texts:
I have a garage remote that stopped working. I changed battery and it worked again, but only for a few days.

I measured the resistance between the poles of the battery terminals and it was about 760ohms. My assumption is that it should be much greater (ideally infinite). So I noticed that what it seemed to be a capacitor (a surface mounted spec, with a yellowish band) and it had exactly the same resistance, so I thought that either that was not a capacitor or it had failed (because the resistance should be also zero).

To complete the picture that capacitor was just after the battery terminals). I decided to remove it.

The end result is that the remote keeps working and resistance between battery terminals is now off the scale. Hopefully it will not discharge as fast.

What was the purpose of that capacitor? (If it was a capacitor in the first place)


texts: Raspberry Pi, SSR, Solenoid Valve Power (Multiplexing?)

texts:
Background
I have a RaspberryPi-controlled irrigation sprinkler system that I am working on. I would like the RaspberryPi and the Solenoid Valve (when the Solid State Relay is closed) to pull power from the same source. I would like to verify I have calculated the correct resistance in the diagram that results in a 5V supply to the RaspberryPi (and that all other connections look ok).
Method

The Pi and SSR are in parallel thus both subject to the same 120VAC
A Pi normally draws 2.5A using 5V resulting in an effective resistance of 2.04 Ohms (V=IR)
Treating the Pi loop as a series circuit, I can get the current across the resistor R by obtaining R_eff=R+2.04 and I=V/R_eff
I must then find the voltage drop across the resistor R that results in 5V supplied to the Pi: 5V=120-dV_R which is the same as dV_R=120-5V=115V
I know how have:
dV_R=115V
and
I=120/(R+2.04)
and
dV_R=I*R

Solving these equations results in R=46.92 Ohms

Did I do all of this correctly?
Components

Solenoid Valve

SSR

Raspberry Pi Model 3 B+

Another Thought
If the 120VAC power is coming through 12-14AWG wire, what is the best way to "connect" that to the resistor that meets the Pi power supply? That is, on paper these connections look fine to me but in practice, how would you do this?


texts: calibration of the BNO055 - how does it occurs?

texts:
The 'internal calibration' in the Bosch IMU BNO055 (datasheet), says that the sensor will be calibrated everytime 'Power on Reset'. What does Power on Reset means?
Does it calibrates itself every time the device and the bn055 is turned on or will it need to be in special mode? Meaning that every time i turn on my sensor, if i want a proper accelerometer calibration value, i will need to turn the sensor to 6 different faces?


texts: Why does placing resistors in parallel decrease the resistance?

texts: This question has been asked before but I don't understand the answers to it. They say that by adding a resistor, it provides an additional path for current to flow  and decreases the resistance. I understand how an additional path decreases resistance but how is adding another resistor  adding an additional path? For example, say a parallel circuit branches off into two paths. You then add resistors to those two paths. How does that decrease the resistance? It isn't adding a new path?


texts: Converting cordless to corded: Pulsing issue

texts:
So I am rather new at electronics and electrical engineering. But here is what I am trying to do and what I need help with.

Some years ago I had bought a cheap set of cordless power tools. Naturally the battery packs died much quicker than most. So I had the idea last night that I could just take some of the extra tablet power supplies laying around and convert these battery-less power tools to being corded. The power tools were labeled as 19.2 volts and the tablet power supplies were labeled as 19 volt output, but registered on the multimeter at about 19.3.

After disassembling the battery pack that went to the power tools, inside were 16 sub C batteries labeled as 1.2 volts and 1300 mAh and connected in series. So by my calculations, remember I am green at this, the battery pack had an output of 19.2 volts and 1.3 amps. The tablet power supply was labeled as 19 volts and 1.58 amps. So everything seemed rather straight forward. At least to me.

So I connected the tablet power supply to the leads in the power tool where the battery pack would normally connect and fired it up. That first half second was glorious. For a brief moment I was proud of myself. But only briefly. What ended up happening was that the power tool turned on and worked for a moment and then stopped. Then a moment later it would do the same thing. As I held the trigger down it continued this "pulsing".

After doing some research it seems the problem may be that the tablet power supply is a "switch mode" power supply and that this is causing the pulsing action? I am not sure. That is why I came here. Maybe someone could help to shed some light on this issue.

All the power requirements seem to match up so:

Why would it pulse like this instead of being steady like normal?
What's a good way to rectify the situation?
If it is a "switch mode" power supply issue, can I somehow convert the power supply to work? Can I just add a capacitor or something somewhere down the line?

Thanks in advance for any assistance and for having patience with a new learner such as myself.

Tablet Power Supply
(from the box it came in)


texts: Carrier concentration in the depletion region of PN Junction graph

texts:
I have just started learning about PN junction with the help of this video

NPTEL

At time 10-15 minute from the start ,we get this

The professor claims that from the linear scale it is clearly seen that concentration drops off to zero and thus it is a depletion region that is no free carriers are present. How are we getting this linear scale plot and how is this concentration dropping to zero but in the log scale it is not?

This is another picture showing the same thing. But how is concentration dropping to zero in linear scale but not in log scale.


texts:
I have a feedback system including an OP-amp in comparator mode and a transistor, in present time it acts like a regulator, constantly limiting the current through the transistor to a certain value.
However, in order to not heat up and burn the transistor the system must be altered so that in the  "off-time", when the current is limited the transistor is completely off instead. (It is an p-channel MOSFET).

What I need to implement is an time delay in order to break the continuous regulation loop and instead have following pattern: "Check if current is too large" > "if too large shut MOSFET for a 0,5-3 seconds or so" "else, conduct as usual".

I need to implement the delay using as few components as possible. This far I have looked at 555-circuits and monostable multivibrators. They could be an option, but however, both require a bit too much components and space. RC-circuits don't seem to cut it as the feedback finds an equilibrium and avoids the delay filters.

I hereby ask for advice and example circuits.

P.S.

My circuit is an alteration of the following one:

Alternative solutions are also welcome.


texts: optical wireless link short range high throughput

texts:
I am student and I want to realize a wireless optical link in order to have a throughput of 100Mbps max and the distance between the emitter and the receiver is about few centimeters.
I have made my research in the Internet for two weeks,  I found IrDA products. this lead was dispaponting because in theory IrDA technology could attain 96mbps (UFIR protocol), but I found no product having this throughput. laser products are too expensive and they are used for big range (kilometers). I found also the LIFI technology but there is no product responding to my outcome.
I realized that I can use simple LED (the cost is lower) with modulation, while I was searching in this forum, I found an interesting answer : Using a LED to transmit data
so we can use leds to transmet data with 160mbps and the range is about few centimeters, The problem is I have to use lens and to package them with the emitter and receiver, I wonder why there is no product (not too expensive) ,using led ,I can buy having these characteristics.


texts:
I am trying to create a small low cost circuit that will allow me to log the output of a solar cell over the course of a month as a student project.

Currently I have a 5V Silicon PV cell and am looking to log the current over the course of a month. I have a circuit that I have designed to allow me to log the voltage and therefore be able to work out the current using Ohms law (see below) but I am unsure it will work.

If anyone could offer any advice or pointers that would be much appreciated. On a similar note if anyone could recommend a low cost voltage data logger that could be used to take readings once or twice every minute that would also be a great help.


texts:
I stumbled across some information about an opamp on the Texas Instruments Site, the OPA1604 and in the datasheet it says:

These devices also feature completely independent circuitry for lowest crosstalk and freedom from interactions between channels, even when overdriven or overloaded.

I would like to construct 4 Howland current sources using a quad opamp and was worried about channel saturation (when a current source is disconnected from its load) affecting other channels on the same package, but this feature seems useful in handling it.
I am trying to gather whether this is more of a gimmick limited to this range of audiophile amps or whether I can find this style of opamp more generally also from other manufacturers? And how would I go about identifying them using parametric search ect..., or would I have to just have to churn through data sheets?


texts: Time Reversal Operation for discrete time signals

texts:
For a discrete time unit step signal 'u(n)' , if time reversal operation is performed then it becomes 'u(-n-1)'.
Is it true for ANY discrete time signal 'x(n)' such that time reversal operation makes it 'x(-n-1)'....?


texts:
From here, I have the following example:

clr r16 ; Clear r16
ser r17 ; Set r17
out $18,r16 ; Write zeros to Port B
nop ; Wait (do nothing)
out $18,r17 ; Write ones to Port B

My question is that what does $18 mean in the last line?

I know it stands for PortB. I would like to know more about its syntax.


texts: How to fix RaspberryPi HDMI-DDC/CEC issue while keeping ESD protection?

texts:
The RaspberryPi (Type B, all revisions before B+) shows a more or less well-known issue with the CEC/DDC of connected HDMI devices. When powered down CEC between the connected TV set and other devices fails to work.

The schematics, pages 2 respectively, show ESD protection by pairs of dual-rail clamping diodes (BAV99). Guesses are that the clamping to +5V0_HDMI (that is essentially +5V0 supply voltage of the Pi decoupled by a BAT54) at the powerless RaspberryPi pulls down SCL and SDA lines of the serial interface.

There are discussions buzzing around to remove the clamping diodes to get CEC working again. Obviously, this also removes all ESD protection from those ports. Some people report issues with erratic behaviour due to suspected static effects.

After checking some other protective circuits of HDMI like the TI TPD5S115 (warning opens *.pdf) or the TI TPD12S016 (same warning) my question would be how to best fix the issue while maintaining a "certain degree" of ESD protection. The TI design shows just clamping to the ground and the mandatory pull-up resistor (1K75 for SDA/SCL) and a pull-up resistor for the CEC line (26k at the connector, 10k at the controller).

Variant I:

Besides completely removing the BAV99's one could just disconnect the upper half, keeping clamping to GND intact. A low-resistance connection to +5V0 is there any way for SDA/SCL. For the CEC line, I think of adding a pull-up resistor too (around 10k to 27k). So the idea is to cut open the connections of the cathodes of the upper halves of D13 through 15 and +5V0_HDMI and adding one pull-up resistor to D13 and +5V0_HDMI.

Variant II:

Dedicated HDMI control line ESD protection circuits are also available, such as the ST HDMI05-CL01F3 (warning opens *.pdf) and ON Semi ESD5384 (same warning) with the later actually being incorporated in the new RaspberryPi B+ designs. While these parts may be hard to come by and complicated to be made fit the given PCB, the ideas could still be used for the relevant data lines using discrete parts (essentially zener diodes and resistors). The benefit of this solution would be a symmetrical clipping.

Any issues to be expected with those solutions? Any better ideas or improvements?

Figure: HDMI circuit of RaspberryPi (top) and TI TPD5S115 protective internals (bottom).

