texts:
I'm dealing with an electrical equipment which should be compliant to the CE low voltage directive (LVD), following the EN60950 standard.
The equipment is connected to the mains (220V) through an external power supply which provides DC power at 12V. The equipment has a metal casing which is not connected to ground.
Is it a requirement to use a Class II double insulated power supply. Or would a standard Class I power supply be enough?


texts:
I'm doing a past paper exam question and I've gotten stuck. The system can be seen in the picture below.

Using initial conditions given in the paper, I've calculated the zero input response Yb(t) to be 10cos(2t-60), it could also be calculated to be Ae^(2jt) + Be^(-2jt) with A and B as arbitrary constants. The impulse response would then have characteristic roots of -2j and 2j. Am i correct in thinking that? The problem comes in with the impulse response of system c. The characterisitc root is -2j. Thus there is a repeated root of -2j. How will this affect the stability of the system? Is the system unstable because of the repeated root on the imaginary axis? Should I consider it this way or should i just leave the impulse response of system B in terms of a trigonometric function - resulting in marginal stability of system B and marginal stability of system C? Any resources pointing in the direcction of how to approach this would be greatly appreciated.


texts: Breakpoints, poles and zeros of a band reject filter

texts:
I'm reading a manual about op. amps. (op amps for everyone) which, at a certain point, speaks about poles and zeros. I'm trying to understand the following example:
Given the following band reject filter's transfer function

the poles and zeros are supposed to be the following:

One of the poles is supposed to be 0.44/tau, however, if I apply it to the transfer function, specifically to 1 + tau*s/0.44 = 1 + tau*j*w/0.44, my understanding is that I get 1 + tau*j*(0.44/tau)/0.44. So the taus multiplying and dividing go away, and the same goes for the 0.44s. That leaves 1 + j. This doesn't make the denominator 0 but it should in order to be a pole. I have the same problem with the other poles and zeros. What am I missing?


texts:
I have 4 basic independent circuits, each circuit consists of 1 x AA battery, some wire, a micro switch and a light bulb.

I would like to control them from a single switch. So that upon the first switch depression, only circuit 1 will illuminate; switching off when the button is released. The second press of button illuminates circuit to release and so on.

I have managed to achieve the desired result with my raspberry pi a micro switch and some relays.

Is there an off the shelf, stand-alone solution that could replace raspberry pie?

My experience with electronics is purely through experimentation, which has made researching this difficult, I don't know where to start. I am not looking for a step by step just a few keywords to point me in the right direction and I'll work it out myself from there.


texts: Is a pn-junction diode ever said to be "on" in reverse-biased conditions?

texts: I know that it takes about 0.6V-0.7V for a pn-junction diode to be on in forward biased conditions, but what about reversed-biased? I mean is it never called "on"? Here is the specific question that my general one stems from. A pn junction diode will be turned on when 1.5 V of an external voltage is applied to the n- side of the diode while the p-side is grounded – T or F ?


texts: Am I compensated by the electricity company for electricity that exits my home on the neutral wire?

texts:
DISCLAIMER: I am not an electrician or electrical engineer.

Let's say that all I have running in my home is a 10 watt LED light bulb (nothing else).  This bulb uses very little of the electricity coming into my home and most of it exits my home on the neutral wire.

Does the electricity company compensate me for this electricity that I return to them, on the neutral wire?


texts: Changing the offset and span on an analog voltmeter

texts:
I have an analog meter. It belongs on an electric e-bike..

The default reading is about 88v-84v DC high side and 63v DC low side.

It has a resistor and diode on one side then two diodes in series on the other side.

I was wondering if I could change this meter to read 140v-130v DC high side than about 88-84v DC on the low side.

I have included some pictures of the project in question.

(Resistor) Green, Brown, Brown (Diode) ST 1N4748a

(Diode) ST 1N4747A then ST 1N4746A in series

(Coil) 0.812 - 0.808 k ohm

Any idea how/what I could use to measure the desired targeted voltage?

Or some math formula for dummies that could be followed for other voltages to determine the best formula for this type of alteration.


texts: I was working on PIC24fJ128GA202 microcontroller for 2 months, Since my application getting more complicated i decided to program on multitasking in pic microcontroller it is much complicated to do multitasking without RTOS . I am using XC16 compiler and Maplab 8.92 v . Can anyone suggest me how to start working in RTOS for 16 bit Microcontroller using XC 16  compiler?. I google it, but i dont get any clear idea and also i found some code GITHUB.com.


texts: Reducing system voltage whilst getting the same output from a PCB antenna

texts:
I have built a small prototype transmitter, based on a schematic available online.  It transmits on a 5Mhz carrier and uses BPSK modulation.  It works well enough for my purposes.

The schematic for the TX output section looks like the below:

My question is: if I reduce Vcc from 5v to 3.3v and also reduce R4/R5 to get the same current, will I get the same output from the TX antenna?

Further details

I would like to replace the current 9v battery & LDO with a single AA cell and boost converter.  I have other existing circuits with a single AA cell but the IC I am using only goes to 3.3v from a single cell.

MOD1 and MOD2 in the schematic are the same for "quiet time" (when not transmitting) and always inverse when transmitting.  When they change a carrier inversion happens.

The PCB trace inductor loops around the outside of the board, it can just about be seen in the image below.  There are 10 turns on the top and bottom layers, winding in the same direction.  I measured this to be ~25uH using a Peak LCR meter (I am aware that the test frequency is not the same as my carrier, therefore this is not perfect).

When doing some research I found a schematic in an FCC filing for a product similar to what I'm prototyping.  Whilst the modulation is different the antenna and capacitors are quite similar.  This suggests that the schematic I found online is at least mostly sensible.  This design is fed from one end (the other is GND) and only has a 22R resistor.

I happily admit that I do not have much idea of how the antenna works, R4 and R5 in my design are there to ensure the 74AC86 current limits are not exceeded.  Looking at it whilst writing this question I suspect R5 could be completely removed.

An answer that explains how this works (in simple terms for a non-EE) would allow me to understand my own question and perhaps refine the design further.


texts:
Is there a Memory IC for 4Kbytes of RAM? I'm trying to make a schematic capture in Proteus and I need a Memory IC for 4Kbytes of RAM, I've searched throughout the library and I can't find one, tried searching for a 32Kbit one too..
It's for an assignment from my lecturer, and he specifically instructed to add 4 Kbytes of external RAM to a AT89C51 Microcontroller.


texts: SPI and word size - what happens with (say) 8 bit and 24 bit data from the same chip?

texts: I have a chip to be read/written via SPI. Some of its registers are 8 bits, others 24 and 32. How does the SPI master (the MCU) handle these different data sizes?


texts: Sharing same battery with two dc motors and two servos

texts:
I have a 12v battery powering two DC motors through an Arduino and motor controller. The 12v battery is also powering the Arduino using the VIN pin.

Now I am trying to hook up two servo motors from the same Arduino. The servo power supplies are connected together and go to the 5v pin of the Arduino. The grounds are also together and go to the Arduino ground pin. Both servos have a 100uf capacitor across their positive and ground.

There are three grounds coming from the micro controller, one of them the power supply and two others to the motor controllers.

When I have all grounds going to the Arduino ground pins the DC motors come on for 5 seconds or so then turn off over and over. It looks like the Arduino might be turning on and off. But I thought maybe it had something to do with the capacitors interfering with the DC motors since they all share ground? I just don't even know.

So when I remove the ground, coming from the servos, from the Arduino the DC motors run just fine.

Is it possible to share the same battery source for the servos and both the DC motors? Does anybody know what's going on here?


texts: how does this humidity sensor circuit work?

texts: This is a resistive sensor that measures the humidity and I want to know how it works based on its circuit diagram.


texts: where the extra electricy in earthing goes?

texts:
excuse me I'm newbie in electricity , can you please explain how electric will go through one cable that is connected to an earthing rod that is not connected to the circuit or the system being protected

and how the power goes in this cable will end ; will it be dissipated in earth or it will transform to another type of energy or what ?


texts: ARM Multi Cores on SoC's at Close Proximity

texts: Could someone help me understand whether it is correct to assume that all ARM cores on a device such as a smart phone must be closely located on die for faster communications ? Otherwise would the device take a performance hit if the cores were located far apart ? Are all ARM embedded cores on die linked (via some control integrated circuit path) to one another ? How can a secondary such as core1 or core2 etc be configured so that it receives ALL and every IO/CPU data/instructions as though it were the main core0 which is made active by default on device power on or reset ?


texts:
In "switching power supply handbook" by Keith Billings P2 is supposed to represent leakage inductance and D3 is a catch diode, but i don't get quite right.
What is that diode for? how is it even connected to the leakage winding while this winding physically doesn't exist?
He also said that this diode connects when the voltage at the collector reaches 2VDC but I don't see how would that happen.
What am I missing here?


texts: I understand that eye diagrams give an indication of the quality of a signal. But I don't understand how they are displayed on an oscilloscope. With proper triggering shouldn't you get either positive or negative pulses, but not both?


texts: how to tell if this proximity sensor is NPN or PNP?

texts:
I have a proximity sensor without nameplate . I have done some tests that made me think it is a PNP Normally open .
is my assumption correct ? is there another method to know ?
TEST setup : Supply sensor Brown (24v) , Blue (0v) , Black is Output . Voltmeter is connected Red always on Output . Black voltmeter wire is used to test Blue and brown. Note: By "triggered" I mean an object is brought near the sensor and its led is ON.
Results :

Without any load resistor :
a. Not triggered : V(black-brown) = -1.5v . V(black-blue) = 0.04v

b. Triggered : V(black-brown) = -0.7v . V(black-blue) = 23.4v

Assume PNP : I added a 10k resistor between output and GND
a. Not triggered : V(black-brown) = -24v. V(black-blue) = 0v

b. Triggered : V(black-brown) = -0.6v . V(black-blue) = 23.4v

Assume NPN : I added a 10k resistor between output and Vcc
a. Not triggered : V(black-brown) = 0.04v . V(black-blue) = 23.6v

b. Triggered : V(black-brown) = -0.8v . V(black-blue) = 23.3v


texts: If a flip flop has a setup violation and goes metastable, is it guaranteed to settle to the input value when it finishes oscillating?

texts:
If I'm using modern D-Flip flops and miss the setup time (i.e. my D input changes close to the clock), the danger is that the F/F will go "metastable" and spend some time oscillating.

Standard designs use 2 F/Fs as a synchronizer to get such an asynchronous signal handled properly inside the local clock domain.  When reading about this design, I've seen mentioned the fact that the F/Fs are there to ensure that such oscillations of the first F/F will die down by the time the second clock edge stores the incoming signal in the second F/F.

