by leaving the Lx lines asserted low until the next line time (1ms instead of the few usec required just for the state read) would give more time for the voltage at B1 to recover, and indeed it worked, with B1 not staying stuck at 1V after the LED was off. Nevertheless, I still don't understand completely these two things:

1 - why when an opto is "disabled" by pulling its emitter high it behaves like "freezing" the voltage at the level it was until the next opto is enabled by pulling its Lx line low (please refer back to figure 5, where it is noticeable this causes the time constant "expansion" if you compare with the case where you never take the Lx line high)

2 - why the "memory effect" happened (B1 staying halfway between low and high everytime L1 or L2 were asserted low, even though there was no more LED turned on anymore)

I hope I could make it a little clearer now! Sorry for the lack of information before, it was really hard to explain without these waveforms.


texts: What is a momentary SPST Push Button Switch?

texts:
I want to buy a switch (push button) where you press it to break the circuit and then press again to connect the circuit.

I believe that this is what I'm looking for:

However, I'm not entirely sure.  I only want to use this for a basic circuit, and I mean really basic, so don't worry about anything there.


texts: What is the purpose of the 2k resistor in the schematic below? I am guessing the current through the diode will be infinity if it were absent?


texts: Preferred resistor (E series) value optimiser

texts:
Is there a tool to find the closest optimum preferred resistor values given a list of constraints?

For example I'm designing a filter but only have a few odd resistor and capacitor values to choose from and was trying to optimise for the combination of values that has the smallest difference from the parameters for the filter I've designed.

Currently as the set of resistors and constraints is so small I'm simply looping through every combination of component value and returning the values with the smallest total difference from the filter parameters.

This seems like a optimisation problem however it is non-linear so many of the tools such as google or-tools would not work.

Is there some tool that already accomplishes this goal?

Thanks in advance.


texts: Why does this JFET attenuator distort the signal this way?

texts:
I have been trying to build a simple VGA using an op-amp and JFET for gain control. I get good results over a small range of voltages (like factor of 10) but as soon as I try to improve this, the signal gets distorted in on or another way. I figured using multiple variable gain stages would be quite bad because the Drain-Source Voltage of the FET needs to stay as low as possible for good linearity. That's why I thought it would be best to make a single variable attenuation stage and then amplify after that. The attenuator looks like this in SPICE:

Unfortunately, I always get this pattern of distortion (both in SPICE and on a breadboard) when I'm attenuating by a lot (\$V_{GS} < -2V\$ in this example):

The negative half of the output sine (positive half of the input sine because it's inverting) gets flattened out for some reason. I'm trying to fully understand why this is happening. I thought it might be because

$$V_{DS,SAT} = V_{GS} - V_P$$

and the positive half gets into the saturation region but this doesn't seem to be the case because \$V_{GS}\$ (blue trace) rises by more than the amplitude of the sine wave without it changing the distortion:

I hope someone can explain why this is happening.


texts: How to effectively control a Peltier device with MOSFETs? (general design and heat issue)

texts:
First, I'm still quite a novice in the electronics, so may miss some basic knowledge, but trying to learn anyway. That being said, here's my situation:
Goal: Control of the direction of the heat transport in a chain of Peltier devices. Basically, a possibility to swap hot and cold sides on demand (or turn them off althogether), by electronic means only.
Current situation: To achieve my goal, I created a circuit controlling the direction of the current in the Peltier devices using MOSFETs (the gates are connected to switches for now, to be replaced by a microcontroller later). I drive everything with a 12V, 1.5A, DC power supply:

And principially it works as expected - switch SW1A makes the current to flow through Peltier devices PE1-4 "from left to right" (on the picture), switch SW2A "from right to left".
Questions: I've got actually two problems/questions related to my design:

Heat of the MOSFETs (Q1-4). They get very hot very quickly; can't give a number, but basically, after 4-5 seconds from closing the switch, the MOSFETs attached to it get so hot, so you can't really touch them anymore. My understanding is that their source-drain resistance should get very small when on, and while some heat is expected, should they really get that hot? Or do I do something suboptimal there?

