texts: connecting a GSM booster directly to a mobile device?

texts:
I live right on the edge of mobile reception. I just get a signal with an external antenna, but it is weak. I am thinking of getting a small indoors GSM booster, like this.

I was wondering if it might be possible to connect the booster out-aerial socket directly to the external aerial socket on my phone, instead of using the phone's internal aerial, as is intended with these devices. I think that it might reduce other local radio noise that the phone picks up, and provide a stronger link. But I'm not sure if it's safe to do so (wrong impedance or something?). If that's the case, would there be a safe way to directly connect the devices, with some kind of coupler? Is it going to provide any benefit over just having the GSM booster set up normally?


texts: How can I modify this voltmeter circuit to show 0.00V when nothing connected to the output

texts:
I have a voltmeter and ammeter combo which sense the voltage and the current at the output. My problem is when nothing connected to the output it shows 0.06V else 0.00V. I tried to connect the output the GND but the value is still the same.

The other problem is it shows a little bit higher value than the real, for example 7.07V the original and 7.10V the displayed.

How can I modify this circuit? The OUTPUT(+) is the output where I want to sense the voltage. The ADC connect to an ADC but no marking on the IC.

The op-amp is LMV358 Rail-to-Rail.

No calibration potmeters.


texts: Cheap isolated mains current measurement

texts:
I'm looking for cheaper ways to measure current in a load switched by optoisolated TRIACs, without losing galvanic isolation (no breakdown below a couple kV) between the microcontroller and the load. The rms current can be anything between 100mA and 5A. A Hall effect sensor would work (say, ACS722), but it would cost me around $5.

Here's what I've got so far:

Regular optocouplers (eg 4n25, LOC110): bad choice because I can't just put them in series since my currents are too high. Maybe there is some way to bias the LED and use it in parallel with a shunt resistor? Would be dirt cheap if it worked.
Shunt resistor + isolation amplifier (eg TLP7820, LIA130S, AMC1100, ADUM3190): with these I can amplify the voltage on a shunt resistor (say, 0.05R). Problem is, I now need a low voltage supply on the mains side. Also, isolation amplifiers aren't much cheaper than Hall sensors. Isolation can be achieved by optical coupling, thick gates (eg AMC1100) or even magnetic isolation (ADUM3190), but they all seem pretty much the same to me.
Current transformers (eg 56200C): these seem like the ideal solution, but everything I find seems designed for SMPSs that operate way above 60Hz. I'm not too sure how to get them or to specify them. The examples I find at digital retailers are all ferrite cores and don't even bother to specify primary inductance or saturation current. Shouldn't I use silicon steel cores instead of ferrite? Should I buy the cores and have someone wind them in bulk? Anyway, it should cost me about $3.50 assuming I get the 56200C, make a primary with 2 turns (that's 7.2µH on the primary I guess?) and amplify the output of the secondary with a cheapo opamp.


texts: PNP high side switching with 100 mA load

texts:
I have this circuit to detect tamper status using a switch. When the switch is pressed (ON) then GND is provided to the base of Q3 (2N3906), so that transistor will be in the saturation region and can get 12 V with 100 mA load across R20. When the switch is OFF, then a positive voltage appears on the base of Q3 & there is 0 V across R20.
Also when the switch is pressed (ON), then GND is provided to the base of Q4 (2N3904), so that transistor will be in the cutoff region and LED D7 will be off. When the switch is OFF, then a positive voltage appears on the base of Q4 & LED D7 will be ON.
I am at a learning stage, please guide me to calculate the resistor values & other suggestions with explanations so that circuit can work for a long time.

I am really sorry for the wrong text initially. Circuit diagram also updated.


texts:
I need to find the Thevenin Resistance between A and B, I have the circuit shown below.

My question here is: are R2 and R3 in series as well as R4 and R5?

If so, can I then by grouping them calculate \$R_{th}\$ because the 3 resistors will then be in parallel?

Here is the circuit:

Original Circuit :


texts: What are some of the reasons for voltage spikes in voltage regulated DC circuits?

texts:
Decoupling capacitors are often used to protect ICs against voltage spikes
even in circuits that contain voltage regulation of some sort (even something as simple as a zener shunt)

What causes voltage spikes to occur even in a voltage regulated dc circuit ?


texts: Tinning wires that will be screwed in to a chocolate block/terminal strip

texts:
This is subjective per say. But I am looking for other peoples experience.

If I am going to screw eight wires into daughter relay board's terminal block, is there a benefit or advantage to tinning the copper end before?

The environment that the units are to be installed is not near the coast and is not normally damp/wet. Rather dry and hot.


texts: Review pin connections between atmega328p and a microSD card?

texts:
Would some kind soul be willing to review my circuit diagram that connects a barebones atmega328p with a microSD card? The partial circuit is here.

Details. This has already been made on a custom PCB, the pin connections to the microSD were based on diagrams like this.

Did I get them wrong?

I also used pullups on CS, D1 and D2 according to the way they did it at sparkfun, and per a general recommendation here.

The atmega328p is definitely working, I'm programming it using an ISP and it blinkulates da led, and runs some other i2c components. If the ISP is working then it seems to me at least MOSI/MISO/CLK were hooked up correctly.

Basically when the arduino code calls:

if (!SD.begin(CS_PIN)) { errorHalt("begin failed"); }

using the SdFat library, the chip hangs. I've used similar connections with SD breakout boards which seemed to work fine, but I'm going to double check the specific atmega328p <--> microSD connections again, very soon.


texts: RFI/AC Filter Rejection for Instrumenation Amplifiers

texts:
I'm attempting to measure the voltage developed across a very long piece of cable (upto 500m bundle). The issue is that the cable picks up a lot of noise from nearby radio stations and also has a 50 Hz component which I assume comes from the mains.

I would like to have a filter before my instrumentation amplifier, which I use to amplify the developed voltage about 500x. What sort of low pass filter should I have before the inputs of the in.amp? Do I gain anything by using a active filter or would a simple RC filter do the job?

Note: I would like to reject all AC signals so they don't interfere with my measurement. I have tried a RC low pass filter with R = 10K and C = 22u. This gives a cut off frequency of 0.72 Hz. Is there any disadvantage of using such a aggressive filter (other than the fact that the capacitor will charge very slowly?)


texts: Is there a way to define 26mV thermal voltage with simple words

texts:
This 26mV thermal voltage at room temperature is used in non-linear diode equation.
I tried to learn about it to see what it means without getting involved in too much physics but failed to find a simple explanation.

Is there a way to describe it without involving in too much theory and background?

Is this just a number that fits the empirical results like a constant?


texts: KCL in 3 loops circuit and two batteries?

texts:
I have the following circuit where i have two parallel batteries and 3 different nodes.
Since I, on purpose, put no resistors between the positives of the batteries, it seems that the resistors R1 and R2 are function of the battery of "their loop". Let's say I raise the voltage of the second battery (that is in this picture setted to 5V) to 200V or 1kV (or any other number) the current that passes through will not change and will stay at 0.01A as shown in this figure

I tried to increase the value of the second battery to 30V and the current that passes through R1 remained the same 0.01A. The increase in voltage of the second battery will affect each other 4 currents but not the one that passes in R1. The following image shows the circuit with 30V battery.

Is this correct? If I try this with a real circuit, will it behave this way?
I simulated the circuit with the software LTSpice, and also with a EveryCircuit software Simulation.
Why the second battery doesn't affect the current that passe through R1?
Thank You


texts:
I can’t find or describe what this component looks like. Out of curiosity, what is it?

I found it on a PCB for a car alarm, but it has no silk-screen label...

It has a grub screw that is adjustable. The screw does not seem to make contact with the outer spring, but current flows through it no matter.

The resistance and capacitance doesn’t change when the screw is adjusted.

Any ideas?


texts:
I have RSSI calculated as vector magnitude.

$$
RSSI = \sqrt{I^{2}+Q^{2}}
$$

I and Q are 12bit values from ADC. Is there a way to convert RSSI to dBFs and how it is done?


texts: Keepout area (courtyard) around ICs for hand soldering

texts:
I'm designing version 2 of a PCB. In the first version, I placed components as close together as possible to minimize board area (i.e. reduce board cost) and, for decoupling capacitors, to improve power supply decoupling performance. In practice this meant that the edge of a bypass cap pad would be about \$0.5\,\text{mm}\$ away from IC pin it decoupled (basically as close as I could get without violating the kicad courtyards). While I was able to do manual rework on these components, it wasn't all that fun. For rev2 I'm considering placing the caps a bit further away. Specifically, \$2\,\text{mm}\$ separation between decoupling caps and the IC, which is the diameter of the tip of my soldering iron.

As I see it, the downsides to this are:

PCB cost for any additional board space used.
Additional decoupling inductance, due to the longer connecting traces and therefore greater loop area.

Given the difference it will make, the first isn't a huge consideration since I won't mass-manufacture this board. For the second, I used this calculator to determine the additional inductance for \$2\,\text{mm}\$ extra distance and it was marginal (about \$0.56\,\text{nH}\$). I had a look at Electromagnetic Compatibility Engineering by Ott and in sec. 11.3 he mentions a good decoupling trace inductance as \$10\,\text{nH}\$ (for most onboard ICs mine should be significantly less than that). This leads me to believe the additional spacing is completely harmless.

There are of course benefits to keeping space around ICs. Obviously, easier hand-soldering/rework and also easier trace routing, to name just a few.

Have I neglected to mention any other downsides, or incorrectly represented the ones I did mention? My main concern is with the decoupling cap performance. Do other people do something similar for hand-assembled boards?

The PCB in question has noisy digital and noise-sensitive analog components. It's a radar operating at \$6\,\text{GHz}\$. It has an FPGA onboard driven by a \$40\,\text{MHz}\$ clock with fast edges (\$\approx 1\text{ns}\$) as well as a 12-bit ADC, a number of switching converters, an RF mixer, an RF LNA, etc. Given the mixed-signal and high-frequency nature of the board, my instinct is to do whatever I can to minimize noise, which includes proper bypassing. However, based on the calculation posted earlier the extra trace length seems insignificant.


texts: Any way to use external power for multi-meter instead of the 9V battery?

texts:
I have read discussions on NOT to use external power, say an ac adapter, instead of the 9V battery.
But what if  I mostly do is to test for continuity, would it be acceptable in such case?
What other alteratives are possible, such as the 6 x1.5V cells battery case or most recently, use Li rechargeable battery (for phone use) (2 x5V or what? ) for this purpose?


texts: Connecting Sharp GP2Y1010AU0 (5V) to ESP8266 (3.3V) - pin nr 3 - do I need transistor?

texts:
I'm connecting Sharp GP2Y1010AU0 to WiFi module ESP8266.

Sharp GP2Y1010AU0 is powered by 5V and ESP8266 by 3.3V.

