texts:
I want to make a voltage regulator for a symmetric power rail +30/-30V. The idea is to use an LM317 and an LM337.
I want to be able to regulate with a Vin that can go up to +60V (and -60 and negative rail).) The LM317 can only have a voltage drop between IN and OUT of 40V. In case of a short that value would be exceeded. After some digging I found that I can do a pre-regulator as in the picture below.

Once the voltage VIN is above about 36V, the Zener diode would kick in and the BJT will do it's thing.
My issue is tgat I don't know how to size that pre-regulator.
More specifically, how do I size R9?
I think it's R9= (Vzener-Bbe)/(Izener+Ibase), but Izener depends on temprature and voltage accross the Zener diode. I'm not sure about the Ibase.
Important note (maybe) my load is around 25mA.
D1 is just there for reverse polarity protection.
EDIT 19/04. As Vangelo pointed it out, with the current disign there is a issu in case of a short on Vout. So I added this simple circutry and it seems to be working. I found this here https://jeangaillat.wordpress.com/2018/03/29/je-suis-fou-des-alimentations-lectroniques/amp/
the 1200 resistor is to simulate my charge at 25mA.

Normal operation:
Short:
And for the negative rail:


texts: soldering input pins to SN74HC595N shift register -- heat tolerance

texts:
I'm working on a project that uses the SN74HC595N shift register from TI. The nature of this project requires that I solder on pin extensions. My soldering skills are not too solid, so I'm worried that I may be damaging it (based on it's performance, I'm pretty sure that I am).

I know that the operational temperature is -40°C ~ 85°C

My question. How hot can this shift register get before it sustains permanent damage. And is improper soldering the likely cause of the shift register's malfunction as I presume?


texts: How do I drive this circuit when the amplifier's input is grounded?

texts:
I'm building this circuit in Multisim. The amplifier's input is grounded, but I'm supposed to see that the output is not zero because of an input offset error. I'm clearly missing something since I don't see how I'm supposed to drive this circuit when the input is grounded. Where do I attach my AC voltage source?
Thank you.


texts: Impedance matching is one of the major application of common collector configuration. Is Common Collector configuration the best method for impedance matching? why?


texts: How to improve SNR by averaging multiple identical sensors - hardware or software?

texts:
My application uses a MEMS microphone amplified by an AD8429 instrumentation amplifier with a bandpass filter to acquire signals. The phenomena I'm measuring occurs at a specific frequency and so I use I/Q demodulation on a 2-second time series sampled at ~16 kHz to extract that information.

I'd like to go one step further and improve SNR by using multiple microphones - six to eight, in fact. My question is how to best approach averaging the signals. One option would be to measure all microphones simultaneously with a simultaneous-sampling ADC like the AD7606 and average the signals after acquisition. The other option would be to connect the outputs of the instrumentation amplifiers to a unity-gain averaging amplifier arrangement (or something similar) and let the hardware do the averaging. The entire arrangement - microphones, amplifiers, and ADC - would be calibrated as if it were a single sensor.

I have two questions:

Which is the preferable method for averaging, hardware or software?
If it's hardware, what circuit should I investigate to perform this?

I'm leaning towards software averaging at the moment. I'm worried about constructing 8 truly identical inputs for the averaging amplifier (resistor choice being what it is). Any guidance is appreciated.


texts: Can I mix different capacity (Ah) AGM batteries in an inverter battery backup setup such that they "balance" in state of charge?

texts:
I have a large 12V (input) inverter that I use to run a shallow well pump during power outages.  I currently have four 75Ah rated 12V AGM batteries connected to it all in parallel that are all in excellent health (each tested with a 100A load tester and all passed with flying colors).  Those alone can run the well pump just fine, but not for very long (perhaps 24 hours of cycling).  However, I also have some smaller capacity 12V AGM batteries (about 30 to 35Ah each), also in excellent health, that I want to parallel with the 4 larger, to get more runtime.  I have a few assumptions I wanted to mention, and then anyone who answers this question can make reference to my assumptions.
Assumption 1) By paralleling smaller AGM batteries with larger AGM batteries, they will stay balanced as far as State of Charge (SoC), since and imbalance in voltage of the individual batteries would cause a flow on current into the lower voltage battery, thus balancing it with the others.
Assumption 2) This balancing mentioned in # 1 should also prevent the smaller Ah batteries from overdischarging, meaning that any and all paralled AGM batteries (of various Ah ratings), should all stay in about the same SoC, while charging, discharging, and "resting", so by monitoring the entire bank voltage and cutting the load at a reasonable voltage (say 11.0 volts under load), I shouldn't damage any of the individual batteries. (Note: I wouldn't actually stop the pump while it was running, but would rather wait for it to finish cycling, then turn off the inverter manually).
So those are the 2 main assumptions.  Another related (sub)question I have is would it be better to connect the smaller capacity batteries using thinner wires, to create more resistance for those during charging and discharging?  For example, put those on the outside of the parallel connections (furthest away from the load and charger connections), so the charge current would have to hit the terminals of the larger capacity batteries first.
Another thing to consider is suppose there is a slight imbalance in the battery bank while discharging.  Since the load is intermittent (on for 1 minute, then off for 20 to 30 minutes), that should give all batteries in the bank ample time to "re-equalize" (balance in voltage).
I may actually try this during the 1st weekend in December 2020 and report the results back, but wanted to get some input as to any potential pitfalls, or if people agree that it should work.


texts: Measuring the Internal Resistance of a Brushed DC Motor for Use in Speed Control (IR Compensation)

texts:
Is measuring the internal resistance of a brushed DC motor with a multimeter the correct way of doing it?  The resistance seems to vary while the motor is being turned by hand; however, the resistance will somehow settle within some (reasonable) range eventually.

Is this the same resistance in IR compensation of speed control?  I am controlling the speed of a DC motor without a speed sensor.

I measured the resistance of 30 brushed DC motors of the same model from the same manufacturer with a multimeter.  However, the reading ranges from 3.x ohms to 6.x ohms and one of them even goes up to 12.x ohms.  The inductance reading by an LCR meter reports 10.x mH to 12.x mH.  Is this normal or more of a problem with the manufacturer?  I previously assume that the characteristics of the same model should somehow fall in the same ball park.

Thanks in advance.

Brian


texts:
I have built the following audio amplifier circuit on a breadboard. The circuit works. However the circuit makes a DC offset on the non-inverting input of the op-amp.

simulate this circuit – Schematic created using CircuitLab

I get the input from a volume control circuit. If I measure the volume control output without connecting it to the amplifier, i measure a DC offset < 10 mV (Still after C1 and with R1).

If i connect the volume control to the amplifier, i am able to measure a DC offset of 350 mV on the non-inverting input of the amplifier.

Naturally if i use the op-amp as a buffer, and use the amplifier without feedback, i will have some DC-offset on the output of the amplifier. I would like to use the feedback to correct this DC-offset. This is not possible, with DC on the input.

Any hint on what i am doing wrong, and where i should start to debug?


texts: Relationship between latency and sampling rate of a digital PID controller

texts:
I am trying to set up a fast digital PID controller. The error signal is read by an ADC and sent to an FPGA. The FPGA uses a PID equation to compute the integer sent to the DAC.
At the moment I am trying to sort out what the sampling rate of my parts needs to be. My naive reasoning is that the total delay of the circuit sets the closed loop bandwidth, and the sampling rate should not be slower than twice that bandwidth (otherwise it will be a limitation). Similarly, the sampling rate need not be orders of magnitude larger than twice the closed loop bandwidth (because that's overkill).
What I would like to know is the following:

How are total circuit delay and closed-loop bandwidth related mathematically?
Is my reasoning about the sampling rate and bandwidth (from above) correct, or is there more to it?


texts:
I am working with a simple LED flasher circuit multi vibrator I think..  Normally alternates on off between two LEDs..

My question is how to change the duty cycle to get different on/off times for each LED..  So instead of 1 on the other off you would have 1 on/off then the other on/off, and repeat.

Schematic:


texts: Best practice for Lightning/Surge Protection on PCB

texts:
What is best practice/recommendation when I want to protect against lighting/surge? More specfically, my application requires passing the following test:

  "ANSI/IEEE C62.41---1.2/50 microsecond (uS) — 8/20 uS Combination Wave. Peak
  voltage is 10kV, peak current is 5kA"

In the past I have had alot of sucess with just using MOVs alone, however, now I am thinking of using a TVS as well as spark gap right at the input for for extra protection on my next board. Here is the schematic for what I am talking about:


texts: What is the initial value of signal'Last_event if the signal has never changed value?

texts:
I'm doing timing analysis on a bus interface and on the first transaction a control line has not yet changed value.  I'm trying to check the setup time of this signal to the timing control and I find the initial value of the signal'Last_event to be an arbitrary number.  Is there a defined default for signal'Last_event when it has not had an event?
Also, if the process running is pended on this signal's event, will signal'Last_event be the current time or the time of the "last" event?  That's sort of like Sinfield's "this" Tuesday vs. "next" Tuesday joke.


texts:
I'm not sure if this is the right place to be asking this question, so close it if it's not, but I need help on a physics project. My current project is a ring launcher (Elihu Thomson Apparatus). I spent the last week winding 4,893 coils of 30 AWG magnet wire around a steel pipe which I filled with some small diameter metal rods (I'm not sure of the material, but it seems to be fairly ferromagnetic). On the steel pipe right next to the coil is a 1 inch copper pipe (the two are insulated from each other) free to move. When I hook the coil up to the wall, I get a nice changing magnetic field (according to the Hal probes in my phone) but nothing else. I'm not following any particular tutorial, but I've seen similar setups around the web that work and launch the ring. Any ideas on where to go?
I can take pictures if those would be helpful. Just tell me what you would like to see.


texts:
It is common to find microcontrollers with an integrated 10/100 Ethernet MAC and PHY. Some microcontrollers, such as the Texas Instruments TM4C129x series, offer both an integrated PHY and RGMII interface for external PHYs, shown in the figures below:

(c.f. this datasheet (PDF))

The external PHY would then be something like a Micrel KSZ9021RL (PDF) or Realtek RTL8201. The internal PHY would just be connected to magnetics and a jack.