Is it actually a good design for this kind of application? I'd be especially interested in reducing the number of transistors needed, but is it possible to build such a circuit without having at least two transistors for each direction of the current? (I know I'd need only one transistor if I was interested in only one direction, but can't find a way to use less than 4 to support both directions).

Note: I've read about PWM modulation, but assuming I understand it correctly, it'd reduce the cooling/heating power of the Peltier devices. What I mean is that I'm happy with how strong they are at the moment and how fast they get hot/cold when switched. My understanding is that PWMing the MOSFETs would inevitably lead to PEs getting less (average) current than they get now, which would reduce their heating/cooling power. Am I right here?
Datasheets:
PE1-PE4 Peltier Modules (TEC1-12706)
Q1-Q4 Power MOSFETs (IRF510)

Bottom note: this is actually the first time in my life building anything with FETs, I only used BJTs before. So generally I'm still a bit confused about them.


texts: How does this old telephone ringer work?

texts:
I bought an old rotary phone with the hopes of cannibalizing it for a doorbell/intercom thing in my apartment building. It looks absolutely marvelous inside:

However, I'm having trouble figuring out how the ringer circuit works without taking it completely apart, since the wires are all bundled together so neatly. But I've been holding off from doing that - the existing system already supplies an AC signal when the doorbell downstairs is pressed, so I think I don't need to do too much to hook that into the ringer.

Can anyone tell me about how these old ringers generally worked? I think if I had a basic idea for how they were constructed, I would be able to achieve what I want without risking breaking it.


texts:
I have got an HP laptop charger who's plug has a marking "Linetek 10 A 250 V" over it.

On the other hand, the labeling says:

Input: 100-240V ~50-60Hz 1.6A
Output: 19.5V  4.62A

At home, I have got 230V supply and 50Hz.

As far as I know it's a "Type D" plug which plugs perfectly into 6 AMP Standard socket. Does the "10 A 250 V" refer to anything here I should be concerned about?


texts: I've read that 18V li-ion batteries are over 18V when charged. How do I make sure this won't harm my motor or anything else?

texts:
I've read that a fully charged 18V li-ion battery is over 18V when fully charged. Is this true? If so how do I ensure that I don't damage my motor?

Here is my setup:

18V Li-Ion Batter -> PWM (Properly Rated) -> 18V DC Motor


texts: Half Bridge Converters - Primary Current Sensing Without Current Transformer

texts:
I'm studying on half-bridge topology and a lot of schematics show that primary current is sensed by a current transformer (1:50, 1:100 etc).

I'm quite familiar with flyback and forward converters and in those topologies, a small resistor tied to low-side switch's source is enough to monitor the peak current.

So the question is: Do I really have to use a current transformer (and of course, rectifiers on its secondary) to feed the CS pin of the controller? Wouldn't a small resistor be enough instead?

Example schematic using LM5035:


texts: Abnormal voltage drop across n-mosfet in multisim

texts:
been playing around with multisim, and i've added in a custom fet from infineon as an example and i noticed something a tad off.

when the Vds in my sim is higher than 12.5, it seems like the voltage drop across the device kinda goes wacky where it sits at 10.6.
correct me if im wrong but i would of expected something drastically less with a RdsMax of 1.5mOlms
im i correct to assume that these a range these components are valid to?
and if so is that standard practice ?


texts: What is the difference between PIC and PICAXE?

texts: The impression I get is that PICAXE is based on the PIC cores, but geared to beginners, but I wanted to make sure before committing to any particular platform.


texts: Advantage of rotary spark gaps in tesla coil design

texts:
I am wanting to build some type of high voltage air core resonant transformer (tesla coil) and have seen some designs with a stable spark gap and a rotary spark gap with a motor. I was planning on using the stable spark gap idea, but I see a lot made with the rotary.

How does the rotary spark gap work?

And what advantage does it give over the stable type consisting of 2 metal balls for the spark to go across?

And for a QUAD-MOT tesla coil, would a rotary spark gap be the best option?


texts:
Design the VHDL components (Register, Decoder, and two Multiplexer
16 bit) and interconnect them to build a register file. The schematic
shows only four registers.  Your solution should implement eight
registers.