What I'm curious about is if the synchronizing F/F is guaranteed to settle to the input value after the oscillation time.  If my asynchronous signal changed from '1' to '0' at the clock edge, will the Q output be a '0' after oscillating?  Or should I assume that I could get an extra clock period where my "synchronized" signal is still a '1'?


texts: TRF7970A - (RFID reader) No field output?

texts:
Quite sure it's a hardware bug, going to replace the chips 21-4-2015... We've got two 'identical' set-ups with the same code on it... but they both act different... (None works)

I'm currently working on a project involving a TRF7970A (SPI), so far I have managed to set up the SPI connection and read/write the registers. But I seem unable to create a RF field.

Project: RFID Reader
MCU:     PIC18F66K22
Reader:  TRF7970A
Problem: No RF field
Working: SPI connection (Reading/Writing registers)

It's quite hard to find any projects with this reader, which are clear on what to set the registers to and I'm hoping if anyone has experience with the TRF7970A.

The register values I set / think are needed are:

Chip Status Control Register (0x00)
Bit 5 = 1 (RF output active)
Bit 0 = ? (3V or 5V operation, tried both, could this damage the chip?)
          (I'm working with PIC (~3,3V) but source is LI-ION ~3,7V)
(This is compliant with an earlier project, in which it did work)

.

Regulator and I/O Control Register 0x0B
Tried Bit 7 = 1  (Auto-regulation)
Aswel as manual settings

I just see that in 3V mode VDD_RF goes from 2,7V to 3,4V and in 5V mode it goes from 4,3V to 5V. Is it possible that in 3,7V (LI-ION/Working voltage) The TRF7970A will not work?

For this moment, the ISO settings/ protocol etc don't really matter, I just want to get an RF field (measured with oscilloscope).
So powering it with a Li-Ion (3,7V) is wrong? Or what register settings am I missing?
The osccilator of the chip seems to be working fine.


texts: Reading data from UMFT200XD or UMFT201XB

texts:
I want to buy either an UMFT200XD-01 or an UMFT201XB-01 from FTDI. According to the datasheet of the UMFT200XD the

  "UMFT200XD is a USB to I2C breakout module"

After I searched for a difference between these two modules I came across this post Not getting any reading from FTDI UMFT201XB USB-to-I2C module

Does this mean I cannot connect one of the modules mentioned above to my Win7 PC and read data from an I²C device (e.g. TMP102)?


texts: Silicon Controlled Switches SCS equivalent circuit with transistors not working

texts:
I was reading about Silicon Controlled Switches SCS's from this book "Practical Electronics For Inventors", it mentioned that an SCS is equivalent to two BJT transistors illustrated in the following figure (section C on the right):

So I decided to make that equivalent circuit to see how it works, this is the layout I used:

simulate this circuit – Schematic created using CircuitLab

However when I tested the circuit the led turned on from the moment I connected the battery without even pushing any buttons:

The led was supposed to remain off until I push the SW1 button and that after I push SW1 the led should remain on until I push SW2 which doesn't. When I push SW2 the led switches off and then on again after I release SW2.

Why is it not working?


texts: What causes power losses in transmission lines?

texts:
From my understanding there are two causes for power losses in transmission lines:

Losses due to resistance:
\$ R = \frac{\rho l}{A} \$, where \$\rho\$ is the resistivity, \$A=\pi r^2\$ and \$ l \$ is the length of the cable.

Losses caused by the transformer, which again can be calculated or the transformer can be assumed to be ideal and to simply ignore the losses.

I assume that skin effect can be ignored in this case, as the frequency is relatively low (50Hz) and the diameter of the cables is not large.
Are there any other causes for power loss in transmission lines or are those the only two (or three as the transformer has core and copper losses)? If there are any other causes, how can they be calculated?


texts: How to read firmware from Altera's FPGA (Cyclone IV) with USB Blaster?

texts:
I'm starting to investigate Altera's Cyclone IV FPGA to use in my projects. Now I borrowed from neighboring company a real device with USB Baster Rev.C. I'd try to use one instead of evaluation board which I don't have for the moment.

Before I will put any code into the device I'd like to download original firmware to make me possible to return the device to it's initial state at any moment.

However after I connected USB Blaster to the device via JTAG and run Programmer I did not find any "Read" button (as I usually see on AVR programmers GUIs):

Brief search in Internet did not help.

EDIT 1

It looks like there are additional memories on the board:

I used to connect via X4 (pointed with a big red arrow).


texts: Why is the AVR GCC compiler using a full `CALL` even though I have set the `-mshort-calls` flag?

texts:
I have set the -mshort-calls flag which is documented to replace the 4 byte long CALL instruction with the 2 byte long RCALL instruction when possible to save flash space and and cycles...

  -mshort-calls

  Assume that RJMP and RCALL can target the whole program memory.

  This option is used internally for multilib selection. It is not an
  optimization option, and you don’t need to set it by hand.

https://gcc.gnu.org/onlinedocs/gcc/AVR-Options.html#index-mshort-calls

...and it set in Atmel Studio here...

Unfortunately the compiler is still using full CALL instructions even for a call that is only 2 bytes away...

    ...
    35f6:   0e 94 fd 1a     call    0x35fa  ; 0x35fa
    35fa:   f8 94           cli
    ...

What am I doing wrong?


texts: 12V 4-pin Noctua NF-A8 on Raspberry Pi 4B

texts:
I am using a 12V 4-pin Noctua NF-A8 fan https://noctua.at/en/nf-a8-pwm and want to use the PWM functionality also read the rpm from it. Firstly, I went over dozens of forum discussions on a 5V 4-pin Noctua A4X10 fan which has actually kinda confused me with the fact that do we actually need an NPN transistor circuitry for the PWM pin or not. reading this thread has got a driver circuitry there
5V 4-pin Noctua A4X10 on Raspberry Pi
The spec pdf says it's not required but they do recommend a CMOS inverter type circuit. regarding the NPN transistor, they printed the same line which idk, of course, a big type error there.

Can anyone first suggest me the wiring schematic to drive a 12V fan where the supply will be given externally since pi has got 5V as max. I am talking about 12V fan variant here. I will be using either GPIO 12 or 13 for PWM pin since it has got hardware PWM and can operate in the frequecny ranges 21K - 28k as recmmonded in the spec sheet by Noctua.Similary for Fan rpm pin , I guess any gpio pin will be fine right?
As in this forum
https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=244194&hilit=5V+4+pin+PWM+Noctua+A4X10+on+Raspberry+Pi&sid
This guy used no driver circuitry for a 5V fan and has got the results too but again I want to reconfirm this that is it important to have a transistor there for the pwm pin if I am choosing a hardware one (GPIO 12 and 13). I dont want to use and boost converter ciruit at the moment and want to keep design simple as I can so I will power this fan externally.
Moreover my aim is to use a temperature sensor which will measure the ambient temperature and then based on its readings the fan speed will be varied using PWM. Can anyone also recommed me a decent temp sensor to for this application and how to code it using python.Sorry I am beginner level rasberry pi and linux user so need help in this project.


texts:
So let me start apologizing if the question doesn't make any sense at all, I'm a total noob and I haven't quite grasped most of the concepts yet.

I have designed this small visual indicator, which roughly consists of two 595 shift registers driving a bunch of LEDs arranged in rows. So the 595 outputs are set to whatever the row must display, and then the row goes LOW allowing the flow of current and turning on said row. It then goes HIGH again, shift register is set for the next row, and so forth. Basic multiplexing (isn't it?), definitely not reinventing the wheel here.

Well, what I'd like to do is break down the design in modules, so that each row is optional and stackable. In theory this should be nothing impossible to do, but I'm stuck trying to figure out the connection between each module.

Enough with the explaination anyway, if anything I'm making things less clear. A schematic is worth a thousand words, so here it is.

The one above is a raw sketch of what I have now. Below is where I'd be going expanding it:

As you can see, my current interpretation forces me to have a 16-pin connector on each expansion module, which honestly I'd love to avoid.
So here finally is the initial question: is it possible to connect new modules via USB, or the limited number of wires simply doesn't allow it without extra ICs? Because well, honestly, despite the rather ridiculous price, I'm NOT going to add any 595 on the expansion modules.

A small but appreciated extra, in case my idea is unfeasible, would be a pointer to anyone manufacturing small connectors (PCB headers just won't do) that I could use in the project. (googling didn't help much in this case, I probably don't have the right keyword)

NB: as you can see the board would be replaced by an ATTiny, it shouldn't make any difference but still I thought it might have been useful to see the whole picture here. There's also a couple other points I haven't quite figured out yet, not to mention parts omitted from the schematics. Again, this is a very rough skecth of what I have and I'm including it only for completeness sake.

Looking forward your point on this.

(extra: this question was originally and mistakenly posted on StackOverflow, I'm now moving it here hoping to find more interest in it)

EDIT: as far as I can tell from the answers received, bottom line here is that it just can't be done unless I'm packing up each module with extra ICs. at this point, question naturally becomes 'what connector+socket pair would you suggest?' I had in mind something similar to Apple's Lightning connector, which indeed isn't a viable option due to its cost (can't find it below 5€ which is crazy imo).


texts: Internal impedance of Class AB amplifier?

texts:
This was a challenge problem that my instructor gave. Here is what a class AB amplifier looks like:

I've looked everywhere to find out about internal impedance but I got nothing. This is the problem I'm trying to solve:

Determine the maximum peak to peak signal that can be applied to a amplifier and the efficiency rating or nstage for the amp. Assume the amp is driven by a sine source and has an internal impedance of 600 ohms.
Given:

\$\text{hfe} = \text{hFE} = 100\$
\$V_{be} = 0.7\$
\$E_s = 32.093~V_{p-p}\$ at 1 kHz
\$R_L = 8~\Omega\$
\$R_1 = R_2 = 1~k\Omega\$

I've tried all that I've been taught so far. I took the internal impedance as \$Z_{input}\$. Then, I used \$Z_{input}\$ and \$E_s\$ to find \$V_{in}\$, since \$V_{in} = V_{out}\$ is the voltage at the load. Finally, I used that answer to find the efficiency as \$P_L / P_{dc} \cdot 100 \$.
I calculated an efficiency over 200%, which must be wrong. What am I doing wrong?


texts: What about the physical contruction or circuit layout of 1GHz+ ADC's make them expensive?

texts:
I was looking through a list of 1GHz ADC's on a suppliers site, they ranged from 300$-1000$ USD which is quite expensive an limits the amount of products they can be used in. (I've never designed with anything beyond 1MSPS, someday it might be fun for a hobby project to design a superfast USB oscilloscope or something)

What about their physical construction or circuit makes them so expensive? It couldn't be the package because there are comparable parts in the same package that are in the 10$ range.


texts: Why transformerless power supply need a capacitor to decrease the current?

texts:
Assuming we have a 12 V load which needs 1 A current, when we connect this load to 60 Ah 12 V car battery it does not need to resistor and it will ony draw 1 A.