What benefits are there to using an external PHY over an internal one if both are available? It seems like using the internal PHY saves on BOM and significantly on PCB routing.


texts:
dB is always power ratio and we can write it in terms of voltage ratio.

Imagine Vx = Vs*sin(wt) where Vs is the amplitude.

In the case of dBVrms the Vref is 1V rms. So:

dBVrms = 20*log10(Vs/sqrt(2))

But if we would take the nominator as amplitude as Vs (i.e not rms value but the amplitude) then:

dB = 20*log10(Vs)

I'm kind of confused which one is the real dB here. I might be also mixing things here.

When we plot FFT power spectrum which one is relevant dB or dBVrms? What is the difference in use?


texts:
I'm going though datasheets of some dual N-channel MOSFETs for li-ion battery protection, like 8205A or ECH8695R, for some thermal and power dissipation calculations.

There are Rds(on) values, like 13.3 mΩ @ 2.5 V (in ECH8695R) or 0.040 Ω @ Vgs=2.5V (in 8205A).
Is this value just for one MOSFET in the package or for both of them (when they are wired in series as they should be)?
It would be huge difference whether it is just for one MOSFET or for whole package, but I do not see any mention of that in the datasheets.


texts: Fluctuations in 7805 Regulator IC Output

texts:
I built an Arduino using ATmega328 on perfboard. To power it, I used an 8V adopter with a 7805 IC. But the ATmega328 IC started to reset randomly. After some efforts I figured out that the problem was not using decoupling capacitors. So I used a 100uF and 10uF electrolytic capacitor at the input and output respectively. Though it helped to solve the problem but the IC still sometimes gets reset. I tried to look online but they do not tell anything except using the decoupling capacitors. I would be grateful if someone could explain:

What other measures can I take to prevent this fluctuation
Which capacitors are best for this purpose of AC filtering
What specific values are good and is there any method to
calculate them based on the load requirement

I hope this would not turn out to be a duplicate question!


texts: Detect if SWD is connected (SWDIO is shared)

texts:
I'm working with a given hardware featuring an STM32F030F4 MCU and a 4-pin SWD connector (VCC, SWCLK, SWDIO, GND). Due to the limited number of pins, the SWDIO pin is also used as an input pin for communication with another chip on the board.
What is the best way to detect at startup if a debug adapter is connected or not?

If the debug adapter is connected, the MCU should not configure the other chips on the board so it is possible to communicate via SWD and upload new firmware.
If the debug adapter is not connected, the other chips can be configured normally, thereby preventing further SWD communication.

Can I simply check for activity on SWCLK? Or are there any reliable bits in the registers that could be checked? How quickly does the debugger connect?
If the other chips are immediately configured at startup, it's no longer possible to connect with an ST-Link or J-Link. I found it out the hard way and had to solder additional wires to get the MCU under control again. But that's not an option for a larger number of boards.


texts:
I know the theory of FM, but I just can't understand how this simple circuit works. So let's say a radio station is transmitted on 100 MHz, as I understand in this case the oscillator should also produce a 100 MHz sign. What I don't get is, how the FM bandwidth (which is around 100 MHz in a range) is picked up from the antenna and demodulated?

Could you please explain how this circuit works?

Thanks!


texts: Narrowband LED performance compared to Laser for Spectroscopy

texts:
I am currently building my own Raman spectrometer and I am in the process of choosing a light source. I am deciding whether I should be using LEDs vs traditional laser modules.

These are my requirements (in order of importance):

Price - I am interested to keep the cost of my prototype as low as possible because there is a possibility of this turning into actual mass production. (For the sake of comparison, a "good" LED costs in tens while a "good" laser source can easily fetch in thousands).
Performance - Ideally, the output from light source should be predictable and consistent. I understand that LEDs produces a lot of heat and this can cause the LED to output different wavelengths.
Energy consumption - I am trying to build a portable unit, so power consumption is a critical aspect of my design.

Traditionally, Raman spectrometers have always employed lasers as their light source. However, I feel this discussion would be helpful to others who are in the same boat as me as there has been significant improvements in LED pricing and performance.

I have also considered using a grating in junction with my LED to focus only a narrow band of light onto my sample but this would result in high energy lost from stray lights.

Note that I am designing this spectrometer to be used exclusively with SERS (Surface enhanced Raman spectroscopy) so my requirements are less stringent as the substrate will greatly enhance the output signal from my sample.

Can someone shed some wisdom on the feasibility of building a low cost light source comprised only of LEDs for my purpose? By the way, I am trying to aim for 785nm.


texts: Why RMS value used in transformer equivalent model?

texts:
The equivalent model of a real transformer is given:

Why do we use RMS values of input and output voltage when analyzing the model? The main confusion comes from the fact that real transformers only work on basis of changing flux ( or changing voltage ), then why would we want to consider the equivalent DC value of AC ( which is RMS value ) ?


texts:
What is the standard way to measure a current of about 10,000 A? DC clamp meters seem to have only scales up to 2,000 A.

Edit

Some background of this question:

I am a high school physics teacher and I am trying to improve some classical experiments using high currents from ultra-capacitor discharge.

In particular I am looking for a good way to measure the discharge current of a ultra capacitor for very short times like in this "jumping ring" experiment:

A safe and effective modification of Thomson’s jumping ring experiment

The second motivation for this question was just because I just want to know it out of curiosity for my background knowledge of what is the usual way to measure such high currents today.


texts: Trouble Understanding Shunt active power filter using instantaneous power theory

texts:
I have a demo Simulink model of a shunt active power filter using instantaneous power theory (Source, unbalanced none linear load and the filter, a very sample one, that i am using to understand the concept). Here is the model :

Here is a look inside the Filter :

Now, I understood that the all idea of an active filter in general is to measure the disturbance (current harmonics content), and generate the same opposite signal, and inject it in the main line, so that the injected current will cancel the harmonic signal only and leave the fundamental in the PCC.

In my model, the universal bridge (blue box) is the one generating the compensation current right (the red arrow) ? (based on the triggers of the hysteresis control block), but from what i know on the universal bridge (and power converters in general) is that they need a source of power to convert from, in our case a DC source right ? i don't see any DC source in the other side of the Bridge (Yellow arrow).

My questions :

1- am i right about my understanding ?

2- am i right about the sens of the compensation current (red arrow) ?

3- most importantly : where does the Universal bridge get its power from in order to generate the compensation current ?


texts: Why are there air(?) bubbles within my LCD?

texts:
Photos: https://photos.app.goo.gl/BvqLVYkMBB7RjaMU7 (Nexus 9 Android tablet)

My daughter's tablet is enclosed in a full-body case, so it's fairly well protected. Still, somehow, at some point I noticed these bubbles and took the case apart -- only to realize that they were not caused by a liquid spill between the cover's window and the display, but rather are within the display!

How on earth did this happen? What's going on? (And if this is not for EE, then please point me elsewhere. Not Android I'm sure, but probably not Physics either?)

I'm not really looking for a fix (unless one readily exists) mainly because the thing works fine still and is "only" a child's toy.


texts: What colors or wavelengths are photoresistors sensitive to?

texts: Using an LDR or photoresistor, are they more sensitive to one color or wavelength compared to another, or are they consistent with any light? Why?


texts: Getting GPS coordinates with GPRS/GSM module

texts: I'm trying to understand if I can get GPS coordinates using only a GPRS/GSM module. Probably I can do it by triangulation using BTS on the terrain and based on the RF signal but is that possible? Where do you think I can get info to guide me in that field?


texts:
I'm looking into high power SCRs. The two common cases i'm finding are TO-209AB and TO-200AB.

The TO209AB are straight forward to mount and connect.

The other, TO-200AB is strange looking and doesn't provide any mounting information. It appears that these would mount into some kind of socket but i'm not finding what that socket should be.

How is a TO-200AB mounted and connected?


texts: Calculating heat generated by resistance wire on 3 phase current

texts:
I am designing a heating element consisting of resistance wires coiled around a tube to heat water flowing in the tube. All three heating elements (loads) will have the same resistance and will be connected in delta. I want to control the  heat output by varying the voltage to the loads by using a variable transformer. I did some calculations to ensure that the design will work as expected. I would appreciate it if people who know better could tell me whether the procedure I employed to calculate the heat generated, as provided below, is correct.

a) I have access to a three phase 250 V, 30 A electricity. I understand these are line voltage and line current. So the phase current would be 17.34 A, and the total power available would be 13 kW.

b) I want a total of 4.8 kW heating power, so 1.6 kW on each load

c) I know the wire diameter and length I need. Hence, for the given wire material, I know the resistance of each heating element.

Here is where the calculations start.

d) In an excel sheet, I list out a range of voltages (from 100 to 300, say), and for each I divide the phase power (total power/3) by the voltage to find maximum current available (assuming no losses).

e) Then for each leg/load, I find the calculated current by dividing the voltage across it by its resistance.

f) Whichever step (d or e) gives lower value for the current, I take that as the actual current flowing through the load, and I calculate the heat generated by each leg/load as I^2*R.

g) Finally, when I find the correct combination that generates the heat required (1.6 kW), I assume that the other two loads are generating the same amount of  heat for a total of the desired 4.8 kW.

So my question is, is this the right way to calculate the heat generated. Also, is it appropriate to isolate each leg/load and perform calculations on it alone, as I have done here.


texts: Is there a common name for this [voltage-boosting] circuit topology/idea?

texts:
In the OPA454 datasheet I found an interesting circuit idea that I'm not sure what is it usually called (if there is a common name for it).