Figure: HDMI control line ESD protection circuits HDMI05-CL01F3 (top) and ESD5384 (bottom).


texts:
I am writing some firmware for the atmega16u2 and have noticed that the usb device hardware does not work correctly if debugwire is enabled. The usb device does not enumerate. Disabling debugwire immediately causes the usb device hardware to work as expected (enumerates correctly). Debugwire debuggin works correctly except for the functionality of the usb device hardware.

Is there a way to allow/make the usb device to work correctly with debugwire?


texts: How do I prepare my SIM card for SIM800L GPRS GSM module?

texts:
Im trying to send a SMS message using the SIM800L GPRS GSM module.
I know this might sound stupid but, do I need to load my SIM first before it can send SMS message?
If possible, can I just pay after it sends the message without load balance beforehand?


texts:
I'm a noob in Electronics. I want to use this module that doesn't have SMA or u-fl connector. my Question is how can I use SMA or u-fl connector with this kind of modules or how can I solder them the connectors?

http://www.hoperf.com/rf_transceiver/lora/RFM95W.html


texts:
The expression for received signal PSD corresponding to a simple cosine wave (frequency fC) being transmitted is given as:
\begin{equation}
  S_r(f) = \mathcal{F}[A_r(\tau)]=\begin{cases}
    \frac{P_R}{4\pi f_D} \frac{1}{\sqrt{1-\Big(\frac{|f-f_C|}{f_D}\Big)^2}}, & \text{|$f-f_C$| $\leq$ $f_D$}\\
    0, & \text{elsewhere}.
  \end{cases}
\end{equation}
Underlying assumptions:

Narrowband channel
Uniform scattering
Amplitude, Doppler frequency and multipath delay do not vary much in the time interval of interest.
Only multipath fading is considered (small scale effect).

However I am unable to prove that this indeed integrates to PR. I found it to be P/4 (limits: fC-fD, fC+fD) . Am I missing something ?


texts: Why does a commercial PCB need this much rework?

texts:
I found a PCB that has had some rework done.  When I saw it, I thought that someone had actually repaired it after purchase:-

It's got additional wiring (white & brown) and under the hot glue are two ceramic capacitors.  The capacitors have been sleeved with insulation (difficult to see).  They smell like decoupling capacitors.

I can understand altering my own boards, but this is a commercial speaker from a successful company (Labtec):-

The work seems to be based around the main amplifier chip (TDA2005).  I've seen other post design changes to boards, but that's only been a wire here or there snaking across a PCB.  Why does a commercial board get sold with this state of rework?

PS. Also note the hand thickened tracks in the top left.

PPS. The two circles also show hand soldered surface mount capacitors added to this side of the board which is clearly a through hole design.


texts:
I have one small question. I know that after passing through a resister, current remains the same in an ideal situation. But then, why are resistors used to limit the amount of current in a load. Also there is potential drop in the resister but what difference does it make if it passes the same current. For example, in LEDs, flow of large current can destroy it, so they are connected to voltage source through a resister. But if the same current passes through resister what effect will introducing the resister have?
I know I'm missing some basic concepts, could you also suggest topics to revise.

Thanks in advance for the help!!


texts: Multiple TLC5940s on PCB "dropping out" when many outputs turned on

texts:
I've designed a PCB to connect 12 TLC5940s to an 8x8x8 RGB LED cube through 3 64-pin headers, which I will include screenshots of below. I have a separate board for controlling the anodes for multiplexing, that's working fine and I've turned off the multiplexing for testing anyways. I have a 5V 20A switch-mode power supply for the whole thing, and I'm powering the TLC5940s through an LM317 regulator set for 3.3V, due to logic level of the STM32F4 Discovery I'm using to control the whole thing. I've put a 2.61k resistor on the IREF pin of each IC to set the constant current at ~15mA.

If I turn on just a few LEDs (no more than 8) at a time everything works fine, but if I turn on many of them the TLC5940s start going crazy. If I just turn on all the outputs of one, it works fine but the rest go crazy. With dot correction set to EEPROM (which has the default data of all 3Fh) they turn off all outputs and start drawing a lot of current on the supply pins, causing them to get rather hot. I have to disconnect and reconnect the power to fix this. If I set dot correction to the DC register and fill it with max values on startup, they just flicker at random brightness as if the DC register is getting scrambled, and don't draw a huge current. A simple re-initialization fixes them in this case, no power reset required.

I've poked around on the various signals with my oscilloscope, and they all look perfect. I even checked all the SOUT pins (since I have 12 of them daisy-chained) and the data is in fact being latched in correctly. The only thing I can think of is lack of proper decoupling, but I have 0.1µF ceramic caps on all the ICs, and some bulk decoupling (a couple 100µF electrolytic caps) on the separate anode control board. Is 0.1µF possibly not sufficient for the TLC5940? Based on the datasheet it seemed like it would be. I even tried poking 10µF and 100µF electrolytic caps in there, which had no effect. Even all the power pins of the ICs look clean on the oscilloscope. I'm really at a loss here.

By the way, the oscilloscope is a Rigol DS1054Z with the 100MHz bandwidth upgrade.

Here's the PCB layout:


texts:
With which IC can I boost the signal on the rf out pin of the MVE1600 voltage controlled oscillator? I lowered the function generator to 500 micro amps by connecting 10k resistor.So it is equal to MVE1600 rf out pin.And simulated to increase it with 74HC04D but I got an error. It has only 3.75 volt 500 mikroamper rf out pin. It is problem.
Which integration should I use to boost the (rf signal out pin) of the MVE1600 voltage controlled oscillator?
The model of the voltage controlled oscillator is in the picture


texts: Getting wrong results when using switched-capacitor filter. (PSpice simulation)

texts:
Okay the idea is to use the following band-pass active filter:

To this filter I want to add a switched-capacitor filter to replace the resistors with capacitors and switches. I'm using the formulas \$f_{c1}=\frac{1}{2\pi R_1C_1}\$ and  \$f_{c2}=\frac{1}{2\pi R_2C_2}\$ with \$f_{c1}=2kHz\$. Using those formulas with \$R1=R2=2k\$ we get \$C_1=39.78n\$ and \$C_2=19.89n\$. Finally, we just need to replace the resistors. For that I want to use a clock with \$T_s=1MHz\$ and to calculate the needed capacitors I'm using \$C=\frac{1}{T_sR}\$. Then, the capacitors have the same value (because of the same resistors) and are qual to 0.5nF. The schematic is:

All seems fine. However I find the following problems:

The bandwidth isn't the desired (it should be 2k, but I get about 4k).
The working of the circuits seems independant of the clock pulse. I tried changing it from 1Ghz to 1Hz and the response in frequency is the same. That is strange because clearly something should change if I change the clock.

So, what is going on here? What could be wrong? Am I ignoring something?


texts: Altium: What are these vertical yellow lines

texts: I was aligning 3D files in Altium and at some point I noticed these solid vertical lines had appeared. They seem to stretch from top to bottom of the entire document and I can't seem to remove them. I tried resetting Altium but that didn't work. How did I add these lines and how can I delete them?


texts:
I've got the attached circuit and layout setup - basic signal conditioning going into an ADC. First we buffer the signal with a unity gain follower. I can verify with the scope that the output at TP2 matches the input as expected. The second stage (single dual op-amp chip LM358) is inverting with a gain of -0.37 to attenuate this to +/- 3.7V for the ADC. (Note that R17 is just an extra footprint and is not populated.) In practice the output of this stage goes to about +3.7V when the input is -10V as expected, but as the input goes up to +10V the output never goes much below about -1V. This non-symmetric behavior has me puzzled as it simulates out correctly in circuit lab and LTSpice. I've also attached the layout for those curious. I've checked it, the pinout of the part, that correct values are populated, and even swapped the Op-Amp. What blatantly obvious thing am I missing here?

Note TP1 and TP11 are on the same net, the layout just worked out with TP11 here.

Update per solution. Simulation shows this to provide basically 0-2V out to the ADC.


texts:
I have a Raspberry Pi and it requires a Externally Powered USB hub to run Portable HDD on it.
So what if I connect +5 and GND port of the USB Client to external power source of 5V-1A directly rather then connecting them to the USB Host ?
OR
What if I use a transistor as a switch and for source isolation ?
Will this work or not ? Or Do I have to give power to D+ and D- ports too ?

simulate this circuit – Schematic created using CircuitLab


texts:
I wanted to make use of a single port RAM to be a single clock FIFO in verilog for an asic project , due to some constraints  i can not use the dual port RAM. My confusion is when I have to perform read and write simultaneously, I thought about using a faster clock and give 1 cycle for read another cycle for write, but that option is not preferable, in the context of my project. There is the idea of making  a system with priority for read however I am not sure how to manage the write request. If I give priority to read I might lose some write requests as well.

Thanks


texts: Need help choosing a power supply for a breadboard

texts:
Hey i want to (in the long term) start experimenting with remaking modules from old analog synthesizers. For example remake an oscillator from a Minimoog or a chorus from a Roland Juno-60 or something for my own pleasure.

And i figured that i would just start out by experimenting on a breadboard. But i have never used a breadboard so i don't know that much about them. I know how it works when there is power put into it. But i don't know how to power it. I can only really find power supplies that supply 3,3/5V and that is too small a voltage for what i want to do. I think i need something that is variable and that can at least output 30V. It is important that it can send out different voltage and that it can be used with a MB102 breadboard.

What could be a good solution for me?

If you have any tips for using a breadboard for something like this or if you just have some tips in general then it would be greatly appreciated.

Thanks in forward


texts: How can the capacitor be connected in reverse polarity?

texts: If the polarity changes every time the AC switches, then why doesn't the capacitor explode?


texts: How to enable Output pin to high by default in Arduino Uno?

texts:
In Arduino Uno, I noticed that when I set a PIN to output, the default initial state is low. Is there a way to set the initial output state to high?

The pinmode documentation supports only input, input_pullup, and output. I wish there is an option for output_pullup. If I put an external 10k Ohm pullup resistor around the output PIN, it does help a little pushing the initial state towards high.

Still, if there is a software based solution (i.e. flash the Arduino Uno to default output to high), that would be much appreciated.


texts: Ripple on tens-millivolts sinus waveform

texts:
I’m trying to make a DDS to generate a sinusoidal signal with tens to hundreds of millivolt amplitude and hundreds kHz frequency using an LTC1666 DAC. But I have some confusing results. Device schematic is in the picture below. As you can see, ripple is too strong. I found that NSD10-12D12 (the power supply) has a ripple voltage of 75mV maximum.

When I short oscilloscope probe with oscilloscope ground and short it to device GND I see huge ripple (see on a picture.) When I place probe on 50R output resistor I see signal with this ripple (how I think.)

