texts: A sinusoidal sketching for peak 60V applied to a diode as shown

texts: This is the sketch of the circuit the peak value of AC is 60V and I need to know how can I draw the graph at Vo the R1 & R2 confuses me I can't understand there effect on graph and how the DC 15V connected is going to affect the graph. Please help me with this concept and graph.


texts: Waste heat in battery pack - large pack vs small pack?

texts:
Are larger battery packs more efficient than smaller battery packs due to "resistance in parallel" rule, assuming eveything else being the same?

As an example let's consider two 48V battery packs - 13S2P and 13S6P (let's assume that individual 18650 cell can handle 30Amp power draw). And electric bicycle that has a motor that consumes 2.88KW at cruise speed.

2.88KW at 48V would imply need to draw 60 Amps.

I found on Internet that Panasonic 18650 cells have 0.05 Ohms inner resistance. So, for 13 cells in series that would be 0.65 Ohms resistance.

With 13S2P battery pack the 60 Amps would be distributed over two parallel branches. Hence 30 Amps per branch. The waste loss due to inner battery pack resistance over both branches summed together would be P=2*(R*I^2)=2*(0.65*30^2)=1170 Watts.

With 13S6P battery pack the 60 Amps would be distributed over six parallel branches. Hence 10 Amps per branch. The waste loss due to inner resistance in battery pack over 6 branches summed together would be P=6*(R*I^2)=6*(0.65*10^2)=390 Watts.

Is there really 780W difference in battery pack waste heat? Does inner battery cell resistance stay constant over different current draws and temperatures?


texts: Input/output from unsynchronized ADC/DAC

texts:
DISCLAIMER : this question is somehow related to this other question of mine, but the latter did not have any satisfying
  answer.

I'm working on an audio DSP project with the STM32F4xx, using 4 audio inputs and 1 audio output.

I need to
 - read each input
 - process each input's signal,
 - mix the processed signals together
 - output the result.

The input is obtained via one of the 3 STM32's internal DACs, 1 channel for each input (ie 4 channels to scan in total) and stored to a buffer using DMA.

The output is converted through a codec using an I2S bus, at 48kHz.

Everytime the codec has finished converting a buffer (or more precisely a half-buffer), it triggers a callback function in which I currently have all the DSP code. In the loop, the output samples are computed and sent to the half-buffer to be output using DMA to I2S.

Granted that I sample my input at the same rate as my output (48kHz which means that my DAC must be clocked at 4*48kHz=192kHz), how can I synchronize the ADC and the DAC conversion?

I have thought of a FIFO inbetween the input and the DSP routine, picking a sample in the queue everytime I need to process one. But I am not sure how to do that when working with chunks of data (a buffer has a depth of 64 samples).

Another solution would be to have an input buffer depth of only 1 sample, and to read this sample in the DSP routine but I am not sure weather this would work.

Does anyone knows what is the best way to do that? Or even better, how to synchronize the STM32's ADC to an external codec?

EDIT: I also thought of using the DAC in "one shot" mode ie triggering a conversion of 64 samples for all the channels everytime my codec raises its "I want samples" flag. Would that work?

EDIT2: Upon request of @Neil_UK, here is an illustrative diagram of what's happening :

4 inputs are being sampled by the internal ADC of the STM32. Each must have a sampling rate of 48kHz so, given that the conversion of ADC channels is not done in parallel, that gives us a total scanning frequency of 192kHz (correct me if I'm wrong).

Then, each input's converted samples are stored in a circular buffer of 64 samples each and an interrupt flag is raised every time a half buffer has been filled (ie 32*4 samples have been stored).

On the other side there is a codec which continuously converts samples that are being sent to it via I2S, from the STM32's DMA. There is also an interrupt triggered every time the half I2S buffer has been emptied.
Between the 2 there is a DSP routine that is supposed to read the input, filter it and put it in the output buffer.

The problem: I have 2 interrupts:

The "I'm done converting" raised by the codec (DAC) ;
The "I'm done converting" raised by the internal ADC.

If I scan at 192kHz, these interrupts should at least be in sync (except for some jitter maybe) but the phase can be completely different. That means that I can have my DAC noticing me that all the samples are sent while my ADC is still in the middle of converting the inputs. And this phase difference can potentially be different every time I reset the board, so I can't really compensate it with an offset.

EDIT3 : It seems like the SAI module is a good way to do that, if anyone has experience with SAI I'd love to have some tips and help on how to use it to interface the internal DAC with an external codec


texts: DC power from speaker amp for power to switch relays?

texts:
Can you—or how do you—switch a relay using the power being directed to a speaker from an AV Receiver?

Here's what I'm working on:

In my kids playroom is an iMac on the East wall, and a projector on the North wall. When we want to watch on the projector we turn 90° to the right to a screen we pull across the middle of the room. This has worked great for the past couple years because my stereo system was old and basic and just filled the room with a blanket of sound.

I recently purchased a used AV receiver (Sony STR-DG720) with 7.1 Dolby Surround Sound, now I have problem because my sound system has a definite front to it. I have it set up with the iMac being in the front and the speakers mounted in the drop ceiling (this made the most sense for the shape of the room). Now I'm trying to figure out a way to rotate the surround sound 90° when we watch a show on the projector.

I went through a number of concepts and this is what I would like to make work somehow:

[SBR & SBL = "Surround Back Right & Left", SR & SL = "Surround Right & Left", C = "Center" (front), FR & FL (B) = Front R&L 'B', FR & FL (A) = Front 'A'. Look at the speaker labels to see which speaker is switched to which channel.]

The AV Receiver has a speaker selector for the front R/L speakers for selecting an alternate set of stereo speakers (Front 'A' and Front 'B'). The idea is when I switch from Front 'B' to 'A' with the remote, the power from the 'A' speakers switches all the relays for the rest of the speakers.

The part I don't know is if the power for the speakers can accommodate this. It's 105 watts for each speaker, but I don't know enough to know if that's a constant voltage or not. I imagine I need at least one more component here if it can work in principle, but I don't know what that component is.


texts: Laptop battery and adapter voltage ratings

texts:
Considering a 4-cell (laptop) lithium-ion battery, the cell voltages add (since they are in series) to 3.7 V * 4 = 14.8 V. However, the adapter says that it has a 19.5 V DC output. I want to know why is it 19.5 V and not some other value like 14.8 V itself or 24 V for instance?

Also, my adapter says Input: 100-240 V ~ 1.6 A and Output: 19.5 V - 3.33 A (65 W). Does it mean that the adapter efficiency is 65 W/(1.6 A*230V) assuming that the mains voltage is 230 V? Am I actually paying bills for 230*1.6 W or is it that 1.6 A is the maximum current that can be drawn and the actual current varies?


texts:
I am using M95512-W M95512-RM95512-DF eeprom for storing my data.
But sometimes it's not storing bytes I want. Instead of it, it's storing successive (wrong)bytes.
Can this occurs because I don't place any wait between two byte writes ?


texts:
I am looking for advice in protecting my circuit from both transient voltages and reverse polarity. I plan to use a unidirectional TVS diode along with a fuse (fuse directly off the battery, and TVS in parallel with the load). Idea being - normal transients found in an automotive environment will be sent to ground as the TVS clamps, and if the power is connected backwards it will blow the fuse. Then I can easily replace the fuse.
I chose this method due to its simplicity and this is a relatively high power circuit (15A continuous current, fused at 20A).
The normal operating voltage I suspect is around 14.6V. The lowest rated component in my circuit is an IC with 40V rating. As for selecting the TVS voltage ratings - I think this is the easy part. Pick a reverse standoff voltage around 20V, Breakdown voltage around 25V, and clamping voltage around 30V. This gives me some wiggle room on input voltage, and still protects the IC.
My main concern surrounds the reverse polarity part. How do I go about selecting the diode power based on the few seconds it will be shorted before the fuse blows? I take it that TVS diodes are not made for sustained current of any kind and might be damaged while it waits for a fuse to blow.
Is there a better, similarly simple way to protect the circuit without introducing any losses or parasitic drains?


texts: Issues with the initial state of a 7447N driver to BCD in a MOD 56 ripple counter

texts: I'm currently doing an assignment for school where I have to construct a MOD-56 BCD ripple counter using JK Flip Flops.  This requires 2 BCD displays and 7447N drivers to interpret the bits from the flip flops as the clock cycles.  After finally figuring out the gates needed to establish the correct MOD value I noticed something weird.  When the circuit is initialized in Multisim, the 10s place BCD is initialized to 7 rather than 0, even though the clock hasn't cycled.  I put some probe lights on the inputs to 7447N chip to see if maybe I could figure out why, and suddenly it was initializing to 6.  I removed one probe, and it initialized to 2.  This makes absolutely no sense to me.  It shouldn't matter in the grand scheme of things since I only have to show that the counter does indeed reset after 55, and it does that perfectly once it resets to 00 after being incorrectly initialized to 70, but it bothers me that I can't figure out why.  Any ideas?  Here's the circuit I've been working with:


texts: How to improve the sensitivity of a piezo assembly?

texts:
First and foremost I’d like to warn you that I’m not a native English speaker. Sorry in advance for my mistakes. And also I’m kinda a newbie in terms of electronics; so go easy on me please, I will try to be as understandable as I can.

I have a project to carry out dealing with piezo technology. I have to flash an LED using a piezo film. Here is the assembly put in place and it’s working (fortunately):

Some information regarding the components:

LED: LW3333-R1t2-5K8L

Op amp : LM358N

Q1: NPN transistor BC337-025G

Piezo film: don’t ask me about it, I don’t have any information. I took it from a device. However it generates within the assembly 50mv (for low pressure) to 1V (for high pressure)

I have some questions in regards of the circuit that I don’t quite understand.

1)  I used to have a resistor right before the diode as you can see on the following illustration, but I got rid of it because it appears to be irrelevant. Having it or not makes no difference. Why?

2)  When I squeeze the piezo (a pulse is generated) then maintain the pressure for some time and then release the piezo generates a positive pulse. Why not a negative pulse? I’d like to get rid of this second pulse that occurs when I maintain the pressure and then release (for brief pressure it doesn’t occur). I’ve added a Schmitt trigger right after the op amp on this purpose but I have the feeling that the sensitivity has reduced somehow. Do you have any suggestion?

3)  The resistor of 560kΩ plays the role of a pull down resistor for me. Is it the case? The assembly is working for a resistor of 250 kΩ (and even less but requires high pressure) to 600 kΩ (perhaps a bit more). Why this gap? This resistor has an effect on the sensitivity, I can more or less guess why but would you like to explain it for me?

4)  At last the main question: How to improve the sensitivity of the circuit?