But on the other side, assuming we have a transformerless power supply circuit connected to 220 V so the DC voltage after diode bridge will be 310 V.  Why can we not connect 100 LEDs in series (each 3.1 V) directly without using a capacitor or resistor?

I know this capacitor is used as reactance (\$X_C\$) to limit the current, but why is it needed since the voltage of LEDs is equal to the output voltage of the power supply?  Shouldn't the LEDs should draw the required current?
According to this equation  R=(Vin-VLED)/I =(310-310)/I = zero resistor needed


texts: Should on board jumper wires be solid or stranded considering integrity of the signal & noise?

texts:
According to me stranded wire is good for carrying power(e.g. Vcc) but for carrying signal(e.g. 100MHz I2C traffic) I feel they create noise & since different strands might have some phase difference between them & since they are so close touching might put some noise in other strands. Also, the position of strands relative to each other can change over time with movement & handling.
Solid wire seems to be better for carrying signal to me.
I think I need some expert advice.


texts: Need to create a magnetic coil (no core) for low frequency field (20Hz-100Hz)

texts:
I am doing some experiments with pulsed magnetic fields. I am using an audio amplifier as a power source, and a simple software as my frequency generator. I use mostly square waves and sometimes sine. Both straight forward, simple waves - sort of like a clean audio test signal of different shape. Nothing fancy. I can even hear them when I run them through my coil and when it is noisy around here, I can just put on headphones and hear clearly whether the coil is working.

I am terribly uneducated when it comes to all things electromagnetic (I only know a bit about audio and that electricity going through a wire will create a magnetic field)… so I need some help. On the upside, I am a fast learner, given right direction.

So far I have been experimenting with a coil I built, that is 4" in diameter, about 1" wide and has about 1lb of 22 gauge insulated copper wire on it (I think that is some 300ft but I don't remember any more) - as a result, it is 8 ohms resistance which was done on purpose as my amplifier is rated at 8 ohms at max power. In any case, the coil works quite well, down to about 300 Hz, and up to 5000 Hz although it tends to get hot around 300 Hz after 10 minutes or so. Haven't tested it lower than that, except today at 20 Hz when it overheated in a second and I had to shut it off. Since I am using an audio amplifier as a power source, I made sure that the coil is 8 Ohms resistance, as that's what the amplifier requires.

Now, I have two questions:

If I need a coil that can take low frequencies, like 20 Hz, the one that I have does not seem to like it, as it immediately gets extremely hot - within seconds literally. It is well varnished (I did it by hand, on every turn) and quite solid, but I imagine that such low frequency makes it vibrate enough to produce high heat. I tried even at very low power setting, such as 1/10 of the max that I normally use, but still it gets very hot very quickly and I am sure that if I let it run, it would melt in about a minute or two. Would using thicker copper wire be better for lower frequency? If so - instead of using 22 gauge wire, what should I use to be able to run that coil as if it is on higher frequency? And if thicker wire would work better, would that somehow weaken the magnetic field? (right now I can run 1000 Hz through it no problem, for hours on end, at max power which is around 1000 W maybe even a bit more). I imagine that since my power amplifier is rated at 8 Ohms I would just use thicker wire but with lower number of turns to achieve the same resistance. If it matters - I am using a Mackie professional power amplifier, the type that is used for concerts. It is rated at 1500 W when in bridged mode (both channels bridged together into one).
How can one achieve an even higher power of the magnetic field using, say, an audio amplifier as a power source? I imagine, getting a more powerful amplifier would be a good start - perhaps a 2000 W or more. But then, how do I build a coil that will not overheat?

Any general advice you can give me in that respect is much appreciated. I think, but I am not sure, that thicker wire is better suited for lower frequencies. Having lots of power, as in - strong magnetic field, is essential. I just don't know how to do it. I understand that there is a practical limit at which coil will necessarily melt, but I don't need to go that far.

One more question: I made an observation that - the lower the frequency the stronger the magnetic field. Am I correct there? Namely, I run 1000 Hz, and I can hear some of the iron stuff on my desk vibrate - from my Luxo desk lamp to the box cutter knife, but it does not attract anything, and can run like that for hours… but at 20 Hz, that same knife stuck to the coil at 1/10th of the power (remember - the coil has no core - it is pure copper)! It was scary for a moment - I imagine that's what happens when someone brings metallic objects into an MRI machine room…


texts: What IC is in this particular black blob on my pocket calculator?

texts: I've taken apart my pocket calculator, and I'd like to know what IC is inside the black blob. Is there an IC commonly used in such applications?


texts: What happens if a voltage is applied to the gate of a MOSFET when both drain and source are shorted?

texts:
Can this damage P- or N-type MOSFETs? Does this affect gate current absorption?

A side question:

Instead of connecting D and S together and letting them float, what if they are both tied to ground, or both tied to a power supply?


texts: Stiff Voltage Divider Bias for an Emitter Follower

texts:
Below is an ac-coupled emitter follower with base bias provided by a voltage divider. I'm having a slight issue with how the resistor values are chosen for the biasing in the design example provided in the Art of Electronics (pg 70). I've included the design steps given in the book up to that point.

  Step 1. Choose VE. For the largest possible  symmetrical swing without
  clipping, VE =
  0.5Vcc, or +7.5 volts.
  Step 2. Choose RE. For a quiescent  current of 1mA, R E = 7.5k.
  Step 3. Choose Rl and R 2 . VB is VE+
  0.6, or 8.1 volts. This determines the ratio  of Rl to R 2 as 1: 1.17. The preceding  loading criterion requires that the parallel
  resistance of Rl and R 2 be about 75k  or less (one-tenth of 7.5k
  times h FE ). Suitable standard values are R 1 = 130k, R2 = 150k.

In step three, it says the Thevenin equivalent of the voltage divider used (R1//R2) should be at least ten times less than the apparent resistance of the load resistor RE (RE * hFE). However, I think that instead of the Thevenin equivalent, we should only consider R2, since R2 is effectively in parallel with the load resistance * hFE. If we don't, then won't the loading effect on the voltage divider be too great?


texts: How to pick correct operational amplifier as unity gain buffer between TLC1543CN and LDR

texts:
This is a follow up question on: Interfacing TLC1543CN adc with 8051

I have a LDR in voltage divider circuit. The resulting varying voltage is outputted to adc. Which in turn passes the converted signal to 8051. Lastly the LDR measurement is shown on a 16x2 lcd module.

My problem is that according to the adcs datasheet: http://www.ti.com/lit/ds/symlink/tlc1543.pdf  source voltage resistance can be max 10k Ohm. However my LDRs resistance varies between 5k Ohm and 0.5M Ohm. My understanding is that the voltage outputted by voltage divisor circuitry needs to be therefore passed through unity gain buffer before passing it to adc.

So we come to my question: What kind of op amp would be sufficient for my needs? Preferably something that I can cheaply order from eBay.


texts: Meaning of "raised structure" in microwave networks

texts:
Can you help me to understand what "raised structure" means and why it determines the following property of the S matrix?

Reference: here.


texts: What is the difference between MibSPI and SPI?

texts:
The following text is from the TI TMS570LC4357 microcontroller features overview:

  Five Multibuffered Serial Peripheral Interface (MibSPI) Modules

  MibSPI1: 256 Words with ECC Protection
  Other MibSPIs: 128 Words with ECC Protection

MibSPI seems to be a Texas Instruments term.
What is the difference between MibSPI vs SPI?

The physical layer is the same, right?
Can I connect standard SPI devices to the MibSPI module?


texts: What is the impedance for this parallel rl circuit?

texts:
I want your feedback on my approach to solving the question.
I also want clarification on the phase angle for the inductive reactance.


texts: How to limit the maximum output of ADC Signal Conditioning Circuit

texts:
So I have been designing an Op-Amp ADC signal conditioning circuit. I ended up with the following:

So, for nearly all parts this is a completely working circuit including:

1) The Gain

2) Bandwidth (w/ 2nd order filter)

3) Specific Input Impedence

However the one point - and issue - I am facing is trying to limit the voltage from 0 to 3 volts. So If my input is too big for the gain it is very possible for the Signal Conditioning output to be outside that range, What is the best way to deal with the issue? I looked over a few ways but many of them (including using Zeners) are just too unusable as the voltage I am using is small (especially since I am using a differential output)


texts:
There are several variables like: concentration of electron deficiencies/holes or electrons (n,p) in p/n-type of semiconductor, concentration of donor or acceptor atoms (Nd,Na) in doped semiconductors, length of pn-juction of diode, electron or hole mobility constant (Dn,Dp), etc.

But all of these variables are unreachable for me. At the beginning I thought at least datasheets should include such data but they don't. Just the ones used practically.

Where/How can I access this kind of information?

BTW: All these variables matter for calculating electron/hole average speed (v), current flux(Φ), density of current (J), which are more theoretical calculations. There are also more practical ones like junction capacitance (matters when reverse-biased) and diffusion capacitance (matters when forward-biased).


texts: Are there circuits to ensure polarity with symmetrical and unpolarised AC plugs?

texts:
There are many different connection systems (socket,plug) which are symmetrical and unpolarised such as

  The Schuko connection system is symmetrical and unpolarised in its
  design, allowing line and neutral to be reversed.
  (source Wikipedia)

I have a setup which I covered in the following sketch

in which I desire to have a circuit, which guarantees the direction of the polarity (L and N) indifferent to the direction / polarity of the connection.

That is, I would like to ask if there is a way to make it possible that no matter if I connect A with N or A with L the outcome is always that "L is guaranteed on left cable"?


texts: segment on 4 digit 7 segment not displaying

texts: Segment E on digit 3 has stopped working for some reason. It was working fine when I first got but just recently stopped working. This segment displays fine on the other digits except digit 2,  that one has started to fade. Here is a picture of the display. Any ideas on what could be causing it to be not working and/or how to fix it.


texts: Freewheeling Diode in Bidirectional Motor

texts:
I want to drive Brushed 12Vdc, 4A motor using two relays to achieve direction control.
But what is the best way to connect freewheeling diode to it, I came up with this circuit.

Is it the right way to do it, or is there a better way to freewheel the inductive current in such direction reversing setup.
Also since it is a 4A motor, what should be the safe current rating that I should assume for the diode.