I wonder if I need a transistor between Sharp's pin nr 3 and ESP8266?
If yes, can it be BC846? And how to connect it (through resistor?)?

I am a beginner in electronics. Excuse my bad English.
Defozo


texts: Interface a high-quality camera to a computer in real time?

texts:
I have a project that requires high-quality video and stills to be acquired (almost) live with computer controls. By "almost" live, I mean that a five second delay is acceptable, but five minutes isn't. (And by "acquired", I mean a computer readable file, JPG, H.264 or otherwise.)

So far, I'm using a Sanyo VDC HD 3500 camera, that gives me 4M stills and 1920x1080 30 fps video through an IP camera. However, 4M is low resolution for stills, and the optics (for both stills and videos) leaves much to be desired. The HD3500 costs ~US$900.

Canon's EOS 550D/Rebel T2i has ridiculously good optics, can do 18 MP stills, and 1080p that is way better than the Sanyo... And costs US$700 - US$800.

A GoPro HERO HD Camera can do wide-angle 1080p with better optics than the Sanyo... For US$260.

And there are others that optically and sensorly fit the bill much better than the Sanyo. However, neither the Canon nor the GoPro seem to yield to computer control and/or live video streaming - they both write their respective streams to an SD card from which you have to read stuff later, when the camera is not taking pictures.

How do I modify a GoPro, T2i or any other cheap point&shoot / DSLR to provide the interface I need? Alternatively, is it possible to construct an SD card which is not actually a card, but rather a computer posing as a card so I can get the streams as they are being written?


texts: I've come across an interesting transimpedance amplifier toplogy, that reportedly reduces voltage and current noise and compensates for large photodiode capacitance. However, as I'm working with an avalanche photdiode, and I need to bias it with at least 65V - how exactly would I be able to adapt the circuit for such high voltages?


texts:
I have a system similar to the one given by schematic. There is a 12V battery used for supplying MCU board and couple of distributed boards(inverter/measurement network etc.). Since I want to measure their current consumption I added low side shunt resistor.

In configuration like this I would also measure MCU board power consumption which is why I didn't connected MCU board GND to "earth" ground.

I need to sense currents from 0 to 30A with ~10mA resolution(12bit ADC is used).

Will this configuration work?
Is it better to switch to Hall sensor due to it's hysteresis and bigger measurement error?

simulate this circuit – Schematic created using CircuitLab


texts: Photon count with ADC, am I doing it right?

texts:
I have this LED and I want to characterize this photodiode.
The LED should produce light of 370 nm, but I measured it and it is around 358 nm, and at that wavelength the quantum efficiency (\$\eta\$) of the photodiode is 0.5141.
Now, I feed the photodiode signal to this ADC, I got data and I turned it into a histogram.
If you are familiar with photon statistics then you know that for poissonian light the mean of those histograms should be equal to their sigma squared, for example in one case I have:

\$\mu\$ = 19,462.2
\$\sigma\$ = 135.785
\$\sigma^2\$ = 18,437.56

close enough I guess.
If I understood correctly this book(eq. 5.56 and 5.57) then the number of photons should be given by this equation:

\$n_{photons}\$ = \$\frac{\mu}{\eta}\$

which in this case would give me some 37,856.83 photons, which seems like a very low number...
Then I started decreasing the voltage and getting things like this:

\$\mu\$ = 7123.51
\$\sigma\$ = 135.7
\$\sigma^2\$ = 18961.29

This is called super-poissonian light. Here to get the photon count I need the general formula (eq. 5.57):

\$\sigma_{counts}^2\$ = \$\eta^2 (\sigma_{photons})^2 + \eta(1+\eta)\mu_{photons}\$

in this case I know 2 of the values but I also have 2 unknowns and as far as I can see no other equation or formula that I could use.
So basically I'm wondering:
1.- If I'm using the formula for the amount of photons correctly
2.- What should I do when the light becomes super-poisonian?


texts: Can I use a transistor and a relay in conjunction to control the speed and directional rotation of a brushed motor?

texts:
The title says it all. I'm working on a project that requires me to power a brushed DC motor that can reverse directions and change speeds. Everything is controlled by Arduino, but an external battery powers the motor. The Arduino steps in between in order to control power flowing to the motor. I'm new to electronics and this is my first project, so I'm hoping for some guidance from the EE community here.

Is my approach of using a MOSFET to control the speed of the motor and a relay (since it can reverse voltage) to control the direction a reasonable one?

How would this look in a circuit diagram if it could work at all?

I hope this is sufficient information, but if you need more details, please most a comment and I will elaborate. If you have any other approaches you'd like to share, please do.

Edit: The suggested duplicate "question" doesn't help me or answer my question because I don't see a question and I don't see how the answers address every part of the question I'm asking here. My main question specifically asks if I can use a transistor and a relay in the same circuit to control the direction and speed of a motor. I'd also like to know how I could implement this by seeing a circuit diagram.


texts:
I have a four layer PCB, with a traditional: signal layer, power layer, ground layer and final signal layer.

Due to the set up with the power rails, there are some large spaces on the power plane layer which do not have any copper on them. I have various options for these spaces; leave them empty, add ground pour or increase size of power planes so that their copper pour fills the space.

The first option is my current plan, but I have got a slight concern about the manufacturing issues this may cause. Most people these days say that there is no need to worry about the imbalance in the PCB causing warping or lamination issues.

The second option seems like it would put copper in, but not really gain anything (so just sit there to balance the PCB stack up).

The final option seems the worst, as I would have to be very careful in which pour goes where to try and keep the correct reference planes for the high speed signals.

Does anyone out there have a conclusive answer for what I should do with these spaces?


texts:
I want to measure the amplitude of a sine current signal (about 1kHz). The signal is of small amplitude, i.e. smaller than 50 mA. I suppose a simple rectifier is not accurate enough or even doesn't. There are RMS-ICs, however, I think it is "oversized" for this problem.

Have someone an idea or knows a simple and cheap way to obtain the accurate peak value of a sine wave with small amplitude?


texts: I am looking for a PCB mount RJ45 connector. I find that there are about 10-12 types of RJ45 connectors( 6pin, 8 pin, 10 pin, 12 pin, 14 pin ). Even the PCB footprint is different for some connectors with same number of pins. If there is no standard connector, I would like to know the most popular one. I concerned about the availability and cost of the connector.


texts:
I'm trying to split an audio signal into 5 channels, letting 5 different ranges through each filter (low, mids, highs, etc..). What I'm finding is that each bandpass filter has different levels of attenuation, which I don't understand.

I expect there to be some attenuation, but my "passed" frequencies for some of the filters are at best -6dB. This doesn't make sense to me because shouldnt the corner frequencies be defined as -3dB and they bandpass should allow signals through between these at an attenuation of less than -3dB.

Here's the schematic I'm working with:

Here's a magnitude/phase plot of the circuit:

I don't know much about filter design but I chose my capacitor value to be 0.1uF and used the following the following equations to solve for a resistor value to match the cutoff frequencies I want.

Wc1 = 1 / (2piRC)

Wc2 = 1 / (2piRC)

I did this for each bandpass filter diving the ranges of 20Hz - 20kHz into five regions. Perhaps the design I'm using itself is a flawed design? I've looked around a bit and see that a lot of designs include some sort of amplifier between the low pass and high pass portion of the bandpass, could this be the reason?


texts:
I want to have an arduino with an xbee (call it xbee1) connected to it and another wireless xbee (call it xbee2) communicating with xbee1. Then I would have DIO1 on xbee2 acting as a digital input and DIO1 on xbee1 acting as an output outputting exactly the input on xbee2's DIO1. Then to be able to do this with more xbees (eg xbee3)

simulate this circuit – Schematic created using CircuitLab

Is this a possibility? Also if so does it matter what series of xbee I use?
Could you also please explain how to do this.
I have spent a lot of time googling but I cannot find anything. Thanks in advance.


texts: Maximum frequency of a passive RC/RL band pass filter

texts:
I'm planning an application for signal strength measurement in a wide band of frequencies (around 800(0)-10000Mhz). The way I want to implement it is by making a series of band pass filters with a step of ~1Ghz and then analysing each range separately.

So some core points are:

Each band pass filter should be able to operate at a multi-GHz frequency and make a more or less meaningful filtering (I'm not going to launch rockets ;) )
Frequency response steepness does not really matter, each range may be overlapping it's neighbors. If filtering can be performed with 2/4-order filter it's fine

I already spend couple of days researching and here are some results (or their absence):

I couldn't find any maximum values which can be obtained using "regular" RC/RL filters, I'm not a radio-engineer so for me it would be pretty hard to design any advanced filtering application
From what I found, regular ceramic capacitors is not the best option for such frequencies, a better option could be mica capacitors
For resistors I guess the same story - use HF versions
Better use capacitors (RC) instead of inductors (LC), since it's easier to predict/calculate the values we need
Premade solutions on the market are usually designed for very specific frequencies
There are some tunable filters, but they are quite expensive and do not cover all the frequencies I'm interested in

So, is it even possible to design a "real" high frequency filter using a "regular" n-order RC/RL approach, assuming that we will be using a high frequency resistors / capacitors? Or maybe you know or can suggest some alternatives?


texts: full load primary and secondary currents of a transformer

texts:
Why does the question mention "full load currents", what if there isn't such currents, would the transformer function differently?

  What are the full-load primary and secondary currents of a 25000/240-V, 50-kVA transformer? Assume that the 25000-V winding is the primary.


texts:
I'm compiling Verilog using the Quartus II for the Altera platform. In my Verilog, I have a Verilog header global.vh, and Quartus II cannot find it:

Error (10054): Verilog HDL File I/O error: can't open Verilog Design File "global.vh"

Is there a way to specify an "include path" for Verilog header files in Quartus II?

(Note that the header file can be found when placed in the root directory for the Quartus II project.)


texts: Input Range of Differential Voltage in Op Amps

texts:
What is the best way to tell the maximum differential voltage swing that an op amp will handle?  This does not seem to be a common specification listed in the datasheets.

The new TI OPAX192 series of op-amps explicitly address this in their datasheet:

  The OPAx192 uses a unique input architecture to eliminate the need for
  input protection diodes but still provides robust input protection
  under transient conditions. Conventional input diode protection
  schemes shown in Figure 53 can be activated by fast transient step
  responses and can introduce signal distortion and settling time delays
  because of alternate current paths, as shown in Figure 54. For
  low-gain circuits, these fast-ramping input signals forward-bias
  back-to-back diodes, causing an increase in input current, and
  resulting in extended settling time, as shown in Figure 55.

Some situations where I would like to have an op amp with these characteristics known are in integrator circuits.  In a thermal system for example, the integrator will be out of feedback range until the oven warms up.  During this warm-up period the inputs will be held apart, possibly damaging the op amp.  Also, the op amp no longer presents high input impedance to the rest of the board (such as a reference on the non-inverting input) and may pull excessive current.


texts:
What is the Frequency and Duty cycle and of the waveform at Z (say if input clock frequency is 1.5Khz)

My Understanding:

Two negative edge triggered MOD 12 counters cascaded and reset when the upper counter is at 0110 and lower counter is at 1001.