Thanks in advance, I'd be truly grateful if you can help me out.


texts:
I have a PCB that has >10 ICs intended to be powered by a 3.3V supply.  Unfortunately, 12V was applied to the circuit and the board now exhibits a short circuit.  The offending power supply is current limited so that now when it is attached to the damaged PCB, the supply limits itself to < 100mV.

My question is this: In situations like this where the supply limits itself after a short develops, removing the overvoltage condition, is it typical for only a single IC to have failed (i.e., the weakest link) at which point the failed IC protects the other ICs on the board, or should I be looking for multiple device failures?


texts: SSR with low-flow switch to control heater

texts:
I'm trying to install a low-flow switch (circuit is open below 0.1 gal/min, closed above that) as a safety measure on an immersion heater, but I have some questions about the setup I've come up with (I've only taken an intro to electronics physics class). I have attached a picture of the diagram of the system and included links to the relevant product pages below. My questions are: Do I need to have some sort of resistor or load in the flow switch circuit between the fuse and switch so that there is something for the voltage to drop across when the flow is too low and the circuit is open? Similarly, would I need a resistor or load of some sort between SSR1 and Fuse 2 for the same reason? Lastly, I need the current in the flow switch loop to be below 0.7 Amps. I see from the SSR specs at the webpage below that the impedance rating is 36,000+/-20% Ohms, so with a 12 VDC power supply and 36 kOhms, I calculate a current of 0.3 mA. Am I calculating the current for the flow switch circuit correctly? Thank you!

Flow switch (0.1 gpm trip point) - http://compac.com/5-21-pp-straight-body-flow-switch-prolypropylene.php
25 Amp DC to AC SSR - http://www.omega.com/pptst/G3NA.html
PID Temperature Controller with two 12 DC pulse outputs - link in comments below

Update: Based on @Michael initial comment below, I'm thinking that the diagram below should work and it will get rid of one SSR and the 12 VDC power supply, please let me know if you think this will work. Thanks for the help everyone!


texts: Can the fake USB flash drive attack happen over Ethernet?

texts:
You may have seen the article This USB Drive Can Nuke A Computer where it shows how a flash drive shaped device can completely fry out all the components of a computer. This is very shocking (pun intended) for me as an Internet cafe owner.

But what's even scarier is the thought that someone could do this same attack over the local Ethernet cables and take out all my computers including my router without looking that suspicious.

My question is: Is the USB flash drive attack also possible over Ethernet and if so, will it affect all my computers.

Also, is there anything I can do to protect against the fake USB flash drive/Ethernet attack?


texts: How do I drive pin 2 on my 555 IC low so the one-shot timer will fire, using an IR sensor in place of my pushbutton switch?

texts:
I have a basic one-shot timer circuit (shown below in schematic).  If I press the button, it brings pin 2 low and triggers the timer one time for a period which with my cap is about 5 seconds.

Use IR Sensor To Drive Trigger Low

What I'd like to do now is replace the pushbutton with a specific IR sensor which I have.  I got it from AdaFruit and you can see the details at:
https://learn.adafruit.com/ir-sensor/testing-an-ir-sensor

This particular IR sensor has 3 pins.  You supply 5 volts on pin 3, ground on pin 2 and then when you fire the IR remote at the sensor it says that pin 1 is driven low.
I have successfully created the circuit which will light an LED with that circuit also -- you can see that circuit below (it's an image from the adafruit site).

How Do I Use This Circuit?
How can I hook this second circuit into my first one so that it will replace the push button and drive the trigger low?

Will I need to implement some kind of gate using a transistor?

simulate this circuit – Schematic created using CircuitLab


texts:
I am trying to implement a delay mechanism out of passive components. The digital input in this case is a PIC input pin. The operation is as follows. The capacitor is pre-charged to 5v, and then the power to the rest of the system is turned on. With the charged capacitor connected to the gate of the SCR, the SCR starts conductions, which in turn allows the transistor to conduct and sink the digital input to ground. Over time, the capacitor will discharge through R to the point where the SCR turns off, and this subsequently closes the transistor and the uC detects this to perform some action.

When R = 100kohm, it takes about 6 minutes for the cap to discharge and all the other stuff in the micro to start.
When R = 120kohm, the cap does not discharge at all. Or at least it does not discharge any visible amount in 30minutes when viewed on a scope.

What is going on here? Why is it with a reasonably small change in resistance, suddenly the cap has stopped discharging?


texts: Low-side switch MOSFET cannot deliver full voltage

texts:
I have designed a portable lens heater prototype. Using:

18650 Li-ion battery
Arduino ProMicro (3.3V , 8MHz) by adafruit (https://www.sparkfun.com/products/12587)
Push button switch
PMV16XN N-channel MOSFET (http://www.farnell.com/datasheets/1961351.pdf?_ga=2.83228374.1514726444.1578912472-1815861823.1560512053)
5ohm heating element (an embedded wire)

The MCU board works as expected and outputs 3.3V on the MOSFET gate when the button selects the correct mode. However, there is only 2.5V across the heating element. At full charge the 18650 should be able to output 4.2-3.6V. I chose this MOSFET because I thought RDson would be in a suitable region. Please see figure below:

I want to maximise the power delivered to the heater element. Is there some other MOSFET property preventing the 4.2V forming across the resistor? Can you recommend an alternative circuit/component?


texts: Simulation shows my op Amp has a gain for infinite frequency spectrum

texts:
I (could not) have designed an Op Amp and made the AC simulation on LtSpice and I saw something annoys me as below:

and here is the schematic, a pretty basic op amp structure:

As you see, at least 10 dB gain is seen through frequency(I simulated up to 100 GHz still same!) domain. How is this possible? Eventhough, I could not design the Op Amp well, isn't this impossible?

I use these directives as seen on schematic:

.MODEL TestP PMOS (KP=60u VT0=-0.5 LAMBDA=0.01)
.MODEL TestN NMOS (KP=120u VT0=0.5 LAMBDA=0.01)

And I have tested it, it works fine. But I do not understand why am I getting a result like this. It is a first for me. So can you suggest anything to fix this issue? Thanks.


texts: What do you call unity gain? 1V/V or 1V/V plus a small tolerance?

texts:
I designed a two stage single ended op amp with an internal frequency compensation. There's a minor problem that I noticed in my loop gain transfer function.

I forced the gain to reduce to around 0.5dB at fz1=200MHz, where fz1 is an LHP zero. In addition to fz1 I've got a pair of complex conjugate poles at about 400MHz. Think of complex conjugate poles as two real poles that merge together. The other poles and zeros are not important so forget about them.

The problem is that the gain is almost constant, starting at 200MHz with the magnitude ~0.5dB and slowly decreasing (due to the nearside complex conjugate poles) to 0dB at 250MHz, which is considered to be the unity gain frequency of my op amp.

So now is the unity gain really at 250MHz? Because the gain is almost 1.05V/V at 200MHz where 1.05V/V is only 5% greater than the unity gain. Maybe it depends on the application and the precision that it requires.But anyway please let me know if my design is any good.

Thanks


texts: Electret Microphone recognize music with FFT

texts:
Do you think is possible that this Electret Microphone https://www.sparkfun.com/products/9964
plus a DSPIC can recognize music frequencys with a FFT, or the electret only recognize the sound levels?


texts: Prevent long press in changing state on D Flip-Flop

texts:
I've made a circuit on Logisim that allows me to switch between three LEDs at the push of a button. Essentially allowing me to cycle between OFF, LED1, LED2 and LED3 repeatedly. I'm doing this using four D Flip-Flops.

However, I'm getting an issue that if you hold down the button it will keep cycling through all the options. This isn't much of a problem at low clock speeds but at like 64hz it's unusable. I want to use a higher frequency clock so essentially I want it to only switch when the user presses but if he holds down the switch it won't go to the next iteration in the cycle.

I'm a software developer and can barely remember the stuff I learned in college about circuits so please explain me like I'm 5.

EDIT

Thank you guys so much for all the help. I ended up trying to make both the version with 4 flip flops and the one with 3. Both are really good solutions and require about the same amount of circuitry.

4 Flops

3 Flops


texts:
I am working on an Arduino project that requires me to be able to handle audio input from a 1/4" input jack, and it needs to be powered with just one 9V DC input. Since the Arduino cannot process negative voltages, my input needs to be centered around 2.5V, not 0V. I found the attached schematic on a similar question, but it uses an LM321, and I only have a TL082. I'm new to op amps, so I don't know much about the differences between them, and I'd rather be as cautious as possible with my components. Therefore, my question is:

Will this schematic also work with a TL082 in the place of the LM321, and if not, how else can I achieve a 0-5V audio signal with a singly-powered TL082?

Cited question: Convert an audio signal to 0-5V using single supply op amp

TL082 Datasheet from TI: https://www.ti.com/lit/ds/symlink/tl082-n.pdf


texts: Is current waveform of given dc-dc converter correct?

texts:
I don't understand how current (in continuous mode of operation ) at steady state is bounded for this dc-dc converter circuit.
What I thought qualitatively that current should keep increasing like this -
My analysis was something like that -
At t=0 ;
We close the switch and initially inductor has zero intial current ,and after that current keep increasing and reaches to some value
$$I1max$$
and at that instant we open the switch which causes inductor current to decay through resistive load and reaches to a value
$$I1min$$
and then again switch closes and again current of inductor rises and  just before opening of switch current will be
$$I2max$$
BUT
$$I2max > I1max $$
Because this time inital condition is I1min while previously it was zero ,and hence we can say that as time passes initial condition keep increasing and which causes current to increase in every cycle and hence it become a  unbounded function!
But whatever I analysed is not what actually happens so where did I make mistake in my analysis ? Or this waveform is not correct?


texts: Chaging EA/VPP by software on Intel MCS-51/8051

texts:
I'm designing a circuit that uses the combined Program/Data bus from Intel MSC-51 as advantage.

By the MCS-51 specification it has an internal 4K ROM and a EA/VPP pin that if set to high will access this 4K internal ROM and if set to low will access any external ROM (using PORT0 and PORT2) and i want to change this value by software connecting this pin to PORT1.0 for instance.

I cant find any reference on datasheet to check how is the behaviour of the EA/VPP pin and if its specific to the MCU design or is default for every MCS-51 MCU.


texts:
I am using a CD4040 to divide a oscillator frequency and reading its period using PCA. The problem is I was using 3 oscillators, 120kHz, 70kHz and 30kHz and dividing it by 32. The problem is, when I shake my board, the measuring get really screwed. I tried my oscillator, I can't see any change on it using the oscilloscope, but the Capture value shows that it changed. What could the problem be? I'm starting to think that I could have harmonics between CD4040 and 8051 input.