In other case when I replace 50R resistor on output by oscilloscope 50R impedance input I found good signal.
Can someone explain me how it can be, how to understand it, and where I have made a mistake?

Probe shorted with osciloscope GND. Noise is too small:

Probe shorted with oscilloscope GND and device GND, ripple is induced by the device ground and has a periodic structure:

Ripple superimposed on the output signal:

On the picture below 50R output resistor replaced by 50R impedance osciloscope input. As you can see, in this case the signal is clear but I can’t understand how this happens:

Device schematic blocks:


texts:
I need to design a 2 stage LC filter for operating in the range of DC-70Mhz frequency.

Can someone provide some inputs on how to get started?


texts: Can I add an SMA tap to BNC HF transceiver?

texts:
I have a bare uBITX 3-30 MHz transceiver board per http://www.hfsignals.com/index.php/ubitx/

Looking at the hookup directions and other pictures on the site, the designer's recommendation is to simply hook a BNC jack to the main board through a (short) two-wire jumper (fractions of hookup schematic and pic below).

What I would like to do is add an additional SMA output in parallel with the BNC adapter to try things with other antennas and gear I already own without re-opening the case and swapping two-wire jumpers.  It seems it wouldn't be much different than connecting a BNC tee to the output with a SMA adapter on one end and only using one or the other and leaving an open port.

What issues are there with mounting multiple RF connectors in parallel if you only intend to use one at any one time?

Are there similar issues with leaving an open Tee on a line?


texts: Damping factor in active low pass filter

texts: I want to calculate the damping factor of this low-pass filter, where vin=1*sin(2π1000t) Volt. How can i find it?


texts:
I am currently designing an audio amplifier using the LM324. I am operating from a single supply of 9 V. Here is the schematic:

Here are the design steps I took:

I needed a gain of 100 so G = 1+(100/1) = 101.
The input capacitor C1 forms a high pass filter with R1||R2. The lowest frequency is 20 Hz so I chose f=15 Hz and C = \$\frac{1}{2\pi\cdot 5000\cdot15}\$ = 2.12 µF so I chose C1 = 4.7 µF as the closest value.
The non-inverting input is biased to VCC / 2 to allow maximum output swing.
C2 is just a normal decoupling capacitor.

After assembling it I am unable to get a decent output from it. Can anyone point out what could be the problem?


texts: Is frequent sleep-wakeup harmful to the electronics?

texts:
I'm programming a large network of tiny microcontrollers (say around 500 of them, but easily more) that communicate with SPI with a hierarchy of masters (say each master controls 32 of them).

Given these numbers, the power consumption of this network can easily get high and I'm trying to keep that under control. It would be ok if there are very short peaks in current consumption, but it shouldn't last long of course.

I have been thinking of frequently switching to a low power mode any chance I get:

Between SPI transactions: this can be powering down, even to halt mode (which turns off all peripherals) and back up as frequent as a couple of times every 40 ms.
During the SPI transactions: this means powering down slightly (only turn off the CPU) and back up with every byte transfer, e.g. every 2 us during the transaction.

Now I'm a software guy, so my knowledge of electronics when it comes to their electrical characteristics is limited.

My question, can this damage the hardware? Is turning the CPU off and on every 2us unhealthy? What about turning everything off a few times every 40ms?


texts: Improving LT Spice DC sweep convergence time

texts:
I have a circuit that's kind of finicky, I'm trying to run a DC sweep but it takes forever to run simulation steps. The main problem is even after adding circuit elements to make the circuit converge faster\better (like parallel resistance and capacitance on sources, and parasitic capacitance and series source resistance), the circuit still takes a long time and won't stop stepping the source or not converging (I don't know whats going on under the hood).

I get this at the bottom of the screen:

To make it run faster I hit esc because it is done stepping but probably not to the tolerance that some setting requires. If I even run 10 steps this takes about 15 mins of my time that I could be doing something else, I would like to run 30 steps, but that would take a long time.

How do I set the limit for the source stepping or stop it?

How can I get the steps to run back to back so I don't have to babysit the simulation by hitting the ESC key?


texts: How to measure output DC impedance of clock oscillator?

texts:
I need to accurately measure the DC impedance of a clock oscillator's (single-ended) output buffer. What are some ways I can tackle this in the lab?

If it helps, I have an oscilloscope (but not a VNA). I'm looking for practical test setups, with or without the scope.


texts: Why can both parties feel static electricity

texts:
Sorry I'm new to electrical engineering, trying to clear up some confusion on how static electricty works and why both people feel a shock when touched by static electricity.

When creating a circuit,  Electrons flow from the source through the load back to the source.  However, lightning an electricity seem more like a 1 way current.

If static electricity is one way,  and you're send electrons to someone why would you feel the shock?

But maybe I have a misconception static electricity and the electrons complete the circuit and then return, In this case:

Do you feel the initial shock (Electrons leaving your body) or is the feeling from the electron coming back in?


texts:
I'm trying to identify a part I removed from a compact fluorescent lamp manufactured around 9 years ago (date on the PCB is 17.12.01).

It is a gray hexahedron and it's 7 mm wide, 2 mm long and about 4.5 mm high. Contacts are on the 2 mm sides.

The inscription on it says in the first line 2n2 and in the second line 630.

Judging by the inscription, device seems to be manufactured in a long sheet on which numbers were printed and then cut into 5 mm high segments.

At first I thought it could be some sort of capacitor (PCB has capacitor mark on its location), but after some testing, I was unable to charge it and then measure its voltage (on the other hand, it could be that it has very low capacitance so could discharge itself in the time it takes me to switch my multimeter form ohmmeter mode to voltmeter mode). Also, part which is obviously resistor was next to the unknown device and it too had capacitor mark on PCB.

I did some research on the Internet, but as far as I can tell, 2n2630 is a transistor and this definitely does not look like a transistor, so I'm looking here for ideas on what it could be.

EDIT
I finally managed to get a nice picture of the part on 1 mm grid. Here it is:


texts: Connecting BMS to charge controller and load

texts:
Im trying to design a circuit that the load will get power from solar panel or a battery (in case the solar panel will not deliver enough current\voltage)
Also wanted to mention that this is a hobby, so I dont have deep knowledge in electronics..
So the question is about connecting charge controller and BMS-2S to load
1. 12v solar panel connected to charge controller as input
2. 2S (3.7 each) Li-Ion batteries
3. RPI Zero as load. will draw about 150~200mA

about the BMS, it says that pins P+ connected to charger+ and load+. And P- connected to charge- and load-.

Connecting that way, that the BMS and the load are parallel to charge controller, will not interrupt the charge controller main goal? Im wandering how it will affect the Constant Current and Constant Voltage mechanism.
Im not sure that the load supposed to be connected that way, ill be happy for guidance.
Thanks


texts: Transimpedance amplifier circuit for water conductivity

texts:
I'm trying to understand the application of the water electrical conductivity measurement circuits based on transimpedance amplifier.

Here the picture of general TIA configuration

And here what I'm talking about

In the second picture, the op-amp is feeded with dual supply.
Two metal and equal pins are dipped in the water and connected to the battery as shown.

Will the current be flow in correct way like figure 1 to accomplish TIA?

p.s. Just to be simple I used a battery as current source, this question is not about the perfect water electrical conductivity activation signal.


texts: What components would I need to build a basic circuit that completes when something is pulled with a certain amount of force?

texts:
As an example, a rope tied to a tree when pulled with Y newtons would illuminate an LED but wouldn't when only pulled with X newtons.

I guess what I'm looking for is a basic force meter.


texts:
I want to run a large inductor coil for wireless charging with a 12V peak, 300kHz AC signal, starting with UK Mains voltage (230Vrms 50Hz). Should I use a step-down transformer and then a frequency changer? What should I use for my frequency changer?

Eric


texts: What is the purpose of the resistor connected across ultrasonic receiver terminals?

texts:
I have seen a few circuits where a resistor is connected across the positive and negative (grounded) terminals of an ultrasonic receiver. It seems to "stabilize" the received signal. I have attached an example of one of these circuits, but I am using a simpler circuit with just a comparator.

What does this resistor do, and how does it work?

Image source


texts:
I plan on using a 555 timer for a PWM signal (variable with a potentiometer) and a gate driver to use a MOSFET as a switch. Essentially, I am trying to take a +300V rail and "step" it down using the PWM. The total current through the MOSFET wouldn't likely be more than 25mA, and would be more likely under 10mA. Mostly, what I am wondering is if it is safe to leave the MOSFET on for an extended period of time- at most, a few hours. I see no problem, but I haven't exactly tried it either.

I also understand that the greatest losses are switching losses, so I'll try to minimize the switching frequency while still providing a, relatively, clean output that capacitors can filter.

The alternative to using such a PWM scheme is to simply put the potentiometer on the voltage rail and generate a drop across that, but that would likely load the circuit more than the MOSFET would, which is why I prefer the MOSFET.


texts:
i have VGA in one side of my circuit and I want to connect that to a connector with 50 ohm impedance. after that I must convert 50 ohm impedance to 75 ohm, because I have a vga cable in other side. in other word I have two VGA cable that there is one connector between them with 50 ohm impedace.how I can Do this?
VGA(1080*1920)


texts: Implementing PID in PWM feedback to lower the settling time

texts:
I have created the following simple PWM feedback:

The step response is:

I have tried to add PID controller and I ran the following code to test it:

L = 1.62;
Lp = -1.232;

Kd = Lp/L + 50;
Ki = 1.1;
Kp = Ki/(Kd*L-Lp) + 5;

s = tf('s');
P = L*(Kd*s^2+Kp*s+Ki)/(s^3 + (Kd*L-Lp)*s^2 + L*Kp*s + L*Ki);
step(P)

The result was as I wanted:

However, when I added PID controller to the Simulink simulation It came out like this:

Is there some way to implement PID at PWM to obtain the desired result (lower settling time and lower overshoot)?

First I used the PID block right after the Sum block and I got the result above. When moving the PID block right before the Abs block (after the split to the sign block) the results were better but still not as the step response.
After running many tests it seems like it takes the respond around 1 sec to get to value 0.5 and it is like a limit that doesnt change no matter what values were taken into the PID.

Thank you.


texts: Can I use a 10A light switch with an appliance with a 13A fuse?

texts:
I have a vacuum cleaner, which I wish to add a switch to, so that I can leave it plugged in all the time and use the switch to turn it on and off. The vacuum cleaner has a fuse rated 13 Amps.

I purchased a light switch, and noticed when I got home that it said that it was rated for 10A on the packaging.

The vacuum cleaner is rated for 1100W at 230V. I used this electronics calculator, which returned a value of under 5A. Why is this? Is it safe, therefore, to use the 10A switch on the vacuum cleaner?