I know that the upper counter is fed with a clock of f/12 if the input clock frequency of the lower flop is f Hz.

The lower counter has 9 states while upper counter has 6 states.Usually when we cascade MOD N and MOD M counters total number of states is M x N.

The lower counter is MOD 9 and upper counter is  MOD 6 and since i am taking the bit next to MSB of the upper counter as the output
The frequency should be :

f/9 *1/6 *2 =f/108 Hz

But, for f= 1.215 KHz, the actual answer is 15 Hz but i get 45 Hz.

My doubts:

Since the upper counter is driven by a different clock, how can is calculate the TOTAL number of STATES of this cascaded asynchronous counter setup?

2.How can i get the duty cycle at the Z output??


texts: Bus pirate interface with with winbond chip

texts:
I have successfully interfaced to my winbond chip via the bus pirate.
I have successfully executed the chip identifier command and chip erase commands via spi, i would like to  read and delete the chips security registers.

This is the command set i push via spi with bus pirate for read:
datasheet: The instructions is initiated by driving the /CS pin low and then shifting the instruction code "48h" followed bya a 24-bit address(A23-A0) and eight "dummy clocks into the DI pin.

What i send:
[0x48 0x00 0x00 0x00 0x00 0x00 r:256] <-  read security register(read 256 bytes)

Each security register is 256 bytes in size and there are aparrantly 4 though i can only see 3 in the datasheet.

My questions is how would i read each security register 256 bytes at a time?

Section 8.2.33 is the reference and the the datasheet is here
http://www.nexflash.com/NR/rdonlyres/A5B6C30B-C174-43CF-867E-E1A2F371A07C/0/W25Q128FV.pdf


texts: How to see the voltage of the output on LCD?

texts:
I designed a circuit which has a output voltage and I want to see that voltage on LCD and how do I do that?

Do I have to use analog to digital converter and programmed it and connect it to LCD?


texts:
I was studying about amplitude modulation and I found this circuit on the internet.

Does anyone know why that ground is needed?
Is the first part(three resistors) an adding circuit?
Does the diode apply the square law?


texts:
I have a host of differential signals from a board thats 3.3V. Now, I need to interface it to a board that can accept 2.5V. Now, is it possible to use a standard level shifter like this ?

Is there any effect on the impedance and will there be any impedance mismatch ? If so, how can I add any passives to compensate for it in case of any impedance mismatch issues ?

Finally, there are some clock signals that need the same level shifting. Can such standard level shifters be used as long as the slew rates and the frequency is not compromised ?

Now, my clock is going from one board to another board. And I foresee a degradation of the performance. How can I rectify that ?


texts: Increasing the input impedance of analog input using an op-amp buffer

texts:
I'm trying to sample a 0-10V DC voltage as an input to my circuit. I use the following circuit to achieve this:

simulate this circuit – Schematic created using CircuitLab
The problem I have is that the op-amp consumes about 500uA from the input signal (in 1.7V signal) which is not good for my application. I want to decrease this current as much as possible. I'm using the general-purpose LM358 op-amp for this circuit.
Could replacing this op-amp solve the problem, or should I make changes to the circuit?


texts: What happens when you divide by zero with a binary divider?

texts: I am curious what would happen if you have a number such as 2 (10 in binary) and divide by 0 (0 in binary). What would happen?


texts: Measuring junction temperature of LED tape?

texts:
My boss at work wants me to figure out a method of measuring the junction temperature of an LED that is part of a reel of tape. Unfortunately, there is no datasheet for the LED modules themselves, just a datasheet for the tape, which is lacking in the information I imagined was essential (junction to solder/ambient thermal resistance etc.).

I was wondering if there is a method, using a thermocouple and a multi-meter, that I can measure the junction temperature of the LED?

Cheers for taking the time to answer.


texts: Buck converter without load - is it dangerous in long term?

texts:
As a followup to my previous questions (Q1 - circuit diagram is here, Q2). I disassembled the LED bulbs, cleaned and resoldered the components on the DC-DC converter boards, replaced caps, and chandelier-assembly seems to work well.

Background: Originally LED bulb is an assembly comprising of both DC-DC converter and LEDs, and (as I now clearly see) is not serviceable. If any part explodes within the bulb, manufacturer does not expect that bulb's chassis explodes (however while plastic it is made of is not flammable, gases are having hard times getting out of it).

Now, when I separated converter and LEDs, I must ensure that any of them do not fail making fire or smoke and dirt.

The issue: when I remove the bulb (which is having LEDs only now), converter remains without load. I was lucky to notice that in this case voltage at its output goes at approx 85 V, and output capacitor rated for 50 V heated and was about to explode.

I have two same model bulbs with different converters: BP2832A-based (board revision 1.0, English, Chinese) and DU8671-based (board revision 1.1, Chinese). While BP2832A says nothing about nature of its output, DU8671 has much better datasheet which says that output of the circuit based on it should be 40 Vdc ~ 80 Vdc on page 5, above the circuit diagram (more or less same reading I get without load). I suspect (maybe wrongly) that BP2832A should have the same range, as long as I also measure its output to be about 85 V without load.

Question: It seems that buck converter is not designed to work without load, right? And resistor of 30 kOhm at output does not make a difference. I suspect that converter tries to reach nominal current set by Rcs resistor, within the defined range (40-80V), and if it does not reach this current, it stays with the clock frequency at the upper limit of voltage level.

Is it OK to run converter in this mode? Let's say I will up-rate output cap from 50 V to 100 V so that it withstands max voltage on the output without heating and explosion, but in general, like in my case - if bulb containing LEDs is removed from the socket, can this no-load mode be harmful for buck converter chip in long term, flyback diode and choke? How much current device is expected to consume in this mode? What are the pitfalls from your experience?

Question 2: How this voltage 40Vdc ~ 80Vdc range in DU8671 for circuit of page 5 is calculated? Is it based on Tleb and Tdelay timings? Or Toff/Ton?

P.S. Bulb's circuit, based on DU8671, is having two parallel 3.3 Ohm resistors on its CS pin, abd my current measurements (120 mA) matches result of formula on page 5. However another bulb based on BP2832A is having the same output current (measured) with almost the same setting, however its formula is missing 2 in the denominator! found the answer, BP2832A's has two formulas with one Ipk and another Iled which is Ipk/2...

Update: here're results of the project

Board from the bottom, power routing

Board from the top

And within chandelier assembly

Bulbs (with LEDs only) are still heating, but I would say they are ~80 C. Central hub heats a little, but still can be touched by the hand.

The design still needs to be tested for durability though.


texts: Op amp Power supply splitter with totem pole

texts:
I want to make a +- 2.5V rail from a 5V supply using an op-amp. I was wondering if I could use a totem pole for driving the output like this:

Image from here
But while I was looking at it, I noticed that since both transistors need to be (almost/close to) half way open, they will act like a resistor and will just sink current to GND (the original GND) even if I do not use the new "Virtual GND)
Am I right? None of the tutorials I watched mentions this.
EDIT:
Also, which is my return path for current for the devices I power from the new "Virtual GND"? Is it the Virtual GND or the original GND?
I need to understand this in order to know where to connect the copper pour


texts: What is the purpose of this jumper in this amplifier schematic or PCB?

texts:
Some time ago I bought a little amplifier kit on Banggood based on the LM386 chip. After soldering the kit I tested it, and it worked great, so I decided to buy a few more of these kits to incorporate them in some audio projects I was working on.
Now I'm working on an 8-step sequencer and I wanted to add this amplifier to my project, and so I decided to draw the schematic for the amplifier and add it to the schematic of the sequencer.
I've scanned both sides of the PCB, drawn out the traces in Paint.Net and merged both sides to get a better view of the connections between the components. Finally, I drew the schematic in EasyEDA, based on the PCB and my drawings. Here are the steps I took:

During this process I was (and still am) very confused about the purpose of jumper JP1. If I haven't made any mistakes, bridging jumper JP1 would mean short-circuiting the audio input, and I have absolutely no idea what that would be useful for. Is this an error in the original design? Have I missed something in the PCB?
Basically my question is: what is the purpose of this jumper, if it is not an error?
Also, as I'm still learning how to draw schematics, I've taken pointers from rules and guidelines for drawing good schematics but if anyone has any comments on how to improve my schematic, I'd obviously like to hear these as well.


texts: Discrete time LTI system's unit impulse response equation

texts:
Hello i have got a question which i could not find an answer below:

A discrete time LTI system's unit impulse response is :
$$ℎ[] =\dfrac{1}{5}([] + [ − 1] + [ − 2] + [ − 3] + [ − 4])$$ so how can i find response signal y[n] for $$x[n]=(\dfrac{1}{2})^nu[n]$$


texts: Internal pullup for input in PIC microcontroller

texts:
Im new in PIC world. I want to ask:

Do I need external pullup resistor for switches and encoders?

When I was using Atmel microcontrollers - I was just turning on internal pullup resistors in software.

In PIC18F25k50 datasheet I found information, that RB port pins are:

"Digital Output or Input with internal pull-up option"

So I assume that some ports may have internal pullups and I have to check datasheet. However I don't know what resistance is there and I can't find it in datasheet.

I'm asking because in many tutorials I see external pullups, so there must be some reason...


texts:
While I was measuring current going in the motor terminals , sparking occurred and the power supply also stopped working including the motor driver, as soon as I connected multimeter across motor terminals of the driver.
Earlier it was working fine , after measuring current this happened. The current measured during that time (for micro second) came out to be 17 A which  happens to be in safe range for peak current of driver i.e 20 A.( I did switch to ampere mode in multimeter before measuring)

Datasheet for Motor Driver :-

https://www.dimensionengineering.com/datasheets/SyRen10-20.pdf


texts:
I'm not entirely sure if I have done the following equation correct or not, but based on the calculations, my multimeter result seems to be incorrect. I have a very simple circuit, containing a 9V battery, an LED (with 3.2 V forward voltage at 24 mA), and a 270 ohm resistor (as shown below).

simulate this circuit – Schematic created using CircuitLab

My question is, when I do the calculations to determine what the current should be in the circuit, I do (voltage / resistance = I), so I get (I = 5.8V / 270 = 0.0214 Amps).  This is 21 mA, approximately. When I insert my meter into the circuit, (inserting the meter between + and the LED, breaking the circuit and properly measuring amperage) I obtain a reading of about 2.1 mA. Did I do the calculation wrong?

I am using a Craftsman 82344 autoranging multimeter. Also, when I insert the multimeter into the circuit, the LED no longer illuminates as it should (at least according to the articles I have studied). Any help would be appreciated, if any more details are needed let me know.


texts: Confusion about positive feedback condition in gain equation

texts:
Closed loop gain A' of the above op amp system is given as:

  A' = A / (1 + β*A)

where A is the open loop gain which is a positive huge number.