Operation: At a time only one relay will be activated.
So initially If I activate relay 1, then current flows through motor from left to right.
But when S1 is opened, and it is halfway in air then current should take this path,

Upward through D1, Left to right through motor, and to ground through S2.

And similarly when Directions are reversed.


texts: What happen if someone will touch 2 electric high voltage cables from different energy supplies?

texts:
I am new to electricity. I know that if someone is touching one hand one cable of a high voltage cable nothing will happen.

The question is: If there are two cables, each is coming from a different power source, someone is touching one hand in one cable, and the other hand the other cable. What will happen to him?


texts: Not getting expected band pass filter response

texts:
I am trying to make a LTE signal repeater and trying to filter all other signals except the band 3 (869 - 894 MHz)
This is what I am getting:

This is the circuit:

Any suggestions on improving the filter and how can I use standard value components instead of exact values?
Edit: The test signal is 1Vpp
Edit: Made modifications as per The Photon's comment.
Still the voltage in the pass band is quite low!


texts: How do I plot the root locus when there are multiple controller gains?

texts:
I am trying to design a closed loop system with a PI controller. I have plotted root loci before, but in those, I had assumed that the controller was only Proportional. This gave a characteristic equation of the form:
1 + K*(n(s)/d(s)) = 0

where K is the proportional controller gain, which was varied to plot the root locus.
However, with a PI controller, there are two gains Kp and Ki, so how do I plot the root locus since both of them can be varied?


texts: PID for pure first order process (no time delay)

texts:
So I have to make a PID control for a pure first order process (DC-motor) to control the rotational speed. I cant use ZN because there is no time delay in the process and oscillation can't be achieved. I tried SIMC and Cohen-Coon but no results.  SIMC needs a delay. The proces
$$
G(s) = \frac{0.042}{0.0001755 s + 0.001764}.
$$
I need PO<5%, not too much steering voltage < 10 volts, GM > 2, PM > 35deg and stability margin > 0.5

So.. Where should i start? What method would be good to tune my pid?


texts: 240v Split Pase to power 12v Dc fans and lights

texts:
Im re-powering an model-81 powermatic bandsaw with a 3Hp Leeson DC Motor(14a max draw) and KBCC-255 motor drive(fused @15a). I want to put some fans to cool the DC drive heatsink and LED pucks in the enclosure for work surface lighting. fans 420ma ea. 1 light @ 170ma.
    I plan to wire the machine with a neutral. 1: Would pulling 120V(fused @ 1a) from one leg to power a MeanWell SE-100 http://d114hh0cykhyb0.cloudfront.net/pdfs/SE-100.PDFpower be fine, similar to how a stove is wired. 2: Running a isolation-transformer 2x-120 primary 1x-120 secondary with neutral to prevent over current on 12v power supply, and un balanced load on 20a double pole breaker? Also iso transformer on 12v PSU transformer acceptable? 3: Would using both 120V legs(no neutral)be an acceptable circuit for the PSU-max input 264v with neutral. 4: Breadboard iso transformer-rectifier-capacitor-regulator in place of the SE-100                    location rural  FL, US No 3phase https://kb.samsara.com/hc/en-us/articles/216671538-What-is-Split-Phase-Single-phase-120-240-


texts:
I want to heat a pipe to 150 deg C. Pipe size aprox 0.5m long, diameter of 0.1m

My plan is to find a 240v to 24v adapter, connect this to some coiled nichrome wire (probably 24g) with a resistance of 12ohms.

Then wrap the nichrome coil around the pipe and insulate the pipe and coil.

I was also thinking of getting a PID temperature controller, where is the best place to connect the relay for this?

Also any ideas to electrically isolate the coil from the metal pipe?

Any comments and improvements would be appreciated

Thanks

Edit: So ill prob need more than one coil, so is it safe to connect the relay between the mains and multiple adapters?


texts:
I modulate input signal with triangle wave to create PWM signal. When I am creating triangle wave I use astable multivibrator and integrating circuit. unfortunately there are offset at my triangle wave because of op-amp so I have to add an offset to input signal for smooth modulation. therefore, output signal have offset like pitcure below. How can overcome the offset problem?

(attention : I can not use negative supply for opamps )

yellow----> input signal

green ----> output signal

pink -----> triangle wave(carrier signal)


texts: Difference between Tubular and Tall Tubular Inverter Batteries

texts:
What is a difference between Tubular and Tall Tubular Inverter Batteries with same configuartions?

Why are Tall Tubular batteries are priced high than Tubular Batteries?

Tall battery have warranty of 3 years and tubular of 2 and half years.

For example, I have 2 option for an inverter battery, but cant judge which to add with the inverter.

Manufacturer - Luminous

Tall Tubular Specs - https://www.luminousindia.com/products-62/power-backup-solutions/batteries/ec-18036.html

Tubular Specs - https://www.luminousindia.com/products-62/power-backup-solutions/batteries/pc-18042tj.html

Can anyone can explain?

Thanks


texts: Replacing a PC's AC-DC converter with a DC-DC converter for mobile power supply

texts:
I'm going to be purchasing a mini PC to act as a mobile work station in a set of field experiments. The field locations do not provide power, so I'm trying to come up with a mobile power supply.

For starters, the mini PC utilizes an AC-DC adapter with a rating of 19V and 65W. I've spoken with a few technicians about the mini PC and I was told that it could theoretically demand more than the 65W supply with everything maxed out (apparently never happens), but the system typically operates around 30W. For the sake of being conservative (insert safety factor here), lets assume I'll be operating the system at 60W under full load.

Based on extensive research, in an otherwise non-existent application of portable mini PCs, there are two options I'm looking at

Portable battery bank for laptop
Auto/marine deep cycle battery w/ DC-DC converter

Let me first identify the power capacity requirements I'm looking for. The system needs to run remotely for 12hrs, with the idea that I could return home in the evening and plug in the battery to recharge it for operation the next day. During the 12hr span of the experiment, the system will be running at full load for 30mins, then "go to sleep" for 30mins. This cycle will be repeated for the full 12hrs.

Based on my power requirements and operating times, I've made the following estimates:

6hrs @ 60W = 360Wh
6hrs @ 20W = 120Wh
------------------
Total = 480Wh

Again, those are pure estimates, which will suffice for this question. Unfortunately, option 1 listed above doesn't present much of a market with solutions in the 500Wh range. The options that did present themselves were relatively expensive in comparison to solutions presented in option 2. I suspect this is due to the Lithium VS Lead Acid batteries. The weight isn't really an issue, so I'm leaning towards option 2, using a marine deep cycle battery with a DC-DC converter. I have found solutions that provide 12V and +70Ah to give +840Wh which is more than enough.

If I go this route, I have to find a DC-DC converter to replace the AC-DC converter to connect the mini PC and battery. Sure, the other option is to buy an inverter, but from what I've read, the inverter is a complete waste of energy, in that it makes a redundant conversion with unnecessary losses. My question is on how to choose a proper DC-DC converter.

I'm not an electrical person, so go easy on me. A lot of this stuff is brand new, but if I cook the system out of ignorance, my boss will have little sympathy. Anyway, if the original AC-DC converter was rated at 19V and 65W, that would give up to ~3.4A. Now I'm assuming the converter is purely a "passive supply", meaning that the mini PC takes what it wants at 19V, but can take no more than 3.4A at a time. That is non-electrical logic for you.

If that is correct, then purchasing a DC-DC converter that is rated at say 100W should be fine? It simply "supplies" more power, but in a "passive" sense, where the mini PC can take it if it wants, or leave it?

I've found some DC-DC converter options that take 12-14V input, and output at a select voltage ranging from 12,14,16,18,20,22V with a maximum output of say 100W. If the logic above is correct, then I should have no problem hooking this up with 12-14V input from the battery and selecting 18V output to the mini PC? The mini PC simply pulls the amps it needs, but can not exceed 100W/18V = 5.5A ?

My confusion comes from how the converters work. Do the "actively" push the wattage through to the mini PC or do they "passively" provide the wattage to the mini PC? If they push it, then it seems that I need a DC-DC converter that matches the rating of the AC-DC converter or less. If they simply provide it, then the DC-DC converter can exceed the specs of the AC-DC converter without any issues.

Any help on clearing this stuff up would be greatly appreciated!


texts: Wrong multimeter readings measuring 12V lead acid battery

texts:
I just got my first multimeter and when I measured a 12V 1.2ah lead-acid battery I get AC 28.8V and DC 13.4V. Is this normal?

In addition I tested an AA 1.5V battery and I got 2.9V (AC setting 200) and 1.58V (DC setting 20).

Is my multimeter broken?

The meter is a UniTrend UT33C and the lowest AC range is 200V.

LATE UPDATE
I went to the store and tested another UT33C and it also displayed an AC voltage. I asked to try a different model (UT39A) and it correctly displayed 0VAC when I tested an AA battery, so I exchanged my multimeter for the other model. Thanks.


texts:
I have a question regarding the reliability of a proposed power delivery system:

We have a power mux (TPS2110A) that is currently switching between outputting 3.7V and 5V, depending on whether or not the 5V power source is available at the time (it isn't always). We have a few chips on our board (LED drivers, single-channel load switches) that can take anywhere from 2.7 to 5.5 volts on the supply pin, and in some modes of operation we need 5V of power to said chips. For our purposes, these chips also need to remain on and operational while the board has power. The proposed solution is to power these ICs off of the power mux output, so that they are on with 3.7V at all times, until 5V power is available and necessary to use.

My question is this: Is there any inherent danger to powering ICs from this variable line as long as the voltage range is within the specifications of the datasheet?

As an example, our switch ICs (SLG59M301V) need to be ON before applying power to the switched lines to ensure normal operation. 5V is applied to the switched input as soon as it is available, at which point the power to the chip ALSO needs to be 5V according to the datasheet. Below is a greatly simplified block diagram of the desired setup:

Please note that while this setup is not ideal and that there are several (better) ways that the end goal could be accomplished, the need is to make an already existing system work with minimal changes.

Thanks in advance for your time and input!


texts:
I am planning to use LTC4015 IC for buck charger application . I have to interface the IC with my host MCU.

LTC4015 PRODUCT PAGE

I have other charge controlller ICs connected over same I2C bus.
other ICs are stating i2c bus speed to be 100KHz, but this LTC4015 IC's specification says 400KHz for clock speed of i2c bus.

so i wanted to confirm, is it possible to drive the LTC4015 ON 100khZ SPPED,

if yes then great.
if not , will changing the speed of i2c bus frequently causes any improper behavior in mcu.(IS IT RECOMMENDED )

We are using NXP MC9S12XEP100.