It involves using two opamps to shift the rails of a 3rd one. Note that unlike a bridged [tied load] configuration this circuit requires a doubling of the voltage supply rails. On  the other hand, the load is not floating in this circuit, so you can combine ts idea with the bridge to get 4X the output voltage swing (relative to using a single opamp). I'm omitting the 6-opamp bridged picture here as rather obvious; you can find one in the aforementioned datasheet.

My question is just what's a/the common name (if any) for this circuit idea. If I were to coin a name, "dynamic rails", "dynamic operating point" or something like that seems reasonable to me. (But these names don't get any sensible results back via google search.)

EDIT: I also saw something similar, but cheaper, with two BJTs instead of opamps for the "rail shifters" (A1 and A2) in a 1999 EDN article titled
"Bootstrapping your op amp yields wide voltage swings" written by [then] AD employees Grayson King and Tim Watkins. Using BJTs would introduce some more non-linearities, no doubt. So maybe "bootsrapping" might be the name for this technique... although Rod Eliott's page discussing the issues with this approach never calls it that, so I'm not convinced "bootstrapping" is the name for it... (EDIT3: Well, this was an incorrect reading of the purpose of that circuit; see comment below the question.)

EDIT2: In another article and in AD app note AN-232 (cited in that article), "supply bootstrapping" or "substrate bootstrapping" refers to something similar (altering the rail voltage via "feedback"), but in these articles it is done for a different purpose: a reduction of the input capacitance non-linearity for opamps with FET input stage... So, I'm guessing "bootstrapping" encompasses the idea I've asked about, but can generally mean the use of this supply-voltage-shifting technique for other purposes.


texts:
I'm designing an Open Hardware door-lock-controller for our hackerspace, to these basic requirements:

Be made exclusively from available and inexpensive parts.
Read external Wiegand keyboard
Read external Wiegand RFID reader
Control various door-locks and other actuators.
Read 125 kHz EM4100 RFID directly with an onboard reader.
Passive POE powered, to make cabling easier.
Run off unregulated 15-30V DC (cheap and easy high-capacity UPS via SLA)
Provide a regulated 12V DC out @ 300 mA to 1.5A peak for external gear.
Talk Ethernet to the server.
Keep a local list of allowable keys, so only power is needed to let us in.
Control external 230V gear using two relays.

This is the second spin of the PCB with a few changes to fix the problems I've found, the biggest change I've made is to throw away the LDO that regulated the 3.3V rail, in exchange for a simple MC34063 based switcher.

I'm pretty sure it's going to work, but I'd like some comments to check if I've overlooked something.

Compromises I've had to make in the design are:

The primary (35V) capacitor is stacked on top of the Ethernet transformer to save space.
The Ethernet transformer is huge, but I have a bunch of them and they were cheap, so I'm going to use them, even if they are huge.

Main questions

Is there a cheaper and better way to implement the two power supplies (I need around 200mA@3.3V and 300mA@12V with peaks to 1.5A) ?
Does the MC34063 switcher circuit/layout look sane?
I have no idea how inefficient the MC34063 is so I've tried to heat sink it as well as possible using the copper I have available, any hints for improvements?

Schematic in pdf

Click to embiggen PCB image


texts: Determine possible thermistor value in multimeter

texts:
I have a Toptronic T835 multimeter that has a cracked component that looks like a thermistor. It is marked TR1 on the PCB. The only text on the component is first row [obscured character]B and second row [obscured character]Mz.

I have been unable to find a schematic for the multimeter and cannot measure it, because it is cracked through. Can anybody possibly assist in identifying the component and its value?


texts: How to DIY BaoFeng radio-to-soundcard cable?

texts:
I've got a cheopo BaoFeng UV-5RE that I'd like to try as packet radio.
I've snipped the plug off of the headset that came with the handheld, soldered it onto some breadboard cables, and did the same to one 3.5mm jack plug connector intended to go in the soundcard. (I'd prioritize getting listening to work through line-in, first.)
But, having done that, at least one after thought hit me: the speaker-out on the BaoFeng is mono, while the port(s) on the soundcard is intended for stereo.
Would anyone be able to help me out with a wiring plan?
Feel free to doodle further on the image for rough illustration.
(Sorry for the hasty sketch. And I realize the line-in and out of the PC is perhaps in reverse location. I'm not entirely sure.)

Push-To-Talk is not very important per se, since the radio apparently have 'VOX' function, but if that's not recommended maybe I could use an Arduino that I got for the task some sort of (Linux) serial-PTT and perhaps also as some sort of a go-between the radio and the PC entirely?
Some (maybe) useful notes:
https://soundcardpacket.org/7cablerx.aspx (notes on 9600 baud cabling et.al)
https://ham.stackexchange.com/questions/1891/whats-the-pinout-for-kenwood-2-5mm-trs-3-5-mm-trs-connector
https://ham.stackexchange.com/a/3638 (this is where I found the plug image)
https://en.wikipedia.org/wiki/Line_level#Line_in
https://pinoutguide.com/Audio-Video-Hardware/Tele35s_pinout.shtml (the jackplug)
https://archive.org/stream/BaoFeng_UV-5R_manual (manual, with specs(?))


texts:
[2

I have a Protek 506 DMM, and I'm trying to troubleshoot an issue.
I found a schematic diagram for the meter on the internet, but it is a copy of an original that has a fold in the middle, right where I am trying to read the value of C58 (I'm not sure if that is the capacitor's number, as the value and the name are on that crease).  The capacitor is mounted between pin 25 and the ground, on the MAX 134 ADC.  Pin 25 is connected to a resistor network, and is one of the four voltage ranges, but it is the only one that has a capacitor to ground on it.  Pin 25 is labelled  "1.11M", and the others are: 101K, 10K and 1K.
Any idea what the value of capacitor C58 would be?
Here is a link to download the PDF of the schematic diagram (6 pages):
https://elektrotanya.com/protek_hung_chang_506_dmm_sch.pdf/download.html#dl
The problem with this meter is that the the diode tester function is not working (won't change from displaying "OPEn" and 3.999V), nor the 4VDC range, and it appears that they are related somehow.  On the 4VDC range, the display alternates between showing 3.999V and 0V.  If a voltage is measured, say a 1.5V cell, then the display will alternate between showing 3.999V and 1.5V.


texts:
Two years ago I was in an internship in a paper plant in the Superintendence of Electrocontrol, in the area of maintenance of electrical equipment. Well, they had a problem regarding some capacitor banks that were installed to mantain the power factor at a certain level. The system was simple, it had multiple capacitor banks that were switched to change the reactive power and control the power factor, and they did have many switchings over a day. The problem they had is that, capacitors would not last long, they kind of exploded on a month basis, and this was expensive due to the maintenance and the need of more capacitors to replace the useless ones. I am kind of puzzled, because it was a 3-phase system, and the capacitors nominal voltage was higher than the voltage of the source they were connected (380 line voltage, and capacitors were approximately 600 V)

My question is, why did capacitors "explode" so quickly? They should have lasted at least 3 - 6 months (1 year expected). I was thinking of over-voltage due to the transients when switching and producing like a "chain-reaction", less capacitors => higher voltage transient. However there is long time since I have not solved a circuit problem, could someome explain it in more mathematical terms? Am I correct in my statement?


texts: Why the "print" buttons are disabled in my AltiumDesigner project?

texts:
Here might not be the right place to ask but I couldn't find the proper place.

My problem is when I want to print a PCB the buttons are not clickable.

If I open print a schematic file, they work.

but they are gray if a PCB file is open.

why ?


texts: Solid State Relay using photovoltaic MOSFET driver

texts:
I am in the process of creating a High power Mosfet based SSR. The idea is using a photovoltaic MOSFET driver such as  VO1263 (SIlabs have similar IC but it uses CMOS coupling to create the isolated power). However these type of ICs are pretty slow since they provide about 10uA of drive current at approximately 10v.
During my research on the subject I have found only one circuit without any explanation that should serve to increase the switching speed (without using external DC/DC converter). Shown in the figure below:

I am not quite sure that I understand the circuit completely and I would like your help in sizing some of the components. off-course this circuit is supposed to work in high side configuration that means Vcc (1-60v DC) is supplied at pin4 and load at pin3.
My logic:

D4,R6 (around 1k ?) work as charging path for the bootstrap diode C1. T1,T2 (normal BJT such as BC537- BC527)are normal push-pull driver they work at turn on Only to provide high current to charge the mosfet gate (Sourced by C1).
Z1 and R7(around 100 ohm ?) are used to protect the gate ( however I think they must be reversed order or there should be zener diode across C1 to keep voltage < Vgs max.
R4 and R5 are pull downs (they should in 1MegaOhm range)?? however they cause power loss as R4 is voltage divider with the VO1263 output impedance. (in simulation VO1263 is modeled as voltage source with Series Impedance of 500k) .
D3 and D5 work to keep the mosfet ON after initially being turned on by bootstrap C1 (which will lose its charge if the relay is kept on for sometime).
The PV mosfet driver is not providing enough current for BJTs , So I tried using Darlington instead . The circuit worked after using 2 diodes instead of D5 and 2 diodes instead of D3 (4 diodes in total) donot fully understand why ?

Is my analysis correct ?
any suggestion on the resistor value range ?
any comments on the circuit is welcomed since I have not found any white paper , appnote or a development board that does something similar to get me started.
best regards


texts: Discrete Time Integrator (VS) Continuous Integrator

texts:
I am trying to Model control for a Micro-controller which (under Real Time Development) does not support Continuous time solver. So, instead i have to use Discrete Time Solver. How do i replace SECOND ORDER INTEGRATOR with DISCRETE TIME INTEGRATOR? The equation i am modelling is a Second Order Differential Equation.

Equation: m.y" = F_coil - Ks.x -mg

where

y" = d^2(x)/dt

F_coil = ((ni)^2)/(2.g^2)

{ where n=number of turns

i=current

g=air gap

Ks = Spring Pre-load

x = distance travelled by the solenoid plunger }

m = mass of the plunger

g = gravitational constant

Intentionally this is easy using a second order integrator.But when i use the discrete time integrator the output is completely different.
Continuous time Integrator Output: 0.067
Discrete Time Integrator Output: 3207

HOW DO I ACHIEVE THE SAME WITH DISCRETE TIME INTEGRATOR?