EDIT: The vacuum cleaner is a ShopVac Micro 4 litre / 1 gallon model. Specs are available here


texts: 7805 regulator outputting 4V instead of 5V

texts:
I followed a tutorial on Sparkfun to put together a 5V power supply. But for some reason I'm only reading 4V coming out of the regulator. I know it's not the regulator because this is the second one I've tried. I checked the data sheet to make sure it's connected right and yet the problem still persists. I'm pretty sure I'm giving it enough power because it outputs 4V with a 9V wall wart input as well as around 15V from two 9V batteries in series. Eventually I gave up and decided to move on, even though 4V is below the minimum rating of the ATmega328p (4.5V,) and now I'm facing problems trying to program the chip, which I assume is because of the chip not getting enough voltage.

Does anyone know why the regulator isn't regulating properly?

The schematic for the power supply is:

from here


texts: Using pull-down resistor, but driving pin high by connecting to Vcc directly

texts:
I have a device that I know very little about.
I have access to Vcc and Gnd pin there, and it operates on +5V.
I need to drive its input pin high or low depending on a switch, that's UART RX input.
I have optoisolator between my MC and that device. Driving LED in optoisolator on my end is done, and I would prefer not to change it.
Here is a schematics from the device's side

I am afraid, that when optoisolator will be on, +5V will go directly into Rx pin with possibly too much current, and damage it.
The device is expensive, and this is supposed to work in production. And, as mentioned before, that's all I know about the tech side of the device.
Basically, I luck a knowledge of how to work with pull-downs and input pins.
I can, of course, change schematic on another side to use pull-up here, but I would like to learn this.
Any help is highly appreciated. Thanks.


texts: Odd distortion in op-amp circuit for audio amplification

texts:
I'm new to electronics, so I apologize if this is simple.

I'm trying to create a simple amplifier mainly for a guitar input, but testing it with an output and input from my sound interface.

The circuit produces a weird distortion that I don't know what is, but it is not clipping.

Here is the signal I'm sending

And here is the signal I'm receiving

And here is the circuit

simulate this circuit – Schematic created using CircuitLab

I would love to know why this is happening and how to fix it.
Thanks a lot in advance


texts:
This one is completely about PCB layout. I have two 26MHz crystals in the design, one for each processor on the board (TXC
7M-26.000MEEQ-T, datasheet: http://www.txccrystal.com/images/pdf/number-crystal-accuracy.pdf). The processors are placed in opposite sides of the board, relatively on the same place, so that they are quite "back-to-back". The PCB is 4 layer FR4.

One of the processors is an RF-chip, while the other one is just an 32-bit MCU.

My question is; Is it good practice to place the crystals "on top of each other", on the opposite sides of the PCB? There is ground plane between the crystals, but I'm thinking if there could be some interference between the crystals..


texts: How do we initialise unpacked arrays in Verilog?

texts:
Suppose I declare an unpacked array of size say 8 bits wide.
reg b[7:0];

If I want to assign b[7] = 1,b[6] = 1, b[5] = 1, ......b[0] = 1, then apart from assigning value to each bit is there a way to assign any combination of bits say 8'bA8, to b?
For instance if I execute this code(below) in verilog:
module tb();
    reg [7:0]a;
    reg b[7:0];
    initial begin
        $monitor("a = %b,b = ",a);
        a = 8'hA8;
        b = 8'hA8; // Line 7
    end
endmodule

I get this error:
C:\iverilog\bin>iverilog -o a test.v
test.v:7: error: Cannot assign to array b. Did you forget a word index?
1 error(s) during elaboration.

I am using Icarus Verilog on a command prompt on Windows 10 operating system.


texts:
I'm trying to connect an ESP8266 gpio to one of the relay modules (please check the image).

As I understand with a very basic background, ESP should be able to trigger this relay modules since all the electronics are embedded in them (they are not just single relay components). I have powered both ESP and relay module with different power sources, with the proper VCC for each (3v3 and 5v, sharing GND). But setting HIGH and LOW outputs from ESP have an erratic behavior (some times the relay module triggers, sometimes it just stays in the same state no matter the gpio output delivered).

Now, digging not just this community but some other sources in the web, I know there should same transistor to help driving a higher voltage to the relay input(s) than the one provided but the ESP gpios.

Its important to point out that:

both relay modules work just fine when they are connected to an Arduino Nano, which of course has a HIGH of 5v, and that seems to confirm the issue with the ESP gpio
2-relay module works "better" than 1-relay module: in terms of accuracy LOW gpio -> relay on; HIGH gpio -> relay off. 1-relay module seems to trigger only once, and then keeps the relay on no matter the gpio value (just like if relay IN is always shorted to ground).
I measured ~2.72v in both IN pins of the 2-relay module, and ~4.33v from the 1-relay module. So that makes me think ESP can't turn off the relay in the later because it will never reach the normal pin voltage value, and almost everything lower will be acknowledge as GND LOW (thus, relay on).

My question is: how can I properly drive LOW and HIGH values from ESP gpio to this relay modules?


texts:
I usually make Arduino protos without worrying about power- there will always be power so why worry. Recently I was asked to make simple device that counts clicks/ticks( a knob turning that makes a click) and logs its somewhere. Easy enough-but the problem is it needs to run concealed inside a device for 3-5 years of a battery(easily serviceable -but prefer not to)
I came  across this
http://interface.khm.de/index.php/lab/experiments/sleep_watchdog_battery/
and the theory is that it can run up to 3 years. Its fantastic because it is nearly what I want.

Has anybody every actually run a device like this for 3-5 years of a battery? In research i came to the conclusion that using Lithium Polymer would be the best battery for long term power- am I correct? and using a single 700mAh LiPo could technically last to 5 years. Is this lifetime of a battery even feasible?

Now I will try and change that project to wake the Arduino every time i get an external tick/click and it will increment,is it possible to wake the Arduino with an external event?

The second part is- Is it possible to store simple small integers inside the Arduino non-volatile memory somehow to avoid keeping it in RAM and using power?or the simplest way to store data on non-volatile memory.

I appreciate any suggestions.


texts: MUR460 diodes get extremely hot - what am I missing?

texts:
I have a 110W solar panel that I use to charge some LiFePO4 battery packs. The panel delivers 18-20V, so I have a DC buck converter between the panels and the batteries to bring the voltage down to 14.8V. To avoid having the batteries feed the buck converter when there is no feed from the solar panel, I put some diodes on the output side of the converter.
Initially I had two MUR460 diodes in parallel, but they got so hot that plastic case for the terminal block they were connected to melted.
According to the data sheet for the MUR460 diodes, they should be able to withstand a 4A average constant current, so two diodes was within the limits for the ~7A that a 110W panel should be able to deliver when the voltage is bucked down to 14.8V.
Due to the heat issue I replaced the two parallel diodes with three parallel, expecting that heat should no longer be an issue.
Those three parallel diodes still get very hot, not enough to melt the terminal block insulation, but still too hot to touch.
I will of course replace them with other diodes with a higher current rating, but I'm still curious: what am I missing here?
Are these diodes perhaps off-spec/bad, or is there something else that would explain why they get extremely hot? Did I just pick* the wrong kind of diodes, these are meant for high frequency switching, so are they perhaps not good for a constant forward DC current?
I would have thought that 3x diodes rated for 4A each should easily be able to carry a 6-7A forward current without producing a lot of heat.
*= the reason I picked those diodes was just that I happened to have a strip of them lying around in a drawer

Update: based on the advice in the answers and comments, I changed to a MBR3045CT schottky diode in TO220 packaging, and attached that to a heat sink. No more heat problems...


texts: Eagle: IC package variant, different pins bonded out

texts:
I'm trying to create an Eagle component for the Altera EP4CE22, which comes in BGA and SMD packages, where different pins are actually available on the outside of the package.

Is it possible to reuse the same symbol for both, not connecting the unavailable pins to outside pads, or do I need to create two different symbols?

If I need two different symbols, is it possible to create them so that it's easy to move between them (realistically, SMD -> BGA when I need more I/O lines)?


texts: DC-DC booster fails with lead-acid battery source

texts:
I have a nominal 10A DC-DC booster PCB with both Voltage/Ampere adjustment. It is intended for charging a 5C LiPo and is adjusted to output 17.5V and 5A for charging.

It works very well when powered with a 12V/20A switch-mode supply. But when powered with a 12V Lead-Acid battery, the DC-DC booster breaks down (short circuit on the booster input after a short while).

I simply don't understand this behaviour and I have now destroyed two boosters on this stunt. There must be something different with the switch-mode versus the battery - although both are a 12V source for the DC-DC booster.

What is going on? Can anyone explain this?

The picture shows the 3 parts (switch-mode supply, DC-DC booster and battery)

Update:

The damage is done after a few seconds (5-10) presumably after the LiPo is disconnected on the output (while testing). Maybe the battery should be disconnected first, although this is not needed with the switch-mode supply. However something points to this may be the cause, as there seems to be no problem while the charging is ongoing from the battery (although this is only tried for the mentioned 5-10 seconds).

It's true that there is a swift rise in the PCB temperature, which is not seen with the switch-mode supply. The manufacturer only suggests adding cooling above 6A (its 96% efficient). So it's not a real cooling problem.

As described, the booster input becomes shorted, which may be from an excessive current that shorts the PCB to the underlying aluminium plate. I lean towards thinking there is a resonance phenomenon, but I have never heard about/seen that. The battery manufacturer states an internal resistance of 37mOhm at 1kHz.

I'm not too happy to try anything before things are more clear.

Update-2:

With a fuse on the input of the DC-DC, I have discovered that it blows when the output from the DC-DC is disconnected from the LiPo-battery to be charged. This only happens when using a Lead-acid battery as power source (aka not with the sw-mode).

The difference is, that the Lead-acid battery can burst up to 40A and by all means the DC-DC apparantly destroys itself by eating all this.

Key to solve this problem is: Why does the DC-DC sukcs all that Amp. when its output is disconnected.

The trivia is gaussian: when the current from a coil is removed, the coil tries to keep the current by raising the voltage and a runaway situations is happening in the control circuit (IC). The sw-mode apprantly prevent this by simply its overvoltage protection etc. which a LA battery doesnt.

The non triva is: Why did they design this DC-DC to self-destruct, well knowing that someone possibly would use a powerfull battery (and not a sw-mode) as the power source.

The not-so-happy-solution is to use a finger-resattable fuse on the input, but a better is recommended.


texts:
I am using a VS1053 (on a SparkFun Music Maker shield) to provide audio for my project. I am taking a line out signal and inputting it into an op amp for signal processing, ultimately being input to an Arduino.

The op amp(s) are using Vcc and ground from the Arduino as their power supply. The module with the VS1053 also uses the same supply connections.