Here as a side note, my understanding is that β being positive means β doesn't cause any phase shift so this causes subtraction hence negative feedback. And I assume β being negative means β causes 180 degrees phase shift and causes positive feedback(subtraction becomes addition at Σ).

But in a text I encounter the following:

  Condition for negative feedback: |1 + β*A| > 1

  Condition for positive feedback: |1 + β*A| < 1

So if the above conditions are correct,
does that mean that even the β causes 180 degree shift, it is not enough to create positive feedback?
I mean |1 + β*A| can still be greater than 1 even β is negative.

Which one is correct?

1-) β being negative causes 180 degree phase shift so there is positive feedback

2-) Condition for positive feedback: |1 + β*A| < 1 . β being negative alone is not enough for positive feedback salutation.

Here is the text where I encountered these conditions:


texts:
I am building the Velleman K1803 pre-amplifier kit. This amplifier has a maximum input signal of 40mv. The audio input to the pre-amplifier will be a piezo-electric sensor, and this can certainly exceed the specified maximum.

I believe that the input can be protected with a pair of diodes, but there is a huge range of diodes available.

It is some time since I have done any electronics, and so far my searches have not resulted in a suitable circuit design which could achieve the protection at the low signal voltage specified. For the record, the input is audio in the range 20Hz to 20kHz, and could possibly lie in the range +/- 0.5V.

I would appreciate some guidance on where to look for a suitable diode and circuit. I can of course supply a circuit diagram of the amplifier if needed

Added:

Following @DrMoishePippik comments on  back-to-back schottky diodes, the lowest switch-on voltage I have found is 0.33 to 0.45 for the BAT43 small signal Schottky diode.


texts: Reading analogue sensors in a noisy environment

texts:
I need to read the values from several analogue sensors mounted on a circuit breaker in an electrical substation. I'm not working with any high voltages, but the circuit must still work as the breaker switches normal operating current (not fault current). The cables to the sensors will be up to four metres long. Some of the sensors have two wire 20mA current loop interfaces. Others are potentiometers. I'm aiming to sample at around 2kHz with 8 bit precision or better.

I'm not familiar with the dealing with noise from other equipment. I'm assuming I'll need to consider interference from both electric and magnetic fields.

Do current loops sensors tend to perform well in the vicinity of electric and magnetic fields? Should I use a twisted pair to reduce the net "loop area" that magnetic fields pass through? Should I have a grounded sheath to reduce capacitive coupling to the HV equipment?
What might I need to do for the potentiometers? Might a single ended signal work? Should I use a voltage dependant current source to convert the output to a 20mA current loop? Or perhaps use an inverting/non-inverting op-amp pair to create a differential output and use twisted pair cable? Or even mount discrete ADCs next to each one and use RS485 to send the signal digitally?


texts:
I was reading a book called "Insiders guide to the Phillips ARM7 based microcontrollers".
There it says "The easiest way to program the Flash is by the built in bootloader which allows the code to be downloaded via UART 0 into RAM and then programmed into FLASH".
In Flash magic when we dump the .hex file via the PC's COMM port to the LPC1778 UART 0 port, does the .hex file go into the RAM and then does the bootloader inside place the code into the flash?
If so,the onchip RAM is 64K in size and the flash size is 512k in size. What if the .hex file size i want to dump is greater than the size of the RAM?


texts: What happens if we connect two signal generators in series?

texts: While searching for a way to add multiple signals together, all the solutions i have come across included sources connected in parallel and a single opamp to make up for the attenuation caused by the averager circuit. My question is: Why cant we connect the signals in series like we do with dc batteries when we want their combined amplitude ?


texts: Do not understand why current flows in undamped oscillator circuit, and getting troubles in practice

texts:
I want to make my own antenna, so I started to make a generator. I found scheme below (only without a K key in the bottom) in internet, and it seems to be exactly what I was looking for.

There PNP transistor, as you can see, assumes that + should be on emitter and - on base (don't know how it will be correctly in English version), but there actually + on the emitter and + on the base - no potential difference, transistor is locked. I understand that the answer is probably inductance. Honestly I am not good in inductance knowledge - I know that it creates a self induction EMF, but I'm confused.

But okay, if it is correct, and I just do not understand why, hence it should work in real. I need a 60 Mhz frequency, so I've calculated that L should be 1.3 µHn, and C - 5.1 pF, so I bought the following components:

Transistor 2N3906(rus. documentation)
Capacitor 5R1 5.1 pF
Inductance 1.1 µHn,  ±20%
As voltage source I used 5V DC phone charger.

I built the circuit, and nothing happens. I changed circuit little to test  as shown below - lamp doesn't light.

What am I doing wrong?


texts: Does keeping a mobile phone plugged in increase its battery's lifetime?

texts:
As far as I understand, keeping a mobile phone plugged in would draw current from the source (i.e. an USB port) rather than from the battery. Therefore, the battery would not be used as long as the phone was plugged in, meaning that it would not experience any current draw. Given that batteries tend to "die" faster when they are used too much, this would mean that if a phone was plugged in most of the time, the battery would last longer because it would take more time to experience an amount of charge-discharge cycles such that its capacity starts to decrease.

Is this idea correct? If so, is there any evidence that supports this? By evidence I mean some kind of circuit or any other physical explanation that is not just based on common sense or intuition.


texts: Stepping Down Logic Level of a Differential Signal

texts:
simulate this circuit – Schematic created using CircuitLab

Suppose I have a unipolar, differential 24V signal, and I want to step it down for use with a 5V differential receiver (such as RS-422), how can this be done?

Can I just use a voltage divider to step it down like above?


texts:
what is the formula for caculating  inductance on the basis of

1)No of turns.
2)Diameter of the wire
3)Diameter of the wounded circle. ?

how to calculate the capacitance value in ceramic capacitor ? which is given as 104 or 103 or 102 etc.

Give me the equation or calculation technique....


texts: Opto Triac driver (moc3051) basic circuit problem

texts:
I wanted to try the basic circuit of MOC3051 which is a random phase optoisolator triac driver.

I used this circuit from the datasheet:

with following parameters:

Vcc : 3.3v
Transistor : BD139
R : 1K
Triac : BTA40-700b
Load :    Resistive 9.4K
AC line : from a    rotary voltage converter    (from 0 -    300 VAC)

I've also implemented zero detection and firing angle handling by a pic microcontroller. The circuit works perfect when the AC LINE voltage is 24VAC and when I checked the signal across the load, it changes perfectly in response to firing angle.

The problem is when I increase the AC LINE voltage up to 90VAC the signal across the load started to vanished at some firing angle and above 100VAC it vanished completely. I've tried different values for R and re-assembled the moc3051 with the new one but nothing's changed.

Do you have any clue why is this happening when AC LINE voltage is increasing while the main purpose of these drivers are to work with 110 - 240vac voltage range?


texts: How to choose the right cables for medium/high voltage applications?

texts:
After two years, I will graduate as an electrical engineer. My job will require installing bulbs, Washing machines, heaters, refrigerators and air conditioners ... etc.
I know that each device requires a specific current. My question is: How to determine the diameter or cross section area of a cable that should be used ?
I've googled and found some complicated calculations and complex tables. I would like to know what the easiest way to know the right cable is. I see some electricians can determine the cable immediately when they are asked, and I don't want to take long time in calculations while I'm at work. So, Is there a simple equation or a method to pick the right cable ?
Thanks in advance,


texts:
If the value of a dependent source (say CCCS) depends on the value of an independent source (say a current source). When setting the current source to 0, would that make the CCCS an open circuit (i.e. set to zero) as well?

Cheers


texts: Cloverleaf possibly blew out transmitter?

texts: I went ahead and built a Cloverleaf antenna, right-hand polarized, for a video transmitter, transmitting @ 1280MHz and 800mW. After about a week, however, the transmitter stopped transmitting. I'm wondering if it's possible that the cloverleaf "overloaded" it somehow? I made it with rather thick, 18AWG wire. From the shield to the pin on the connector, I measure 8 Ohms resistance. If it helps, I'm using a RangeVideo transmitter. Is this a possibility? My only other option is that the antenna broke off in a quadrotor crash, leading to the "no antenna = letting the magic smoke out" situation that the manufacturer warns of, however, I don't remember this happening... Secondly, is there any way to test if my antenna is built "correctly" (whatever that may mean, I'm new to radio transmission and reception) without expensive test equipment? Thanks!


texts: Why does the voltage across the DC-link capacitor in a boost PFC circuit usually equals 400 Volt?

texts: In a boost PFC circuit connected to the grid (230Vrms,Europe) the DC-link voltage is usually regulated to 400 Volt. Why is that? Is that because it is efficient to boost it to that particular voltage? If so, why then?


texts:
I quote from Wikipedia (https://en.wikipedia.org/wiki/Joule_thief):

  ... This self-stroking/positive-feedback process almost instantly turns the transistor on as hard as possible (putting it in the saturation region), making the collector-emitter path look like essentially a closed switch (since VCE will be only about 0.1 volts, assuming that the base current is high enough).

Referred to this schematic:

My question is: How the transistor can go in the saturation region?
If the transistor is in this region, it means that Vce will be around 0.4 V. That's impossible, because on the primary coil there will be Vcc-0.4 (assuming Vcc=1.5V, it will be 1.5-0.4=1.1 V) and because of the low coil resistance (lower than 1 ohm for a typical homemade toroid transformer for this circuit) the Ic current should be excessively high (for 0.7 ohm resistance of the coil it should be I=V/R=1.1/0.07=15.71 A).

It shouldn't be more probable that the core of the transformer will saturate and thus the primary coil won't induce any voltage into the secondary (so the transistor will be forced to turn off)?


texts:
I'm trying to connect TI's MAX232 to my Arduino so that I can communicate with my PC. I have connected it exactly as the picture shows:

Tx/Rx are not connected because I just wanted to see if I can get proper V+/V- on pin 2 and 6. At Vcc=5V I'm reading 1.9V on both - pin 2 and pin 6. I connected my 1uF capacitors so that the longer leg represents the white part of the capacitor symbol, and the shorter leg is in place of the black part. Should I connect some other signals so that I can read +10/-10V on pin 2 and 6?

See an image of my circuit below. The brown cable is Arduinos GND and the grey cable is Vcc.


texts: Can the stability of higher order Sigma-Delta Modulator be relaxed with higher level ADC?

texts: I have been studying about the Sigma-Delta modulators having multi-bit ADC  (with low OSR) instead of single-bit ADC (high OSR). We see an improvement in terms of stability. I just want to know if we keep increasing the number of bits of ADC (like 6-7 bits), can a stable 5th or 6th order Sigma-Delta ADC be realized? (serving an increased bandwidth)


texts: VCC pour and decoupling capacitors on a dual layer board

texts:
I am designing a simple dual layer board which has some ICs that I have to put decoupling capacitors near them.