I am grateful for any input and please tell me if you need anymore info!!

EDIT:PLEASE CHECK THE IMAGE(it corresponds to the given equation):


texts: Extend smartphone camera outside the device

texts:
For a project, I would like to move the camera of a smartphone (Honor 7 in my case) ouside of the device by an extension of some sort.

I have determined that the connectors have a pitch of 0.4mm. The socket has 34 (17+17) pins while the header has 38 (19+19) pins, with the outer pins not being connected.

My current approach is to find a FFC/FPC with this pitch and connect it somehow, just to verify that this works at all.

The problem is that I am unable to find such a cable. The only way I can see is by custom order from a manufacturer, which I as a private person cannot do.

How would I best create this extension?


texts: Incidence of vias in the middle of a net

texts: Talking only about power and not interferences or inductance/capacitance, and taking note that all copper loosed by the hole is gained by the cilinder inside it, what is the incidence of vias in the middle of a net and not on a branch?


texts: what should be the reverse voltage of diode

texts:
In AC/DC converter using 240V/12V step down transformer,the diode used for rectification should have reverse voltage of more than 12v.

what should be the diode reverse voltage,if it should rectify directly 240V AC from mains(step-down transformer is not used)

should the reverse voltage be more than rms voltage-230 AC or peak to peak voltage 320V


texts:
If i have 2 separate processes in 2 different components
One with:
address_regIM <= address_regIM + 1
And another with:
y <= address_regIM
If address_regIM has an initial value, what will be the value of y?
Will it be the incremented value or the initial value since all process statements are executed in parallel?


texts: Controlling a stepper motor with a Siemens S7 1200

texts:
I'm working on a project that requires a stepper motor and that motor is controlled by a Siemens S7 1200 PLC.

The motor in question:
http://www.omc-stepperonline.com/nema-34-cnc-stepper-motor-5nm708ozin-30a-34hs383008s-p-32.html

The driver:
http://www.omc-stepperonline.com/bipolar-stepper-motor-driver-max-4a-current-40vdc-input-16-subdivision-st6600-p-246.html

My question is how to wire the S7 1200 outputs to the motor controller. The 1200 has the required pulse outputs and I believe I can figure out most of the software aspect. I'm just not sure how the 1200's outputs correlate to the pulse, direction, and enable inputs on the controller.

Thanks in advance.


texts: Input impedance of oscilloscope and BNC terminator

texts: Assuming an oscilloscope has the input impedance of 1MΩ, you could adjust it to 50Ω by using 50Ω BNC terminator. And I think you could do the same thing by just changing input impedance option in the oscilloscope. Could anyone please tell me what's the difference between them?


texts: Inductors in parallel won't share current well

texts: I have a question about putting two power inductors in parallel.  It seems like they won’t share the current very well. The reason I say this is that inductors lose inductance as the current increases.  So if I put two of them in parallel, then the one with slightly less inductance will get more current, and move to a lower inductance and get still more current and move lower still.  Seems like one of the two coils will tend to hog the current due to this fact.  Any thoughts?  I can't find any articles saying don't do it, but it seems intuitive that they won't share the current well because of this behavior.


texts: LTSpice .Step (2nd dimension) Syntax Error

texts:
I am currently attempting to use the step function to simplify/increase portability of some of work circuits.
Can't share the exact circuit, however I am simply attempting to define a variable/s, use those variables within some calculations, and finally pipe the equations output into the step function.

A simplified version of what I am attempting to do may be seen here:

When I try to simulate the circuit above I get the following error.

I guess my question has two parts:

Is there a way to force LT to perform the calculations first?
Is there possibly another command or action that might be better suited for what I am trying to accomplish?

Thanks in advance!


texts: Reliability of Sampling Rate vs Absolute Timestamps

texts:
I am building a system with multiple sensors and I want to sample the different sensors at different rates. For the sake of an example, I am using two MAX30102EFD-T sensors. One of the sensors I want to run at 50Hz and the other I want to sample at 1000 Hz. I have the ability to configure this sampling rate (samples per second) on the sensor and when each sensor has a new sample (supposedly at these frequencies), in the interrupt I can record this sensor value (and optionally record a timestamp like the number of milliseconds since boot.
As an example:
TIMESTAMP SENSOR VALUE
0         1      1.2
0         2      0.1
1         1      1.3
2         1      1.4
3         1      1.5
...

The issue is that storing timestamps along with the time series from both sensors can add significantly to the output file size. If the sampling rate of these sensors is reliable enough, I could just record the initial timestamp and the sampling rate and assume uniform sampling, but I'm hesitant to trust these types of sensors to have that uniform and accurate of a sampling rate. Is that distrust warranted in general?
I'm curious if anyone has any experience with such a thing and was interested to see if there was a robust approach short of storing timestamps for each sensor alongside the data.


texts:
In the given figure, the steady state is reached with the switch open. At t = 0, the switch is closed.
Find Vc(t) for t > 0.

How do I proceed solving this question?
So far, I've tried applying KVL in both the meshes, and solved them simultaneously, but I'm getting incorrect answer.


texts:
I am trying to build serial-in shift register (non cycled) based on synchronous RS flip-flop, but i'v got a problem with synchronization. My clock generator was configured to long on period and short on period. In first case all flip-flops are setups to value that comes to first flip-flop in scheme (example at first time chart). It's looks obliously, because S-RS is level-triggered flip-flop. In short on period case register gives right result exclude one case (between 20ns and 25ns on second time chart).
Are there ways to solve this problem, without changing or adding a flip-flop than that used in the scheme?


texts: Relationship between Zener voltage and current?

texts:
What's the relationship between the current flowing through the Zener Diode? I simulated the following for various values of R, and the voltage drops quite a bit with small currents. The 1N750 has a Vz of 4.7V.

The only information related to it on the datasheet I could find was the following, however I'm not sure what curve I'm meant to be looking at:

So then, I simulated the circuit with a current source instead of R1:

10mA of current gave a voltage of 4.66V
0.45mA of current gave a voltage of 4.13V

This suggests it is the righter curve. However, then I simulated the circuit at 0.01mA (the bottom of the graphs). This gives a voltage of 2.65V, which suggests the left curve. Which is it (if either)?


texts: Accessing I2C address of ADT7516 ( Temp sensor )

texts:
I have a BeagleBone Green and an EVAL board of ADT7516. I connected them by SDA and SCL pins and as they are to be connected with the PC by the usb port, they will have a common ground.

After this setup, I did i2cdetect -y -r which gives me the output as 0x51.

This address doesn't seem to be the address of the ADT7516 sensor. Instead, I can see that there is another part on the I2C bus, a serial rom chip 24lc64, which indeed has the I2C address as 0x51.

Page 11 - http://www.analog.com/media/en/technical-documentation/evaluation-documentation/512585584eval_adt7516eb.pdf

But my goal here is to be able to talk to the temp sensor ADT7516. I tried out to ask for some help on IRC and google groups and they said that it might be possible that the mux which is connected to the temp sensor is sending things in a wrong way. - page 11 of the datasheet

How can I talk to the adt7516 sensor here?
Find out the picture of EVAL board here.


texts:
I have a 36 mosfets to drive them with a microcontroller (of course not all at the same time) and a gate drivers but i'm trying to figure out a way on which i minimaze the number of gate drivers as 36 one will be very costly.

So can i from one gate driver output multiply that PWM signal to the others mosfets ?  like using a demultipexer( even that using a demultiplexer will devider my frequency and then i will loose my signal)

Is there any solution to drive many mosfets with a single PWM signal without losing the frequency of the signal ?


texts: Trying to start i2c communication on dspic33fj128gp802, but I cannot write on the SEN bit of the I2CxCON register

texts:
Good evening,
I was trying to start the communication with the I2C on my pic. I only set the bits in the control register in the code for now and the inizialization of both the pins and the PLL, and I found that the lower 4 bits( RCEN, PEN, RSEN and SEN) could not be written.
Since I cannot write on the SEN bit, the clock does not start. Also, I am setting the register so the device operates as master.

Here is my code:

int main(void)
{
InitOsc();
InitPin();
InitTimer4();
InitTimer5();

MCUinit();  //initialization MLX

//enable I2c
I2C1CONbits.I2CEN=1;
I2C1CONbits.I2CSIDL=0; //continues operation in idle
I2C1CONbits.SCLREL=1; // releases clock
I2C1CONbits.IPMIEN=0;   //ipmi should be disabled when operating as master
I2C1CONbits.A10M=0; // slave address are 7-bits
I2C1CONbits.DISSLW=1;   //slew rate control bit enabled
I2C1CONbits.SMEN=0; //disables smbus imput threshold (!!)
I2C1CONbits.ACKDT=0;
I2C1CONbits.ACKEN=1;

// Apparently no effect from here on! If I set a breakpoint here and track
// the variables none of these are on even for a single clock cycle!
I2C1CONbits.RCEN=1;
I2C1CONbits.PEN=1;
I2C1CONbits.RSEN=1;
I2C1CONbits.SEN=1;

return 0;
}

Is there anything I am doing wrong? I am quite a beginner with this microcontroller, so any explanation would be of use.

I tested the SCL channel with an oscilloscope and nothing at all comes out of that, just stays at a flat 0V signal.