But line out is referenced to the audio ground created by the VS1053. In order to see the input signal, somehow the op amp and VS1053 must have a common reference.

An early circuit connected the audio signal ground to the circuit ground. But this is explicitly prohibited in the VS1053 data sheet. It seems to work but probably does do as a matter of luck. And will likely fail eventually.

How do I connect the line output of the VS1053 to an op amp?

Thank you.


texts:
I scavenged a loop antenna from a meteo-station that gets synched from DCF77 (77.5 kHz) clock signal. My idea was to implement a direct down-conversion with a microcontroller and decode the message based on the envelope.

As a first test, I connected the antenna to an oscilloscope. I was expecting a FFT peak @ 77.5kHz corresponding to the received signal from the radio station (the antenna should be tuned to this frequency)... But the only spikes that I can see are around 21.75 kHz.

If I don't see anything @ 77.5kHz with an oscilloscope, I strongly doubt to see anything with an uC ADC.

Am I missing something? Suggestions?

Thank you


texts: Heatsink for diode and mosfet in 12V 15A LC circuit

texts:
I am trying to design simple step down bulk voltage converter:

This circuit will be 'stepping down' 12V to lower voltages depending on needs (driven by 20kHz PWM with variable duty cycles). The load is non-inductive (peltier) with 1 Ohm resistance so it will be eating up to 12A.

I wonder what size of heatsink do I have to use for both: diode (which is actually MBR3045CT barrier rectifier) and mosfet (IRFZ44N).
Let's assume the mosfet gate will be properly driven and alwasy fully on or off (spice tested).

Here are the pictures of the setup I am thinking of (heatsink with fan) so you can see it in proportion:

I was hoping to use 1 heatsink only for both of them. Do you think this is enough, too much or would you recommend to go bigger?
I have an other option (bigger, more massive and heavier heatsink at the right):


texts: Synchronous buck using BJT's in stead of MOSFETS

texts:
Recently I came across a schematic of a synchronous buck converter using normal transistors in stead of MOSFETS, like this:

I was always under the impression that when the top switching device turns off, the inductor generates a large negative voltage because it wants to resist the change in flow of current. That's why the reverse biased freewheel diode is there in a asynchronous buck regulator, so the current can keep flowing.

How does the above circuit work then? The bottom PNP transistor, taking the place of the freewheel diode, cannot conduct current in that direction afaik. Current can flow emitter to ground but not from ground to emitter, can it ?

I built the circuit and it appears to work, measuring point before the inductor, where both emitters meet (excuse the poor quality):

Although I'm not sure what I'm seeing here. There appears to be a dip below ground on the negative cycle. At first I thought this was the inductor's negative voltage spike, somehow being cut off by the transistor. But the same is happening on the positive cycle, with a little 'bulge' above VCC.

Could anyone enlighten me about how this works and what is happening?


texts: Please help me identify this noise on my ADC

texts:
I have a CS4270 codec hooked up to a Raspberry Pi more or less according to the "recommended layout" in the datasheet (P7), shown below. This device sinks power from three different places (VA = power for analog subcircuits, VD = power for DSP, VLC = power for control port (I2C and clocks). Currently VA is sourced by an LT1965 (in turn powered from an Adafruit Powerboost connected to a LiPo battery) while VLC and VD are sourced from the Raspberry Pi's 3.3V output.

I am able to record from the device as expected using SoX on or arecord on the Pi, however I am confronted with a troubling amount of noise on the signal. These images are representative of what I'm seeing:

Full spectrum, 0-96kHz

Bottom of the spectrum, about 0-1kHz

In the top spectrogram, I see spikes of broadband noise repeating at about 33.3Hz, though the exact period seems to vary from recording to recording (I just saw some at about 50Hz in another recording). In the bottom spectrogram, I see narrowband noise at 50-60Hz and some bad harmonics. I haven't even started work on the signal chain leading into the ADC yet because these artifacts are everywhere on the board — I've plugged the inputs into ground, VA/2, even the codec's own midpoint reference voltage (VQ) and I see the same kind of thing everywhere, albeit with varying levels of intensity.

Clearly, 60Hz harmonics screams noise from the power main, but the whole setup is disconnected entirely from the wall (powered by battery at the moment).

Here's a shot of my actual current layout. In this case the ADC inputs are tied to VA / 2 through a simple passive filter (lower board), which in an ideal world would produce a bunch of zeroes on the ADC. The LT1965 is powered through a filter with a few decades' worth of caps and a ferrite bead — not strictly necessary but it did seem to help with actual mains noise. These particulars aren't super relevant since varying the power source or the input still results in the same artifacts.

I would really, really appreciate some assistance in identifying potential culprits for this noise. Is this something characteristic of the topology? Or is this to be expected on a $1 Chinese breadboard with jumpers everywhere, and I should just order a PCB with the same layout for further testing? Obviously this is difficult to debug remotely — my hope is that someone will see this and say, "aha! I've seen this before!"

EDIT: highly unlikely to be relevant, but here's the driver (mostly a wrapper around the CS4270 driver currently) that I am using, along with a device tree overlay that is almost identical to the HifiBerry DAC+ Pro one in RPi Linux. Unlikely to be part of the problem, but may be of interest to Linux nerds.


texts: Can I share charge pumps between multiple L6206 H-Bridge drivers?

texts:
I'm building a board to drive 8 separate motors, and I'm planning to use four L6206 dual full H-Bridge drivers.

The device uses N-channel MOSFETS all round and, from the datasheet:

  Using N-channel power MOS for the upper transistors in the bridge requires a gate drive
  voltage above the power supply voltage. The bootstrapped (V BOOT ) supply is obtained
  through an internal oscillator and few external components to realize a charge pump circuit
  as shown in Figure 5. The oscillator output (VCP) is a square wave at 600 kHz (typical) with
  10 V amplitude. Recommended values/part numbers for the charge pump circuit are shown
  in Table 6.

So, fine, done that, all works. But if I have four of them, do I actually need four separate replicas of the charge pumps? My guess is that they're pulling the MOSFET gates up, which suggests minimal current draw on the VBOOT pin. Can I reasonably save some space/parts/assembly by making one circuit and sharing it? The datasheet doesn't specify characteristics for the VBOOT input as far as I can see.

simulate this circuit – Schematic created using CircuitLab

Or is this in the "might work but stupid and high-risk" category?


texts: multiple diode problem computer simulation and hand answer don't match

texts:
I am trying to solve this circuit-

Here is what I have done till now-

Assumed every diode is forward biased.
Used mesh analysis to find that in left mesh the current is -1.63 mA, that means my initial assumption was wrong about D3 diode. And it's reversed biased.
In the right mesh I found 1.74 mA. That means both D1 and D2 are on.
I again solved this circuit by starting with D3 off and D2 D1 on and found out current in the right circuit is 0.678 mA.

Is my process and results correct? Does the values and diode states correct?

And in PartSim my simulation produced this output which is not matching, but why?


texts: How to choose the resistances for this current generator?

texts:
I have to design a current generator (schematics in figure) which gives as output about \$10\ \text{mA}\$ if it receives as input \$5\ \text V\$. I have to choose the resistances \$(R_1, R_2, R_3, R_4, R_5)\$ which allow me to get this output.

I think this is the datasheet of the TCA0372.
I do not understand how this circuit works, and how can I choose the resistances
EDIT:
I chose  \$R_1=R_2=R_3=R_4=1\$ \$\text k\Omega,\$ in order to get the gain $$G=1\implies V_{out}=V_{in}=5 \ \text V$$ Then \$R_5=465\ \Omega\$ so \$I_{out}=V_{out}/R_5\$ and the load resistance \$R_L=150\  \Omega\$
and I got \$I_{out}=11\$ \$\text{mA}\$


texts: Why is impedance represented as a complex number?

texts:
Let me know one thing. Why is impedance represented by a complex number when considering loss?

Usually it is said that imaginary part is because of loss. Is it True?
If it is true then does that imply that a line with characteristic impedance Z0=50 ohm has zero loss?


texts: Brown-out detection with an external clock ATmega1280

texts:
I'm using ATmega1280 with an external clock and I have some questions about the "safe operating area" for preventing EEPROM corruption with BOD.
The external clock is: Crystals 14.7456MHz 18pF HC49S SMD by CITIZEN, without clock division.
In the datasheet of ATmega1280 the flash and EEPROM unit gets two clock arrows as below: (page 39)

and the "safe operating area" is: (page 358)

The line is linear between 2.7V and 4.5V, so according to this figure I'm supposed to be above 4.21V to be in the safe zone, but my Vcc is 3.3V and the system works great without any problems. what I'm missing? this graph is for the internal clock? (page 359)

How do I need to calculate my safe zone according to my external clock?
LINK to ATmega1280 datasheet
Thanks!


texts:
The PMBus specification (>= Rev1) specifies that the query command returns a data byte with a binary bit pattern of 001 in bits 4:2 if the format used for the queried command is a "16 bit signed number".

this is the only mention I can find of this data format (distinct from other 16 bit formats already covered by other bit patterns) within the PMBus standard.

What does this relate to? (AVS maybe?) Am I missing something silly?

*Note that I come at this from the device designer side rather than the host system side


texts:
I am in need of some help designing my battery pack. I have a few concerns, mostly around charging.

My plans consist of using a microUSB boost converter to bring the voltage to 16.8V for charging. This will go into a balancing charging BMS board hooked to four 18650 LG MJ1's. The output from those will go to a buck converter to bring the voltage to 12V and be hooked into a USB-PD car chargers guts. If the design is right I should get my USB-PD charging capability, an ability to charge the batteries with a CV setup.

The CV setup has me worried. I have seen posts warning about the high amps a highly discharged 18650 pack can pull when charging on CV alone. Since I plan on really only charging at 5V 1A (boosted to 16.8V) or at max 2A (again, boosted), do I need to worry about that? I am by no means an electronics expert and that is why I am asking.

I've seen some posts suggest wiring a resistor in series with the BMS to lower the number of amps that could be pulled. Through my poor calculations, I figured the required resistance to be around 56 ohms. Is this required? I don't want to starve the batteries of charging capability unless I have to.

If you have any questions or ideas for my build let me know!

I said screw it, I will find out temps and potential problems with the circuit to hopefully answer some questions others like myself may have. These will be coupled to a 4S setup with LG MJ1 cells. Here are my purchases:


texts: How to explain the reflected voltage on the oscilloscope when a pulse is sent through a transmission line with a capacitor at the load?

texts: This is waveform that I got on the osciloscopewhen experimenting in the lab. A pulse was sent through the coaxial cable was used with a capacitor at the load. I have my own idea why is this happening but I am not quite sure.


texts: Identification of 6-pin chip marked W134H?

texts:
Would like to ask for help in the identification of 6-pin chip marked: W134H  (it's not a clock signal generator)

I think it conditions very low voltage (5mv-200mv) analog voltage inputs for a chip marked AX4A which is an LMH6611 single supply rail-to-rail Amplifier.