Initially I wanted to make both top and bottom layer as ground plane and route signals and power with traces. But then I found this answer here and decided to make my top layer a power plane (but honestly did not understand why!)

So my question is, should I forget the VCC plane and make both top and  bottom planes as ground?

My board has only one 5V supply input called VCC_IN which then goes into a EMI filter (which I am not sure if it is going to be any good) and after R11 (R11 and R12 are going to be 1206 ferrite beads) and C14 it will be called VCC and turns into a power pour.

So, I wonder what kind of effects I am going to see on C1 and C2 as decoupling capacitor compared to if the top pour was also ground and I just routed VCC using a normal track?

The ground plane is ripped off in the image for better visibility of top layer


texts:
Considering using a Load Switch like DigiKey FDC6330LDKR-ND for powering on and off a device at the far end of a cable.

The voltage and current requirements are well within spec however load capacitance is not.

My understanding is that the load capacitance is spec-ed in order to reduce inrush current when the FET is turned on.

Voltages are +/-12V and +/-5V with the currents all being less then an amp.

Has anyone overcome the maximum capacitance restriction in a similar application by adding an inductor?  Or is the application all wrong and I should simply use a small relay? (am trying to stick with a solid state solution)


texts: Could a PIC18 running two functions simultaneously?

texts:
I am building a robotic car with stepper motors (for wheels) and infrared sensors(avoiding obstracles) using PIC18F4550 microcontroller.
So, I have created a function to drive the stepper motor steps by steps and it works fine.
void move_forward(int steps)
{
   // Code to drive stepper motor step by step
}

Then I created a function to read the infrared sensor output.
Let's say
int read_distance_from_sensor(void)
{
 // Code to read the analog input and return distance
}

It works fine too. But my problem is how do I run the read_distance_from_sensor() function while the stepper motor function is running?
From what I understand, everything gets executed one after another in the PIC18  and it is not possible to execute 2 tasks at the same time simultaneously.
If I do the following:
void main(void)
{
    while(1)
    {
        move_forward(20);
        if (read_distance_from_sensor<10)
        {
            // Stop
        }
    }
}

It will move forward first then it stop to get the distance measurement.
I want it to return the distance measurement while it is on the move.
Do I have to call the read_distance_from_sensor() function inside the move_forward() function everytime i move a step for motor?
Is there a clever way to accomplish this?


texts: Automatic control - linearization with two states

texts:
I don't understand a part of the solution to c) of this problem, namely linearization at a stationary point using Taylor series and partial derivatives.

I am used to linearization of \$ f(x,u) \$ (two variables) using Taylor series but not \$ f(x_1,x_2,u) \$ (three variables) at a stationary point.

Taylor for two variables is given by (where second row is ignored):

Are we supposed to linearize using Taylor series for three variables or just find the partial derivative of \$f_1\$ and \$ f_2 \$? We get a term \$ f(x^0_1,x^0_2,u^0) \$ (which looks like \$ f(a,b) \$ from Taylor series formula for two variables above) present in the solution which is set to zero that is not present if we were to just find the partial derivative of \$f \$ with respect to all terms and just sum them up?

Sorry if the question is a bit messy since I have trouble connecting the mathematical theory with the control theory.

Solution:


texts: STM32 Wakeup from Stop mode using GPIO EXTI event

texts:
I am using an STM32L0 series MCU. I configured my MCU to wake up from Stop Mode using an EXTI line (EXTI0 at PORTA0) during falling edge. At the beginning, it wasn't going to the Stop Mode after I called _WFE(). After tried several things I called _WFE() twice, one after another and that did the trick. Although this solved my problem I was wondering if anyone can shed some light. Maybe I am missing something.

Here is my code:

void HW_WakeupPinInit(void)
{
   GPIO_InitTypeDef gpioInitStruct = {0};

   gpioInitStruct.Mode      = GPIO_MODE_INPUT;
   gpioInitStruct.Pull      = GPIO_PULLDOWN;
   gpioInitStruct.Speed = GPIO_SPEED_HIGH;

   HW_GPIO_Init( WAKEUP_PORT, WAKEUP_PIN, &gpioInitStruct );

   LL_APB2_GRP1_EnableClock(LL_APB2_GRP1_PERIPH_SYSCFG);
   LL_SYSCFG_SetEXTISource(LL_SYSCFG_EXTI_PORTA, LL_SYSCFG_EXTI_LINE0);

   LL_EXTI_InitTypeDef EXTIinitStruct = {0};
   EXTIinitStruct.Line_0_31 = LL_EXTI_LINE_0;
   EXTIinitStruct.LineCommand = ENABLE;
   EXTIinitStruct.Mode = LL_EXTI_MODE_EVENT;
   EXTIinitStruct.Trigger = LL_EXTI_TRIGGER_FALLING;
   LL_EXTI_Init(&EXTIinitStruct);
}

void HW_EnterStopMode(void)
{
   uint32_t tmpreg = 0U;
   BACKUP_PRIMASK();
   DISABLE_IRQ();
   HW_IoDeInit();

   /*clear wake up flag*/
   LL_PWR_ClearFlag_WU();

   RESTORE_PRIMASK();
   tmpreg = PWR->CR;

   /* Clear PDDS and LPSDSR bits */
   CLEAR_BIT(tmpreg, (PWR_CR_PDDS | PWR_CR_LPSDSR));

   Set LPSDSR bit according to PWR_Regulator value */
   SET_BIT(tmpreg, LL_PWR_REGU_LPMODES_LOW_POWER);

   /* Store the new value */
   PWR->CR = tmpreg;

   LL_LPM_EnableDeepSleep();

   __WFE();
   __WFE();  // <------- Calling __WFE() second time works.
}

Thanks in advance.


texts: Arduino Interfacing Breadboard with SD Card + Shift Register

texts:
I have a small circuit, and use a shift register (74HC595) to help add output ports to drive an LCD display.

As far as I have found, the latch pin can be connected to any digital pin, and I have it connected to pin 10.

However the other 2 input pins require connections to the Arduino on pin 11 and 13, and as far as I am aware these cannot be changed? If this assumption is incorrect please let me know.

Now I also wish to connect an SD card reader with the Arduino, and this requires a connection on pin 11 (MOSI) and pin 13 (SCK).

I have tried connecting it to the same track as the shift register on the breadboard and it all seems to work.

I was just wondering if this is bad practice or if anything could go wrong. Also as the MOSI and SCK pins can't be changed is it possible to move the shift register pins or not? I'm guessing NO as presumably they rely on the internal hardware too but would appreciate some clarification.

Thanks.


texts: Can a 24VDC 14amps rated power supply provide more current than it's rated?

texts: I am having some problems with understanding power supply. Can a 24VDC 14A rated power supply provide more current than it's rated? I thought the maximum current the power supply can provide is 14A. Imax= V/(Ri+RL), when RL = 0. (Ri=internal resistance, RL=load resistance) Even if I short the power supply with a wire, the maximum current that will flow through the wire is 14A? If not, what's the maximum current? Can you explain why?


texts: Difference between reactive load and source?

texts:
Probably a silly question, but I am coming across terms like reactive power load and reactive power source in some articles in web. Does it matter if a reactive component is a source or load? Say between an inductor in induction motor and coils in synchronous generator, is there any difference in the way they work?
Also, direction of current tells if a component is load or source in DC. How to get similar sense in AC, and understand if something is load or source?


texts:
I got this board from ebay, seemed to be a cheap deal. It is decent product from what I can say at this time.

The question is, what is the most appropriate way to connect a daughter board to this board on the wide shrouded male header? The obvious answer is to use a ribbon cable. However, won't that introduce a lot of parasitic capacitance? What decides how long the ribbon cable can be?

I have searched for 2x13 2.54mm female header socket for the daughter board. However, it seems that its dimensions are such that it wil not "come off" the edge of the PCB sufficiently to be pushed fully into the male header fully. Any ideas or pit-falls I need to look out for?


texts:
I am a digital design engineer and am struggling to come up with an analog circuit that could produce an (RC) curve like below. It does not have to be an exact RC curve. Something that comes close would do perfectly fine.

Thanks,

Robert


texts: What is the origin of the standard 0.1 inch pin pitch?

texts:
I'm curious which company started using the standard 0.1 in (2.54 mm) pin pitch for components. This is surprisingly difficult to Google. I see 1956 and Cicoil Corporation when it comes to ribbon cables but I doubt this was the first use.

On one hand, a tenth of an inch is kind of an obvious measurement to use, speaking as an American. On the other hand, I suspect that the choice had just as much to do with the manufacturing capability of "the time" (whatever "the time" was). For example, now we also have pins twice as dense (0.05 in), but the legacy of the original choice remains.


texts:
If I have the following equation: y[n] = 0.5*y[n-1] + x[n]
How do I know if this is a causal filter or not?


texts: Problem initializing 4-bit mode LCD(DEM 20486 SBH-PW-N)

texts:
I've got an ATMEGA16 with a LCD display DEM 20486 SBH-PW-N (datasheet) connected to port C like so

C0 - RS
C1 - RW
C2 - E
C3 - not Set
C4 - D4
C5 - D5
C6 - D6
C7 - D7
D0-D3 are grounded

I haven't been able to find much detailed information on how to work with the LCD and I've been trying this for a good two days, so any information as to what I've been doing wrong would be helpful.

#define LCDPORT PORTC
#define LCDPIN PINC
#define LCDDDR DDRC
#define RS 0
#define RW 1
#define EN 2

#define D4 4
#define D5 5
#define D6 6
#define D7 7

#include <avr/io.h>
#include <util/delay.h>

void LcdFlash() {  // Flash enable flag
    LCDPORT |=  (1<<EN);
    _delay_ms(2);
    LCDPORT &= ~(1<<EN);
    _delay_ms(2);
}

void LcdSendNibble(char cmd, char rs) {
    LCDPORT &= ~(1<<RW); // Write mode
    if(rs)
        LCDPORT &= ~(1<<RS); // Command mode
    else
        LCDPORT |=  (1<<RS); // Data mode
    LCDPORT |=  (cmd<<D4);
    LcdFlash();
}

void LcdInit() {

    LCDDDR |=  (1<<RS);     // SET(LCDDDR, RS);
    LCDDDR |=  (1<<RW);     // SET(LCDDDR, RW);
    LCDDDR |=  (1<<EN);     // SET(LCDDDR, EN);
    LCDDDR |=  (0x0F<<D4);  // ASSIGN(LCDDDR, D4, 0x0F);

    _delay_ms(150); //Wait for boot
    //Function set
    LcdSendNibble(0b0010, 0);
    LcdSendNibble(0b0010, 0);
    LcdSendNibble(0b0100, 0); //N = 0, F = 1
    _delay_ms(50);

    // Display on/off control
    LcdSendNibble(0b0000, 0);
    LcdSendNibble(0b1100, 0); //D = 1, C = 0, B = 0
    _delay_ms(50);

    // Display clear
    LcdSendNibble(0b0000, 0);
    LcdSendNibble(0b0001, 0);
    _delay_ms(50);

    //Entry mode set
    LcdSendNibble(0b0000, 0);
    LcdSendNibble(0b0110, 0); //I/D = 1 SH = 0
    _delay_ms(50);
}

int main() {
    LcdInit();
    while(1) {}
}

I would also appreciate information as to what some of the different flags mean during the initialization.
specifically the line-mode flag N and the shift flag SH.