Edits:

I can't send my setup pics unfortunately but about the mechanical problem, if I hold my board and try to hit it softly at random places, the only place my measurement becomes different than it should be, is when it hits near the 8051. I can hit my LC tank, I can hit my 1:1 transformer, I can hit my transistors and etc. I tried to resolder all my SMD components again and even got a new 8051, but the problem continues. Later today I'll change my CD4040 exit to a lower divider so my frequency gets a bit higher, because I'm afraid my lower frequency can be causing this sensitivity.

About the PCB, it's a real PCB, we designed it, made it at a PCB house and soldered the components.

My major problem is: My uC can detect the period variation, but my oscilloscope can not. I'm using a Tektronix TDS-1012.

It's a "Differential Amplifier" configuration, but one of my NPN collectors has the LC Tank. My L is a 1:1 transformer inside one of these and my Inductor is a loop for metal detection. So for values I don't know them very well, because I didn't measure the loop inductance nor the transformer's mutual inductance. The Tank's capacitors are polyester, mostly bought from Digikey.


texts: 555 timer boost converter doesn't meet spec

texts:
I've been messing around with nixie tubes lately which requires a high voltage source (~150V-200V) to turn on.

I searched around for a simple high voltage generator and found this circuit which uses a 555 timer to get an adjustable, regulated high voltage output between 170V and 200V.

I got all the parts and I prototyped it on a breadboard. After plugging in a 9V battery and being absolutely sure that it wouldn't explode in my face (e.g. by accidentally install a cap backwards), I measured the output voltage and got a nice 210V output without a load and with the trimpot adjusted to give maximum voltage.

Unfortunately, the voltage dipped down to about 170V as soon as I connected up the nixie tube. I measured exactly how much current was flowing and found that the configuration was barely 15% efficient. The circuit draws about 100mA on the input without a load! The Nixie tube itself drew about 0.8mA at 170V and the input draws about 120mA.

$$
\frac{170V \times 0.0008A}{9V \times 0.1200A} = \frac{0.136W}{1.080W} \approx 12.59\% \text{ efficient}
$$

I put it down to losses due to inefficiencies in the switching (I did lay this out on a breadboard) so I spent the afternoon making a PCB version while carefully following whatever SMPS PCB layout guidelines I could find. I ended up replacing the output capacitor C4 with one rated for 400V since 250V was still cutting it too close. I also used ceramic caps instead of the film caps suggested in the instructable.

However, there was still no significant difference in efficiency.

I also noticed that the output voltage seemed to vary proportional to the input voltage. At 9V, it would give voltages closer to 170V with a load and about 140V at 8V with a load.

So right now, I'm starting to think that I've either missed something obvious or this boost converter circuit just kind of sucks. Needless to say, I'll probably be looking into other, more efficient designs but I'm still rather keen on discovering why this circuit behaves this way.

I suppose the voltage drop when a load is connected can be explained by the fact that the 555 isn't producing a long enough duty cycle for the switching so there isn't enough power being delivered to the output.

The varying output voltage proportional to the input voltage can probably be explained by the absence of a stable reference voltage. The feedback loop uses the input voltage as a reference so it's more like a regulated voltage 'multiplier'.

But I still can't figure out where the 100mA drawn from the input is going when there isn't a load. According to the datasheets, the 555 timers draw very little current. The feedback voltage dividers certainly don't draw anywhere near that much. Where is all that input power going?

tl;dr can anybody explain or help me understand why this circuit sucks?


texts: What are the parallel branches shorted out in one but not in the other case?

texts:
Case 1

simulate this circuit – Schematic created using CircuitLab

Case 2

simulate this circuit

Why in case 1 only R1 is shorted out. whereas in case 2 both R1 and R2 are shorted out?


texts: How to drive an IGBT with an optocoupler?

texts: What's the proper schematic for driving the IGBT (IRG4BC20UD) from a microcontroller (MSP430-g2553) pin through the optocoupler (FOD3184)? I am going to design a full bridge inverter to drive 9W CFLs (220V/50Hz)? PLEASE HELP!


texts:
While I have a good idea how this circuit works, there are few doubts.

1, what is the purpose of R1(10K), R2 (18k) and C102 (47u)?

2, Also I notice that few of these PIR modules have an input diode, other than the obvious polarity protection, is there any important purpose for D1?


texts: Is there a device which replaces soldered pin headers?

texts:
I have to flash several devices and up to now I was soldering pin headers to attach the device to my PC.

I will soon have 20 or so to flash and would like to avoid messing up with the soldering part (soldering is great but I just need the header pins to be available for 30 seconds and never reuse them afterwards).

Is there a device I could use to avoid soldering them? I saw some hacks where people were doing all kind of gymnastics with bent pins and it worked or not -- I was rather thinking of some kind of a prong to reliably touch the contacts during the flashing.


texts: I am trying to simulate a wheastone bridge amplified with an AD8422. In principle, with a Rg of 500 ohm, it should give me a gain of 40, according to $$ G = 1 + 19.8k\Omega/R_G $$  but instead I get a gain of 0.45.I checked the circuit several times but I cannot see what I am doing wrong. It's the first time I simulate with LTSpice, but I don't think the error will be related with the program.


texts: Capacitive coupling: how to collect 60uA from this set-up?

texts:
I need to collect at least 60uA via capacitive coupling between a high tension Cu cable with PVC insulation and a connector that is acting as the opposite face of the capacitor (can be a copper plate wrapped around the wire insulation or some turns of Cu wire around the insulation, or any other way).

Here the details:

The cable insulation is made of PVC (dielectric constant 3.19) and is 3mm thick.
The inner cable is made of copper 1mm thick.
The voltage provided to the cable is 14 000 V.
the voltage is provided by an ignition coil, with about 1000 spark each minute

How can I act? is it possible to collect the  60uA in any other way?


texts: Does anyone perhaps know what type of connector this is please? It's 8-pin but not a normal DIN connector. It's the remote control port for a peristaltic pump. I've asked the manufacturer for the connection type - they refuse to tell me, and only offer their own cable for £25 + c£100 in minimum order charges!


texts: Assistance in finding proper sensor for short-range object detection task

texts:
We are working on a research project. We try to measure the distance from an object to some static line/pole. The area of interest is within a range of 1 to 5 meters, and the tracked object is a human.
Our desire is to precisely measure the distance with a max disparity of up to 2cm.
Our region of interest is an imaginary tube with a radius of up to 40cm, but it may be less. The length of this tube is about 5 meters.
The attached pic illustrates our case - an object goes over the virtual "tube" (a region of interest, essentially). The distance (x on the pic) we would like to measure.

We tried stereo vision approaches, but we also want to compare results with lidar/ultrasonic sensors. Can anyone suggest some proper sensor? Our technical limit for this sensor system is a weight. This system should be less than 3 kg. Our project has flexible budget, so costs are not much of a limit.
One of the possible solutions we consider is a set of small lidar/ ultrasonic sensors. A very primitive scheme is drawn on the attached pic. Tiny same size sensors are depicted in red. Pole to which the distance we interested in is depicted in gray.

The moving object goes over the static object, and "cuts" the beams of several of the 1D Lidars in our array.
We thus know the object position with a precision of the space between Lidars in our 1D array.
We have searched for various lidars to achieve this purpose, and because of the precision being tied to spacing between sensors, the following constraints arise:

Something small is necessary for this purpose - a diameter of max
2cm, assuming this is still a circle-shaped sensor.
Since it's tracking a moving object, a scanning frequency of, say, >30hz would be good. The range is up to 5 meters.
The beam is very directional and focused so that there is no
crosstalk/interference between elements of lidar array. Because we
need very directional beam, FOW for one sensor should be less than
0.5 degrees.

The precision of distance from sensor to object is not important for
us, we just need to know if there is an object present or not.

The closest candidate that fulfills the requirements by size is actually an ultrasonic sensor, however that has issues with focus and interference.
If anyone knows of a sensor that fulfills this purpose or can guide me to who might offer one, I would appreciate it. Thank you.
P.S.
A friend of mine posted the same question in Robotics, but we have not received any answers.


texts: Totally noob here,help me choosing the best method of powering led

texts:
First of all im sorry for the grammar because english is not my 1st language,so bear with me.

So im trying to power up 100 0603 red smd led,its a generic brand and all data i could gather was its 1.8 - 2.0V and 20ma

I tried to powering all of them for a diorama (mostly plastic) with a 5v 1A phone charger (its just laying around and easy option),parallel with 100ohm resistor (at first i though every led was rated 3v,i bought pack of them and realized it was wrong,i used it anyway) at each one of them.

Everything light up perfectly and so bright,but sh*t happens when i let them on too long,its melting some of my diorama especially the one that i glued on tight place,i never really try to touch the led (i though if its light up then its fine),so i touch it and its fells like its sting me,its hot to the level you cant hold it but not enough to kill the led but i think the life span would shorted.

Then i tried to power it up directly from my pc USB port,its rated 5v 500ma,led became cooler,just warm but its okay to touch. On another try i just double the 100ohm resistor (at first i though it would dim the led,turn out not much) and the led seems fine,no overheat or noticeable dim at all only warm just like usb pc but it would be my last option since i already wired everything and to add another resistor one by one again woulf be hassle.

Any idea i could solve the heat problem without too much hassle? Also a thing bugging me is every answer on google said i could put 1 billion amperage on 20ma led and it still gonna take 20ma from it so it would be fine,but why i notice a significant temperature change when i switch from the charger to the usb port with less amperage? Too much current or too much voltage? Oh btw im not yet to wire all of them together,only a small pack like 20 - 30 at a time for testing,i wonder what happen if i wire all them up and put it on,should it be pulling 2000ma at once?

Thanks.


texts: Is it safe to charge a Li-Po battery at a lesser C rate than its usual routine?

texts:
On my Quad Copter I have a 5400mAh Li-Po battery (3S 11.1V) and its charger charges at 0.5 C since it takes 2 hours to charge the battery.

That charger has broken down, I have ordered a replacement which will arrive in a few days, however I do have some other chargers that can charge at different rates.

There is one specific charger that only provides 1 Amp which is almost 1/3rd of the usual charge rate those batteries have been witnessing.

All I want to know is whether it is safe to charge a battery with less current than its regular cycle?

At 1 Amp it will take 5.4 hours to charge that battery. It is a balance charger like the existing one so balancing is not an issue. I'm fine with 5.4 hours I just don't want to ruin the battery.


texts: I cannot select certain parts of my board?

texts:
I have been dealing with this issue for the past 3 hours, and have moved nowhere from this. Very frustrating, considering this is a one credit course. My main issue is that I cannot move some of my board components when I select them. I have tried selecting a box, unchecking all the protected elements, and utilized the selection filter, to no avail. I still have the following error. All the parts that are not able to be selected have the following out of board issue:

https://imgur.com/a/uJnJ6vm

Any constructive feedback/help is appreciated!


texts: So which direction do electrons really flow?

texts:
As I understand it, electrons (which are negatively charged) flow towards positive.