MC9S12XEP100 PRODUCT PAGE


texts: How does the bandwidth have something to do with speed

texts: They are saying that, if the bandwidth of a certain device becomes narrow, then its speed decreases. However, how does the speed has something to do with the bandwidth? If you are saying that the bandwidth is located at very high frequency, then perhaps if you shift the bandwidth to lower frequency, then the speed decreases. So, how does that has something to do for speed?


texts: Suggestion for easy way to solder between LED strip and flexible PCB

texts:
I have an LED strip that I need to solder to a flexible PCB (designed in Eagle).

What is the easiest way to solder the LED strip to the flexible PCB? Also, what can be changed in Eagle to make it easier to solder to the LED strip?

How do they accomplish the connection on the image below?


texts: Why do motors buzz when are applied PWM?

texts:
Why do motors (DC) make a buzz sound when a low duty cycle PWM is applied to them?

Once I applied a 10% duty cycle PWM to a gear motor and it didn't move. just made a buzz sound. What does a low duty cycle do to a motor that makes it buzz?


texts: How to control optocoupler and relay by using microcontroller

texts:
I have a question about controlling relays by using optocoupler. I have some optocouplers to isolate MCU's power and Power supply for the relays (to control LEDs, DC and AC drivers).

1) Can I control the relay according to the schematic below but without FET? Do I have to use FET.

2) I have a 24V DC and 220V AC to control relays, can I use the same schematic for AC connections?

Thank you so much.


texts: What is causing these switching transients on a 3 phase motor driver?

texts:
One time I built a 3 phase motor driver, which works quite well in the original configuration. Recently, I changed the physical layout to this rectangular form factor, and now it has quite large switching transients accompanying the rising and falling edges of each switch node. The transients go so high that if I run at full 60V, they kill the board dc/dc converter!

Here is the old form factor board which works quite well and has driven a BLDC motor at 4kW from 48V (there is a logic board which goes on top and capacitor board which goes behind):

Here is the new board which has very large switching transients:

Here is the rising edge:

Here is the falling edge:

Attempted solutions: I tried changing the gate resistance. The circular board has gate resistors of 12 Ohms and no resistor on the bootstrap line. The rectangular board has 40 Ohm gate resistors, 4.7 Ohm bootstrap, and much longer deadtime, but the transients are totally un-affected. Snubbers don't seem to do anything. Ringing is ~17MHz. Adding or removing ceramic caps doesn't do anything noticable, nor do schottky diodes.

What did I change between the two layouts that causes this type of ringing? The only real difference I can point to is the B2B headers. Board power, and the fet driver signals come out the right, along with the bootstrap lines. Board ground is on the left, along with the analog sense signals. I'm hesitant to spin another board, buy new parts, spend 6 hours assembling and all that without some clue as to what I did wrong on this revision :( Does anyone have an idea?

Edits:

I am going to re-do the layout of this board according to two principles: 1) put a ground plane under all of the control lines 2) keep the highgate+bootstrap, and lowgate+return as close together as possible. I will then share my results (and probably change careers if it doesn't work).

Here is the layout plan for the switching board. There is only one B2B connector. It gives 4.3mm between boards. The paths of the control lines are in blue, and they travel in between the drain and source connections, where there will be heat vias coming down. I have extended ground on the inner plane it such that the HF signals will always be over the ground plane, and will do the same on the bottom layer, so that the signals are sandwiched by ground planes. I would like to not have gate-resistor-per-fet, but because of the situation I am in a mood to follow all best-practices.

I appreciate any comments if you have them.


texts: What is the PSPICE model of my probe + oscilloscope?

texts:
The oscilloscope and probe manufacturer gives me the following input impedance data:
Oscilloscope

Input impedance/capacitance: 1 MΩ ± 2%, 16 pF ±3 pF

Probe characteristics

Bandwidth DC to 75 MHz
Switchable 1:1 or 10:1 attenuation ratio
Input resistance of 1 MΩ (1:1) or 10 MΩ (10:1)
100 pf (1:1) of 15 pf (10:1) input capacitance

What will be the PSPICE model


texts:
I'm designing an auto-ranging voltmeter using the on-board ADC of my micro for A to D and a digital potentiometer as a programmable resistive divider to control the range.

My concern is the possibility of the ADC input being momentarily shorted to the measured input voltage before the micro-controller has adjusted the pot for the appropriate range.

How is over-voltage protection usually implemented in this type of scenario?

Also if there are resources for digital multimeter design, e.g schematics etc, that would also be very useful for ideas (as I'm sure there are probably better ways to approach this than mine), Ive have searched but haven't found much.

Update

Thanks to everyone for the informative answers.
Here is the over-voltage protection circuit that Iv decided on.
I plan to use schottky diodes for greater precision.

  During a negative voltage transient,
  the bottom diode will conduct, thereby
  clamping the voltage to one diode drop
  below ground. During a positive
  voltage transient, the top diode will
  be forward biased, thus conducting the
  surge to the power rail.

From: http://www.conformity.com/artman/publish/printer_116.shtml


texts: Calculate current in circuit with a current and voltage source

texts: I need to calculate the current of Is, I'm stuck after getting the voltage across the 4k ohm resistor which is 16V.


texts: How to verify if all 3 AC phases are in order?

texts:
We have 220V main lines where we currently live and we have a 3-Phase connection. We have an Air conditioning unit that requires 3 phase AC input with the correct phase sequence.

If the phase sequence is not right, it displays an error code for that. A while ago there was an electricity breakdown in our area and ever since that was resolved we are receiving that error. This happened a year ago as well but a quick phase load wire rotation by the electrician solved the problem.

This time, however, no matter what combination they try it does not seem to work. I have a sequence detector tool but that does not work now either.

The electricians from our maintenance company refuse to admit that the problem lies somewhere in the supply and claim that 380V - 396V are there the problem is with your unit. But if the unit had gone bad how come another device has also gone bad at the same time?

How can we verify their claim?  The Air conditioning unit's electrician says that the main line is not supplying the 3 phases correctly and their electricians say that all our 390 volts are there between every 2 phases and the fault is indoors.

Please note: I do know that this is dangerous work, and I am not doing it myself. Only (so called) qualified electricians are working on this. I am just asking to learn so  i can plead my case with their manager.


texts: How far is "too far" when routing traces for crystals, and how asymmetrical is "too much"?

texts:
I'm routing a breakout board for NXP's LPC23xx microcontroller. This MCU requires two crystals if one is using the RTC. These two crystals connect to the MCU with only 3 pins in between:

From this question, it is clear that "as close as possible" is the recommended distance, but there are tradeoffs to be made, especially when dealing with two different crystals that must be connected "as close as possible" and with traces that are "as symmetrical as possible".

In my particular design, I'd like to use rather large crystal packages (TC38 for the RTC and SM49 for the 12 MHz) for cost reasons, but even with much tinier packages, layout is not simple.

Therefore, we have several factors to consider when laying out a PCB with these two crystals:

Crystal trace length
Crystal trace symmetry
Capacitor trace length
Capacitor trace symmetry
Common ground connection for capacitors

And, of course, each of these exists for both crystals.

How should I prioritize these factors? Should I sacrifice trace symmetry in order to minimize the length of one of the traces? Should I make the traces as symmetrical as possible, even if that means that the traces will be ~12mm long? Further, which of these crystals should I place closer, assuming I can choose one to be close and one to be further away?


texts: Control LED panels via a relay and a PIR sensor

texts:
I bought 6 x 48W LED panels and a PIR motion sensor to light a shed/workshop area. All 240V rated.  I did not appreciate that the LED drivers have a high inrush current.  My question is whether I can place a non-latching relay between the PIR and the LED panels?  If so, please can you help me to spec the relay.  I don't know anything about the electrical properties of a relay, particularly whether the PIR could handle it.  This is the model of PIR, with its nominal ratings
http://www.timeguard.com/products/light/pir-presence-detectors/360-surface-mount-ceiling-pir-presence-detector

Alternatively, I could fit an inrush limiter but I would again need some help to spec it.

Thanks in advance,


texts: Do packages have to be centered in eagle to export valid pick and place data?

texts:
I am working on a PCB featuring this SD card connector
http://media.digikey.com/pdf/Data%20Sheets/Amphenol%20PDFs/101-00313.pdf

In the technical drawing, it seems that the origin of the part is the intersection of the axis of the component with a line through the middle of the pads for the signal pins. For example, the dimension for the topmost hole (24.31mm) is measured from the center of those pads.

I created the component in Eagle and I've used the same center as in the technical drawing. However, I can imagine the pick and place machine won't be able to pick up the connector using that center.

My question: do I have to make sure to manually calculate the center of the part body (without pins) and then use that as the new center for the package, when I'm done designing the package? So basically, I move the package so it centers around the origin when I'm done? When I called my SMT subcontractor they said the software automatically calculates centroids when you export pick and place data (e.g. using mount-smd.ulp) but I'm thinking that it's up to the machine operator to decide how to pick up the part and place it correctly on the footprint?

I'm just not 100% clear on whether eagle uses the centers of the packages when exporting centroid data or if it just determines the centroids of the parts automatically (such that where you put the origin originally in the library editor won't matter).


texts: I've been spending a lot of time trying to know why the gate voltage of M2 is 2Vt + 2Von. I know that if all transistors have the same characteristics then all the Vgs = Vt + Von. Can somebody explain me why it is 2Vt + 2Von?


texts: When is a common emitter amplifier a good idea?

texts: In the datasheet for the LT1789 they have this application circuit. This TIP127 appears to be a voltage controlled by that opamp and placed in a common emitter configuration so it has an exponential dependence on it's base voltage. Why is this stable/a good idea? How is this opamp capable of stabilizing this? Is there some back of the envelope calculation/intuition for when designing a circuit like this is okay?


texts:
I have a fuel level sender installed in my custom built car which supposedly should read ~50 Ohms when empty, and 2 Ohms when full. I've measured it 30 Ohms empty, but this could be because the arm/float is resting on the bottom at half-engagement.

I want to read this sender with a 0-5V input and from what I've gathered so far I need some kind of voltage divider for this to work.
I have access to 5V and 12V.

My EE skills are nowhere what they used to be, can anyone help me out with this?


texts: Zero or low-current voltage divider for switch identification

texts:
Is it possible to design a voltage divider circuit with switches that uses zero current, or very low current?  Would it work to use a transistor to connect/disconnect the end of resistor string from ground?
Background
The circuit will do two things.  Each switch in the circuit will wake up a IC (ATMEGA328P) by using a transistor to send an interrupt pin LOW.  Once the IC wakes up, the ADC will sample the voltages coming from the circuit, allowing the IC to know which button was pressed.
The entire project will be battery operated, and having this voltage divider may significantly impact battery life.
The project will 1) read files from an SD card, 2) go to sleep, 3) wake and play sounds when one of 16 buttons is pressed, and 4) go to sleep and repeat process starting at #3 on button press.  I anticipate that when it is running it have a significant current draw.
Existing Voltage Divider Circuit

Possible Transistor Solution
Placing a transistor between the end of the resistor string and ground, and having the button press activate the transistor, connects the end of the voltage string to ground.  This will result in an initial voltage reading of 5V, and once the transistor is on, the actual read voltage will be the intended voltage.  I have no idea if this will work.