The diagram provided as a example uses a 2:1 and 4:2 multiplexer, this dealt with 4 bits. Now that I've to create a circuit with 16 bits, what are my inputs into the multiplexer, in relation to vhdl code?

I've completed a sketch of the circuit, am I correct?

I did the VHDL code for the first multiplexer

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity mux8_16 is

    Port(in0,in1,in2,in3,in4,in5,in6,in7: in std_logic_vector (15 downto 0);
         s0, s1, s2: in std_logic (1 downto 0);
         z: out std_logic_vector (15 downto 0));

end mux8_16;

architecture behavioural of mux8_16 is

begin
z <= in0 after 5ns when s0 = '0' and s1 ='0'  and s2 ='0'else
     in1 after 5ns when s0 = '0' and s1 ='0'  and s2 ='1'else
     in2 after 5ns when s0 = '0' and s1 ='1'  and s2 ='0'else
     in3 after 5ns when s0 = '1' and s1 ='0'  and s2 ='0'else
     in4 after 5ns when s0 = '0' and s1 ='1'  and s2 ='1'else
     in5 after 5ns when s0 = '1' and s1 ='0'  and s2 ='1'else
     in6 after 5ns when s0 = '1' and s1 ='1'  and s2 ='0'else
     in7 after 5ns when s0 = '1' and s1 ='1'  and s2 ='1'else
     '0000000000000000' after 5ns

end behavioural;

Is the code the right format?
For the decoder is this correct?

entity decoder_3to8 is
        Port(din:in std_logic_vector(2 downto 0);
        dout: out std_logic_vector (7 downto 0));
end decoder_3to8;
architecture behavioural of decoder_3to8 is
begin
     dout <=    ("10000000") when (din="000") else
                ("01000000") when (din="001") else
                ("00100000") when (din="010") else
                ("00010000") when (din="011") else
                ("00001000") when (din="100") else
                ("00000100") when (din="101") else
                ("00000010") when (din="110") else
                ("00000001") ;
end behavioural;

Is this code correct for the instance of a regsiter?

   architecture GEN of REG_BANK is
   component REG
    Port(Load,Clk,D :in std_ulogic;
        Q : out std_ulogic);
end component;
begin
    GEN_REG:
    for I in 0 to 7 generate
        REGX : REG port map
           (LOAD,CLK,DIN(I), DOUT(I));
        end generate GEN_REG;
end GEN;


texts:
It’s the first time I come across a problem like this. This is the circuit given.  I want to find the voltage difference across the capacitor at steady-state before the switch closes.

From what I’ve learn at SS we consider the capacitor as an open circuit. Therefore the bottom line connects the circuit on the left (current source ) with the circuit on the right (voltage source ) .

I’m specifically interested in what happens at the node  bellow 5kΩ. Since it connects with the voltage source part of the current coming from the resistance has to go towards  the right circuit. But that current never goes back to the current source. I can’t use any of my techniques  (node or loop analysis ). It might be possible but this circuit seems a bit odd for me to follow my usual steps.

Well, the voltage drop across the 5kΩ is 50 Volts. If the current goes to the right there is another voltage drop of 4V so the total Voltage difference across the capacitor is 54?

Does the current source provide power to the right current ? What is the potential before entering the current source ?


texts: LDR / photoresistor issue: resistance is constant in different light conditions

texts:
I have installation with Controllino mini, it's essentially an ATmega328, and with 6 LDRs and 6 lasers, creating laser rays/barriers.

The system acts as a lasers labyrinth for entertainment purposes, and it's working for approximately a year.
One of the LDR's - just generic one you can buy in every electronics component shop, stopped working as it should.
Meaning - it outputs constant voltage no matter what are the light conditions.
The installation of the sensor consists of +12V input on one pole, and connection to the ATmega328 based PLC analog input on the another pole with a 10K resistor to GND.

simulate this circuit – Schematic created using CircuitLab

After taking it apart, the measured resistance on the LDR was constant (don't remember the exact value) and not reacting to different light conditions.
I did replace this sensor, but after a week or so, the same problem occurred again.

This, and the fact that it was working for a year without issues, made me believe there might be external factor affecting it/ taking it out of order.