As a convention, we say that current flows from positive to negative. Is this to say that what you connect the positive terminal of a battery to, say, VDD of an IC, and the negative terminal to the IC's GND, what is actually called the "positive terminal" is really ground/negative? Are the electrons flowing from "positive" to VDD, or "negative" to GND, etc?

Are the flowing electrons themselves responsible for the work done, or is it the "holes" moving in the opposite direction?


texts: MCP73831 Li ion battery charger problem with load sharing circuit

texts:
I am building a device which is being powered by single cell Li ion battery (1100mAh), i am using MCP73831 Li ion battery charger and controller in my design to charge the battery.

I am using below Load sharing circuit in my design

I have got the schematics from this page : LINK

Note : R3 is 2K in my case.

I am having problem with B130LAW diode (D1), This diode is heating when the battery is kept on charge and it's extremely heating for the first few seconds when the battery is kept on charge from 0%

What could be the problem of heating of that diode.? OR anyone can provide me any other Load sharing circuit for my requirement

My load is around 200mA, i am also boosting battery voltage to 5V using LTC3426 chip, Keeping in mind MCP73831 is charging the battery at it's peak charge current 500mA.

Edited below :

I have just noticed that mcp73831, D1 and Q1 are all heating only for 5-8 seconds.
Is this because of mcp73831 is in preconditioning state? It's only happening when the battery is totally down.

When I check current going to the battery from mcp73831 is about 750mA only for few seconds then it's coming to 500mA..

Testing Voltage across pin of Q1 and D1 (when the D1 is not heating):

I have disconnected battery to test voltage drops across diode and Mosfet, Vin to Diode is 5.06V and other end it is 4.88V.So voltage drop at diode is 0.2V, on the other hand voltage reading at mosfet pins are at Drain : 4.87V, Gate: 5.07V, Source : 4.33V

When connected to battery and charging voltages are as follows :
Diode : Vin 5.00V and other end 4.74V voltage drop 0.26V
MOSFET : Drain : 4.74V, Gate : 5.00, Source : 4.09

See voltages when all three are heating up, charging from 0% battery charge.

Thank you


texts: Reducing Common Mode Voltage at the ADC input

texts:
I need some help from you expert engineers.

I have to automatically measure VCE / IC and VBE / IB of a big bunch of transistors under specified collector and base voltages.

Since Vcin and Vbin can be either positive or negative voltages (NPN and PNP transistors) I chose an ADC (ADS122C04, http://www.ti.com/lit/ds/symlink/ads122c04.pdf) capable to work
with such voltages.

To stay in the ADC's maximum voltage ranges (common mode voltage) I tested two different solutions:

Use two voltage dividers one for AIN0 and the other for AIN1. But, any small mismatch between resistors values leads to very high errors.
Use a virtual ground tied to AIN1 and a single voltage divider for AIN3.
Virtual ground tied to AIN1 keeps the AIN1 voltage to 0 and AIN0 to a voltage which is below the max ADC's input voltage.
This works well to measure VCE and IC, I get values very close to what I measure with my bench multimeter (see output below replacing the transistor with a 10K resistor between collector and emitter).

Problem is with IB and VBE. Following the same approach used for IC/VCE I  should also tie VGND to the base but this shorts base and collector.

To overcome this issue, I used an IC switch (ADG1636, https://www.analog.com/media/en/technical-documentation/data-sheets/ADG1636.pdf). Hence the microcontroller, using the Sel signal, switches AIN0, AIN1 between R1 and R2 (collector and base) before the ADC reads the voltages.
I chose ADG1636 because the low series resistance.

Everything works well up VCin = 2.6 - 2.7V after that the measured voltage across the burden resistor gets smaller than the actual value (again the transistor with a 10K resistor between collector and emitter).

I understand that the IC switch has a series resistance which get larger when voltage increases but, since the current on AIN0 and AIN1 is quite small, I thought it shouldn't impact the measurements.

I stuck here.

I need any advice either to get rid off the IC switch and read VB/IB without shorting base and collector or to make the switch working up to larger voltages.

More generally, how can I reduce the Common Mode voltage at the ADC's input?

By the way, I simulated the classic approach with a non inverting level shifter based on Op-Amp (one for each input) but apparently readings would not be very precise.

Other option could be using an instrumentation amplifier (like INA826) but this would increase circuit's complexity and price.

Thank you in advance.


texts: Arduino: better microsecond resolution than micros()?

texts:
The micros() documentation notes that the return value will always be a multiple of 4.

Is there any way to get a higher resolution microsecond click, preferably down to the 1 microsecond level?

Dropping down to the AVR level is acceptable.


texts: Using 10 bit ADC for only 8 bits on a PIC MCU

texts: I have a PIC16f1824, which has a 10bit built-in ADC, but I only want 8 bit precision. I don't just want an 8 bit value, but actual 8 bit conversion i.e. higher samples per second at the cost of bits. Here I am stuck because the ADRESH register get loaded only once whole 10 bit conversion is performed.


texts: How to adjust linear voltage regulator equivalent?

texts:
I'm attempting to build a linear voltage supply. (I'm not touching the mains yet.)
My first thought was to use an adjustable linear voltage regulator. Unfortunately, I found that linear voltage regulators have minimum load requirements as well as a reference voltage which translates to your minimum voltage output. On most linear voltage regulators I found that reference voltage to be ~1.25V.
I want to be able to go from 0V-30V with current limiting from 1-3A. So, I looked at the equivalent circuit of a linear voltage regulator on one of the datasheets and came up with this...

Since op-amps don't pull much current (in ideal op-amps zero current), and can have a maximum input voltage above 30V I thought that this circuit would be perfect because really my only limit was the maximum collector voltage and current of the BJT connected to the op-amp output, and I can get 0V!
Since the op-amp inputs don't draw current anyway* the voltage divider just has to establish a low current voltage reference. I thought that would be easy, but I was wrong.
Assuming I replace R1 and R2 with a potentiometer, when I'm at a high total resistance everything will be fine. When I drop lower power gets in the way. If I'm at 0 resistance (0V reference) the voltage divider will basically be a short and I'll be fine:
$$I=V/R$$
$$I=30/0Ω$$
$$I=0A$$

$$P=VI$$
$$P=30V(0A)$$
$$P=0W$$
But, when I want a very low voltage power becomes a problem.
(Let's assume total resistance is at worst case resistance of 1Ω)
$$I=V/R$$
$$I=30/1Ω$$
$$I=30A$$

$$P=VI$$
$$P=30V(30A)$$
$$P=900W$$
And even if my constant current regulator was working before hand and only let me draw 3A, I'd still be having power troubles.
My second solution was to leave R2 as a high value resistor and substitute a potentiometer for R1. In this case I wouldn't be having power troubles anymore but something would be funky with the control scheme. Let's say the potentiometer replacing R1 is at 0Ω.
In this case R2 acts as a current shunt, and I get my full rail voltage as the reference voltage. But the potentiometer would have to go from 0Ω - ∞Ω...and I don't think that's feasible.
The third solution I thought of was to use a linear voltage regulator as a voltage reference but...that kind of defeats the purpose.
The fourth solution I thought of was to replace R2 with a potentiometer instead of R1. I wouldn't have power issues, but the power supply would go from 30V to 0V turning right, and again the potentiometer would have to go from 0Ω - ∞Ω.
There must be a way to do this, but how exactly?


texts: Find the differences between two signals with an opamp

texts:
I have been trying to find an answer to this question and I am sure I probably just don't know what the circuit is called so I am unable to find it. Basically I want to take two input signals that for example are exactly the same (ex. 1Vp-p @ 1hz) and put it through an op amp to only get the differences. Image below of what I am kind of thinking:

So for the above circuit the two buffer opamp's create 2 signals that are the exact same. Then the second opamp stage add's a gain of 2 to each individual signal. The thought on the third stage is to take the the two signals and cancel each other out to have a 0Vp-p output signal. To do this I thought just putting each signal to the input of an opamp with no gain would give this result since the voltage on each input terminal would be the exact same. But when I simulate it with the circuit above it only acts like a buffer. The through is that I can then add noise to one (or both) of the signal paths and only have the 3'rd opamp output the noise and no signal, which then I could sum the two similar signals together and remove the non-common noise.
Sorry for the question I am not an electronic engineer (just a hobbyist) and I am just trying to learn things by trying and then looking up/asking questions.


texts: How can I generate a 13GHz sinosoidal wave with a multipilier circuit?

texts: I have heard with some multiplier circuits we can obtain a low phase noise oscillator. For example, by using a 100MHz OCXO and a multiplier circuit with a multiplier factor of 100 we can obtain a 10Ghz with low phase noise. My question arose on how to generate a 13GHz signal with this procedure when the multiplier factor is not common.


texts:
I'm attempting to interface a PIC18F4520 to a 25LC640 via SPI protocol. I'm using the built in MSSP hardware of the PIC. The PIC18F4520 is the only master on the bus. I'm reading 16 bytes of data from the EEPROM 32 times per second. I've double-checked the following items:

TRIS Registers for SDI, SDO, SCK, and CS
Baud Rate ~ 1 Mhz
SPI Mode 0,0

I've checked the signals on an oscilloscope and everything looks fine. I've tried using a BusBee to log the data coming from the EEPROM and 99% of the time it's correct. Every once in a while there are a string of requests where the MOSI (SDO) line does not seem to contain the correct EEPROM read instruction causing the data being clocked into the micro to be invalid. This happens even though I'm writing the same read instruction in the SSPBUF each time. What else can go wrong with a SPI bus?


texts: Why doesn't the emitter resistance of a BJT depend on the AC current?

texts:
When designing BJT transistor amplifiers, one calculates the emitter resistance of BJT:

\$r_e=\frac{26mV}{I_c}\$

where the voltage is the thermal voltage at room temperature and \$I_c\$ is the bias current.

This is how it's usually done, but why do we calculate it using only the bias (DC) current? If the resistance depends on collector current, why doesn't the \$r_e\$ resistance swing up and down as the collector current swings with the input (base) current?


texts: The IDCODE read from the device does not match the IDCODE in the BSDL file

texts:
I checked many different posts with the same problem, but none of the advises were helpful thus far. So, I am using ISE 14.7, DLC9G USB Cable, and trying to program the XPLA3 256 CPLD. After successful generation of programming file I click on the 'Configure Target Device' in the processes window and this lunches the IMPACT. The CPLD is directly connected to the programming cable pin-to-pin with no extra peripheral components.

Then I click on Boundary Scan and then right click Add Xlilnx Device and choose the .jed file from the project folder.