Thank you!


texts:
Main goal
My main goal right now is trying to understand what negative voltage means, since I know AC can have a negative voltage and so can any electric component. I've pretty much read and seen most articles/posts forums/video's on negative voltages, but it's still confusing me. I hope understanding the following will help me grasp this concept.
My confusion
I read in some articles that "the direction of current is dependent on the electric potential, because charge flows from high potential to low potential". I, however, always thought that the potential had nothing to do with this, because the direction of current depends on the rule "opposite charges attract, like charges repel". So in convential current, the charges move from the positive to the negative terminal. I just viewed potential as a property, i.e. the amount of joules that charges are carrying (joules/coulomb).
Please correct me where I'm wrong. If it's true that current flows from high potential to low potential, negative voltage would make sense to me, because it means the side of the positive terminal always has a higher potential. Assume point A is at the start of the circuit, and point B at the end of the circuit. So when the positive and negative terminals switch (which happens in AC), point A will have a negative potential, and point B will have a high potential (instead of the opposite), which means the voltage is negative.
Just to be clear, I want an answer to these two questions: Does electric potential influence the direction of current? And is the little story I wrote correct?


texts: How do I solve transformer numericals with additive polarity?

texts:
Ok, so for subtractive polarity in transformers(dots at the same side of the windings) E1/E2=N1/N2

But if it's subtractive polarity E1 and E2 are out of phase so shouldn't E1/E2=-N1/N2

Edit:
Ok here is what I tried out. I just need to understand the first step. I solved the same question for a transformer with additive polarity

!


texts: Does the capacitor dielectric experience heating due to rapid charge/discharge cycles?

texts: Does the dielectric in a capacitor when subjected rapid charge/discharge cycles heat up?


texts: Which is worse for a relay? High inrush current or large voltage difference between the relay contact and the signal being switched

texts:
simulate this circuit – Schematic created using CircuitLab
I am working with a high voltage relay (Cynergy3, DBT72410) to discharge a 70 uF capacitor charged to 4 kV using a string of resistors and a relay to ground. I have placed a resistor between one contact (low side) and ground.  I am trying to decide if a capacitor connected between the other contact (high side) and ground is a good idea or not.
The thought process is as follows:
With the cap in place, the high side contact sits at whatever the main capacitors voltage is. So when it switches, the voltage difference between the contact and the signal is ~0.  This will minimize arcing, but it produces inrush current which would be infinite without the low side resistor (it limits the current to about 8 A).
Without the cap, the high side contact is close to ground. So the voltage between the contact and the switched signal is the full cap voltage (up to 4 kV).  This will eliminate the inrush current, but create arcs during the switch over.
Both are not good for the relay, but which is worse?
The power supply is off when the output cap (C2) is charged. The cap I am asking about is C1. During charge C1 is also charged to 4kV. When the relay closes, C1 is at 4kV, so the high side contact is also at 4kV, so no arcing. During relay chatter, the cap is continually recharged to the output cap voltage through the resistor stack (~60uS), as long as the open period of the chatter is greater than 60uS. This will continually keep the upper contact at the output cap voltage.
R1 always limits the current through the relay to no more than 8.5A. The carrying current of the relay is 2A, so inrush is limited to 8.5A for 60uS. Which I think the relay should handle with no problem.


texts: Which low pass frequency filter to configure to measure/calculate DC-DC converter efficiency?

texts:
I am measuring the DC-DC converter active power (P in watts) efficiency of a TI (Webench) LM3150 PCB that converts 12 to 5VDC.

In the answer of question Measuring precisely the efficiency of a power converter it is suggested to use:

an averaging function on the (multi)meter
low pass filtering to get rid of any high frequency measurement noise

Our Zes Zimmer LMG95 precision power meter has got several low-pass filtering options available:

AAF: analog anti-aliasing-filter
AAF + 30Hz
AAF + 60Hz
AAF + 87.5Hz
AAF + 175Hz
AAF + 1.4kHz
AAF + 2kHz
AAF + 2.8kHz
AAF + 6kHz
AAF + 9.2kHz
AAF + 18kHz

The frequencies here are digital low-pass filters with a cut off frequency of about ... Hz.

Which low pass filter - I can choose only one - to best configure in this active power efficiency measurement setup? And why choose that one?


texts: what happens if I apply a negative voltage across a zener?

texts:
I have the following circuit (just the input portion of a larger circuit)::

The 6V is coming from a walwart or other 6v source.  The Schottky diode (UPS120) is there to guard against the input voltage coming in at the wrong polarity.   The output is connected to a couple of LDO regulators, and the guaranteed maximum forward voltage (450 mv) of the UPS120 gives me enough headroom for the regulators.

However I also need the full 6v for a bias voltage elsewhere in the circuit.  Although the walwart I am planning on using is a switcher, my experience is the walwart may go slightly above 6v (e.g. 6.4v) under little load so I added a 6v zener to make sure my bias voltage does not go above 6v.

What happens though if the wrong polarity is applied to the input?  My regulators are protected because of the Schottky diode.  But what will happen to the zener?  Will it clamp to ground (ok) or go below ground (not okay)?  In the latter case, how can I mitigate this?


texts: Transmit digital signals over long distances using current (voltage to current converters)?

texts:
I want to transmit signals over a long distance wire.
Let's imagine that I want to transmit the temperature information from the LM35 sensor over a long wire: instead of transmitting the voltage (which is proportional to the temperature) through the wire because the noise will change the voltage value, I can use a voltage-to-current converter and then transmit the information by current (lets say 0ºC-50ºC -> 4mA-20mA). I just need to make sure that at the receiver I convert the current back into voltage.
But now let's imagine that I want to transmit serial data, i2c or spi between long wires (+ 20 meters). Do you think it is possible to use voltage to current converters as well? I read somewhere: "Apply the signal to a digital to current converter unit and then use the current loop transmission, with 4 mA representing" 0 "binary and 20 mA representing" 1 "binary. This allows transmission rates up to 9600 bit / s over transmission distances up to 3 km. "
What do you think?


texts: Extract a motion filter using camera movement in number of pixel and angle, in VHDL or Verilog

texts:
I have read some papers about the topic and searched some MATLAB algorithm. There is one called 'fspecial' in MATLAB. And it could return a Motion filter, when  motion is given in number of pixel and angle. I have read 'fspecial' working principles and and it contains many MATLAB built-in function like max, mod, cos, sin, sign, fix, meshgrid, sqrt, abs, find. Is it difficult to implement this MATLAB code in VHDL to obtain a Motion  -blur filter.

... This code is portion of 'fspecial' in MATLAB ******
case 'motion' % Motion filter uses bilinear interpolation

 len = max(1,p2);
 half = (len-1)/2;% rotate half length around center
 phi = mod(p3,180)/180*pi;

 cosphi = cos(phi);
 sinphi = sin(phi);
 xsign = sign(cosphi);
 linewdt = 1;

 % define mesh for the half matrix, eps takes care of the right size
 % for 0 & 90 rotation
 sx = fix(half*cosphi + linewdt*xsign - len*eps);
 sy = fix(half*sinphi + linewdt - len*eps);
 [x y] = meshgrid(0:xsign:sx, 0:sy);

 % define shortest distance from a pixel to the rotated line
 dist2line = (y*cosphi-x*sinphi);% distance perpendicular to the line

 rad = sqrt(x.^2 + y.^2);
 % find points beyond the line's end-point but within the line width
 lastpix = find((rad >= half)&(abs(dist2line)<=linewdt));
 %distance to the line's end-point parallel to the line
 x2lastpix = half - abs((x(lastpix) + dist2line(lastpix)*sinphi)/cosphi);

 dist2line(lastpix) = sqrt(dist2line(lastpix).^2 + x2lastpix.^2);
 dist2line = linewdt + eps - abs(dist2line);
 dist2line(dist2line<0) = 0;% zero out anything beyond line width

 % unfold half-matrix to the full size
 h = rot90(dist2line,2);
 h(end+(1:end)-1,end+(1:end)-1) = dist2line;
 h = h./(sum(h(:)) + eps*len*len);

 if cosphi>0,
   h = flipud(h);
 end

I wonder, whether I have in correct way to implement a motion filter in VHDL. Maybe there should be an effective way to this task? Or is there already implemented motion -filter in VHDL or Verilog ?

Thank you.


texts: Digitally Pressing a keyfob button with a microcontroller

texts:
For a project I'm working on, I need to press a car keyfob button with a microcontroller.  So I soldered two wires to the circuit thing on the keyfob so I can send signals to it.  This is what it looks like.

This is what I've tried so far:

1)  I've tried writing 3.3V to one of the wires I soldered to with a netduino 3.3V digital I/O pin.  I tried it by directly connecting it to the digital output port, and also with a 100 Ohm, 2.35kOhm, 4.7kOhm, and 9.4 kOhm resistors.

2)  I've tried shorting the cables to each other, and that didn't do anything either.

I also have made sure the microcontroller and the netduino had a common ground.

I have no idea why it doesn't work?  Especially when I short it.
When I take the rubber part of the keyfob,  and press it against the circuit it works every time.

EDIT:  I also know the keyfob isn't fried because when I power it with the netduino (3.3V) or the lithium battery (3V) and press the circuits with the rubber, it works just fine.  So the keyfob is still good.

Does anyone have any ideas?

Thank you so much!

-Phil


texts:
I am measuring AC signal using an instrument amplifier AD623.
This will be fed to an ADC in the 0/+5V range. Therefore the signal must be centred on 2.5V. A voltage divider will create the 2.5V using two 10k resistors.

Do I need to buffer the output of the divider with a follower circuit?

The impedance of Vref is 100k (AD623 datasheet). Is this large enough compared to the 10k?


texts:
I need to interface door phone system to a pc soundcard to listen and talk to the external unit.

The door phone to interface is an as yc/200 of BPT and its a classic analog 4+n wires Door phone system and I have access only to the internal unit.

In the internal unit I have a cable with 4 wires: a Ground wire, a call wire, an audio in, an audio out; going through the power supply to the external unit.

This is a picture of the phone.

(source: intercomsrus.com)

Unfortunately the datasheet doesn't say nothing regarding the audio lines and their signals.
What I know is that they are probably standard for every 4+n wires door phone.

Now what I would like to understand is how to connect the audio signals to the sound card without damaging it.

Are those signals usually high voltage or high impedance?