Thank you for any help!  (uploaded a better photo)

https://ibb.co/4TnsGJM

https://ibb.co/xLKkHqm


texts: Control of 12V stepper motor using L293D dual H-bridge

texts:
I've been trying to get a new 12V stepper motor to turn using the circuit below. I connected the 12V to the IC but this led to my Arduino smoking and burning out.

I'm thinking that the 12V is being pushed into the Arduino due to the common ground or my wiring is wrong. Should this circuit work be safe or will it burn out another Arduino if I connect it up again?


texts: Prototyping with a very small surface mount connector/socket

texts:
I've got a Satellite modem with a connector that mates with a tiny 10pin by 10pin Samtec SS4 series surface mount connector.

The question is, how would I prototype with this component? I am thinking I will need to get a custom breakout board created and someone with precision equipment to solder the socket onto it for me?

Essentially, the strip has a centre-to-centre pin pitch of just 0.4mm and head pin is 0.23mm in width, making the distance between pins a tiny 0.17mm.

More information on the socket:
http://www.samtec.com/documents/webfiles/cpdf/SS4-XX-X.XX-X-D-X-XX-TR-FOOTPRINT.pdf


texts: How does the diode work out the reverse voltage spike of DC motor?

texts:
I'm learning myself a simple circuit, where a BJT is used as a switch for a motor load. It'd look like this example; you can easily find tons of such.

In the internet, they say that I need a diode that:

allows the current to flow in only one direction
can hold out some short-time high voltages
is connected in the opposite direction of usual current flow (thus opposite to a short-circuit for the motor)

because, when stopped, the motor (especially its inducting part) creates a reverse voltage, and it can damage the transistor.

There are some parts that I can't understand for the moment.

1

When does the motor do that, in this circuit? Is it when the switch is powered off (by having GND to the base)? If so, if I do a PWM with the transistor switch, would it occur a hundred times a second?

2

What does the motor really draw?

Some says it tries to pull a certain amount of current, thus driving the voltage way up high, until it gets what it wants (or unfortunately fry up something else). Is it right?

Some just says it creates a voltage difference.

3

They say that if we put a diode like that, and the motor inducts some current, the current will not be forced out from the transistor, but rather flow through the diode.

Then, is there no voltage difference between the (+) and the (-) of the motor (which is respectively the two nodes of the diode)? Current flowing without a voltage difference feels a little weird for me. Is it about the induction thing? I thought that the induction creates an electromotive force, which I thought of as a voltage difference. If the motor makes a reverse voltage spike, then I would need a resistor (in series to diode); if not, the high node is connected directly to the low, passing infinite current.

Thank you very much for your answers, in advance. I think I learned some electromagnetics years ago, but it's like a whole new thing to apply in real-world.


texts: Modelling priority/importance in a digital circuit

texts:
I'm attempting to create a digital circuit that has three inputs representing binary numbers. For example 001 would equal 1 in decimal , 011 would equal 3 and 111 would equal 7. So overall the highest number you can make is 7.

I have been designing a circuit that compares two of these sets of 3 numbers and I have realised that what I'm actually doing is comparing sets of 3 inputs, rather than looking at the numerical values 0-7. What this meant for me in practice was that my circuit output whichever set contained more 1's so that 101 would equal 110 because they both have 2 1's when in fact they are two different numbers when we convert it to binary.

I was wondering if anyone could tell me how to go about modelling the binary logic within my system so that I can be comparing numbers from 0-7 rather than sets of 1's.


texts:
My question is about the below power bank charging module. We connect 3.7V 18650 type batteries to this module. Then the output voltage of this module via USB is 5V. My question is how it returns 5V using 3.7V batteries.

Here is the product link :
Mobile Power Bank Module


texts: PI Filter After Bridge Rectifier - Inductor at Positive Line or Negative Line

texts:
I was reading the InnoSwitch-CE Family Datasheet for a design I'm currently working on.

At the Circuit Board Layout Recommendations section, it's stated that the inductor should be placed between the negative terminals of the filter capacitors if a pi type (C-L-C) filter is used.

In schematics language, they recommend this:

simulate this circuit – Schematic created using CircuitLab

instead of this:

simulate this circuit

What's the difference? What could be the point? What makes the first arrangement more preferable (according to the datasheet, at least)?


texts: How to design a fair Synchronous Arbiter?

texts:
The problem i am facing is this, i need a Hardware circuit which decides fair between for example bus requests which happen at the same time.

Example:
A and B are the two components which do memory requests:

if A does alone an Request he is immediately accepted.
if B does alone an Request he is immediately accepted, too.

The tricky part come when they do a request at the same time, so it should be that they win at the same ratio.

How to design such an algorithm?
Which books do teach about such stuff?
Exists there some standard algorithms which do what i need (doesn't need to be hardware specific, but it should be easy to convert them in hardware)

Edit 1

How do i need to change the algorithm if i have > 2 components?
Would a counter for each component enougth which i count up if i had serviced the component, so i can easily decide which to serve if there are races?


texts: I currently intend to measure the Plane Capacitance of a PCB I'm going to build. I do have the measuring equipment (an VNA from R&S) but am unsure how to design the testpoints I am going to use (which connect to the relevant planes). Is there some kind of industry-standard connector type or how would you go about hooking up the equipment to the PCB?


texts:
I am attempting to build a circuit that excites a sensor which requires an AC current of ±1mA and 20kHz frequency. For this, I used voltage to current converter integrated circuit XTR110, which is controlled by a sine wave generator. However, this IC can only produce a positive current, so the output is AC current with DC offset. To ensure that the sensor is excited only by ±1mA current, I added an inductor of 39mH between the output terminals of IC and a capacitor of 100nF in series with the sensor to completely remove the DC offset as shown in the schema.

The sensor is represented by the R_Loud in the schema. I got an AC current with no DC offset flowing through the R_Loud. However, the peak to peak of the AC current is affected by the resistance of the R_Loud. In other words, when the resistance of the R_Loud increases, the AC current reduces.
is there another way to remove the DC offset and ensure a stable AC current?!
Or, is there another integrated circuit that can provide a negative current as well?!
Note: I'm not an electrical engineering specialist


texts:
Does anyone know what kind of connector this is? It is used in a battery pack of a car for Can bus, k-line and power.

Dimensions: 12mm x 10mm x 6.5mm

Edit: this is a similar 12-pin female connector (on the right):


texts: Saturation current in Ebers-Moll equations for BJT: what is it and how to measure it?

texts:
In Ebers-Moll Equations for common emitter BJT the inverse saturation current \$I_s\$ appears as a parameter. What is the saturation current \$I_s\$ exactly and how should I measure in a common emitter BJT (like the one in picture)?

More precisely there is an approximation of the model where the current \$I_{ES}\$ appear :
$$\displaystyle {I_{\text{E}}=I_{\text{ES}}(e^{\frac {V_{\text{BE}}}{V_{\text{T}}}}-1)\\I_{\text{C}}=\alpha _{F}I_{\text{E}}\\I_{\text{B}}=(1-\alpha _{F})I_{\text{E}}}$$
The first equation is simply the diode model for the junction BE and that current \$I_{ES}\$ should be the reverse saturation current of the base–emitter diode.
So can I measure it by simply doing the following steps?

Invert generator VBB (to get reverse bias of BE junction)
Put ammeter in series with Rb and measure the current \$I_{ES}\$

If this is the case, can the junction CB be reverse or non reverse biased? Does it make any difference on  \$I_{ES}\$?

(A secondary doubt is about the parameter \$\alpha_F\$, the common base forward short-circuit current gain: is it easily measurable or should it be read on the datasheet of the BJT model used?)

Nevertheless in the complete Ebers-Moll model there is  \$I_S\$, which is simply defined as saturation current. Is it still the inverse saturation current of the BE junction? How to measure this current?


texts:
Li-Poly battery voltage changes a lot while discharging — from 4.2V to 2.7V. Most modern digital ICs (I'm currently thinking of Cortex-M3 microcontroller and an RF module) require input voltage levels of 2.7V-3.6V.

So, I think that connecting them to 4.2V power supply will most probably result in a dead IC. How this problem is solved in actual devices?

I can only think of two solutions: the first is a buck-boost converter, which should certainly work, but is really hard to build (at least for me; I never had success with self-made DC-DC converters, not to say the ICs for them are hard to obtain in local Russian stores); and a linear LDO regulator, which will still incur some dropout, maybe as low as 0.7V, but it means that the smallest battery voltage with which the circuit is usable is around 3.4V, and quite a big part of charge is then left unused.


texts: Servo does not rotate to the absolute minimum position

texts:
I did a bit of Googlin' but I couldn't find anything about this.

My hexapod uses analog servos (these ones) to move the legs around.

I have the control line hooked up to a servo controller (which is in turned controlled by an STM32 Discovery board's I2C lines).

The power line is connected to an output of a voltage regulator circuit capable of providing 11A of current - each one of these regulator circuits connects to 9 servos, there are heatsinks on the LM317 and the Darlington pair.

The ground naturally... goes to ground.

Anyways, the servos do move, but for some reason they do not reach the minimum that I can achieve when rotating it by hand. I'm trying to figure out if I'm an idiot or what.

The pulse width that the servos accept ranges between 0.5ms for minimum and ~3 ms for maximum. This constitutes about a 160 degree rotation.

When I set the pulse width to 0.5ms, it moves to a position and stops. It will not move if I reduce the pulse width any more (so 0.4 ms will not move it). However, the position it reaches for PW = 0.5ms is not the minimum or the maximum, there is still quite a bit of room to move (about 15 degrees I think). I can move it further when I shut the power off.

Is there any way to make it move there? I kind of assembled the whole robot while considering it would move to the extremes, but since it doesn't, the hexapod can't lift his feet up as high as I wanted to, for example.


texts: Precision timing using arduino and external clock

texts:
I'm working on a very time limited project (8 weeks). Basically I need to perform measurements and save to memory.
2 identical boxes, 4 hours and no wireless or wired connection.
Each box is measuring on accelerometers.

Due to the limitation in time I need a platform with minimal soldering, PSU design and so forth.

The Arduino is an obvious choice but the crystal is simply to unstable. I need precision of +/- 30 ppb of clock frequency.

I've found OCXO that meet spec but not at 16Mhz..(or 8)..
Changing the clock speed to 12 MHz would help me a lot - but then the libraries becomes an issue.