Looks like the device is added successfully. Now, when I right click -> Program on the device, I get a properties window and press OK:

but programming fails. Here's the console output:

----------------------------------------------------------------------
GUI --- Auto connect to cable...
INFO:iMPACT - Digilent Plugin: Plugin Version: 2.4.4
INFO:iMPACT - Digilent Plugin: no JTAG device was found.
AutoDetecting cable. Please wait.
*** WARNING ***: When port is set to auto detect mode, cable speed is set to default 6 MHz regardless of explicit arguments supplied for setting the baud rates
PROGRESS_START - Starting Operation.
Connecting to cable (Usb Port - USB21).
Checking cable driver.
Driver file xusbdfwu.sys found.
Driver version: src=1027, dest=1027.
Driver windrvr6.sys version = 11.3.0.0. WinDriver v11.30 Jungo Connectivity (c) 1997 - 2013 Build Date: May 12 2013 x86_64 64bit SYS 14:54:36, version = 1130.
Cable PID = 0008.
Max current requested during enumeration is 74 mA.
Type = 0x0004.
Cable Type = 3, Revision = 0.
Setting cable speed to 6 MHz.
Cable connection established.
Firmware version = 1303.
File version of C:/Xilinx/14.7/ISE_DS/ISE/data/xusb_xlp.hex = 1303.
Firmware hex file version = 1303.
PLD file version = 0012h.
PLD version = 0012h.
PROGRESS_END - End Operation.
Elapsed time =      1 sec.
Type = 0x0004.
ESN option: 000016D4573401.
INFO:iMPACT - Current time: 5/29/2014 5:22:52 PM
PROGRESS_START - Starting Operation.
INFO:iMPACT:583 - '1': The idcode read from the device does not match the idcode in the bsdl File.
INFO:iMPACT:1578 - '1':  Device IDCODE :        00001111111111111000000000000001
INFO:iMPACT:1579 - '1': Expected IDCODE:    00000100100101001000000000000001
PROGRESS_END - End Operation.
Elapsed time =      0 sec.

Then I tried Debug -> Chain Integrity Test, but it fails too:

INFO:iMPACT - Current time: 5/29/2014 5:26:04 PM
Maximum TCK operating frequency for this device chain: 10000000.
Validating chain...
INFO:iMPACT:1209 - Testing for '0' at position 9.The Instruction capture of the device 1 does not match expected capture.
INFO:iMPACT:1206 - Instruction Capture = '11111111111'
INFO:iMPACT:1207 - Expected    Capture = '10101000001'
INFO:iMPACT:2130 - Boundary-scan chain test failed . Please check tdi->tdo connection between  device:'1' ( 'xcr3256xl') and the cable .
    A problem may exist in the hardware configuration.
    Check that the cable, scan chain, and power connections are intact,
    that the specified scan chain configuration matches the actual hardware, and
    that the power supply is adequate and delivering the correct voltage.

So I checked the connections all over again and everything looks intact.
I also checked the BSDL file for this device and in contains the following:

...
attribute INSTRUCTION_CAPTURE of XCR3256XL_TQ144 : entity is "00001" ;
attribute IDCODE_REGISTER of XCR3256XL_TQ144 : entity is "XXXX0100100101001011000010010011";
attribute REGISTER_ACCESS of XCR3256XL_TQ144 : entity is
...

I tried to mask the "Manufacturing section" with 'X's, but it did not help. Please, any more suggestions?


texts:
I have to make the CMOS-equivalent of this function: \$A'*B'+C'\$. I made this CMOS-circuit, but I'm not sure if it's correct:

simulate this circuit – Schematic created using CircuitLab

The course I'm following isn't very clear about this subject.


texts: I am working on an electric longboard, retaining the original battery pack and brushless hub motors. I want to be able to control this with an Arduino. I want to know what size ESC I will need. The battery pack is 30V and the hub motors have a 1200W rating each. Will a 50Amp ESC be sufficient for each motor?


texts: How to create a component from a pre-existing one in Altium Summer 09?

texts:
I'm using Altium summer 09, I need to use "D connector 15" , however, I need male and female connectors. I do not know which of them was made, male or female, in the footprint of the compenente "D connector 15" of the library "Miscellaneous Connectors Intlib" . So I figured I thought to copy the "D connector 15" that is available into the "Miscellaneous Connectors Intlib" library and create my own library to be able to modify it as I want. Does anyone know how to do this? I looked for some explanations on the internet, but it is not working. I did the following?

File »Open
 in the path C: \ Program Files (x86) \ Altium Designer Summer 09 \ Library
the file:  Miscellaneous Connectors

So, a window pop-up appeared and ask me to choose "Extract Sources" or "Install Library" I choose "Extract Sources".

Then, in projects, the extracted library appears.

However, I can not access the "D connector 15" component, nor the schematic nor the footprint. How then can I copy so I can generate another component from it?

[edited]

After to extract Micellaneous Connectors intlib, I openned the SchLib and PcbLib and, as I informed before, I couldn't find the component D connector 15, however, I did:

Tools -> Next Component

I kept doing this until the D connector 15 appeared. So, I could copy it and paste to my own library and modify it.


texts:
A dependent voltage source E2 is changing between 0 and 12 volt. Most of the time it is floating around 12 V but it can go dramatically down sometimes. So this voltage source is not constant, i.e the voltage across R1 is not regulated. L1 in the picture does not interfere with the circuit, it is just a current sensor.

Since my DAQ device's range is maximum 10V,I need to scale this changing voltage maybe to half the amplitude and record it in in time series. So I will connect it to a DAQ board to log the data(I will hook up the Voltage across R1 to DAQ).

I will add an interface(circuitry with an op-amp or something else) between R1 and DAQ in the picture.

I need to satisfy the following conditions:

1-)The interface I will add should drive almost no current. In other words L1 sensor's current measurements should remain almost exactly the same as in the case of the original setup above.

2-)The interface I will add should almost exactly half the E2 voltage so I will have the same time series profile as in the original setup above.

Which op-amp configuration would be recommended?


texts:
I have a wall-powered embedded device that has several sensors. The MCU collects all sensor data, packages it and then sends it to an on-premise server through UDP. It is sending data every 100ms, which works fine.

A Python script is running in the server that collects sensor information, takes some decision and sends it to the cloud if necessary.

Now I have several of these embedded devices which need to do the same, send data to this server, every 100ms.

I am having some doubts about the UDP part. I needed a wired communication and UDP was easiest to implement. Now, as I am scaling I was wondering, considering my situation, if it was the right way to do it?

I looked up CoAP and MQTT, MQTT vs HTTP, but I don't have the right metrics to decide. I guess the question is: How do I decide what protocols I should use?

Note:

The devices are not battery operated.
The device to the server has to be a wired communication.
The data I send from the device to the server is not more than 100 bytes. (The device is modular, I can plug-n-play sensor modules, so depending on the number of the sensor the payload might vary).
I am sending data every 100ms. That's a hard requirement.

Any suggestions would be much appreciated.


texts: Is there a double standard or has something changed with NRTL and CSA requirements?

texts: I've been going over threads about having NRTL or CSA certified electrical equipment.  Everyone comments the seriousness of this.  But I am confused that Home Depot, Harbor Freight, Target, on and on any major chain store is selling equipment and appliances with only the CE mark.  I read that Canada requires all electrical equipment to be CSA certified but see that stores there are also selling CE equipment from China.  Has something changed when they made these trade agreements?  Or is the law just not enforced?  Because if it was enforced all of these stores would be out of business and nothing from China could be sold in the USA or Canada.  I was just at an equipment manufacturing trade show in LA. and there were many companies selling large manufacturing equipment with only the CE mark.


texts: 5 volt small UPS design (review request)

texts:
I'm designing small 5 volts UPS that would allow me to run on battery or 5V source.

If source is unavailable, step-up module takes power from battery.
If this 5V source is restored, then this source is taken for step-up module, but also battery is being charged

There are two diodes, so only one source will be taken to step-up module, by comparing voltages - 5V or from battery (3.7-4.2V),

I've decided to do it semi-DYI, so I used some ready made components,
but I'd like You to review these connections.
Connection and modules in short:

charger module is a widely available TP4056 module, available for few bucks. It stops charging at 4.22V and resumes charging when battery voltage below 2.8V
Li-ion battery is a 18650, 3.7V one, scrapped from battery bank (no protection)
two diodes shown on image below are Schottky 1N5819 1A / 40V
at the output, I have step-up module that gives me a stable 5V/500mA source for devices connected

Is this module safe to leave it unattended, or maybe you would change something here, like adding extra protection, modules replacement ?
I used Schottky diodes, but since this is my first real electronic project (without the ones did for a fun and learn), I didn't want to complicate this design with PNP/NPN transistors. I need to know them more, or learn all theirs weaknesses first.


texts:
What's wrong with this scheme? I expected to be able to set the output voltage value modifying the values for R4 and R5 (I can replace them with a potentiometer), and why do I have negative voltage at the zener diode when it should be 6.2V (it's still negative if I remove the negative feedback)?

Before you ask:

ZTX696B -  medium power high gain NPN transistor

ZTX869 - medium power high current NPN transistor

Second version:

I thought that the output should be 9V + 1.4V , so 6.2V x (R4+R5)/(R5)=10.4

that means (R4+R5)/(R5)=1.67

But I don't get the expected voltage...

Also, I changed the op amp model, the new one is unity gain stable (I don't know if it helps).

Third version: (It works but I don't understand why, and the output is not 9V for any input higher than 12V)

For example if Input=16.00V then Output=15.00V

the op amp is "rail-to-rail"

4th version:

"rail-to-rail" op amp, "unity gain stable", supports up to 16V
changing zener diode value has no effect, same for R4 and R5
output should be less or equal to 9V

what's wrong now?

does the op amp AOL value matters?

5th version: (The final one)

I wonder if the "improvements" are good...

I used a PNP transistor for short-circuit protection (How can I find the value for Rsc? and when does Q4 enter in saturation?), Rsc Is actually a fuse...
A schottky diode for protection in case you power a motor
A capacitor at the input (I don't know what is it for)

Q1 has Icmax = 5A

Q4 has Icmax = 4.5A


texts: Increase in SMPS output voltage with RF amplifier as a load

texts:
I am trying to use an SMPS of 50 V output ,16 A current capacity from meanwell make for powering one of the RF amplifier operating at 13.56 MHz.
The amplifier is evaluation module of MRF300AN.

The issue is that as soon as i increase the drive power to the amplifier, the voltage on the SMPS goes on increasing from 50 V to 100 V and more.
( for eg: When I give around 0 dBm , voltage is ok, but as we go more around 10 dBm,the voltage from the SMPS increases to 82 V and goes on increasing with more drive power)

Have tried with a benctop switching power supply from APLAB too, here the issue is different. The output voltage goes down and that too without much current drawn, much lesser than the Cc limit set.