My goal is simply to get the screen to light up, and then to write a character to the first position though this is not attempted in the first place


texts: How to vary DC (0-450mA) current using Arduino output voltage(0-5 v DC)?

texts: I want to vary  output DC current(0-450mA) Of LED driver  keeping voltage constant  using arduino output voltage (0-5 Volt)  is there any IC or current regulator operated on  arduino (0-5 volt )i.e at 0 volt(of arduino ) 0mA current and if 5 volt(of arduino ) 450mA current i.e  whene i increase  or decrease output voltage of arduino then output  current of driver is also increase or decreases respectively


texts: I have a rf signal generator (50 ohm, 3.2mw max power, going to be transmitting 13.56mhz. It's a HackRF SDR) , which I want to connect to a homebrew RF power amp.  As a newbie to RF design, I know that whatever I do, I'm going to let some magic smoke out on my first try building this amp. In this case, I'd rather that the smoke not be emitted from my $400 RF gen. Thus, I'd like to somehow isolate the output of my RF source from the input of my rf amp, so that I can tinker around with the amp (adjust base currents to the amp transistors, for instance) without being nervous. Keeping the same impedance would be a plus. Is there some way to do this?


texts:
I was trying to simulate on proteus ADC with potentiometer and get the reading to control dc motor with PWM it's working but the problem is the ADC value not accurate. ADCH reach max value before potentiometer is 100%. I don't know why this behavior. Hope you can explain it to me.Here is the code.

#include <avr/io.h>
#define F_CPU 1000000UL
#include <util/delay.h>
void pwm_init()
{
DDRB |= (1<<PB3);
TCCR0 |= (1<<WGM00) | (1<<WGM01) | (1<<COM01) | (1<<CS01);
OCR0 = 0x00;
}

void adc_init()
{
DDRA =0x00;
ADMUX |= (1<<REFS0);// AVCC ref
ADCSRA |= (1<<ADEN) | (1<<ADPS2) | (1<<ADLAR) | (1<<ADATE); // 1MHZ With
prescaler 8 gives adc freq 125 khz
}

uint8_t adc_read()
{
ADCSRA |= (1<<ADSC);
while(!(ADCSRA && (1<<ADIF)));
ADCSRA |= (1<<ADIF);
return ADC;
}

int main(void)
{
pwm_init();
adc_init();
while (1)
{
    OCR0 = adc_read();
}
}

You can also see in below picture duty cycle is almost 100% while potentiometer is just 12%.


texts: AD4610 - Is it possible to eleminate this single overshoot

texts:
I am trying to compensate input capacitance of the AD4610. It does not matter if it is actually over- or undershooting - there is always a spike:

I do not have this problem with the OPA4141 for example:

Is it possible to eliminate this single spike?


texts: Power supply issues when using LiquidCrystal and WS2811

texts: I have been attempting to run a 16x4 liquid crystal display with both an Arduino UNO and I have also used a MEGA..  I loose power to the screen (flickering, etc) when attempting to animate 29 WS2811 LEDs.    So my question is, would there be another way of doing this to make it work off the arduino power?  I know I have a few other options, such as power the leds separate, use a dual voltage power adapter, etc.. but I am looking for another solution...  I know that I can power 60 WS2811 LEDs with 1 Arduino Nano without any issues.. So the arduino by itself can power 2x as many LEDS.. but its just the LCD is taking power also..   I am running a 12v 1amp power supply to the arduino power jack.


texts: How to make a wired input IR demodulator?

texts:
Objective: I'm trying to make a wired infrared input for a microcontroller. Incoming signal would come from a remote control device that has an IR emitter output jack.

I believe that all I need is the demodulator and perhaps schmitt trigger portion since the incoming signal will be well controlled and will not contain IR noise or variations in level.

notes: I've found a few older ICs that were designed for use with a separate diode and seem that they could fit the bill but are not available any more.  I also found a Vishay line of apparently current devices (VSOP584) that could work but are very tiny and I'm not sure that I could fab one up in a way that would survive.  I have to think that a relatively easy to build circuit could demodulate the signal since it's wired and doesn't suffer most of the issues that a real IR input would have.

I think I have 3 options:

A) use an ir emitter coupled to an ir receiver inside my device.
 B) keep searching for an IC that will do the demodulation.
 C) design a demodulator (perhaps try with a basic envelope detector).

Any suggestions on which option I should take?


texts: generate log .txt file on PC for arduino serial terminal log (send and receive commands)

texts:
I am trying to generate a .txt file on my Windows 10 PC of Arduino serial terminal data. I am not using SD card on Arduino Mega board just need to send commands to Arduino baord from serial terminal and save the generated results in .txt file on PC.

Please guide for best possible solutions.

Thank you....


texts: Two different types of solder alloy used in process - allowed or not?

texts:
Recently it come to my attention that using two different lead-free solder alloys in one process should not take place.

Example: populated PCB is flown on wave solderer with alloy X and then (if required) alloy Y used to rework any nonconforming joints. Is this practice allowed? What kind of electrical/mechanical downsides can be expected from reliability of this joint in long-term situation? Unit is exposed to vibrations and shock in it's life.

Thanks for answers,
Seb


texts:
Im' working with a STM3f429 dev board and a Mipot 32001353 LoRa module. This module communicates over UART. I have initialized my UART interface with cubeIDE. When i don't connect the wire between TX of module and RX of microcontroller, everything is working fine. I can use a logic analyzer to see the uart communication in both directions. As soon as i connect the TX from module to RX from microcontroller the UART goes crazy. I have no idea why. I already checked all wiring's and power supply and everything looks ok. Does anyone have an idea why this is happening?

EDIT:
Problem solved!
The RX pin on the MCU was damaged. It was pulled to ground.
Using another UART interface on the MCU solved the issue.


texts: What would the current be if I plug an LED into a perfect circuit

texts:
If I had an LED that had a forward voltage of 2.2 volts with a forward current of 20mA and I somehow created a battery that was exactly 2.2 volts and I put that LED, and only that LED, on that battery, what would the current be?

I'm just confused how diodes/LED's work. I understand usually you would have say a 5V battery and the resistor that you put in series with the LED would control the current.  I'm just trying to better grasp LED characteristics.

Thanks


texts: 4.5 V on gate of Mosfet while switch open

texts:
I have a strange behavior with the circuit below.

(the bidirectional logica level should be read as:

VL = Voltage Low
GNDL = GND Low
VH = Voltage High
GNDH = GND High
L1 = Low channel 1 (I did only draw 1 for simplicity, there are 4 in total)
H1 = High channel 1

This is the level shifter:

Voltages read:

When the switch is open:

1.98 V between GND and L1 (of the shifter)
4.57 V on the gate of the Mosfet
LED is on

When the switch is closed:

3.30 V between GND and L1 (of the shifter)
5.26 V on the gate of the Mosfet
LED is on

Of course the LED is always on since the gate voltage is in both cases high enough.

How can there be 1.98 V between GND and L1 while the switch is open (I assume the gate does not return any voltage) and 4.57 on the gate?

earlier tests

When I change the 10 KOhm resistor by a 200 ohm, the LED works as expected (on when closed, off when opened).
Without the level shifter and using 5 V for the entire circuit, also the LED works as expected
Without the level shifter and using the 3.3 V than the 2N7000 does not get enough voltage on the gate (therefore I want to use the shifters, at least until I receive my better mosfet, IRL44N).


texts:
Trying to control a 220v electric convection panel heater with a Fotek SSR (SSR-50DA http://akizukidenshi.com/download/ds/fotek/fotek_ssr.pdf) which is controlled by an nodemcu esp8266 (arduino).
It is a pretty straight forward setup, with a digital pin from the nodemcu is connected directly to the low voltage SSR terminal to trigger switching of the higher voltage SSR terminals.
Things kind of work as expected, in that the heater turns on and off when requested.

However. The heater has a little LED light on it, and when it is turned on via the SSR it flickers. There is also a very slight ticking sound coming from the SSR. Both the LED and the ticking sound appear to be in sync and happen very fast. The heater still works during this. But if I turn the heater on and off, the LED light on it comes on strong, and there is no longer a ticking coming from the SSR. (note that the heater temperature control is set to max during this)

I'm not sure why the ticking is happening or if there is anything I can do to stop it?


texts: LM386 not passing white noise signal that was generated by a second LM386 (updated)

texts:
I am using an LM386 to generate white noise. The circuit also has a second 386 for an on-board audio amplifier. Both chips are powered by the same 9V battery.

The audio amp won't pass the white noise signal and I can't figure out why, is there an impedance-matching issue? I have tried different value capacitors to buffer between the two ICs, resistors, resistors-to-ground, and an op-amp with 1:1 ratio.

When I turn the noise generator on and off, I can hear like a DC 'pop' on the speaker, but I can't hear the noise. When I tap the signal at C3 (between the two 386's) and plug that into a commercial amp, I can hear the signal fine. There's just something about that second amp that won't pass the white noise.

https://www.circuitlab.com/circuit/g85pxv/white-noise-and-lm386-amp/


texts: Getting PWM with an astable multivibrator (square wave generator)

texts:
I would like to use this schematic:

to create a square-wave generator but I would like to modify it by getting an output that runs from 0 to +5V, as well as changing the signal so that I can change the duty cycle of the pulse(PWM).

Should I replace the resistor R2 with a variable resistor so that I can get the PWM signal? If not, what would be the correct approach?


texts:
I have a stackup like the following:

Top
GND
Power
Bottom

I am routing a trace that I have discovered is especially sensitive to noise; for example, when working with the signal on a bread board, the signal doesn't work properly if my jumper wire is too long (i.e., when connecting multiple thin ones together). Also, on a previous revision on this board I discovered that if the power supply is noisy, I can see problems, e.g., one of those cheap USB bricks you see at gas stations. This problem has somewhat resolved after running the power through a TPS62162DSGR (buck converter), which seems to clean the power up too.
To minimize the noise on this line I am wondering what, in general, is the best routing strategy for reducing noise on this line.
The destination pad is on the top. Currently I am routing it on the bottom layer and bring it up to the top layer with a via. This seems to work OK.
Can I improve on this design? The things I was thinking was:

Route it on the top layer (since GND) is right under it.
Increase trace width (to like 20mils)
Keep the trace as short as possible.