Other Solutions
Per question 28897 I could use high values of resistors such as 10 MOhm.  But this will still have a current draw of hundreds of nA.  I'd prefer zero.


texts:
If I want to make ISP loader for 89Sxxxx(8051),can I simulate it by multisim or others before I really build it?

I follow this link:

http://m955.com/wp/archives/142

I found it has a little hard to make it because multisim seems doesn't have printer port component to simulate.Am I right?

Thank you~


texts: How to wire 3 x 12 V batteries to increase both voltage and amperage?

texts:
How to wire a battery bank for a voltage of 24 V and a maximum amperage providing 3 batteries of 12 V having respectively 125 Ah, 125 Ah, 120 Ah?

Click below for

Improvements and Specifications


texts: Switching input to instrumental amplifier with an analog mux (ECG, EEG)

texts:
I'm trying to find a cost effective method of taking samples of electrical signals of the body (and potentially plants).

Can you have one high precision instrumental amplifier and then use an analog mux to read different inputs (different electrodes on the scalp, chest)?

I looked at this mux (CD74HC4067). Is the on resistance a problem?

Do you have any other suggestions for a cheap EEG device?

Thank you for reading and best regards.


texts: Ways to power my circuit during brief power outages to retain switch state?

texts:
I have a very simple project where I have a ttp233 touch sensor which I'm using to control my relay module which in turn switches my fans on and off. The problem here is whenever there is a power loss the relay defaults to a low state and I have to touch the sensor again to turn on my fan (My house has an inverter so power outage is not the main issue but when there is a power loss my inverter takes about 2-3 sec to kick in and in this gap the relay returns to default of off state).
So I thought of using a battery to compensate ,so I want help regarding this. I want to have it in such a way that when the power is there the relay and sensor should run on wall power and the battery also should be charged but when there is a power loss the battery should kick in and power the circuit with no delay so that my appliances stay on during power loss and when the power comes back on again the circuit should again go back to using wall power or any other way that my relay state remains where it is after a power cycle(The state of the relay is determined by the state of touch sensor so if there is a way to power my touch sensor during this brief power cycle please tell me.). Is there any way I can achieve this?
This is the touch sensor im using and this the relay module im using
the power consumption of touch sensor is 1.5 U to 13 uA
and the relay is about 100-120 mA.


texts:
I am using MPLABX v2.25 and XC32 compiler v1.33 on a Mac.

Maybe I am not fluent with the use of the preprocessor, but the macro expansion window in MPLABX seems to produce rather unexpected results.

Example-1:

#define PIBO TEST
void ftest(void)
{
#if (PIBO == TEST)
  printf("Hello");
#endif
}

Expected Result: printf() should appear in the macro expansion window
Result: printf() does appear in the macro expansion window

So far so good.

Example-2:

#define PIBO FOOTEST
void ftest(void)
{
#if (PIBO == TEST)
    printf("Hello");
#endif
}

Expected Result: printf() should NOT appear in the macro expansion window
Result: printf() does appear in the macro expansion window

Example-3:

void ftest(void)
{
#if (0)
    printf("Hello");
#endif
}

Expected Result: printf() should not appear in the macro expansion window
Result: printf() does not appear in the macro expansion window

Is the MPLAB X macro expansion window showing faults or is it my code or understanding of how this is supposed to work?


texts: RF switch(1:14 or 1:16) without signal distortion

texts:
I am looking for an RF switch with no signal distortion in the 1 to 2 GHz band.
I need a 1:14 or 1:16 switch, could you recommend switches(for example, an optical switch or a semiconductor switch etc)??

And I wonder if the RF switch has a lot of signal distortion. Does it change much in the case of amplitude or phase?


texts:
I am new to circuits and electronics.
I was building a portable mobile charger(Battery Bank) an had to connect a USB port.
The tutorial I was watching had 2 wires , Red for +ve and White for -ve.
The USB connector I have has 4 wires , Green , Yellow , Blue and Black.
Can you help tell me which one +ve and which one is -ve.
It would be of great help !
Thanks !


texts: How do you select pin functions on an EPM7128 CPLD?

texts:
I have some old Altera MAX EPM7128SLC84-15N CPLDs kicking around that I want to use to interface with 5v TTL logic.

If you look at the pinout, some of the pins have more than one function (eg. Pin 2 can be an input, output enable or global clock). How do you select which one it is and which one is it by default?

In Quartus II (I'm using version 13.0.1 Web Edition 32-bit), if I go to assignments -> device -> device and pin options everything is greyed out. Everything is greyed out in configuration as well. The only configuration scheme I get is "n/a in MAX7000S".

By the way, I'm aware that this is an obsolete part and there are modern 3.3V CMOS CPLDs that are compatible with 5V TTL logic. I have these parts in hand and would like to use them if at all possible.


texts: Charging marine battery while powering equipment

texts:
I've got a quite delicate setup with a PC and some other minor equipment such as a microcontroller connected to a large 100Ah sealed (AGM) 12v lead acid battery.

I need to be able to run my equipment non-stop for months and only charge the battery at night time. I would love to get some advice on how to run this setup as smoothly and safe as possible.

Is the best way to just leave my stuff plugged into the battery and just hook up a charger to the battery as well?
Should I use two batteries and just swap them, plugging in a fresh one in parallell before disconnecting the old one? And that way I can just charge them one at the time.

The first solution feels easier but I'm not sure how my sensitive equipment handles the plugging in and out of a charger. Or the swapping of batteries for that matter.

Are there some good practices for creating a setup like this? What precautions should I take, do I need a diod to prevent surges while connecting a charger? Do I need any voltage regulators to prevent bad things happening?

Grateful for all advice on this. Thanks.


texts: Why use 2 isolated grounds in Mackie 220W Power Supply?

texts:
I recently took apart a Mackie 220W power supply for an analog sound board. Much to my surprise I found the following scheme:

Earth grounded:
48V
-18V
18V

Seperate, isolated ground:
12V
5V

I am not sure if this has something to do with it being a supply for a sound board, but why would there be 2 isolated grounds?


texts: Full wave bridge rectifier circuit in multisim

texts:
I need to get this laboratory report done but I am stuck in this multisim exercise where the circuit I have produced should be a functional full wave bridge rectifier with a simple resistive filter but it is only reducing the magnitude of the output sinusoid as opposed to actually doing a full wave rectification.

I made it based on this diagram provided to me by my lecturer:

Can anyone pin point the reason why this circuit is not acting as a full wave bridge rectifier?

Thanks,
Simon.


texts:
For the past hour, I've been trying to calculate the gain of a differential amplifier in the following form:
\$ \frac{V_{out}}{V_{in}} = \$ some function of resistors

I went to this site and tried to figure out what they were doing but I just cannot follow. I understand the current equations, and I understand that \$ V_a = V_b \$ for ideal op-amps but I just don't get the rest. Why do you get two different equations for \$ V_{out} \$ when \$ V_b=0 \$ and \$ V_a=0 \$, if they are both equal. Can someone explain?


texts: Conservation of power\energy in transformer through the secondary coil?

texts:
Using a step up transformer we could, for example, take a 10V source and get 20V in the secondary coil. This doesn't violate the law of conservation of energy because the current will be halved.

The answer I can't find anywhere is HOW the current gets halved? V=IR therefore it seems to me that the load attached to the secondary coil will determine the current passing through it. So to my understanding, if we place a 10Ω resistor on each coil, we will get 1A through the primary and 2A through the secondary. Quadruple (2Ax20V) the power for free - impossible!

Where am I going wrong?


texts:
I have a 12 V 7 Ah battery. In order to charge a battery, we need to supply the voltage greater than the voltage of battery. Now lets say I have a power supply which is giving 14 V and battery current status is 12 V. When I will plug in the power supply pins to the battery, the battery voltage will reach upto 14 V and battery will start charging.

Now I have a solar charge controller PCB where I am using solar panel to charge the battery. Below is its schematic:

In the above image, X1 is the connector where will connect solar panel. A microcontroller is used to read the solar voltage through voltage divider circuit. CHARGEPIN is the pin which is used to enable the charging of battery.

So lets we have a full sunlight and solar output is 18 V. Now the problem I am facing is as soon as I connect the solar panel and start the charging, the voltage of solar panel reduces to 13 V but in the above case where I was using a power supply, the voltage didn't drop. It was same (power supply voltage was still 14 V). Because of this scenario, the battery is taking too long to charge.

Is the schematic wrong? Am I missing something?


texts: Understanding Noise Figures for BJT transistor

texts:
I am trying to design a low noise preamplifier with the following part: 2SC3324. This is one of the lowest noise BJTs around I could find and I like to make sure I interpret things correctly. My supply is 5V. The signal I like to amplify is coming from a source with 50 ohm source resistance. My target frequencies are between 1-5KHz. I will be using a common emitter topology with an NPN part.

The noise graph is here.

I like to achieve the optimum noise given a 5V supply. I can design the bias point and dynamic range using commonly available examples. According to the graph below. 1dB noise figure can be achieved if my source resistance is about 100ohm where the Ic is about 1mA.

The key part I cannot figure out is if I should add another 50 ohm resistance before the  coupling capacitor (C1) of the amplifier so that the perceived source resistance become 100ohm.

The other problem is the specification provides Vce of 6V graphs. Using my 5V it will not be possible to achieve this Vce separation. I assume noise will increase when Vce is around 3V. How can I estimate the noise? (Will it be 2x or 20x, I am trying to get a sense).


texts:
I'm designing a 555 timer circuit where I want to control the brightness of an LED array. There is a minimum lux requirement for the array so I need to know the output current when I have a 4.8 V source.

This is a similar diagram. The only difference is I have a 4.8 V source and an LED array instead of an LED.

Without the 555 chip (simple circuit with 7 LEDs and resistors connected in parallel) I have about 140mA current going to the array. I would like to know if the values of resistor and potentiometer at pins 6 and 7 will affect the output current. I don't have tools to measure lux so my only guidance is 140mA current output.