I felt that could be an issue with RF superimposing on DC lines and creating some issue in control/sense circuitry in the power supply.

But the same issue is not happening with MRF 101 eval board, even if the whole electrical environment is almost same. The power supply works fine in this case.

Can anybody give a hint on what could cause such problems with switching power supplies. I would like to understand and resolve the issue.

Thanks


texts:
In my area, due to frequent storms, there are frequently short mains power cuts lasting a second or two at most. While the shorter several-millisecond outages don't usually cause issues, the longer momentary outages frequently cause my computer to shut off, resulting in filesystem corruption and other issues.

I want some type of system capable of providing around 600 watts for 2-3 seconds, just enough to hold the system over until mains power resumes. Ideally, this device would be small enough to fit inside my computer case.

The various UPSes available online are all either (a) really expensive or (b) not capable of providing the wattage I need. Besides, I don't need the hours or minutes one of those provides, just a few seconds.

I have considered just putting some supercapacitors between the power rails, but I think that could cause problems when starting up (the PSU would have to charge the capacitors, so the voltage would take much longer to reach the required supply voltage), during these momentary outages (not sure I want to be backfeeding power to the PSU, but I don't want to have to connect every line coming out of it), when shutting down (since they would continue supplying voltage), and during service (since things could potentially still be energized even after the PSU is unplugged). I have some ideas for how to solve some of these issues, but not all of them at once, and I am not sure this is the best way to solve this problem.

What is the best way to solve this problem?


texts: My first project, looking for a review and comments

texts:
This is my first project. I haven't built it, just laid out the circuits for it. I'd like someone with more experience than me to look things over and give me any advice, suggestions or comments.

The project is a nixie clock and display. I'll have 6 IN-12a nixies (numbers) for the clock and 12-16 IV-17s for a alpha display. I also have a few 5V Solenoids for the chimes.

If anyone has any comments or non-answer things to say, I made a chat room.

Power Supply:

Logic:

original

IN-12a Socket:

original

IV-17 Socket:

original


texts:
guys, I tried to make an SSR for my window Air conditioner 2 Tonnes "2.5kW" the problem the Triacs get damaged instantly I tried 4 Triacs so far 2 BTA41 and 2 BTA24 I tried different circuits, I'm suspecting the Triacs to be counterfeited or something because I calculated the current to the compressor it was around 11A@240V and those Triacs can handle 41A and 24A.
I mean by damaged that they fail closed, they will not turn-off even if I cut the DC from the Opto-isolator and when I checked the terminals there was continuity between MT1 and MT2.

The circuits I tried so far

I know it's better to use contactors with AC but they are so bulky and need transformer and a big one 4A@24V to control them.

Is the problem with my parts or I'm missing something?
PS: The resistors are 1W, The Opto-Isolator is MOC3063.


texts: Electrolytic Capacitor Internal Resistance

texts:
I'm doing an experiment to investigate the internal resistance of an electrolytic capacitor in a DC circuit. Doing this I am measuring the discharge voltage against time, finding tau and from there finding the total resistance in the circuit, which then I subtract the known resistance from to find the internal resistance. I was wondering if there is a relationship that I can find between capacitance and internal resistance, from my research all I have found is information regarding AC current.

Any help would be much appreciated.


texts: Controlling a 300V node with 5V from a micro-controller

texts:
The goal is to drive a 47k load that requires at least 5mA of current. The design is as shown, with FET values matching their part number:

An LTSpice simulation (with generic pmos and nmos devices) demonstares that ideally the circuit should behave as follows when V1 is cycled from 0V to 8V:

Currently the voltage across the resistor remains at 300V even when the input is 0V. I've exchanged the pmos and it keeps the node at 0V but does not respond to a 5V input from V1.

I'm unsure as to what values R1 and R2 should have, originally they were both 100kOhm, or if there is something damaging the pmos that I have not considered. I haven't worked with such high voltages before and originally this circuit was designed for 5V (with R1=1k and R2=10k).


texts:
Im having a hard time finding the spects for this piece
I know is a metal film resistor, according to the colors its a 470? is this correct, does anybody know where can I purchase a ton of this?


texts: Are there any disadvantages to having a thicker PCB?

texts:
Similiar to the question What are the advantages and disadvantages of thinner PCB thickness (<1.6 mm)?, but going the other way.

If we look at the picture in the previous question's answer, we have the following

If I increase the dielectric/prepreg spacing to something much higher, say 0.1 in, are there any negative effects ?

Will this stackup perform just as well as if the dielectric/prepreg was 0.04 in with all other things equal ?


texts: Does this diode need to be replaced with a higher current rating diode?

texts:
In an application simulation a fly-back diode 1N4001 current is peaking upto 3A and decays to zero in around 25ms as shown below:

The datasheet says the max forward current is 1A. But it also says 30A for 8.3 ms.

In my case it is a peak decaying from 3A to zero in 25ms.

Do I need to change this diode? What can be an alternative?


texts: Determining control voltage of variable gain amplifier to achieve fixed output amplitude

texts:
I am wondering if there are any well known methods for determining the control voltage of a variable gain amplifier required to achieve a constant amplitude output without requiring prior knowledge of output amplitude. In other words, I am looking for an equation that relates output amplitude to control voltage so that the amplifier produces a fixed output level for any input level.

The VGA I plan on using is an AD600. For this VGA, the gain of the amplifier is given by Gain(dB) = 32*Vc + 20, where Vc is a control voltage between -0.625 V and 0.625 V. The only way I can think of accomplishing my goal is to use a microcontroller with and ADC and DAC to measure the output voltage of the VGA, and then adjust the DAC output to control Vc accordingly. With a microcontroller, I could keep track of previous values for output amplitude and amplifier gain, making the Vc calculation much simpler.

However, it would be a good learning exercise for me to use an equation for Vc in terms of the current output amplitude to design analog control circuits to accomplish my goal (I am studying analog circuit design as an undergrad EE). To be clear, I am not interested in designing control circuits that involve any kind of sequential digital logic, or use sample and hold circuits. If I need to use either I might as well just use the microcontroller.


texts: What is the impact high current through of narrow trace?

texts:
A 20mil external trace with a copper weight of 0.5oz can carry ~2.5A with  a temp rise of 30C (according to Saturn PCB Toolkit)

If my signal was a digital signal < 10khz with rise/fall time in the low ns with 2.5A flowing, what would happen if I narrow my trace to 7mils for a short distance ( < 5cm) ?


texts: How is the magnetic field radiated in a microstrip patch antenna?

texts:
If we talk about dipoles or any other antenna, we discuss the electric field as well as the magnetic field. But while discussing micro-strip antennas, only the electric field is explained.

Why?

EM waves are made of both fields and antennas radiate both fields.


texts:
I would like to have some help on this system:

I have to consider that all initial conditions at t = 0 are null. I've tried some things and I have some answers but I don't know if they are true. Could someone shed some light on this?

Here is what I've tried:

(Original image showing calculations)

Is this right? or wrong?

Also, is this system asymptotically stable if and only if a <0 ? Or does B effect on that?


texts:
I am solving a problem where I have to find the transfer function of a system. The system is
$$A = \begin{bmatrix}2&-1&2\\0&1&-2\\0&0&-1\end{bmatrix}, B = \begin{bmatrix}1\\1\\0\end{bmatrix}, C = \begin{bmatrix}1&-1&0\end{bmatrix}, D =0$$
When I solve for it's transfer function, it gives $$H(s)= 0.$$ What is the physical meaning of this?I am not exactly sure of the reason why is this happening, because from what I understand, the output is clearly dependent on input x as the matrix C is not null. But again the definition of transfer function is
$$H(s) = C(sI-A)^{-1}B+D,$$
so there might be other things in play here which I don't get.


texts:
I am looking to create a simple circuit that utilizes a very small vibrating motor such as the one here: http://www.adafruit.com/products/1201#Distributors. I would like the small motor to be powered by a small battery and to be controlled to vibrate once every 30 minutes or so. For more advanced versions, I'd like it to be able to vibrate at either every 30 minutes, 15 minutes, or at random times (at least once every half hour). Ideally, all the parts would be no bigger than a wristband.

Any help that can be offered would be much appreciated. The main area I need help with is the interval timing of the vibrating motor using some type of controller.


texts: Difference effect filter in before and after amplifier

texts: Is there any difference between low pass filter that put before amplifier and after amplifier? Which one is good for PC audio amplifier?


texts: multiplexing solution for high number of inputs in a grid pattern?

texts:
So, I'm working on a project right now to implement a large electrode sensor array for measuring bio-potential (128 x 128 sensors) that are in close proximity to each other (~0.06cm along horizontal and vertical). The signals themselves are relatively small, being on the order of tens to hundreds of micro Volts.

I want to select an arbitrary 64 sensor subset of these signals and route them to an amplifier circuit and then to an ADC circuit sampled at 250Hz (each selected signal has its own respective amplifier/adc path. Thus 64 amps and 64 ADCs, one of each for each selected signal). The configuration of selected signals only changes once every half minute or so, thus switching speed is not of paramount importance.

That said, I'm not sure how to go about selecting the signals to use properly. It doesn't seem practical to directly select 1 signal from over ~16,000 possible sources by having an enormous number of inputs to a multiplexer(s). I imagine (and vaguely remember reading some approaches like this) I could leverage the grid pattern to select from the analog inputs without massive amounts of logic, but I'm not entirely sure how I could go about doing that.

I would supply some datasheets to help out, but I'm still looking at this from a very top-down angle in order to get it conceptually straight in my head before hammering out specific components and such.

Thanks in advance for any help you can provide.


texts: Why my full-wave bridge type diode rectifier circuit begins an analysis from 8. second on Matlab Simulink?

texts:
Hi, I am working on Matlab Simulink's work page to get full-wave and half-wave bridge-type-diode rectifiers as could be seen in the picture. But, according to my Scope2 screen when I double clicked from simulink white-area it begins from 8. seconds not from zero?? How can I made it to begin with zero point to analysis?

AC voltage: 50HZ Vpp-max=10Volt
RLC Load: only Resistance 1KiloOhm


texts: Circuit working in breadboard but not perfboard

texts:
I am making a circuit to unlock my car doors. The central locking in my car works with 2 wires one at 12V, the other at 0V. When the 12V line is pulled low, the door locks. When the 0V line is pulled high, the door unlocks.

I breadboarded a circuit to let me do this ( testing circuit uses push buttons - will be replaced with remote arduino commands in future), and that works fine. I soldered up the same circuit, but when connected the doors continually lock and unlock - even when the gates on the transistors have no voltage applied. I've included a photo of the soldered perfboard (please excuse the shitty soldering) in case there is something there.