My idea so far is to use arduino, write a program that sets a digital pin high, then waits x microseconds and then sets digital pin low. This way I can calibrate the x using a oscilloscope to land the right frequency of sampling.. hmm

Ideas?


texts: Why do we add Resistors on differential op. amp

texts:
Why do we use resistors i differential op. amp circuitry where the relation between the resistors is constant?..
Is it only to define the gain, or does it have more to it?

The question is linked to this picture

it is said that R2/R4 = R1/R3, but why does it has to be like that?

the formula for V_Out is given to be


texts: Please explain the purpose of the resistors in this scenario

texts:
I came across this schematic and I am wondering why there are two different resistors on the output pins. I know that there has to be some resistor because otherwise if one pin was hight and the other low it would cause a short, but how would one determine the required values of these resistors and what other purpose could they serve? The pins output 5v.

The circuit is taken from Arduino TV out and the MCU pins are from a 5v Arduino and connect to a composite RCA cable.


texts: Can I use two DC-DC Converter modules to generate a +5V and -5V Rail?

texts: These converters from Pololu look great (https://www.pololu.com/product/2831), but I need both a positive and negative rail. Can I use two of these to make a +5V and -5V rail? For example. if I tie the + terminal on one to the - terminal on the other and tie that node to ground and then use the respective output terminals as +/-5V rails, would that work?


texts: Too High Voltage Drop across Transformer's Output

texts:
I want to get very high current flow thought secondary winding of transformer on my 3 Ohm load. As I apply high voltage of secondary to the load the voltage across it drops dramatically. Only about 2% of initial voltage (of unloaded secondary) is presented at the load. What can I do to achieve larger voltage drop across the load?

If the secondary winding would have same ohmic resistance as load R1, that is 3 Ohms, would then half of secondary's unloaded voltage be then dropped across R1 (and half across secondary winding)?

Here, I used two transformers to power up my load. I need higher voltage (+100V), so 220V was only accessible, but I couldn't plug my load directly into wall socket because the fuse would break at the same moment I would plugged in my load - so I used transformer which would allow me to use same voltage but higher currents. In addition, I was counting for load to sink few tens of amps, but transformers weren't made for such currents. But I meant to use them just for a few milliseconds - in pulses so transformers would have time to cool down and not melt. Here are actual specs for both transformers: 220V to 15V - secondary's current is 4A and primary's 1A, 15V to 220V - secondary's current is 0.5A and primary's 1A.

I know that none of two transformers meet my requirements but I was sure that second transformer could generate few tens of amps only for a fraction of a second. And that is really basically what I want; a transformer that could supply around 220V or so while generating current of few tens of amps for a few milliseconds then a second or so of pause until next current spike. But would I need a transformer that can supply 100A of continuous current through secondary, even if wanted to use same amount of current for only a fraction of a second?

simulate this circuit – Schematic created using CircuitLab


texts: What is the total resistance of a LED array?

texts:
First time poster and a hobby EE enthusiast here.

I want to turn on a LED array with a transistor switch and I'm having trouble with determining what will the total resistance on my transistor collector be. And without that I can't determine what should my base resistor be.

This is part of my schema, the switch will be a pin on an Arduino that can supply 5V and max 40 mA:

I got the LED array scheme from an online LED array calculator and it gave me the info that the array draws 60 mA current - from which I figured I could get the total resistance of the array with Ohms Law: 12V/0.06A = 200 Ohm. If my collector resistor is 200 Ohm that would mean that my base resistor should be 2k7 Ohm.

Is that correct? Can a treat the array as 200 Ohm resistor on the collector? Or is the total resistance the parallel of 3 resistors -  110 Ohm? Any advice or a hint in the correct way is appreciated.

Thanks,
Tadija

Edit: LED Red 2.0V, 20mA


texts: HF RFID 13.56MHz Interference from WiFi/BLE 2.45GHz?

texts: If a Wifi/BLE antenna were placed within a multicoil loop antenna for 13.56MHz HF RFID, would there be significant crosstalk/interference?


texts:
I have an infrared emitter connected to a Raspberry Pi which allows me to send signals to my air conditioner so that I can turn it on / off / set settings etc.
The problem with my current electric setup (which I found somewhere in the Internet) is that the range of the IR emitter is very limited (<10cm). However, I would like to place the Raspberry Pi incl. IR emitter somewhere further in my room (<5m distance). Currently, I have to mount the Raspberry Pi and IR emitter in such a way that the emitter is very close to the AC IR receiver area.
Does someone know which parts I need to rewire / change so that the range increases?
I’m using the following parts:

IR Emitter (e.g. 940nm IR LED 40deg - 40 degree viewing angle. Bright and tuned to 940nm wavelength)
Transistor (e.g. PN2222 Transistor - to help drive IR LED)
Resistor (10k Ohm resistor - goes between RPI GPIO and the PN2222 transistor)

And here is a link to the repo where I documented the setup and code: https://github.com/SilverJan/rpi-ac-control


texts: Safely driving a SG90 servo with AVR PWM

texts:
I've read that servos tend to draw anywhere from 10mA to 200mA. Is there a standard configuration to drive servos using MCUs without directly connecting them to the output pins of the controller? Or is the high current drawn from the supply rather than the PWM control signal? I do not have a DMM immediately available with current measuring capabilities to test this.

Also, I get significant dimming of LEDs also connected to my supply when driving these servo devices. The supply I'm using is rated at 5.5V 750mA that I regulate to 5V using an LM7805 (rated at 1.5A), so I do not think over-current conditions is the issue here.

Any ideas?


texts: Clearance and creepage requirements in EU

texts:
I'm looking for the clearance and creepage requirements between live voltage (230V) and SELV (Safety Extra Low Voltage) in the EU.

I had a look at this and other questions, but I rarely see numbers mentioned, and when I do see them, they often contradict each other. So far I've seen clearance distances of 3mm, 5.5mm and 6mm. For creepage I haven't any numbers at all.

So, what is required?

(PS: can somebody add the selv tag? Thanks)


texts: Broadcast range of an FM radio station with given transmit power

texts:
I'm buying FM transmitter 0.2 watt at Lazada to broadcast for my village community at my area. Not a normal small FM transmitter for car or portable low watt (about 10mW-100mW) which broadcast up to 10 metres.
Is it possible to broadcast up to 500 metres? Because I don't want to get trouble to broadcast and get caught. I want to broadcast for my community only and play my own music without any ads (like what commercial radio does).
P.S. I'm from Malaysia and planned to broadcast up to 500 metres. Not long range like what commercial radio and government radio does.


texts: Building a heat press: Nichrome question

texts:
I would like to build a 2ft x 2ft x approximately 1.5" heat press consisting of 2 heated plates, a PID controller with thermostor, and a hydraulic press. The plates will need to maintain 60-80c as evenly as possible.
I don't have much electrical experience but have been researching this for a week or so now. It seems the ideal thing would be to use a thin insulated nichrome, machine out a piece of aluminum that is 22" x 22" x .5", run the nichrome back and forth as many times as possible, and embed the aluminum in a 2ft x 2ft x 1.5" piece of steel.

The more nichrome with lower amps running through the plates the more even the heat but I run into insane voltage requirements the longer I stretch it.

Is there a way around needing thousands of volts to run 40awg nichrome 100 or more feet?
Does someone have a link to a prefabricated version of these plates that would be cheaper than building them?
Not an electrical engineering question, but would these plates stand up to a 20 ton press?

Any design input, helpful equations, or other advice is greatly appreciated!

-Mac


texts: SIM808 always returns the same temperature

texts:
I have a SIMCom SIM808 module built up on my own breakout board. Whenever I query the temperature I get back the exact same temperature, 24.11 (deg C) despite the actual temperature in the room varying. This happens for days on end, over dozens of queries.

AT+CMTE?

+CMTE: 0,24.11

OK

I have tried this exact same AT command sequence on a Adafruit FONA with a SIM800H module and I get proper varying temperatures.

AT+CMTE?

+CMTE: 0,23.26

OK
AT+CMTE?

+CMTE: 0,23.29

OK

The User Manual is the same for the entire SIM800 series, So I haven't been able to find any specific guidance on my SIM808 vs the SIM800H

Everything else on this SIM808 module seems to be working well, just not the temperature. Has anyone else run into this? Is there some SIM808 specific setup I'm missing?


texts: Monitoring software for embedded application

texts:
I'm looking for a Windows application to collect data to a host PC from an embedded application (PIC microcontroller).
The communication between host and embedded application is via Ethernet.

It would have to be the application that sends data rather than the host go read them.

I was away on a solution using SNMP (with MRTG on the host PC, for example) but this protocol does not send data when they are present on the embedded application : the host retrieves the data at regular intervals.
If the host was a UNIX machine, I could use inetd to start the recovery values with MRTG but I don't know an Windows equivalent (and I do not have the skills to program a Windows service).

My next solution is to use a HTTP server on host and send data via GET or POST.

But perhaps there is a better solution. Do you know of software that would do that?

Thanks


texts:
We are designing a SD card interface with a processor.The processor supports  SDR104 with clock frequency of 192MHz. Along similar lines,the UHS modes and corresponding clock frequencies mentioned are,
SDR25 - 48 MHz ;
SDR50 - 96 MHz ;
DDR50 - 48 MHz ;

Don't we need at-least 208 MHz clock frequency to transfer 4 bit of data in SDR104 Mode(at 104MB/s) or about 50 and 100 MHz for SDR25/DDR50 and SDR50 modes?
  If the maximum achievable clock frequency is 192 MHz,are we still operating in SDR104 mode?

Please help me to understand these data rates and clock frequencies.


texts: active bleeder circuit for capacitor discharge

texts:
I have a circuit with a large capacitor, a solenoid and an N-channel FET fed by a 60VDC supply.  When I trigger the FET the capacitor discharge activates the solenoid.  This all works as expected (there are additional components -- resistors and diodes and such).

Now I need to add a safety circuit such that if the power is turned off and the supply line quickly falls towards ground potential the capacitor will quickly (e.g. <2sec) discharge to prevent accidental firing of the solenoid.  Due to various constraints a bleeder resistor will not work.

I have done a pretty thorough online search and haven't come across a simple circuit that does this.  It seems that a P-channel "safety" FET connected across the capacitor in series with a bleeder resistor, with the gate connected to the power supply would do the trick -- when the supply is high the FET is off, and vice versa.

Is this a reasonable approach?  Some of my concerns: What happens when the supply is turning on?  Will the safety FET also be on causing a large load on the supply?  What about limiting the source-gate voltage to something reasonable (or is there a FET that can do the job and handle 60V)?  I'm trying to get away with as few components as possible due to severe space constraints.