The power supply output 11 volts DC and 15 volts AC.
Also the pushbutton that open the door is connected to the audio out towards the external unit. What kind of signal is sent to open the door?


texts:
My bench is overflowing with stuff ... I have several racks of little drawers, and another bench that has heaps of stuff on it. My label maker works hard. And yet, stuff gets temporarily lost all the time.

How do you keep track of all your parts?

If you have any ideas on how to keep track of your inventory, please share. This is driving me nuts and spending money to solve the problem is certainly on the table. My latest idea is to have everything ordered by supplier part number, and use a database to look them up. Any better ideas?

(My goal is to optimize findability, not (say) everything being reachable - walking around and collecting stuff is OK).


texts:
I found -3dB frequency \$f_H\$ of the following circuit using both OCTC and Miller's theorem:

OCTC:

\$f_H=1/(2\pi [C_{gs}R_{sig}+C_{gd}(R_L(1+g_mR_L)+R_{sig})+C_LR_L])=652KHz\$

Miller's theorem:

\$f_{Hin}=1/(2\pi [C_{gs}R_{sig}+C_{gd}R_{sig}(1+g_mR_L)]=788KHz\$

\$f_{Hout}=1/(2\pi R_L(C_L+C_{gd}(1-1/k)))=3.79MHz\$

Hence,

\$f_H=1/\sqrt{1/f_{Hin}^2+1/f_{Hout}^2}=777KHz\$

I was then asked to shortly explain the discrepancies between the two results in view of the fact that OCTC and Miller's theorem give almost the same results in terms of time constants. Why is there over a 100KHz difference in this case?


texts: Can I use a 640x200 STN LCD controller to drive a 640x240 STN LCD display?

texts:
I have an old LCD display controller that drives a 640x200 STN LCD display. The interface has a Frame Pulse/Frame Line Marker (FP/FLM), Line Pulse (LP), and LCD Clock control lines and D0..3 data lines.
Given the scarcity of 640x200 displays, I was wondering if it could use the controller with a 640x240 display panel. If after sending data for the first 200 rows the controller generates a FP/FLM, will a 640x240 panel simply display the first 200 rows correctly with no adverse side effects from not writing data to the remaining 40 rows? Or will those remaining rows suffer from bias or other issues?
This question would apply to any LCD controller using the standard control signals above being used to drive a display with more rows than the controller supports. Does the energising activity up to row 200 bleed over to rows 201 to 240 above over time, resulting in a DC bias effect? It’s something that isn’t covered in a data sheet, but through experience.


texts: Determining the ROM contents of a circuit

texts: I have a state transition table and  a truth table stored in a ROM. The truth table was obtained from the state transition table but I'm not sure how. Could anyone explain how the truth table is obtained from the state diagram shown in the image below?


texts: What is the purpose of a resistor between the and gate output and ground?

texts:
I found this image of a transistor-based and gate:

and I can't understand what the purpose of the 4.7K resistor is. If the component controlled by the gate is placed between "Out" and ground, then that resistor is just a waste of energy since the circuit should work with or without it.

What am I not understanding?


texts: Trace width in small PCB board designed to combine battery cells in series

texts:
I am  designing a PCB board that will combine 6 cells in series. However, I am thinking this might not work because of the amount of current that is required from those cells. My battery has to be able to provide up to 100A for few seconds, and 50A for continuous.

Here a quick layout I did of what it will look like:

The yellow plane (5mm in width) is what will be connecting each cell in series, however with most calculators it is asking for at least 55 mm with a 20C temp rise. I can't  go higher on the temp rise because this will be a battery board and don't want my battery to heat up. I also can't make the board any bigger because of my mechanical requirements. However, I can go thicker with more layers, but I have no idea how to calculate how many layers I will need to make this connection work.


texts: Is this a delay circuit? / Which resistor is responsible for load impedance?

texts:
I just stumbled upon this circuit of a microphone preamp. However, I`m not entirely sure about two of its components/ properties.

My first question regards R3 and its closely located capacitor. Someone online claimed this was in order to reduce any clicking when phantom power is switched on, and after some googling I found that this might be a simple delay circuit. Am I correct in thinking that?

My second question regards R4/ R5. I´m aware that these together with C1/ C2 form a high-pass filter, but someone told me these would also present a load impedance of 2.2k to the microphone. Since impedance is still quite the conundrum to me, I thought I´d ask here wether that is correct.
I was under the impression that R1/ R2 not only limit the current to be drawn from the 48V supply, but also play a role in the input impedance of this circuit. This is because that´s what I gathered from the diagram here http://educypedia.karadimov.info/library/mic1dat.pdf where a 2.2k resistor in series with the 2V supply indicate a 2.2k load impedance in the table above said diagram.

I apologize for the convoluted question and many thanks in advance for your help =)


texts: Boost converter drops voltage to 0 V when activated.

texts:
I have built an automatic watering system using an Arduino board and a boost converter for powering the 5V DC pump (1-3W), but I have a problem. Each time the pump is activated, the DC-DC converter (bough from here) shows that the voltage drops to 0V, although the pump still works and I'm not sure if this is normal or not. I am powering it by a 2.6 Ah 18650 LCO battery and it should be enough power in it to drive the pump.

The question is... why does it drop to 0V when the pump is turned on?

And moreover, if I try to connect also the Arduino board to the same power, the voltage drops from 5V (which I set manually) to 4.8V and I can't change it anymore in the booster.

Is there something wrong with the switching or is it a normal behavior of a DC-DC Boost Converter? If not, what can be the cause for this drop?

Please see the diagram of my system and the components below :


texts:
I am about to build a wien bridge oscillator circuit which is shown in the figure below:

However, I need a dual potentiometer to do so, because the resistors VR1a and VR1b must have the same value always, and this is hard to achieve using two single potentiometers.

The problem is that I think that dual potentiometers are not available in the local market. Can I build a dual pot from two single pots? Is there another way to have a dual pot?


texts:
I wonder how can I make Altium autorouter to place a short track and then use via to connect SMD IC pads on one side to a polygon on another side?
Should I define any rules?
Should I change any preferences?


texts: How to detect 220 VAC voltage using an opto-isolator

texts:
I created the following circuit.

I plugged it in and it works!!

Now I thought of adding an opto-isolator to the circuit in place of the LED. The value of C was the same.

$$
X_c = {(({220volts-1.4volts})/0.01A))} = {(2*π*(50Hz)*C)}^{-1}
$$

$$
solve for :C=150nF
$$

so I ended up with the circuit below.

The two diodes in series are actually present and on the first circuit to achieve a drop-down of 1.4 volts same as the external LED and for the internal LED.

The opto-isolator used was ln4n25

The diodes are proper voltage rating. Why a drop down of 0.7 volts

The problem is that gate of the transistor is not getting high when connected to mains. Meaning that the internal LED is off so GPIO is always HIGH.

Any thoughts?
Is the internal LED even turning on? How can I check?

Also I currently have access to this and only this opto-isolator.


texts: Discussing FreeRTOS architecture for sort of a data logger application

texts:
I'm fairly new to RTOS architecture and been reading up on articles on FreeRTOS.org, but as it's commonly agreed, practice clears things up even more.
I have a basic project idea which I'd ideally want to be RTOS-based as I'll explain below along with some questions:
My understanding is RTOS comes in handy when you're computing multiple tasks concurrently. Based on that, I came up with the idea which involves a BLE-supported MCU, sensors, BLE-supported app, and some sort of a display component be it LCD, and how it works is a request is sent over BLE from an app, which is processed by the MCU, and does the following concurrently:

sending the data from the desired sensor back to the app over BLE
updating the display with the value on an LCD

In an RTOS context, I'd then have:

TaskA - constantly reads the requests coming over BLE from an app

Process the request in either TaskA or a different task (?), and obtain the desired data and put it in queueB.

TaskB - as soon as queueB is no longer empty, send the data out to the app over BLE

TaskC - as soon as queueB is no longer empty, update the display with the data

I think with this approach, there isn't any shared data that I need to worry about locking mechanisms...unless I'm missing something. Is the use of RTOS justified? If not, what else could be done?
A usecase:
I have a BLE-compatible phone (acting as a central) with an app that's connected to, say, the BLE of nRF52 (acting as a peripheral). After the connection, the user wants to retrieve some information from sensorA, so they send out "A", which is received by the peripheral device, processes it, and responds back to the central with the desired data which was requested, and at the same time, the LCD display is updated with the data as well


texts: Determine range of proportional gain with given overshoot

texts:
I have given the open-loop transfer function
$$
G_{ol} = 1.42 \frac{(s+3)^2+6^2}{(s-1)(s+2)((s+4)^2+4^2)}
$$
The task I was given is determining the range of the proportional gain, which makes the overshoot less than 10%.

I know that the overshoot is calculated using the formula
$$
\delta=e^{-\frac{\pi}{\tan \varphi}}<0.1
$$
$$
\varphi < \arctan \left(-\frac{\pi}{\ln(0.1)}\right) \approx 53.76°
$$
which also gives me the damping ratio
$$
-\frac{\pi}{\tan \varphi} = -\frac{\pi \xi}{\sqrt{1-\xi^2}} \to \xi = 0.59
$$
So every pole with a higher damping ratio than that would fulfill my condition.

The root-locus of this transfer function is given as

My question now is how do I determine the range of the proportional gain, which fulfills this condition?
I think what I would need is the natural frequency for determining the poles which have this damping ratio.
The characteristic equation of the closed-loop transfer function would be
$$
1+KG_{ol} = (s-1)(s+2)\left((s+4)^2+4^2\right)+1.42K\left((s+3)^2+6^2\right)=0
$$
And I'm stuck here.

Using Matlab, I got the two poles, which have an overshoot of exactly 10%
$$
p_{1,2} = -0.343 \pm 0.47j
$$
which gives me a proportional gain of
$$
K = 1.18
$$
But how do I get there? I would like to not use Matlab and understand how this is calculated.
Can anybody help me?


texts: Problem with too-high logic level / floating signal in 15 x 5 keyboard matrix

texts:
I'm pretty rusty with electronics, so please forgive me this question.
I've built a keyboard matrix with 15 columns and 5 rows.