Thanks.


texts: What will be te rise and fall times of DAC, based on Slew rate and settling time

texts:
I plan to use LTC2641-12 DAC in some application and I simulate the analog part with LtSpice. For the DAC, I used a pulsed voltage source with this parameters:

PULSE(0 50m 10u 1n 1n 16u 32u)

Obviously, the rise/fall times cannot be 1nS but just to see the response.
On output wave I can see some spikes due to very high given rise/fall.

Now the question is what will be the real (worst case) DAC rise/fall based on specifications:

Slew rate: 15V/uS
Settling time: 1uS
DAC Glitch Impulse: 0.5nV/S     <-- what is this ?
Digital Feedthrough: 0.2 nV/S   <-- and this ?

My DAC will output up to 4.096, so according SR, will "jump" from 0 to 4.096V in 15/4.096 = 3.66 uS

This is the rise/fall time?
What will be the worst case scenario?

Thanks for clarifications.


texts: Relation and difference between Fourier, Laplace and Z transforms

texts:
I have become a bit confused about these topics. They've all started looking the same to me. They seem to have the same properties such as linearity, shifting and scaling associated with them. I can't seem to put them separately and identify the purpose of each transform. Also, which one of these is used for frequency analysis?

I couldn't find (with Google) a complete answer that addresses this specific issue. I wish to see them compared on the same page so that I can have some clarity.


texts: Linux-friendly PICs to timestamp an intermittent 4 µs long TTL pulse

texts:
I've got an experimental box of tricks -- the console of an MRI scanner -- that spits out a 4 µs long, +5V TTL about every 100 ms, when something interesting happens. I'd like to ultimately create a timestamp in a file every time one of these happens, and write the data to disk on a linux computer that runs the show next door.

At the moment, as described on Stack Overflow, I've just wired the TTL into a parallel port on the linux box, and I poll it regularly by a high-priority process when the scan starts. Unfortunately, sometimes the process is suspended, and I miss a few (or a lot) of the short pulses.

Rather than handling the TTL as an interrupt, as my original question was about, it's been suggested that I use a hardware PIC to deal with the signals, and spit data back over USB (or ethernet) to the host machine.

Can anyone suggest a good PIC that can deal with short pulses, has an accurate timebase, and ideally already has a USB or TCP/IP stack implemented? I get the feeling that this has got to be a solved problem, I just don't know what to look for!


texts:
I'm still trying to wrap my head around I2C as well as the ATTiny. I've found plenty of tutorials on how to use the tiny as an I2C slave as well as master, but is it possible to use it as both at the same time?

I basically want to create a device similar to the BlinkM smart LED but that also had a connected EEPROM for some extra storage. Maybe there's another way to connect the EEPROM but I didn't figure I'd have enough pins (only talking about the 8 pin ATTiny variety)....

Any thoughts of how to do this?

Clarification:  Note, that ONLY the ATTiny needs to access the external EEPROM or should access it. I definitely want it to be on a separate bus. So I realize that I will need two pins for ATMega -> ATTiny and 2 more for ATTiny to EEPROM (hopefully leaving me 2). My major concern here is if only 2 pins on the ATTiny can be used for i2c or if you can configure ANY 2 pins for that?


texts: Run two boards with different crystals (MCP2515 specifically)

texts:
I have one CAN bus interface that's using a 16 MHz crystal, and I want to set up my own interface to talk / simulate CAN packets with first one. I do have 20 MHz crystals for my own interface, but whenever I connect those two together, setup my own to 500 kbaud, the other one discovers only 50 kbaud... therefore this question.

It is worth to mention that the already-setup interface does work flawlessly with vehicle CAN and is verified to work as expected.

Does it matter (in CAN) if the other device uses different crystal?

For those who wonder, this is an Arduino setup though I'm generally curious about this in an electronics setup.


texts: Is there a safe method to revive dead Li-ion batteries?

texts:
My dad has an electric leaf blower with a huge 56V battery pack. It broke so he let me dismantle it and salvage the Li-ion batteries inside. There were 16 18650 cells I got, but the voltage on all of them were about 1V. They had been critically overdrawn. I really want to keep these since they are high quality and worth like $80. I read a bunch of stuff online about recharging these guys and I've seen a ton of different answers.

Some answers say that it can be extremely dangerous and to just buy new ones. Other answers talk about boosting it for recharging like there's no risk in it. Some answers say if they have been depleted recently then it should be fine (mine are also recent). Some answers say if the battery is low quality, then don't do it (mine are high quality). One answer which I found particularly interesting is that charging it slowly at <100 mA which "will reform the chemistry on the plates, but if you charge too fast it will cause uneven forming of the plates and WILL cause dendrites." which are dangerous. I don't know what is true and what is not. Can I have some clarification?

Although this last answer has unknown credibility, I like that it had a chemical explanation of the dangers. So, can I recharge them at low current? I plan on using a charging module with 1 A max draw, but connected to all batteries in parallel, so the current is distributed and <100 mA per cell. I am also going to closely monitor them with an IR thermometer to make sure nothing gets too hot.


texts: Is reversing speaker polarity worse than listening off center?

texts:
I am certain that for all frequencies above about 440 Hz, there is only about a few cm of listening zone within which the polarity of the audio makes any difference.

Am I wrong?

If you connect a sound speaker cable black to red, it will reverse the + and - of the sound pressure waveforms.

440 Hz is about 78 cm wave periods, 34 cm from max + the min -, and 4 kHz sound is about 8.6 cm, 4.3 cm from the wave peak to trough another, then by being to close to one speaker you change all the sound range completely just as much as using reverse polarity on one of the speakers?


texts:
I am trying to understand the technical meaning of the term 'feed-forward', when and where it can be used and where it cannot be used? I have seen this term in various different areas.

For example:

Vector Field oriented of AC Motors

Convolutional Neural Networks

Digital Filter Design

It looks like that this is a fundamental term. But I could not find its fundamental technical definition.

What phenomenon is encapsulated in this term. And if a certain phenomenon is labeled as 'feed-forward' then what are the attributes and properties that are understood that will be possessed by that phenomenon?


texts: Can you safely connect the LED side of an optocoupler to AC Mains(120v)?

texts:
I have looked at several questions on EE.SE as well as searching the internet and nothing I came across has answered my question in a way that makes me feel safe dealing with mains.
Having read many questions and answers on EE.SE I know that when dealing with mains you want to apply galvanic isolation to your circuits to minimize the possibility of someone getting electrocuted/injured.  Below I have a circuit that is designed to indicate the phase rotation for a 3 Phase 120V 400Hz power line.  It was designed and simulated via https://www.falstad.com.  While the design is not the focus of this question any design input is highly appreciated since the simulation (probably) works as an ideal environment.
So on to my question...how would you connect the optocouplers to the three AC lines without damaging them or injuring anyone who uses the PCB?  The entire circuit would be housed in a plastic case.


texts: Is there any ultra strong electrical wire at about AWG24 (0.22mm)? I want something that would be strong as a steel wire rope but also with low resistance that can used as electrical wire.


texts: Is amperage constant or relative to the device?

texts:
I have a pull chain ceiling light, very small.

The pull chain mechanism broke. Instead of buying a new mechanism I decided to try and do some Arduino experiments. Prior to that though I need the light to work because it's actually the light by which I solder and work.

So, I removed the pull chain mechanism (similar to this) added in some TL-6 Wires with alligator clips on them and attached that to a small switch. Just to get me up and running.

Shortly after doing this though that little voice in my head started voicing concerns. I have only ever used these wires for small projects. They have a very small gauge and I am worried that if to much is pulled through them there could be a fire.

I researched the wires and it says they can take a max of 1.5amps. Home electrical lines can send up to ~20 amps in the United States. My multimeter, assuming I am using correctly says that there is only 22 mila-amps going through the wire.

SO my questions are:

Should I immediately disconnect this and be thankful I'm not talking to my insurance company right now?
Do devices determine the amount of pulled amperage?
Does it sound reasonable that this like is only using 22 mA?


texts: How can I turn off automatically, say after a fixed number of cycles, a 555 in astable mode?

texts:
I looked at the answer to "How to turn a 555 in astable mode into a decaying square wave" but this is really for an input to a speaker.
  I want the input to go into a counter to count the number of square wave pulses.
  I thought of using 2 555s the first one generates a square wave
the second in monostable mode generates a square wave of some length ( acting as a modulator envelope). Then combining them with an AND operator. What do you think of this idea or is there a simpler way?
   I should explain in more detail what I am trying to do. I have a 4 digit Digital Counter panel meter.

There are 2 input leads when the input is high the counter increases by 1 . It also can increase by1 if I connect the input to a switch. When the switch is closed the counter also increases by 1. What I want to do is have the counter increase by fixed number. So say the switch is closed and I want the counter to go up by 5  or see set number.


texts: DIY Spectrometer/Colourimeter 430nm and Log Amps, Are all log amps equal in this case?

texts:
received some good help in the past on another project (vacuum pump). I'm now moving on to my current project, to build a colourimeter or 430nm spectrometer for measuring the colour of beer.

This project will be encased in a wooden box with brass fixtures and fitting and use an analog output device - I'm thinking of a needle Voltmeter with a graduated colour scale, but that's quite a way down the track.

Currently, I am following this paper, http://www.academia.edu/6985992/Simple_Cheap_and_Portable_Colorimeter_for_Introductory_Analytical_Chemistry_Laboratories as the starting point using a 430nm diode and some white Das modeling clay to make a cuvette holder and housing for the LED and LDR. However it relies on resistance measurement with a multimeter, which is not part of my longterm plans.

So, I'm going to need a log amp to produce a voltage output. Which, I believe, is where all the fun begins. I guess I could build a log amp circuit, but temperature compensation, apparently, is critical to accuracy especially when dealing with transmissive sampling.

I've also looked at two log amps, the Texas Instruments LOG112 & the Analog Devices ADL5306. The first is insanely expensive, and the second not available via ebay.de which brings me to the question: for this particular application, what other options do I have, or should I just bite the bullet and get the LOG112 and move on?


texts: How to minimize high dV/dt device wich is connected to analog electronic load

texts: I designed an Ac electronic load and tried to connect it to a switch mode half bridge (for testing purposes)as can be seen in the figure. Since the switch mode half bridge has high dv/dt output voltage during the transition time for turning the switched on and/ or off across the analog electronic load, the generated output current of the analog electronic load has large spikes due to internal capacitor between gate and drain of the Mosfet in analog electronic load. in this case, how can i eliminate or reduce these spikes from analog side? i would appreciate if someone could give ideas to reduce this effect.


texts: I scored a couple of panel meters stamped PCIM 176J.  Anyone have a datasheet for this thing? Google found nothing.


texts: Independent analog sensors have dependent readings?

texts:
I was working with a Nucleo f411re (STM32 MCU) in order to read several analog sensors.
I started testing a single temperature sensor (LM35) and all was fine.
When I added a linear potentiometer for reading its extension, a strange fact happened: the temperature read increased proportionally to the extension of the potentiometer. Here's the circuit:

simulate this circuit – Schematic created using CircuitLab

PA0 and PA1 are analog pins, connected to stm32 ADC. Here you can find the ADC datasheet.