Why did the LDR or circuit fail after a long period of time?


texts: Delaying all incoming signals by 2 ms using VHDL

texts:
I have two incoming signals that I want to test the coincidence between. But, I first want to delay all of the signals from one channel by the period at which the signals are being sent (2 ms) and compare the coincidence this way. So basically, I want to store the real-time information for 2 ms and then replay it as soon as it finishes collecting, and continue this process on and on. Is this feasible using an FPGA? I was thinking of using one of the following:

outputA <= inputA after 2 ms;
outputA <= inertial inputA after 2 ms;
outputA <= transport inputA after 2 ms;

but from what I understand, these are only used for simulation? What other method(s) would be better to accomplish such a task? Using a shift register, or something similar?

edit:

In my setup, I have two detectors (single photon counting modules) that convert photons of light into a digital signal (3.3V, about 50 ns pulse width). The signals are then being sent to an Altera DE2 board, where they are tested with AND gates for coincidence (note, the signals are being shortened from 50 ns to around 15 to 25 ns beforehand, with internal logic and no timing loss). The clock on this board runs at 50 MHz, which has a rising edge every 20 ns. The laser sends a pulse every 2 ms. The real counts and random noise counts from these detectors follow no clock, so they will not necessarily share a rising or falling edge exactly the 50 MHz clock. Testing the coincidence is not the issue I'm having, what I need to do now is delay one of the signals by the period of the laser and test the coincidence then. Because the laser is so slow, it is impractical to delay the signal phisically (it would require around 1 km of optical fiber). So, I am trying to do this delay through the FPGA itself. Now to rephrase my questions:

(1) Is it possible to maintain temporal accuracy (down to very few nanoseconds) when using a FIFO buffer to delay one of the incoming signals, or will sending the signals into the buffer lose that accuracy and only share rising/falling edges with my clock? (Does the buffer say that block of data is either entirely zero or entirely 1, depending on whether the signal was in a high or low state at the rising edge of the clock when it collects the data?)

(2) How would I begin to write code for such a buffer, is this something I can find a copy of online or would there be any "buffer wizards" that I can create using a VHDL program like Quartus II?


texts: How to connect a device to ground using negative signal with high impedance

texts:
simulate this circuit – Schematic created using CircuitLab

I have a device that enables a ground connection when I press a key on a remote control. This negative signal used to control other devices. But It has about 1k ohms resistance. When nothing is pressed, it provides infinite resistance (no ground). I cannot change this aspect of the circuit.

The problem is that the impedance of this signal is about 1k ohms, so this ground signal does not provide adequate current when used by the other device. It provides only 15ma, that is not sufficient for the second device to activate (150ma).

Both sides of this are correctly powered (12v) and working fine. So how can I provide a sufficiently good ground connection to the other device, using this restricted negative signal?


texts: My touch faucet died.  I can use a z44n mosfet to activate the solenoid with the 6V battery pack but I need to have the polarity switched each use to drive the solenoid in the opposite direction with the next touch.  What can I put in the oval in the diagram to make the polarity switch on the battery?


texts: Speed control of DC motors and voltage being lost

texts:
I am experimenting with speed control of DC motors using L298N and TB6612FNG. In order to compare the two chips I am supplying the motor with the same voltage in both cases \$ V_m = 4.7V \$. For the case of TB6612FNG when driving the motor at full speed, I measure the output voltage at the pins of the chip and I measure around \$ V_{out} = 3V \$ and for the case of L298N I measure \$ V_{out} = 1.5V \$. Is this difference due to the fact that BJTs (inside L298N) have a forward voltage drop of around \$ 0.7V\$ and bacause two of operate we get a total forward voltage drop of around \$1.4V\$ where in the case of TB6612FNG MOSFETs have really low forward voltage drop ? And my other question is where is the voltage being lost in both cases ? I mean I supply \$4.7V\$ and in the one case I get \$3V\$ maximum and in the other case I get \$1.5V\$ maximum. Where is the remaining voltage being lost ?
EDIT: Connections are pretty simple and basic. I got a laboratory power supply (voltage lost while transmitting power is pretty low - only \$ 0.007V \$) from which the motor drivers (so the motors) are powered and I have an Arduino UNO sending the PWM pulses to the motor drivers. In order to control the duration of the pulses I got a simple linear potentiometer wired up to the arduino.