The 5 rows are connected to GPIO pins on an Atmega 32u4 MCU.
The 15 columns are connected to GPIO pins on an MCP23017 I/O expander.

The matrix is wired as 15x5 (well, a couple of over-size keys means that there are a couple of spots where the matrix is one row shorter, or skips a key in a given column).

The matrix is scanned in the usual fashion: row by row, set the row to Output/Low, then read the columns (this is done over i2c, reading back 16 bits for all of the pins "at once"), then reset the row to Input/High and continue.

For the most part this works fine, but there are some keys that don't register; these are in the final column and bottom row.

When I attach nScope to a key in row1 and press it, I can see the transition from logic-high to logic-low.  When I repeat the same for lower rows I can see that the logic-low level gets higher (the trough gets shallower) as we get closer to the bottom.

I've attached a screenshot from nScope; the green trace is attached to the node labelled row5 in the schematic fragment included here.  The orange trace is the other side of the diode, where the arrow points and says "floating".  The square wave is due to the matrix scan selects/de-selects rows.  The trace is without any keys being pressed.

SW3 in this schematic doesn't register when pressed, but SW5 (in the column above) does register.

My hunch is that the pull-up resistors for the columns are not right.  I have tried with and without pull-resistors on the column GPIO pins; external 4k7 and then swapped those for the internal 100k pull-ups; the symptoms remain the same.  Disabling the pull-ups just results in garbage as you might expect.

How do I debug this?  What's the likely cause of this and what should I try to do to mitigate it?

simulate this circuit – Schematic created using CircuitLab


texts: Placing a key variable in internal flash Memory

texts:
I am trying to place a variable named secret_key at location 0x08002000 in STM32Nucleo-board which has STM32L476RG on board with 1MB flash.

Question 1: Why am i unable to place code in custom ROM (SECRET_IROM1 )section?
Question 2: What is the mistake i am doing?

I am still newbie to Linker topic.

I am able to do it(still do not undestnad, why other RO section also follows my new address of secret_key variable) if i define the address which is in the default section for RO in the scatter file. If i create a new section, mapping is not happening. I can see the address assigned as expected but the value of the secret_key is not visible at that location.

below image shows what happens when i declare the address out of range from the default section.

Code section where variable is declared:

unsigned long long int array4[6]={0};
unsigned long long int array[6]={12};

unsigned long long int arra2[4] = {0x1111111111111111,0x2222222222222222,0x3333333333333333,0x4444444444444444};
const long secret_key[3] __attribute__((section(".ARM.__at_0x8001800"))) = {0xABABABAB,0xCDCDCDCD, 0xEFEFEFEF};
extern int addsum(int, int);

int main()
       {
    long long int array3[100] = {1,2,3,4,5,6,7};
    array[1] = arra2[1] - array[0]+array3[1]*2+array3[2]*2+addsum(array[1],array[2])+array4[2]+(int)secret_key[0];
    while(1);
}

Memory map below:

Scatter file contents below:

; *************************************************************
; *** Scatter-Loading Description File generated by uVision ***
; *************************************************************

LR_IROM1 0x08000000 0x00100000  {    ; load region size_region
  ER_IROM1 0x08000000 0x00002000  {  ; load address = execution address
   *.o (RESET, +First)
   *(InRoot$$Sections)
   .ANY (+RO)
  }

  SECRET_IROM1 0x08002000 0x00000030  {  ; load address = execution address
  *(.ARM.__at_0x8001800) ; secret key
  }

  RW_IRAM1 0x20000000 0x00000100  {  ; RW data
   project2.o (+RW)
   }

  RW_IRAM2 0x20000100 0x00000100  {  ; RW data
   project2.o (+ZI)
   }

  RW_IRAM3 0x20000200 0x00000300  {  ; RW data
   project.o (+ZI)
  }

  RW_IRAM4 0x20000500 0x00000200  {  ; RW data
   project.o (+RW)
  }

  RW_IRAM5 0x20000700 0x00001000  {  ; RW data
   .ANY (+RW,+ZI)
  }
}

Second case: where it doesn't work

Code here:

unsigned long long int array4[6]={0};
unsigned long long int array[6]={12};

unsigned long long int arra2[4] = {0x1111111111111111,0x2222222222222222,0x3333333333333333,0x4444444444444444};
const long secret_key[3] __attribute__((section(".ARM.__at_0x8002100"))) = {0xABABABAB,0xCDCDCDCD, 0xEFEFEFEF};
extern int addsum(int, int);

int main()
       {
    long long int array3[100] = {1,2,3,4,5,6,7};
    array[1] = arra2[1] - array[0]+array3[1]*2+array3[2]*2+addsum(array[1],array[2])+array4[2]+(int)secret_key[0];
    while(1);
}

associated scatter file here:

; *************************************************************
; *** Scatter-Loading Description File generated by uVision ***
; *************************************************************

LR_IROM1 0x08000000 0x00100000  {    ; load region size_region
  ER_IROM1 0x08000000 0x00001800  {  ; load address = execution address
   *.o (RESET, +First)
   *(InRoot$$Sections)
   .ANY (+RO)
  }

  SECRET_IROM1 0x08002100 0x00000030  {  ; load address = execution address
  *(.ARM.__at_0x8002100) ; secret key
  }

  RW_IRAM1 0x20000000 0x00000100  {  ; RW data
   project2.o (+RW)
   }

  RW_IRAM2 0x20000100 0x00000100  {  ; RW data
   project2.o (+ZI)
   }

  RW_IRAM3 0x20000200 0x00000300  {  ; RW data
   project.o (+ZI)
  }

  RW_IRAM4 0x20000500 0x00000200  {  ; RW data
   project.o (+RW)
  }

  RW_IRAM5 0x20000700 0x00001000  {  ; RW data
   .ANY (+RW,+ZI)
  }
}

memory map below:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Results of suggestion fron Jeroen3

I am expecting the values loaded into the variable secret_key to be visible in the flash memory region, but it is not.


texts:
I have an Arduino project which needs to simulate a human button press on a third-party board, an 883LM garage door opener controller. The other board has its own power supply which is separate from my project. My multimeter shows 3.3V DC across open the button. I don't have an oscilloscope to verify that it's DC.

I thought the easiest way to interface with this would be using a 4066 "bilateral switch". I checked it with my meter and can see the continuity across pins one and two changing when I would expect.

The problem comes when I connect it across the button on the 3rd party board. The board behaves like I am holding down the button, regardless of the 4066 state. I have verified that my poor soldering has not resulted in contact between the two sides of the switch. The physical button does not respond until I disconnect one side from the 4066. If I connect it momentarily, it behaves like I have tapped the button.

I don't have much understanding of how the commercial board would not be compatible with this electronic switch. Is there anything else I should try before I start thinking about a completely new approach?


texts: How to have Wye-connected Potential Transformers(PTs) and Neutral Ground Resistor short circuit detection at my ground fault protection relay?

texts:
Detecting if the Neutral Ground Resistor (NGR) is shorted is something that must be checked at the Ground Fault Protecting Relay. The typical way to do this is to inject a DC component and to measure the voltage drop in the NGR. If no voltage drop is seen, it is assumed that the NGR is shorted and the relay trips. I would like to have Wye-connected PTs, used to monitor the quality of line to ground voltage and NGR monitoring with NGR short circuit condition detection at the same time on a 4160 V transformer secondary.

Having Wye-connected PTs may confuse the ground fault detection relay as for the DC component the PTs provide a low impedance parallel path which can be confused with a shorted NGR and this must be avoided.

Is adding a Potential transformers Ground resistor (PTGR) the only way to achieve both things? Wouldn't this affect the reading of the system monitoring the quality of line to ground voltage?

Update: There are also PTs that are build with a capacitor voltage divisor on their primary but I haven't found any operating at 5 kV


texts: Controlling millivolt fireplace with Wi-Fi wall switch

texts:
My whole house is setup with Wi-Fi wall switches. They're just like basic 110V wall switches, but they can be controlled via Wi-Fi. I'm in the U.S. I'd now like to enable my fireplace. The fireplace runs today from a standard wall switch, it's not a millivolt switch. The switch turned on releases the gas, lights the pilot, and then turns the gas on full via 3V DC.

So, I'm in a place where I need to control extremely low voltage DC with 110V AC. I thought about an SSR, but AC-DC relays don't seem to exist. I thought maybe an A.C. SSR-25AA that I had laying around would complete the millivolt circuit, but resistance doesn't seem to change with the SSR. Would it on an electromechanicsl relay? I then thought about transforming the AC to DC, but I was hoping for something smaller with fewer components. While testing, I found that when I switched from 1K to 10 ohms, the multimeter's resistance turned on the fire. Switching back up turned it off. Maybe a resistor on my SSR would work?

What is the best way that I could switch low voltage DC with house AC? Can AC being on just complete a simple DC circuit somehow?

Thanks.


texts:
While studying about Semiconductors I couldn't get why "Negative charge stop electrons from further diffusion and Positive charge stop holes from further diffusion" as stated in (p.6) of the semiconductors.

Also which carriers(minority or majority) take part in the diffusion process?Do both of them take part in the diffusion process?Could anyone help me.


texts: In the world of bipolar stepper motors, what is dead time and blanking time?

texts:
I have a stepper driver documentation which speaks about dead time and blanking time, however I do not know what it means.

L6470 dSPIN

What is "Dead Time" and "Blanking Time" in relation to stepper motors?


texts:
I'm trying to pick apart a signal conditioning board. I found a SOT23-6 package marked "4DLB" which doesn't seem to have any matching SMD code in any charts I found.
I suspect it may be a type of multiple diode(s) package given the rectification application. Is there any other way to ID this chip? No searches for the IC in any databases I am aware of returned useful results.
Hoping to use techniques discussed here for future hunts.
Added image:
Thanks


texts:
The image above shows how a typical AC to DC adapter works, high voltage (230V) at low current is fed into the primary coil and then gets stepped down to a lower voltage with higher current, afterwards it gets rectified to DC and finally a capacitor turns this DC to pure DC.