Are these ideas misguided? Any help/guidance/sage words would be greatly appreciated!
(Adding More Detail)
Ok, not to go all Sherlock Holmes, but I think I know what is going on here:
So the component in question here is a SK6812 5050, controlled over SPI. When I see the problem, the LED will flash wildly different colors. If I am connected to a power supply like a battery bank or my computer it's fine. Cheap USB bricks, I see the issue.
On an early version of the board, I designed the basic LED array as a header for a TI SimpleLink board (to retain the pin exposure and otherwise be able to debug easier.) I autorouted it just for times sake, and the routes came out like this in the area in question:

The signal comes IN on pin 4 and leaves on in 2.
To give some more detail, the way the TI board is designed, is that it passes 5V straight through, no power conversion. It uses a buck converter to create 3.3 for the MCU and other components. So any noise on that 5V line will be passed straight through.
What I think happens here is that 5V+ is too close to the data line. Hence the signal is getting corrupted.
I later revised the board, including my own MCU layout and so on and I manually routed the board. Now that area looks like this:

THIS version of the board doesn't display that problem. Even if it is connected to a cheap power brick. It's worth noting all power on this board is 3v3, and passed through the buck converter. The stackup on this board is as noted in the start of this post.
What other details would be helpful? Happy to add more.
In general, there are several of these led components chained together; they transmit the data line to each other. To catch it, I tapped one of my leads into the third one in the chain and I see this on the "noisy" one:

And I see this, on the properly functioning one.


texts: How can I model an optical filter using python?

texts:
Say I have an RGB LED which transmit intensity modulated signals, at one symbol transmission I want to send a symbol with all three chips.. Can I just model three bandpass optical filters like RF filters to filter out the individual intensities impinging the PD? I can't seem to find any design procedure on optical filters.

Basically I want to use color shift keying (CSK) to modulate the data symbols into the LED chips and be able to detect the CSK data symbols on the receiver side (as defined by the IEEE 802.15.7-2018 standard). On the transmitter side I am able to modulate (using python) the symbols but however I do not know how to model the RGB filter and I don't really understand the optical filter design process. Some details regarding CSK can be found at [ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7482661]

Any direction to relevant literature is appreciated.


texts: What is the difference between a GAL and a PAL?

texts: I was reading this article (unfortunately a lengthy Dutch discussion) talking about a GAL. I have come across the GAL device before, but never really understood what a Generic Array Logic is. I know what a PAL is and I am under the impression that they're closely related, how do they compare?


texts: Rotating a gyroscope's output values into an earth-relative reference frame

texts:
For whatever reason, I seem to have gotten myself twisted into quite a confusion on how to process data from my 3 axis gyro and 3 axis accelerometer to get gyro rotation values related to the earth's reference frame. i.e. Given my accelerometer measures gravity (we assume it's stable) along the sensors (x,y,z) reference frame, how do I adjust the values of my gyro, measured along the sensors same (x,y,z) reference frame such that I am actually measuring the rotating about the Earth's frame x (North), y (West), and z (downwards) direction?

I just can't seem to wrap my head around the use of the rotation matrix. Do I simply employ a 3d rotation matrix, and multiply the vector, \$[gyro_x, gyro_y, gyro_z]^T\$, by a rotation matrix, R? I then assume the rotation angles, are somehow derived from the filtered accelerometer outputs, but I'm having trouble deciding on what those should be.

I have yet to find a concise reference on how to move the rotation and acceleration values from the sensor reference frame into the earth global reference frame. Perhaps someone can help? Thanks


texts:
I have a question concerning this circuit I have found on internet since I would like to replace it with a mini dc motor vibrator.

Is there any chance someone could explain to me how it works?

As far as I can see. You have an input of 5.9V to operate and PWN 4KHz from the output of a MCU.

How does can you control the intensity of the vibrator using this circuit? I would replace the buzzer, PKLC1212E4001-R1 with a dc motor, does that seem okay?

Thank you


texts: Decreasing an ATX PSU voltage using the sense wire?

texts:
I am trying to decrease the voltage of an ATX PSU to about 11.9 volts or so (it's 12.2v, a bit higher than what I would like for my project).

I did read some stuff about using the voltage sense wire with some resistors, but that only works to increase the voltage, not decreasing it. So I had this idea, of actually connecting the 3.3v sense wire to the +5v wire through a high resistor. Do you think this would work? And if so, what kind of pot range would you recommend?


texts: Are USB and/or Ethernet payload agnostic?

texts:
I'm working on a project in which I'm trying to reduce the number of conductors in a high-bandwidth, multi-signal communication interface that requires a fiber connection for isolation and a back channel. From my research, it seems that Ethernet and USB meet bandwidth requirements, but I'm wondering whether, for example, I can transmit both I2C data and the primary content data from a video IC over one or the other simultaneously. I Suppose that if possible it would require significant time in the firmware weeds.
Thanks in advance--new to the EE industry and I feel lucky to have you all as such a great resource...


texts: Do open source libraries exist for VHDL the way they do for C++ or python?

texts:
When I'm approaching a problem in C++ or python, there are many libraries that exist which do the heavy lifting of my code. I'm thinking about GNU GSL, BOOST, or FFTW for C++, and NumPy or SciPy for python. In many ways, the fact that these resources exist make coding in these respective languages worthwhile, as the libraries prevent you from having to rewrite all the low level things from scratch.

The IEEE standard libraries seem to cover only the very basics, such as data types (sort of akin to the C standard libs).

It seems like in VHDL, you can buy/find some "IP Cores" that will solve a problem, rather than using an open source library. In python, if I want to talk to a serial device, I just import serial and I'm basically done. In VHDL I would either be stuck writing a serial protocol from scratch, or I would have to google around on the various repositories until I found someone who had produced something that sort of works. I would then be patching bits of code into my project, rather than just including something and calling that. In a similar way, if I want to perform an FFT, I can find examples of FFTs in VHDL via google, but there is not something simple like FFTW that I can find.

Are there any comprehensive open source libraries available that I can import into my projects? Why does everyone seem to roll their own code for so many of the same things?


texts:
I am working on a USG project where power cables placed in a 6" conduit along with fiber optic cable are specified to be no longer than 500' from an antenna control unit to a power subsystem distribution cabinet (PSDC).The PSDC is supplied by a 30 AMP or 45 AMP breaker depending on cable lengths.

The work is being done by a contractor with specifics in what is required to be supplied.

One installation will only need 250' of power cable and fiber optic.

The contractor intends to no make at least the power cable shorter without looking for a major change to the contract issued and proposes to coil excess power and fiber optic.

I have fears of 250' or coiled power supply either creating induction, or starting a fire.

I could not find anything in NFPA 70 (National Electric Code) that says one can or cannot have an excessive amount of coiled power cable.

A general industry standard is 12' (manholes + handholes). Some say it is not a good idea to place power and comms in the same conduit.

Does anyone know of a citable authority on the maximum length that a power cable can be coiled?

The power is 208 VAC, 3 phase60 Hz 45 Amps per phase.


texts: Determine the transfer function using these values (Capacitors)

texts:
This is my circuit.

simulate this circuit – Schematic created using CircuitLab

These are the values of the components

Determine the transfer function using these values

This is what I thought to do in first place but I am not sure, if this it, if I still need to do something.


texts: How to regen a DC motor from the high-side of a boost converter?

texts:
I am planning to drive a 24v motor from a 12v battery, using a DC-DC boost circuit to generate the 24v and an H-bridge to PWM drive the motor.

A problem arises when the motor goes into the regen quadrant. The motor will just dump energy into the high-side capacitors of the boost circuit, overcharging them since there is no way to send current back out to the battery.

So here is my idea: Place a P-channel mosfet between the high and low sides of the boost circuit, with a voltage comparator and reference connected to the gate. This way, the mosfet would be programmed to dump from the high-side capacitors to the low-side whenever the output is above 25v.

Obviously this would put a lot of stress on the caps and mosfet, so I'm looking for any advice on how to achieve this more elegantly. Maybe if I threw an inductor in there somewhere it wouldn't be such a harsh dump of current?


texts: Circuit Design for Managed Draining of NiMH Cells

texts:
One of my pet peeves is the prevalence of devices powered by odd numbers of standard batteries (AA, AAA). Since I try to avoid using disposable cells and all of the chargers that I've so far owned charge cells in pairs, this means that it is almost impossible to get the odd cell to the same state of discharge as any other. Therefore it is impossible to charge said odd cells without damaging one of the pair.

I'd like to create a simple device that could safely bring any two rechargeable cells to the same level of discharge. I presume that other than mechanical and wiring bits, all that would be needed would be resistors and diodes. But, being an electrical retard, I'm not quite sure... not at all sure, really, where to begin.

My immediate focus is on LSD NiMH cells; but discussions that are applicable to other chemistries are more than welcome.


texts:
it's been difficult to find the answer to this problem I have. My project is based on home automation.

I need to control the direction of the rotation and if possible the torque of an AC synchronous motor like this one with the Raspberry Pi 2, to close and open curtains.
The RasPi is already connected to a relay switch like this one to automaticaly turn on some lights.

Does anyone know which is the best way to control the motor?


texts: Bounds of impedance matrix of a passive two port network

texts:
If we consider the impedance matrix of a linear, reciprocal   passive network (Z12 =Z21 because of the reciprocity),
$$
\begin{bmatrix}
   Z_{11}  &
   Z_{12}  \\
   Z_{12}  &
   Z_{22}
   \end{bmatrix} =
\begin{bmatrix}
   r_{11} + i x_{11} &
   r_{12} + i x_{12}\\
   r_{12} + i x_{12} &
   r_{22} + i x_{22}
   \end{bmatrix}
$$
will the following condition be always true?
$$
r_{12}^2 \leq (r_{11}r_{22})
$$
If true, what is the rationale behind it?
If not, what would an example circuit?


texts: Guidelines on PCB design with components only partially wired on PCB traces

texts:
There were a number of questions/answers here somewhat related to this question, but not exactly the same. I am developing an inverter with half bridge MOSFETs with high voltage and current over 100 amperes using parallel MOSFETs.

MOSFETs drains are connected to the copper power bus which will mount outside of the PCB. All the components are undoubtedly part of the same schematic as some of the MOSFETs pins are placed on PCB traces, but a chunk of circuits will be outside of the PCB.

This is a common task for motor controllers and for power supplies, but I can't find guidelines on PCB design. Whatever PCB CAD software is used, the rule check will fail in unconnected parts of the schematic. Please share your experience.