texts: I am reading a research paper Eyer 1999 in which they used these terms so I want to know about them since there is no source on which I can learn about these terms so that's why asking it here, it might be a simple question but I want to know about Pseudo period and Pseudo periodic signals, what does it mean and how to describe it?


texts: I have come across this term many times while studying amplifiers. How does this effect affect an amplifier circuit(or any other circuit in which it plays a role) and why is the input impedance kept as high as possible to negate it?


texts: Screened serial cable - Connect screen to ground pin

texts:
In my company I'm often using RS232 connections between PCs and old peripherals (sub-D 9 pin). I'm only needing RX & TX signals, so I usually use audio-like coaxial stereo cable, to keep it simple. I use both signal cables for RX & TX signals and connect the screen to ground pin. It works fine, but I'm not sure if it is the best practice and the possible caveats...
I suppose it will be better to use 3 wire cable (RX, TX & ground) and then connect the screen to the connector frames, but then the cable will be bigger, more expensive and difficult to find.
So, when using 2 wire screened cable... Is the noise protection assured? There may be ground issues?


texts: MCP2200 - which GPIOs for DTR, DCD, DSR and RI?

texts: Due to the recent controversy surrounding FTDI, I'm looking for a replacement for future designs. I'm looking very hard at the MCP2200. The only thing I can't figure out is that they have several GPIO pins, but none of them are explicitly marked as being intended for DTR, DSR, DCD or RI. RI is certainly optional, but depending on what I'm using it for, I'd rather not do without the other 3. Are these signals supported by the default drivers? If so, then which pins do they use?


texts: Common gate amplifier with load connected to negative DC bias

texts:
What's the difference between the following two circuits? Note that the capacitors are DC blocking, and the FET is on.

I understand that usually, the load is connected to ground. But what would happen if it was connected to the negative DC bias? What about the positive DC bias? Does the mode (constant-mobility, constant-velocity, ...) make a difference? I saw this circuit in a small-signal analysis problem.

Of course, if the capacitors are NOT high enough that they become an open circuit at DC and a short circuit in AC, then that will affect the circuit in obvious ways. I'm asking about any other effect this would have.


texts: Why does M4 turn off and Vout be equal to zero?

texts:
From this picture,when\$ V_{in} = V_{DD}\$,I know \$M_1\$ and \$M_3\$ will turn on,and \$M_2\$ will turn off because their \$ V_{gs} \$ are \$V_{DD}\$ and 0 ,but why will \$M_4\$ turn off,and \$V_B=V_{DD}\$, \$V_{out}=0\$ ?

If i know \$V_{out}=0\$ and  \$V_B=V_{DD}\$ first,then of course i know \$M_4\$ will turn off ,but if now i don't know the value of \$V_B\$ and \$V_{out}\$,and neither do \$M_4\$ ,how do i know \$M_4\$ turn off,and \$V_B=V_{DD}\$, \$V_{out}=0\$ ?


texts: No longer getting the expected default values from nrfl2401 radio module

texts:
So I've been playing around with nrfl2401 and I see I am no longer getting the expected default value when I read the configuration register. The default value is 0x08 and I get 0x20. I have tried resetting the device by disconnecting the wires and plugging back in to no avail. Even though I writing 0x08 to the configuration register didn't help in terms of value remaining maintained and not getting set to 0x20.
Here's the config register.

Here's the capture.


texts: Non-manufacturer microcontroller selection site?

texts:
I'm  looking for a site which I can input my desired micro-controller characteristics. I have found the manufacturer websites...but those will only show their micro-controllers.

I.E. there's a site for PICS and a site for AVR, etc. but I'm  looking for one that will select possibilities from ALL manufacturers, other than that it's  just running around in the dark...


texts:
Why are the Outputs of many function generators earth grounded?

As far as I understand grounding the generator or Parts like the chassis can reduce shock hazards if something fails within the generator.

But it also produces ground loops when I try to measure things with my osci.