My first thought was that I had cooked the transistors, so I took another piece of perfboard and redid the whole circuit (wires were wrapped together), but I still had the same problem of it continually unlocking and locking.

This is my first time using perfboard so I am not sure whether this is an issue related to that, or something else. Any help would be much appreciated.


texts: Why is seed value getting changed on its own in this code?

texts:
In the following code why is seed value getting altered each time it enters for loop?
http://www.edaplayground.com/x/J8s

module Tb();
integer num,seed,i,j;

initial
begin
    seed = 0;

    for(j = 0;j<10 ;j=j+1)
    begin
        num = { $random(seed) } % 10;
        $write("| num=%2d |",num);
        $display(" seed is %d ",seed);
    end
end
endmodule


texts: Voltage-divider bias common emitter calculations are yielding unexpected results

texts:
I performed an analysis on this voltage-divider-feedback common emitter.  My result in simulation is relatively close, but doesn't quite check out.  Where did I go wrong?  I'm new to this and expecting it's either something I've missed in my learning or some simple mistake I made and didn't notice.

The circuit has a quiescent current of 3.4 mA, and the collector is nicely centered at 6V.  \$\beta = 250\$.  For the AC analysis, I redrew the circuit using the hybrid-pi model.  I assumed \$C_C\$ is open to AC at the frequency of interest:

I started by finding \$g_m=\frac{I_C}{V_T}=\frac{3.4mA}{25mV}=0.136\$ and \$r_\pi=\frac{\beta}{g_m}=\frac{250}{0.136}=1838\Omega\$
Next I used nodal analysis of the output node to determine \$A_V\$.
$$ i_{in}+i_c+i_f=0$$
$$ \frac{v_{out}}{R_C} + g_mv_{be}+\bigl(\frac{v_{out}}{R_F} -\frac{v_{in}}{R_F}\bigr) = 0 $$
$$ v_{out}\bigl(\frac{1}{R_C} + \frac{1}{R_F}\bigr)=v_{in}\bigl(\frac{1}{R_F} - g_m)$$
$$ {v_{out}\over R_C||R_F} = -v_{in}\bigl(g_m-\frac{1}{R_F}\bigr)$$
$$A_v = {v_{out}\over v_{in}} = -\bigl(g_m-\frac{1}{R_F}\bigr)\bigl(R_C||R_F\bigr)$$
$$ A_v = -\bigl(0.136-\frac{1}{390k}\bigr)\bigl(1760||390k\bigr)$$
$$ A_v = -238$$
Then I found \$R_{in}\$ by comparing expressions for input voltage and current:
$$ R_{in} = {v_{in}\over i_{in}} = {v_{in}\over i_b-i_f} $$
$$ R_{in} = {v_{in}\over{\frac{v_{in}}{r_\pi}}- {\frac{v_{in}-v_{out}}{R_F}}}$$
$$ R_{in} = {v_{in}\over{\frac{v_{in}}{r_\pi}}+ {\frac{v_{in}-A_vv_{in}}{R_F}}}$$
$$ R_{in} = {1\over{\frac{1}{r_\pi}}+ {\frac{1-A_v}{R_F}}}$$
$$ R_{in} = r_\pi||{\frac{R_F}{1-A_v}} $$
$$ R_{in} = 1838||{\frac{390k}{1-(-238)}} $$
$$ R_{in} = 864\Omega$$
\$R_{out}\$ was simpler to see by inspection, and is simply \$R_F||R_C = 1752\Omega\$
The problem is, when I simulate the circuit it does not yield the expected values.  I set \$v_{in}=0.02V\$ peak-to-peak at \$1kHz\$.  Given my values for gain, I should expect an output voltage of \$4.7v\$ but I get \$4.0v\$.  I tried a range of voltages for input, and anything up to around \$40mV\$ gives a consistent gain of 200, instead of the expected 238.  Similarly, my current \$i_{in}\$ should be \$v_{in}/R_{in}=0.02V/864\Omega=23\mu A\$.  When I simulate this, the input current is approx. \$10\mu A\$.  Output resistance isn't correct either.  Expecting an output resistance of \$1752\Omega\$, I added an \$R_L=1752\Omega\$ to the circuit expecting my output voltage drop to 50%.
The circuit I analyzed behaves as if it is:
$$ A_v=-200 $$
$$ R_{in} = 2066\Omega $$
$$ R_{out} = 3280\Omega $$
What is/are the error(s) in my equations that are causing my gain, input resistance, and output resistance to be so different from the simulation?
If you'd like to see the simulation it can be found here:
https://everycircuit.com/circuit/6222614442541056


texts:
Hello, can  anyone help me with this problem. I need to find the value of Vx but I can't seem to find any progress.
However, I do know that voltage between 6ohms and 1A is equal and that the current is equal between 3ohms, 2ohms and Vx.
However, I can't seem to move past that.
Please help me, though pls post only hints or direction of the solution [not the ans. itself,  still vying for that sense of accomplishment]
Thanks for advance.


texts:
Today I have looked over the port diagram presented in the datasheet for the Atmel 7810 controller (Chapter 13.2), in the logic diagram of the I/O ports, I noticed a strange logic gate, which I have not encountered until now and I have not found any information regarding this one.

Logic gate picture:

What kind of logic gate is this? Is it a composite of two logic gates like "inverted buffered gates in mirror"?

I have no explanation in this regard.


texts: How to pick an amplifier for very fast transient signals?

texts:
I'm coming to this with a Physics background. I work in solar cells. I would like to flash the solar cell with a laser and measure the voltage response. The University has a spare 10 GSPS (gigasamples per second) data acquisition system that I can use. Ideally, I'd like to measure up to a second - but with particular interest in the ns range.
My question is  - *how I should pick an amplifier to amplify the signal from the sample in these time ranges *.
I understand I need to pick an amplifier with input impedance as close as possible to the source pick up. I'm not sure yet of what the output impedance of the sample will be.
Say, if it were 50 ohms output impedance, would something like this, an amplifier block with quoted specifications of

wideband, 10 to 2500 MHz
high IP3, 35 dBm typ.
low noise, 5.5 dB typ.

be reasonable?  What else should I consider when making a purchasing decision for these time ranges?
I don't think any single amplifier will cover the range I want (1 Hz -1 GHz), so that suggests what would be the easiest way to switch amplifiers for different time ranges? I imagine even a switch could generate electrical noise in these nanosecond time scales.
Any background reading would be incredibly appreciated.


texts: Battery/Charger Not Reaching Float with Load Attached

texts:
I'm trying to add a backup/UPS to a system I have outside with the following battery charger - https://www.meanwell.com/Upload/PDF/ENC-180/ENC-180-SPEC.PDF . The DIP switches are set for AGM mode.
My load is ~72W or 6A @ 12V and I have a SLA 12V 75Ah battery attached in parallel with my load and the charger.
I've noticed with the load attached, the voltage drops about ~0.1V. I've metered the battery and the charger keeps the battery at about 14.43V indefinitely in Boost, while the manual says in the AGM mode it needs to reach 14.5V for boost before it switches over to float. If I disconnect the load, the battery reaches float instantly. I'm assuming this isn't sustainable for the health of the battery, so I would want to make sure the battery is reaching all 3 phases correctly.
I'm not sure what the next logical step should be to get this set up working? Should I program the charger myself?


texts: Wiring proximity sensors to parallel port inputs

texts:
I have a couple of proximity sensors that came without documentation. I'm planning to use them as home sensors for a CNC router.

The label says that they're NPN sensors, 6-36 VDC, 200mA. There are three wires, which I understand to be +V (brown), -V (blue) and output (black). My expectation was that, since these are NPN, they would be current current sinking, and that there would be no electrical connection between brown and black. What I found was that if I apply +V to brown, I get +V on black, with a resistance of 10K Ohms. It seems like there's an internal pull-up resistor between +V and output. As expected, if the sensor comes within 2mm of metal, output is connected to -V (with 10 Ohms resistance).  Am I interpreting this correctly?

Any recommendations on the simplest safe way to wire these sensors up to a parallel port input? Although the label says 6-36V, they seem to work with as little as 4V, though obviously that's out of spec. I had been expecting to supply my own pull-up resistor between output and +5V.


texts:
So my homework question is: Estimate the value of C needed in the RC circuit below if it is to act as an integrator for frequencies above 10 kHz.

I've been stuck on this question for a while. At first I thought I had to use \$T = RC\$ to find \$C\$, but I'm not given much information at all.

Then I thought I could use this:

$$X_c = \frac{1}{2 \pi fC}
      = \frac{1}{2 \pi \times 10 \times 10^3 \times 100 \times 10^{-9}} = 159 \Omega$$

I'm really confused. Could someone guide me to a starting point for this question?


texts:
I have had a few issues recently with an electrical boiler and I have replaced a few electrical parts (relays, time delay switches,...) to keep it running.

Doing so, I noticed that the internal wiring was quite different from the wiring diagram on the panel cover. The diagram includes both a 120 VAC relay and a 24 VAC relay, while the boiler as actually wired runs only with the 24 VAC relay.

The question that came to my mind is: Does the actual wiring include all the safety interlocks required for the safe operation of this 20 kW electrical boiler?

To answer that I started studying the wiring diagram, but there is something I cannot quite understand: the 24 VAC relay is energized when the 120 VAC relay is activated, AND the 120 VAC is energized when the 24 VAC relay is activated.

Take a look at the wiring diagram for this 240 VAC, 4 elements, 20 kW boiler.

I cannot make sense of the operation of both relays. My  question is "Why is it like that and how does it work?"

Thank you very much for your insights on this.

Note: I first posted this question on diy.stackexchange.com, but did not get any  help.


texts: How to track motion of a moving ovendoor

texts:
At work, we are measuring various parameters to test out a newly designed oven prototype. To make things more efficient, I am trying to create an electronic setup to automate the measurement, in particular of the door's motion (from fully open to fully shut).

The goal is in measuring the instantaneous velocity of the door at the various points of its motion, which is a fixed radial path. Note the emphasis on instantaneous velocity logging, as opposed to an average velocity as determined by timing alone.

What is a way I can measure the ovendoor's velocity / track its motion with reasonable accuracy? (Reasonable implying error < 1-2 cm/s)

Since it is only fixed radial motion (and no component along any other axis), and since there is a moving component and a stationary component, I presume this should be an easier problem than, say, measuring the velocity of an independent body like a person or hand.

My first thought was an accelerometer-gyroscope-IMU-based method, i.e. integrating the acceleration over time to get the velocity, but reading up on this subject suggests that this will lead to sizeable errors.


texts: Use of a connector beyond OEM's voltage rating

texts:
I've been looking for some time for a suitable connector for my device, and happened upon a seemingly perfect option. It has the right number of pins, the right mix between signal and power pins, the right footprint. the right mounting type and the right price point. The connector is designed for automotive use, and is only rated to 14VDC by the OEM. My device is rated to ~27VDC, but would operate in the 12-14VDC range during normal operation.