Note: I am using DipTrace for schematic and PCB design, but the workflow should be similar for any CAD to fully use capabilities of CAD and yet escape DRC errors.


texts:
I built a 2.1 subwoofer circuit.  The  schematic is below.  The problem is the sound is low volume.  It should be louder than this. I want to confirm the coupling capacitor values are ok in every stage.
The main chip amplifier is TDA7377.  It is configured as a stereo bridge.
Note: The diagram shows only a single channel & a subwoofer filter.


texts: Understanding Working of High-Pass RC Filter

texts:
I was trying to visualize what happens when frequency is swept from 1Hz to 1GHz. In case of capacitor, voltage lags behind current by 90 degree and capacitor reactance depends upon it's frequency.

I have tried simulating the RC filter using LTSpice. The picture is given below but my question is very general and for theoretical understanding.

I want to understand the phase response of the filter. Since, voltage lags behind the current in capacitor (which is connected in series with voltage source). Therefore, they will be some voltage across capacitor and it's intensity will depend upon the frequency (decreases with increase in frequency). I have tried to understand the RC filter working. I have tried to explain what happens in RC filter when frequency is swept from 1Hz to 1GHz.

Stop-Band:
The frequency will be low and reactance of the capacitor will be very high. All of the voltage will be across capacitor and will be delayed by 90 degrees. The output (voltage across resistance will be nearly zero).
Transition-Band:
The reactance of the capacitor will start to decrease relative to the resistance. The voltage at output (across resistance) will be subtraction of Voltage source's voltage and delayed version of voltage source (90 degree). Therefore, overall phase of the system will be less than 90 degrees.
Pass-Band:
In this band, reactance of capacitor will be nearly zero and hence, there will be 0 phase delay. Although there will be some voltage across capacitor which will appear as ripples in the pass-band.

Is my understanding correct?


texts: What is the maximum static voltage of LiFePo4 batteries?

texts:
I've been working with a pack of batteries from a DIY electric vehicle. The batteries in the pack are LiFePo4 chemistry and were chosen for safety (greater resistance to thermal run-away), flat discharge curve (3.2-3.3v for 70% or so of the charge) and longevity vs other lithium chemistries. The flat discharge curve makes it difficult to determine state of charge (SOC) with a voltage reading alone since a reading of 3.3 volts could mean 50% charged or even 70% charged. The voltage does climb from 3.4 to 3.6 over the final 90-100% SOC levels which should mean that if you see a reading of 3.4v you are at 90% charged.

Most chargers are CC (constant current) / CV (constant voltage) chargers set at 3.6-3.65v. When this voltage is reached the amperage of the charger declines rapidly and stays low for the final 15-30min of the charge. This final phase of the charge could be considered similar to an absorption/float stage.

My question is - if most of the literature on this chemistry shows 3.6v as 100% SOC, then why after a round of charging  do my batteries fall back to 3.33v after "resting" for 24hrs (could be the chemistry equalizing). Is this what is called a static voltage/open circuit voltage? Am I supposed to let the float stage of the charge go for longer at 3.65v so that my batteries stay at 3.4v after resting? I'd like to get them up to a 90% charge (3.4v) before doing a vehicle test run.

Thank you all.


texts:
I am using a 5V regulator (LP2950) from ON Semiconductor. I am using this for USB power and I'm feeding in 9V from an adapter. USB requires maximum of 500mA right? So the maximum power dissipation in the regulator is (9V - 5V) * 500mA = 2W. My Question is whether this regulator can take that much power with 10x10mm copper as heatsink on the PCB?

Also I was looking at another regulator (LM2940S-5.0/NOPB) from TI. Which one would you thing would be a better regulator to use with the same 10x10mm copper area as heatsink. Remember I am using this to power up a USB port (not on the computer side because that provides 5V, 500mA)


texts: Nested parallel RC inner capacitor voltage function

texts:
Fiddling a little bit with RC circuits, I thought of this DC circuit :

simulate this circuit – Schematic created using CircuitLab

Trying to fully define this circuit, I deduced this :

\$V_{C1}(t) = 5*(1 - e^{-t/(R1 * C1)})\$

\$V_{R1}(t) = 5 - V_{C1}(t)\$

\$V_{R2}(t) = V_{R1}(t) - V_{R3}(t) \$

\$V_{R3}(t) = V_{C2}(t)\$

The thing is, I don't see how to figure out \$V_{C2}(t)\$... The thing is, that I don't know the way C2 charges because it's fed by \$V_{R2}\$ which is not a DC voltage nor a sinusoidal voltage (or any voltage that has a frequency anyway I believe).

So I'm pretty much stuck... How to solve this kind of problem (a capacitor being fed partly by another capacitor) ? And in general, how to solve a capacitor's charging voltage equation from a varying voltage source of equation \$V = f(t)\$ ?


texts:
This is the first schematic I have made that was not a simple LED. I want to know if it seems good before I go and build it (and buy the parts). Here is the schematic:

Here are a few of my concerns:

1.) Are there any silly shorts that I should address?

2.) Did I connect the 556 correctly (In monostable mode, don't worry about the resistor and capacitor values too much)

3.) Are there any pullup or pulldown resistors I am missing?

4.) Did I make the h - bridge correctly (I will change the transistors as I need more current. I have not decided on a motor yet).

It is essentially a tennis ball machine (using logic gates because arduino is too easy :P). There are three lasers and photo transistors and a button. The only important thing really is that when the laser is tripped, the signal should go low (unless I got this backwards) and when the button is pressed, it should go high.

One last thing - pretend that voltage regulator you see is a UA7805 (I couldn't find it in Eagle).

Thanks!!

*EDIT: I UPDATED THE SCHEMATIC (I THINK I GOT EVERYTHING)


texts:
I just study about flip-flop in my class and this is the picture from the slide my teacher used that explain the construction of SR Flip-flop

However, I find something was wrong with this figure. If the input are S=1, R=0, Clk=1 at an instant then the out put of the master Latch is Q=1 and Q' = 0. Take that to the input of the Slave Latch. Q = 1 => S of slave latch = 1 but Q' is inverted that make R of the slave make also equal 1 which is forbidden condition.
I think my teacher make a mistake. The right figure should not have the inverter at the complement of output of master Latch but on the clk to en gate of slave Latch


texts: Will a parallel crystal toggle on its own?

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I'm having trouble with this part of my circuit.  I have this crystal connected, but I see only a 3.3V DC signal on Pin 1 and 3 of the Crystal, and a 0V signal on Pin 2 and 4 of the crystal.  I'm wondering two things:

Does a crystal have polarity?  (I don't believe it does, but want to confirm)
Do the XTIN and XTOUT pins need to do something to get the crystal to oscillate?  FYI, this part on the right that the crystal is connected to is FT2232H.


texts: I am trying to build a Wien Bridge Oscillator in Multisim that has a frequency of 500kHz. I went through all of the necessary calculations to choose values for R and C. When I build the circuit in Multisim it says I have a frequency of 25 kHz and the oscilloscope does not show any oscillations, just a constant voltage of 5V. Any ideas of how to correct this issue?


texts: Why do high voltage / low amperage shocks hurt?

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I learned that when electric shocks happen, the amount of danger a person is exposed to depends on the amount of current: 10mA is enough to be felt and progressively higher amperages causes muscles to contract, heart failure, etc.

Picanas and cattle prods, however, seem to operate with high voltage and low amperage, so as not to cause severe injury. Picanas even operate with as little as 1mA of current.

One difference is that the terminals are very close together when they contact the skin, but that doesn't fully explain to me how such low current suddenly becomes painful.

It's also not clear to my why voltage matters. Doesn't voltage only exist as a way to "pressure" current through the circuit? If the rate of electrons flowing through is the same, why would any level of voltage make any difference?


texts: Comprehensive way to indicate error code using single LED

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I am implementing Altera remote update mechanism, and it does not work, configuration falls back to the factory one.

I need to get the cause of it, and the only output I have is single LED.
Remote update state machine outputs 5 bits (page 35, 111 in the table).

My thoughts:

Blinking number of times binary represents is bad idea :), thus LED should somehow display bit states;
Circuit is having input clock, thus I can time the blinking for easy value readout;
Separating start, 1s, 0s and end: display "message" in loop, starting with 1 second long turn on (start), then one short blink for 0 or two short blinks for 1 within the second, then pause of a second, then display next bit, and at the end of 5-bit sequence the start goes again (1 second long turn on).

Is there any better way, or even standard and proven way in semaphore signalling, to achieve value readout effectively by the human?

P.S. I do not know which tags for my question are the right ones! Please edit if needed.


texts: How to be sure the bistable circuit is set completely

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Sometimes when input signal is close to 1.4v this circuit is not set completely and the output can   stay in the middle of Vcc. How to ensure the voltage at Q1 collector will be 5V, or stay 0v in case of the low level input signal, but no way in the middle?
I am thining about using avalanche effect, when it happened the energy forced to Q3 base will be high enough to switch the output completely. Maybe trigger monostable with timing about 10us should be enough to set the ouput of bistable correctly.

Edit:
It is similar to this state, it is unusual but from time to time it can happened:

Is there some circuit which has sharper peak point?


texts:
This is my first time to design STM32 circuit and I have no experience about the power down procedure.

In my opinion, it may be very rude to shut down the power supply as soon as the user presses the power down button because STM32 may need some time to store important information before shutdown.

Therefore, I guess the procedure may be like this: after the user presses the power button, the circuit should send the highest priority interrupt to STM32 who stores all necessary data immediately. After that, STM32 sends the disable signal to the regulator who provides the power to the whole system.

I'm not sure whether my guess is correct. If it doesn't like this, can someone tells me how what should the power-down procedure be in a real product or tell me where can I get the tutorial about power-down design? Thank you.


texts: TLE2141 op-amp alternative (in DC load circuit)

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I recently found a schematic for a DIY electronic load, which I think is based on Dave Jones's EEVBlog old DC load design (attaching the source link: Dynamic DC Power Load (updated), but I am attaching the schematic too):

The problem is that it is using the TLE2141 op-amp, which seems to be difficult to me to find. I have already searched for an alternative, but I can't find anything useful.

So can you tell me some alternative/equivalent op-amp I can use?


texts: Find impedence given per unit value-transformer

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I really can't wrap my head around this. Three single phase transformers are connected to create a 3 phase transformer. They all have the same nominal values :

voltage conversion : 1.2kV/120 V (primary/secondary)

impedence: Z=0,05 pu

power: 7.2 kVA. They are connected in 4 different ways , star-star, star-delta, delta-star, delta-delta.

My problem is finding the actual value of the impedence when the primary side is connected in delta. I would normally find the base in the primary side like this : $$Z_b=\frac{V_b^2}{S}$$ where Vb is the primary side voltage and S the nominal apparent power value given.

Having a look at the solution manual though the base is supposed to be this $$Z_{b,old}=\frac{(V_b/\sqrt 3)^2}{S}$$

I've wasted too much time on this. Can somebody help?  How can the connections matter since that 0.05 per unit value was assigned for the single phase transformers. Does a transformer's impedence change based on how it is connected?