Ok but why are the BNC Outputs also ground referenced?  Cant I simply cut the ground wires from the Outputs to ground so the Chassis is still earth grounded but my outputs are not to get rid of my ground loops?  Or does this have any effect I am Not seeing?

update:
Thank you all for your replies.  What I did not understand was: the gnd wire is also connected to ne neutral wire in the transformer.
I really did Not get how a current could actually Flow if I only have the signal wire (inner BNC)  and only gnd aa the outer shell.


texts:
Edited, see bottom of this post.

What would be the best method for preventing damage to multiple audio input devices that are connected to a home made audio patch panel?

Im wanting to make a device or cable where I can connect multiple 1/8" 3.5mm stereo audio sources, and have them output thru a single lead/port/connector.

My concern is potentially damaging the other sources by having the signal/voltage feed back to the others because all the leads would be interconnected.

The sources would be low power devices like mp3 players and cell phones.

I don't know the terminology,  but im basically looking for an electronic "check valve" that would prevent signals from one device back-feeding to the rest, while (preferably) not inhibiting the signal strength going to the output port.

Edit:  So what I'm looking to do is make a device or wire for connecting my phones audio out via headset Port, and my xbox ones headset (headphoneout + mic in... On the controller) to my headset with mic, all at one time.  The console doesn't support background music, so id like to mix the game audio and phone audio into a single set of headphones, while having the mic feed return to the controller.

The "damage" concern is that I'm worried about damaging my phone by running xbox audio, but not phone audio, and having that signal voltage back-feeding into my phone audio out Port (or vice versa).  Idk if that should be a concern or not, but for peace of mind, I would rather not have voltage going into an out Port on either device.

Hence the "check valve" reference. Something that would allow voltage to move forward, toward the headset, but preventing it from running back to the other device. Hope that makes sense.

More or less, I could easily make a Y adapter that has 3 female trrs Jacks, then connect all devices, but im wondering if I should put a resistor or something on two of the leads to stop or lessen voltage from device A going back to device B, but allowing both to flow freely to the Headset.

EDIT 2:  I found this diy inout mixer in my searches that seems like  it would be what I need. Can you check it out and give me feedback on the design, and if it seems 'proper'?  Thanks.

http://www.instructables.com/id/Altoids-Tin-18-Stereo-Mixer/?ALLSTEPS


texts:
I have bought a 100 led flashing led string which I want to use as 2 50 led strings for the holly balls I have made for either side of the front door.
I have a few questions for you all in this.
Firstly I want to have the joint in the middle of the front door so I will make up a socket to plug a string for either side into. When I have cut the wires I will end up with 2 50 led strings which will receive too much power and burn out the leds so what if I add a resistor to each string and what size resistor would I need? The output voltage from the transformer is 31V and 0.12A.

Secondly as I have to make a termination at the end of the cut string could I put the resistor in there or would I need to locate the common and put it in there as it's a 3 wire string?

If I can use the termination of the cut string to add the resistor would I be better removing the last led from the original string and adding the resistor for that string in the same way?

Many thanks in advance as my head is starting to hurt working this out.

Andy


texts:
How to measure Johnson Noise precisely practically?
I tried using opamp/ low noise amplifier in cascade with band pass filter followed by multiplier circuit (squaring signal) and measured output which deviates from expected by nearly 10^(3 to 4) order.


texts: Transmit video wirelessly from on board camera over short distance

texts:
Possible Duplicate:
  Cheapest way to wirelessly transmit video

I asked a similar question a few days ago, but I think I was unclear about my requirements, and they have changed a little since then too.

Here's my proposed setup:

I have a small robot which travels around my room (max 10 ft away from origin). The robot has a small camera fitted into it, and a way to transmit that video to me wirelessly. I am retrieving the live video feed from it, and based on what I see on the screen, I give it further instructions.

So essentially, I need a camera -> transmitter -> receiver setup for a video signal. I would appreciate recommendations for those three components, and what the cheapest way I can achieve that setup is. I am having difficulty finding this info online, perhaps because I don't know what the keywords I should be searching are.

My main requirement is that it has to be cheap (EDIT: in the tens of dollars). I don't care too much about the video quality, frequency, or range (as long as it is roughly 10 feet or more).

Please let me know if more details are required.