What are my options in terms of using this connector? I've reached out to the OEM, with the aim of discussing this issue with an engineer, but I've so far only received sales support and 'here are the emails of our distributors'. Would an alternative option be to independently test/verify the use of the connector at my intended voltage rating?

The OEM rates the power inputs (2.8mm blades) to 25A and the signal inputs (0.64" pins) to 11A. I don't expect to exceed 12A on the power inputs or more than 3A on the signal pins. I only expect the voltage to exceed 14VDC during fault conditions.


texts: design for a PC/104 interface bus expansion

texts: Can someone tell my why this won't work or tell me a better way to do it? I have a TS-5500 from Technologic Systems that has a PC/104 bus which I am building a card to expand the IO ports. Pin B19 on the PC/104 bus decodes IO addresses 0x140->0x15f. I'm also using address 0x148 to latch the inputs at the 374's into the chips so I will have to read that IO address before I read any/all of the IO ports 0x140->0x143. The outputs will have 10K pull-up resistors and be protected by 5v diodes.


texts: How to identify SMD devices from the codes on top of the component?

texts:
I have a PCB and I am trying to identify a couple of the ICs and other SMD devices that are on there but can't find anything on or offline that tells me what the package codings mean.

I have a couple of pictures of the components that are of particular interest to me and if anyone could:

Help identify these components and,
Tell me a way I would be able to try and figure it out in the future?

I have tried a number of websites and none of them have really offered much help for any of these components below...

codes are: KT3 (SOT23) [top left], CVL (two pin) [bottom left], not sure of the right hand side one. Could either be 1P+backwards K, or Kd+upside down 1, or the K could be an x - it really is not clear, even under a microscope)

This is slightly clearer and is A48 I believe - no luck on this one either. I imagine it is some sort of single op-amp but again, I can find nothing.

Any help on this and a source of information for this type of question would be great!


texts: Electronic sensor for monitoring photosynthesis

texts:
I have to develop a sensor that can detect photosynthesis.  So when the plants are exposed to sun I should get an indication that photosynthesis is happening inside the leaves.

I found many products on internet but these are very costly, except this one (must be cheaper since used for kids) which shows a video of a sensor.

Can somebody tell me what is the main sensor which has been used here?

Another link

This says that:

  During photosynthesis, leaves soak up blue and red light but reflect
  invisible near-infrared light.

So may be there is an infrared sensor under the pcb.


texts: Why are the current directions in the hybrid-\$\pi\$ model for BJT the same for both NPN and PNP?

texts:
Here is the hybrid-\$\pi\$ model:

with \$I_c\$ and \$I_b\$ going in, and \$I_e\$ going out.
The same circuit can be used for both NPN and PNP, the only thing changing being \$V_{be}\$ for NPN and \$V_{eb}\$ for PNP.

The currents direction does not change, which is what I don't understand.
We know that for a PNP in active mode, \$i_c = i_e+i_b\$.

For a NPN in active mode, \$i_e = i_b+i_c\$, which corresponds to the current flow shown on the hybrid-\$\pi\$ model.

Why is it the same for PNP?


texts: Is it possible to raise the temperature of water almost instantaneously  Using electricity ? I want to raise the temperature of tap water to 180 degrees F.


texts: Logic gate using current source and diodes

texts:
This circuit is supposed to work as a logic gate. I need to find out the logic operation it performs. Suppose the diodes are ideal.

https://www.circuitlab.com/circuit/egg3wh/logicgate/

simulate this circuit – Schematic created using CircuitLab

Now when the circuit is implemented with voltage sources, I know the general approach to solve this. You check the voltage at the anode and cathode of the diodes and determine whether or not it is conducting....

With a current source I am kind of confused on what to do. I can't determine the state of the diodes for a given input combination (00, 01, 10, 11) because I don't know the voltage at the anode of the diodes.

I think the problem is that I am not used to current source driven diodes.

Can anyone provide some guidance?

Thank you.


texts: How to meaningfully compare Xilinx MCS files?

texts:
Brief

I have two different boards with Xilinx designs that might be the same design. I am trying to compare the different MCS files to see if the designs in them are in fact the same design. Can this be done?

Details

I am looking at two old designs which both employ Xilinx XC3090 FPGAs. (Yeah, like I said... old.) Let's call these two designs "Jekyll" and "Hyde". I am trying to figure out how to replace these old FPGA designs with a newer FPGA design. Jekyll and Hyde look like they might contain identical FPGA designs. If they are in fact identical, then my task is twice as easy. I'm trying to figure out if they are truly identical FPGA designs.

Both Jekyll and Hyde contain three of the same devices (XC3090 FPGA) with different designs in each of the three devices.
The designs for Jekyll and Hyde look very similar. The pin names on FPGA1 on Jekyll are almost identical to the pin names on FPGA1 on Hyde, and so forth. The differences look like they could "probably" be just naming differences rather than differences in actual function.
One major difference between Jekyll and Hyde is that Jekyll uses one single Xilinx boot PROM to configure all three FPGAs, while Hyde is using an individual boot PROM for each of its three FPGAs.
I have a full set of design files for Jekyll, so it's pretty straightforward to figure out what's going on there.
For Hyde, I only have the .MCS files that are used to program the Xilinx boot PROM. Unfortunately it looks like the design files have been lost to the mists of time.

The Basic Question

So I have one design (Jekyll) which has a .MCS file that configures all three FPGAs in a daisy-chain, and another design (Hyde) where I have three individual .MCS files. Is there any reasonable way for me to confirm whether the three .MCS files from Hyde contain the same FPGA logic as the one .MCS file from Jekyll?

The Advanced "10,000 bonus points" Question

If we can confirm that Jekyll and Hyde are in fact different, is there any reasonable way to see whether the differences are trivial (e.g. just one more signal in the overall design) versus substantive (e.g. a whole collection of other flip-flops and gates)?

A Little More Background -- Things I Know and Have Tried Thus Far

So, for the record, I already know that a .MCS file is just a flavor of Intel HEX file, and I've already taken a look at these .MCS files in that light. In these files, there are only really "Data" records (there is one "Extended Segment Address" record, which is 0 0 so I'm ignoring it).

When I compare the first .MCS file from Hyde with the first portion of the .MCS file from Jekyll, it looks very similar. But not quite identical.

Is there any way for me to make more sense of the address + data items I get out of those .MCS files? And for me to separate the meaningful parts of the configuration bitstream (the part specifying actual logic configuration) from the parts that are just ancillary stuff (like specifying the configuration clock rate or similar)?

For those of you that have actually read this far... thank you!


texts: Protoboard components being used for applications with high current

texts:
If I have a few pins of a relay (which is rated for the correct current) that will carry 5A when the relay is triggered, what's the best way to wire this up?

Details: I have a breadboard with a circuit on it, but a small loop in the circuit will carry 5A when the relay closes. I want the pins that trigger the relay to stay on the protoboard, but obviously the breadboard can't handle that kind of current. I'm wondering what's normally done in situations like this, and what the different options are.

Thanks!


texts:
I'm running some permanent wires for DMX control in the small theatre in our facility, and we have a box of this cable left over from a different job.

I've read a lot about how you shouldn't mix wires with DMX because improper impedance's can mess with your signal.

Is this cable suitable for DMX control?


texts:
I was browsing through some OFCOM Frequency Allocation Tables for use on a small project I'm doing. I require the use of some unlicensed ISM bands in the UK, and found that the lowest unlicensed band has a limit on the transmit power/power density of "42 dBµA/m at 10 m"

The document in question is: http://stakeholders.ofcom.org.uk/binaries/spectrum/spectrum-policy-area/spectrum-management/research-guidelines-tech-info/interface-requirements/IR_2030-june2014.pdf and the table in question is on page 17.

1) What does this mean?

2) Can this limit be converted into something a little more intuitive, like an effective radiated power in Watts?

Thanks!


texts:
This my first electronics project and it is based on this project.

I'm using a TI SN754410NE H-Bridge to control 2 small dc motors. I'm using an Arduino UNO for the control signals (USB powered) and a 6 V battery supply to power the motors. The battery supply negative is connected to Arduino GND.

It is actually working but there is something a bit unusual. When I measure the voltages being supplied to the 2 motors I get voltages for one motor of +/-4 V but for the second motor it is 3 V in one direction and -4 V in the other. I have checked all the connections and they are fine. Also, is it to be expected to get a significant voltage drop when using this type of device (h-bridge) ? I was naively expecting to get 6 V.


texts: A circuit that outputs one input voltage by default, or another if it is present

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I'm trying to come up with a simple design that will take two analog inputs voltages (~0.2-1.6 V each). One is an "internal" voltage and should always be present. The second "external" input can be present, or can be not connected, floating, etc.

The circuit should output the external voltage if it is present, and the internal one otherwise.

The simplest idea I can think of is to have a comparator on the external line, which should output a logic high when the voltage raises sufficiently above ground, and use that to control an analog multiplexer. But I was hoping for a simpler idea.

The context linked here, an external controller port for a Nintendo 3DS. The internal voltage is from the circle pad, and the external controller should override this when it is connected. So, there are also two axes, so I could duplicate the circuit twice or find a more elegant method. And it has to fit inside the console.


texts: Estimate the value of an inductor by its steady state response

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I have the following circuit:

simulate this circuit – Schematic created using CircuitLab

The duty cycle of each sw is 50% and the frequency is 160kHz, at steady state I end with the following response:

Since I now the value of R I also know the current at R

Can I get from this data the value of L?

EDIT.

This will be the derivate:


texts: Is it possible to reverse the polarity of DC using diodes?

texts: From my humble understanding of a bridge rectifier, it "flips over" the negative cycles of AC, turning it into DC. Is it possible to modify this circuit so it can be used to reverse the polarity of DC as an alternative to using switches or transistors. I am trying to work it out, but can't grasp how to exploit the bridge rectifier's "flipping" for this purpose.


texts: Secure signals on boot time to prevent unwanted operations

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How can I be sure that at boot time my module won't get random values to it's control signals and write to an address* before I reset the module?

*(or anything that shouldn't be done before reset)

If the question is considered too general: I'm trying to make some code in System verilog with a Xilinx Zynq platform as a target device in mind.


texts: Better workflow in Atmel Studio 6 for building and transferring program

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After having modified my code in Atmel Studio 6, I write the program to my MCU in the following steps:

Click Build or F7
Click Device Programming or Ctrl+Shift+P
Click Apply (to choose programmer+device+protocol)
Click Memory
Click Program

How can I do all of the above in one step in Atmel Studio 6?