Here is what I had in mind (solenoid and trigger FET not shown). A further constraint of the problem is that each of the 64 solenoid circuit "units" (the dashed box) is independent and, because of cabling/connectors and such, additional wires to it are not allowed. So, there can be no separate "discharge" signal to each unit -- the only notice a given unit gets is that power has dropped.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm using planning to use CP2102 as an USB/UART transceiver. Datasheet (can be found here: https://www.silabs.com/documents/public/data-sheets/CP2102-9.pdf) on page 21 shows example of self-powered  schematic, and that's exactly my scenario: external 3.3V LDO regulator which feeds several ICs on the board, including CP2102. In this case divider circuit is needed in order CP2102 could safely detect USB Vbus presence. However, same picture shows that in total 4 decoupling capacitors are required, 2 on Vdd pin, and 2 on REGIN input to internal 3.3V regulator.

But these two pins are physically adjacent to each other, see picture below:

Do I really need to use 4 caps? Or I can connect these two pins by a trace, and use 2 capacitors for decoupling?
My schematic for this part of the board so far is below:

Also, can I omit resistor from 3.3V to RESET pin? It would be very convenient to connect them directly by short trace underneath the chip.


texts: What is the most efficient method of storing statistics in an FPGA?

texts:
I'm trying to work out the most efficient way of storing statistics in an FPGA.  Here is a point form summary of the situation:

Many 32bit and 64bit values are calculated / stored.
Any number of the values could update in any clock cycle.
A number of the values will be updating in most clock cycles (byte counts, time counts).
The frequency of change is something on the order of 200MHz, so running a separate clock faster to do multiple calculations per system clock is not really possible.
The calculation of the values is generally pretty simple, it's the storage and updating of them that I am worried about.
I am looking for efficiency of resource usage, as implementing all counters in FF's will not be possible with the available resources.
If I put the stats registers in logic RAM (LUT's), then I can't access more than one at a time, so updates get really complicated.

Is there a good way of storing statistics in LUT's where it is possible to update more than one at a time, given that they may update in consecutive cycles?


texts: Can Average Power of a 3-Phase AC motor be calculated from Mean Current & Voltage RMS from each winding?

texts:
If this is possible could a formula be provided. + Explaination.

Thanks very much in advance.

FYI I am completely new to this site so please be kind. Could I ask that any criticism be constructive. Any questions/further clarity of the problem required please feel free to ask.


texts: Max switching frequency of GPIO pins of modern cheap FPGA

texts:
How can we estimate maximum switching frequency of GPIO FPGA pins? What is maximum data rate achievable when connecting two FPGAs together without using of integrated high-speed transceivers? Or when we are bitbanging GPIO to VGA, what is maximum pixel clock?

I'm interested in modern cheap Altera devices, like Cyclone IV, Cyclone V (E version, not GT), and Xilinx devices like Spartan 6.

There are some figures in datasheets saying 300-400 MHz for GPIO pins, but are they real? How can we drive pin at 300-400 MHz when maximum core clock is only 100-150 MHz?


texts: What could happen to my cells? I overcharged them a bit

texts:
I left my 3.7 V Li-ion cells charging for a long time with a low current 5 V charger. Now when I check the voltage, it is at 4.31 V. The cells didn't get hot, not even warm, but I'm afraid of what this could mean, since they were only supposed to charge till 4.2 V.
Does this mean they are now useless? Or lousy? It's a lot of cells in parallel and losing them would be the worst, so I need to know if 4.3 V is not so bad or have I destroyed them, or maybe decreased the capacity?


texts:
This is a capacitive moisture sensor circuit. C1 is the equivalent capacitor it tries to measure. Input v1 with 54.7% duty cycle is a square wave generated by a 555 timer. Output is v3 (point 3 in the graph to GND).

I tried to represent the square wave as Fourier series and use impedance model to find the steady state output. However, it seems that the diode is the key here but I don't know how to get the impedance of that diode.

Ultimately I'm trying to understand how to analyze this circuit and get the relationship between C1 and V3. I'm guessing there is an entirely different way other than the impedance model?

Thanks for any help!


texts:
Here is my task:

How to solve this? I'm confused because of only one input in opamp.

Edit:

Here is solution:

But I'm still confused why is there only one input to opamp


texts: What is the way to calculate the Voltage gain of cascade common-emitter BJT amplifier?

texts:
I have a problem of calculating the voltage gain of cascade common emitter BJT amplifier using small-signal model

Assume that the reactance of the capacitor is negligible. The circuit is bias at \$I_{C1}=0.1mA\$ and \$I_{C2}=1mA\$ and \$\beta=100\$ for both BJT

simulate this circuit – Schematic created using CircuitLab

$$A_v=\frac{V_{out}}{V_{in}}$$
$$V_{out}=100i_{b2}*R_2=100(\frac{100i_{b1}\frac{R_1r_{be2}}{R_1+r_{be2}}}{r_{be2}})R_2=100(\frac{100\frac{V_{in}}{r_{be1}}\frac{R_1r_{be2}}{R_1+r_{be2}}}{r_{be2}})R_2$$

using \$r_{be}=\frac{25\beta}{I_c}\$, \$r_{be1}=25k\Omega\$ and \$r_{be2}=2.5k\Omega\$

by then I get the result \$A_v=1785\$

However, the result of my text book says that it's 1765 and \$r_{in}=25.25k\Omega\$ which I think that \$r_{in}=r_{be1}\$

Can anybody explain what I missed in calculating or what I did wrong.


texts:
On schematic below LDO U4 is disabled and U2 is not powered.
Can the high output from U1 feed U2 inadvertently through the ESD protection diodes on U2's input?

simulate this circuit – Schematic created using CircuitLab

Assume that U2's input protection is implemented this (rather standard) way:

simulate this circuit


texts: VDC for little centrifugal pump. How much tolerance?

texts: Can I run a little 7 VDC (1.2 watts) pump with a 9 VDC/0.5 Amp power supply?  (The pump is for a drip to attract birds.)


texts: Simplifying a (Sum of Products) Don't care Function with a (Product of Sums) Function using (K-Map)

texts:
The functions:

f(u,v,w,z)=π(0,4,8,12,9)
d(u,v,w,z)=E(1,5,3)

π represents the product of sums(pos) a.k.a the product of maxterms
E represents the sum of products(sop) a.k.a the sum of minterms
f represents the regular function
d represents the don't care function

The K-Map:

uv\wx
   |00  |01 |11 |10
00 |0   |d  |1  |1
01 |0   |d  |1  |1
11 |0   |d  |1  |1
10 |0   |0  |1  |1

So I know for pos you're supposed to group the 0's in the k-map.
I know in the don't care function, the designer picks if they want to make it a 1 or a 0, my prof told the class if you can group a d in the k-map then do it.
I know for sop you're supposed to group the 1's in the k-map.

Since the second function is a don't care function does the E(sum of products) become irrelevant in solving this problem? So I would try to group the 0's in the k-map together since the first function is a π(product of sums function)?
I've never come across an example like this and couldn't find any similar examples online. Any help would be greatly appreciated.


texts: The right way to control EN pin of TPS63806 using STM32 MCU

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I have a 3.3v STM32L4 MCU powered by it's own supply and an external circuit powered by a buck-boost TPS63806. The power source is a 18650 battery, providing from 2.8-4.2 volts.
I want to turn on and off the TPS63806 using a digital pin of the MCU connected to EN pin of the converter and I would like to know the right way of doing that. For now, I have 2 options:

Use a 2N7002 FET (as in the attached circuit). I have no idea how to calculate the value of R17.
Use a voltage divider with 10 and 15 kOhms (or a single resistor) between EN and the PIN of the MCU, but I need to get about 2.5 volts on the EN pin. Could I also use 100 and 150kOms?


texts: Raspberry C code getting stuck due to infinite for loop

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I am new to raspberry pi (Raspbian). Any guidance in the matter will be appreciated!

I have written a C code which includes C Filehandling & wiringPi.h library for GPIO manipulations.

I have narrowed down the problem to the empty infinite loop. If I include it in the main function, my terminal freezes and not even Hello world! gets printed.

Should I do implement this infinite loop in some other way because it's a raspberry? If so, then how?

This is how the main() function looks:

// Main function
int main (void)
{
  printf("Hello world!");
  delay(1000);

  // Read updated preferences file
  readPrefs();

  // Initialize WiringPi Library
  wiringPiSetup () ;

  // Setup falling edge interrupt on INPUT pin
  wiringPiISR (INPUT, INT_EDGE_FALLING, &myInterrupt0) ;

  // Setup OUT1 & OUT2 as output
  pinMode (OUT1, OUTPUT) ;
  pinMode (OUT2, OUTPUT) ;

  // Initialize motor
  motorSTOP();

  for (;;)
  {
    // Empty loop since all the work is done in Interrupt routine

  }

  return 0 ;
}

Here is the interrupt routine:

// Interrupt Service routine
void myInterrupt0 (void) {

    motorFWD();
    delay(FWDDelay);

    motorSTOP();
    delay(WaitDelay);

    motorBCK();
    delay(BCKDelay);

    motorSTOP();
}


texts: Mapping the hex address representation to a specified conductor of system bus

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I interested in how does implement the mapping of hex address representation to the specified contact of system bus. For example:

Let we have logical address 0xAABBCCFF00 and we want to read a byte located by that address.

How does a contact the system bus used to impulse transferring will be determined using that address representation?


texts: Can batteries in series be reverse charged if the circuit is open?

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Suppose I have four AA batteries hooked up in series and I forgot about them and one of them eventually got completely empty due to self discharge.  Also suppose that these batteries are not connected to any external circuit.  Can that empty cell be reversed charge by the other cells?

My understanding of batteries is that the chemical reaction which releases the stored energy cannot proceed unless the batteries are connected to a load so that the electrons release by the reaction can flow through the external circuit.  So in my example the batteries should be fine.  But maybe something can occur in the empty cell that somehow make a current flow even though there is no external load to complete the circuit?

The reason for my question is that I am wondering if it is safe to leave four rechargeable NiMH batteries (in series to provide 5V) in an DIY device I built if I have a switch that disconnected the batteries from the circuit.


texts: I have two separate breadboards, on each breadboard I placed NE555 and both are configured in astable mode. Breadboard 1 is configured to 200Hz @ 50% duty cycle and Breadboard 2 is configured to 1.8Khz @ 50% duty cycle. Each breadboard is tested separately and measured with oscilloscope and the output of both is perfect. Now when the two breadboards are connected to the same battery 12v 7AH, the output of breadboard 1 changes to 1.2khz with fluctuating duty cycle while output of breadboard 2 stays at 1.8Khz and 50% DC, but if the breadboards are connected to different batteries, the output is OK, that is breadboard 1 gives 200Hz and breadboard 2 gives 1.8Khz. The problem only happens when both breadboards are connected to the same battery, and the circuit will be powered from only one source. Please, this is strange, I've not seen it before, please I need help.