So I measured the output voltage from LM35 with multimeter and it was stable even when I was extending the potentiometer; while, if read from Nucleo, the temperature was "following" the potentiometer read.

I solved this problem adding a 1 µF capacitor between ground and the V_out of LM35. But I'm not satisfied, because I would like to know the reason of the strange temperature read behavior. Any Idea?

EDIT:
I have found something that could explain this problem at section 3.4.1 of the ADC datasheet. It seems a known issue, due to the sampling switch in the internal sampling circuit of the ADC. Can you confirm this?


texts: I am trying to find the voltage near the resistance with 4 Ohms. Now I took an easy example so that I can understand well. I think I can do it using Kirchhoff laws to find the currents then apply a current divider in order to find the current near the 4 Ohm resistance. Is there an easier or more direct way? Thanks in advance.


texts: How does LED Flashes One by One in my Project Some Queries?

texts:
I have a project called LED Flasher which Flashes LED’s one by one….but I have following Query about my project…..if anyone can explain me it in simple words it will be great help for me…..one can use Below image for reference…or use this link

How does capacitor C1 and C2 being charged through resistor R3,R4 and Diode D3, D4?
Couldn’t understand how LED D1 and D2 Flashes one by one…what is the actual Current flow in this Circuit? Could anyone explain it in Simple Word?

Thanks……a lot....


texts:
I'm currently messing around with a TENS unit and would like to block/unblock the signal from reaching the muscle (Alterations to the TENS unit circuitry aren't possible).

The unit uses a 2 mm jack which runs two wires to a conductive pad each.

My assumption was that splicing one of the wires into a relay would give the desired effect, which for the most part it does.

What I'm finding, however, is that if the relay is turned on while the TENS unit is generating a signal, a sharp spike is being sent to the muscles.

Is there an easy approach to solving this issue?

(I found the following at a quick glance: Preventing spikes when plugging jacks
Could this possibly be the right solution to my issue?)


texts:
I am designing a circuit which uses the LM317 variable voltage regulator to power a device from 1.25v-3.7v. The device powered by the LM317 will accept +-0.2V from the output of the LM317 and takes about 100mA.

The device that will be powered is a  small DC motor.

If I am powering the LM317 with a 9v battery, is it required that I install parallel capacitors on both input and output?


texts: What needs or works better with DC than with AC electric?

texts: Solar power is becoming more popular, and it seems a lot of people who have solar panels have a DC to AC inverter. It seems ironic to convert DC electric to AC, and then the the AC gets converted back to DC to run a computer. I believe all digital hardware runs on DC power. Do LED light bulbs, LED TVs, LCD TVs, have to convert AC to DC? How about motors. What are the trade offs between AC and DC motors?


texts:
I design a frequency divider in FPGA. It is nothing more than the D flip-flop, which use the inverted output as input. Then on the output of D flip-flop is signal with half-frequency of input CLK signal.

http://www.radio-electronics.com/info/circuits/logic_d-type_divider/d-type_frequency_divider.php

The problem is, that the output signal is bad. For a half-period of input signal, it is OK, but in the second half period there is a lot of impulses in output signal.

Everything goes to sufficient state when I try to measure signal in input. When I connect to input just the piece of cable, it helped too. So I think the input signal is with some noise (it has hairs or fur or how to say it) and that make this problem.

More information:
Frequency of input signal is 500Hz

This input signal is generated by the device I need to use. I tried to look at this signal by oscilloscope, but I influence it by measuring. So I don't know whether the input signal is already noisy, or the noise is generated somewhere in the trace to FPGA.

There is a level-converter (sn74lvc4245apwr) connected between the source signal and FPGA, it changes voltage level from 5V to 3V3. There is a rather long trace between output of level-converter and input to FPGA.
There is nothing else connected to this trace.
The GND is located between every signal path on the board.
The schematic of the board on which I test it is complex and therefore it is difficult to share it here.

The FPGA belongs to Darnaw Module (Enterpoint, .uk, pga-modules), which is connected to PCB by soldering (it is in a socket)

The FPGA dessign is done in HDL.

HDL code:

Port (
 CLK_IN  : in STD_LOGIC;
 CLK_OUT : out STD_LOGIC;
);

...

   process(CLK_IN)
   begin
        if falling_edge(CLK_IN) then
             CLK_OUT <= not CLK_OUT;
        end if;
   end process;

I got an advice - to connect this CLK_IN signal to another I/O pin inside FPGA and then use this new signal.
Image of this workaround:
http://dl.dropbox.com/u/37820110/circ.gif

This advice helps, the output of the FPGA is better.
I think the signal in input improves due to I/O circuits, it has to pass through. But it consumes two more pins of FPGA, so I don't like this solution.

Is there any other solution I can do in the input of FPGA or in FPGA inside logic? I can also give something into the trace of input signal, some termination or logic gates to improve this input signal. But I cannot change the source of clock signal.


texts: Verilog counter made of 32 bit adder (syntax error)

texts:
For a school assignment I have to make a counter, based on a 32-bit adder, that increments with 1 every clockcycle if 'enable = high' and 'reset = low'.

When I try to use the adder in my counter module, verilog gives me a syntax error which i dont know how to solve, near 'adder adder_count(.a(a), .b(b), .c(count));'

can anyone of you help?

 module half_adder(
    input a,
    input b,
    output sum,
    output Cout
    );

    assign sum = a ^ b;
    assign Cout = a & b;

endmodule

module full_adder(
    input Cin,
    input a,
    input b,
    output sum,
    output Cout
    );

    wire sum1_w;
    wire Cout1_w;
    wire Cout2_w;

    //Half adder 1

    half_adder half_add1 (.a(a), .b(b), .sum(sum1_w), .Cout(Cout1_w));

    //Half adder 2

    half_adder half_add2 (.a(Cin), .b(sum1_w), .sum(sum), .Cout(Cout2_w));

    //Resulting OR gate

    or or_cout (Cout, Cout1_w, Cout2_w);

endmodule

module adder(
    input [31:0] a,
    input [31:0] b,
    output [31:0] c
    );

    wire [31:0] carry;
    genvar i;
    for (i = 0; i < 32; i = i + 1) begin
        if(i==0)
        half_adder half_add (.a(a[0]), .b(b[0]), .sum(c[0]), .Cout(carry[0]));

        else
        full_adder full_add (.Cin(carry[i-1]), .a(a[i]), .b(b[i]), .sum(c[i]), .Cout(carry[i]));

    end

endmodule

module counter(
    input clk,
    input reset,
    input enable,
    output [3:0] count
    );

    reg [0:31] a;
    reg [0:31] b = 32'b00000000000000000000000000000001;
    // b starts as 1, a as 0

always @(posedge clk) begin

    if (enable == 1'b1 && reset == 1'b0) begin

        adder adder_count(.a(a), .b(b), .c(count));

        // every step:  a + 1 = c
        // a becomes c
        // repeat
    end

     if (reset == 1'b1) begin
         //reset

     end
end

endmodule


texts:
My Doubt is that, This is synchronous counter, all the flip-flop are activated simultaneously Right?
Suppose at t=0 clock is activated then j0 and k0 will be activated instantly but my doubt is that in this time what will be the content of j1 and k1 or j2 and k2 does they have previous value i.e value they contain in previous clock cycle? Right? Okay now t=0 j0 and k0 will output qo complement this will reach AND gate and after 10 ns they will reach j1 and k1 right? Does my understanding is correct? Please help me to visualize how to calculate delay. Somewhere i read we taking only maximum delay I'm all confused here Please help.


texts: How to read Torque-Power diagram for an asynchronous motor

texts:
I'm sorry if my question is too stupid, but I am not able to correctly understand how to compare the information showed by the torque-power diagram with the motor test data for a 2000W Asynchronous motor powered at 48V.

If I am correctly reading the diagram, for example, when the power is P=1000W, then the torque is T=5Nm, but in the test data table, it says that when the output power is 1,06W (total power from battery 1310,4W), then the torque is 2,53Nm. I can't undertand why; Or, for example, when in the diagram the power is P=2000W, the torque is T=10Nm, while in the test data table there is written that at P=1960W, then T=4,83Nm.

How should I interpret this set of data?
Please, can you help me to figure out how to read this diagram?


texts: Does a capacitor in an inverting op-amp make a difference?

texts:
Just a quick question, does a capacitor in an inverting op-amp make a difference to the transfer function? Or, are just the resistors taken into consideration?

Non-Inverting op-amp:

\$ \dfrac{R1 + R2}{R1} \cdot V_{in} \$

simulate this circuit – Schematic created using CircuitLab

Inverting op-Amp:

\$ - \dfrac{R2}{R1} \cdot V_{in} \$

simulate this circuit

In both of the above equations, capacitance is not a factor, yet in a number of circuits, capacitors are present as voltage regulators.


texts: Will this selectable CAN BUS termination circuit work?

texts:
I'm trying to find a simple way of having software selectable termination on the CAN bus of a device I am making.
I think a Solid state relay is the best bet so I have come up with the following circuit.

The typical network this connects to will could have around 15 nodes and could have a bus load of upto 35%.

My device is solely 3v3 and I'm not sure if this panasonic relay will work with 3v3 or if this circuit will even work? The reason for the 90ohm rather than 120 is because the relay has a on resistance of 30ohms.

So my questions are:
Will this circuit work?
Is there any better alternatives?
Is the 10pf output capacitance of the SSR acceptable and what issues will the cause?

This is the relay I plan to use:
https://www.panasonic-electric-works.com/cps/rde/xbcr/pew_eu_en/ds_x615_en_aqw227ns.pdf


texts: Microchip programming with network connectivity

texts:
Back in my college days (which is about 3 years ago) we used to do some microchip programming. I've always enjoyed programming those things.

Now I'm thinking about buying such things to make me enjoy it once more :)

But to be very honest, I only have knowledge about the programming part, and not about the differences between the microchips (since there are so many available).

What I am basically looking for is a microchip which we can connect with buttons, lights, etc but which we can also connect to the internet using UTP or wireless (preferred).

The lights and buttons are easy, but what about the network connectivity?

I hope I can find some help here, since I really lack this knowledge...

BTW, the programming language does not really matter, if I can choose i'd go for C#. But I will be able to work with most of the languages. (C, C++, Java, ... but again I'd prefer c# if possible)

BTW What about Arduino or Netduino?