The power from the primary coil has to be the same as the power at the secondary coil (assuming no power loss). Let's for instance use an example, a phone charger, most phone chargers normally output 5V@1A DC which means 5W. Since the voltage from the wall is 230V this means that for there to be 5W there has to be 5W/230V = 0.0217A which means that the resistance at the primary coil is 230V/0.0217A = 10599\$\Omega\$

This is the part that I don't get, how can an inductor (coil), something with almost no resistance, have so much resistance. At first I thought that they would put a resistor before the coil but then I figured out that all the power would be used up by the resistor and wasted as heat instead of reaching the coil.

So what is really going on? Do they make these coils with materials that have really high resistance or am I missing something? Probably the latter is true.

Any help is appreciated.


texts:
I recently bought protective BNC caps for my oscilloscope input. When I screw them on or off I need to apply a much greater force than when connecting the probes. Is this normal? Could this damage my oscilloscope inputs?
Thanks in advance for your help


texts:
I have a non-rechargeable 3.6V, 19Ah lithium polymer battery, and I want to calculate the remaining time for the battery from its measured voltage assuming that the average consumption current is constant.
I've read about the state of charge but don't have a curve for it in the datasheet.
The voltage battery will be measured by a voltage divider.
Any help how to estimate the approximate reaming time?


texts: Sine/Cosine encoder: Fine position interpolation

texts:
In a sine/cosine encoder, position information is encoded in two 90 degree phase shifted sinusoidal signals. Typically, the approach to decode this information is by generating a coarse quadrature signal and sum a finer position information, interpolated through the arctan function:

My question relates to this implementation. Since both signals originate from the same source, I assume that the cosine signal does not encode any extra information that can be extracted purely from the sine signal. Although they are both generated from the same source, the cosine signal will have phase, gain and offset errors in relation to the sine signal, which limit the accuracy of the previous calculation.
So why are both signals used? To obtain the fine position information, can't the arctan function be applied to an original signal, for instance the sine wave, and a "virtual" 90 degree offset signal, cosine, generated from this sine wave, therefore eliminating these sources of error?


texts:
I'm working on a board that has to control some LED chains. Each chain requires about 17-18V (power rail is 24V) with a nominal current of about 450 mA.
An MCU will provide the PWM to control the LED brightness. I selected HV9910C as a LED driver. The LEDs are placed quite close to the driver board (< 10 cm) and a key point is to avoid flickering, especially at low PWM values.
Reading the datasheet in chapter 3.0 Application Information I read:

Constant frequency peak current mode control has an inherent disadvantage – at duty cycles greater than 0.5, the control scheme goes into subharmonic oscillations. To prevent this, an artificial slope is typically added to the current sense waveform. This slope compensation scheme will affect the accuracy of the LED current in the present form.

However, a constant off-time peak current control scheme does not have this problem and can easily operate at duty cycles greater than 0.5. This control scheme also gives inherent input voltage rejection, making the LED current almost insensitive to input voltage variations.  However, this scheme leads to variable frequency operation and the frequency range depends greatly on the input and output voltage variation.

In my system, I have a stable input voltage of 24V, so I'm not interested in voltage-variations rejection.
It's not clear to me how to decide which's control scheme is better for my application: it says "the slope compensation scheme will affect the accuracy of the LED current" but I cannot find how much the current is affected! Are we talking about 1-2% or 10-20%?
About the constant off-time mode, the chapter 3.3 Oscillator says:

If the resistor is connected between RT and GATE, HV9910C operates in a constant off-time mode and the above equation determines the off-time.

But again, I don't understand how to choose the appropriate off-time and how to calculate the frequency range that "depends greatly on the input and out-put voltage variation".
Would you mind clarifying how to design such a LED driver?


texts:
I've often seen devices with power requirements specified only in Volts (e.g. 7-12V) but never the amperage. I've wanted to run various embedded devices of wall warts and batteries (the devices have regulators don't worry) however I've been hesitant because I'm not aware of the amperage requirements for the devices.

My question is: Is there a standard amperage that is "understood" for microcontrollers and the like?

I have been told that amperage doesn't matter however I beg to differ, since I am quite sure that if I supplied a 7-12 volt device with 9 volts at 1 billion, amps that it would explode.

EDIT: To put it simply. A power supply is rated at the amps that it will tolerate before overheating and taking damage?


texts: Why were the fuses not protecting the circuit?

texts:
I bought a Aprilia SR 50 Scooter with a "small" problem, the frontlight and the horn are not working, because the 10A fuse does blow up if the key is turned...

I don't know what happened today, but I installed a new battery (which had 12,6V), then after I turned the keys to position "On" the fuseholder started to heat up and the plastic on the fuses melted, but both fuses stayed alive!! There was also a little bit smoke coming from the rear. I turned the key to position off immediately. The circuit was damaged and not protected by the fuses. I used the right fuses on the right place as shown in the circuit (10A and 15A), a few parts broke. My break light broke and the scooter is not making any noise when trying to turn it on, the starter seems to be broken now.

I am lucky that I had all front parts including cockpit disconected (except the ignition), only the rear of the scooter was connected to the circuit.

Is it possible that this happened because most of the electrical consumers were disconnected and thus the whole current was too strong for the small number of remaining consumers?

Or maybe because the ECU was laying on the floor, im not sure if it is allowed to put electrical parts on the floor.

Why were the fuses not blowing up and protect the circuit? And do I have to throw my scooter away now, or can I still fix it?

This is the circuit:

LEGEND FOR SWITCH PANEL - SR 50 PUREJET
1) multiple plug
2) dipped beam / high beam relay
3) Oil level switch
4) Fuel level sensor
5) Cockpit (matrix)
6) Immobilizer antenna
7) Ignition key switch
8) Horn
9) Left light switch
10) Rear brake light switch (on left
Switch)
11) Right light switch
12) Front brake light switch (on
right switch)
13) Rear turn signal, left
14) Tail light
15) Double light bulb for stand
/ Brake light
16) Rear turn signal, right
17) License plate lighting (only at
Versions USA / CH)
18) Pick up
19) generator
20) Voltage regulator
21) injection relay
22) Starting relay (fault protection)
23) starter motor
24) Battery
25) fuses
26) Fuel pump
27) Air nozzle
28) Fuel Injector
29) Pressure sensor (or in the control unit
integrated)
30) Cylinder head temperature switch
31) HS coil
32) spark plug
33) Gas control sensor
34) Serial connection (Diag.) 35) Oil pump
36) ECU control unit
37) Speed sensor
38) Front turn signal, right
39) Front parking lights (only at
Versions USA / CH)
40) low beam
41) high beam
42) Front turn signal, left
43) headlights
44) diode
45) -
46) -
47) -
48) -
49) -
CABLE COLORS
Ar Orange
Az light blue
B blue
Bi white
G yellow
Gr Gray
M brown
N black
R red
V green
Vi Viola
Ro Rosa


texts:
I've built a simple LED sequencer using PIC 18f4550. Outputs are 10 pins on ports C&D.  I have now built (soldered) this circuit 3 times and it still only powers on intermittently.  I installed a very low current "power on" LED to help troubleshoot.  I notice if I touch the chip or certain areas of the board, the circuit works (& power light on).  But it intermittently goes out.  Almost like there's a loose connection or some capacitive issue.  Circuit works fine when the power light is on.  Symptoms are the same whether breadboard or soldered.  Ideas?

Thanks

please excuse the crudeness of this drawing.


texts: Switching power supply delays delivering power

texts:
I am powering a 1A bipolar hybrid stepper motor driven by a DRV8825 with a 12V 10A switching power supply. There is a 220uF capacitor placed at the motor power supply near the driver. The driver's current control is set to 0.5A.

When the driver is in sleep mode, it is woken up and there is a 2ms delay for wakeup time in the code (avr-gcc) before the direction is set, then 1us delay for setup time and then the step pulses are sent, starting pretty slow and accelerating with a linear profile.

All works just fine when powering the driver/motor with a linear 12V 2.5A power supply.

But when powered with the 12V 10A switching power supply (plugged in/switched on, idling), there sometimes is a short interruption shortly after the motor starts and the motor is losing steps. Looking at the voltage of the power supply, it actually breaks down some volts when this happens.

I am not aware of such behaviour, but I have the impression that the switching power supply needs a bit time to deliver power from idle state. Interestingly enough, if I let it continuously power another consumer drawing about 1.5A at the same time, it is stable and all runs fine.

Is my observation correct? Does a (switching) power supply need a short moment to stabilize? If yes, is this by design or some soft start or power saving feature?

I can easily change my code to wake up the driver and give the power supply some time to stabilize before the motor starts stepping.


texts: Installed 555 timer socket backwards - can I reverse the chip in the socket?

texts: I installed the socket for a NE555 timer ic backwards on a PCB.  Can I just reverse the chip in the socket to cure the mistake?


texts: Why are devices like the MCP23008 or PCF8574 still around when cheaper alternatives exist?

texts:
INB4: if this question doesn't fit this board, please delete. But I don't know where else to ask.

There're plenty of I/O port expanders available. Most of them add 8 I/O lines at the cost of two I2C lines (SDA, SCL). Here's the pinout for the MCP23008, taken as an example:

And here we have a pinout of ATtiny404 MCU:

The chip has 12 I/O lines, from which:

Two lines are for I2C, connected to hardware I2C module;
One line is reserved for RESET;
One line can be used to generate interrupts for external MCU;
8 general purpose I/O lines.

So such MCU can easily substitute dedicated expander like MCP23008 or any of a kind. It will of course require some programming to do so. I self-rank my own programming skills somewhere between 'awful' and 'very poor', and still I think it will take me maybe 4-5 work days to write such firmware. Experienced programmer, I guess, can make it in 1-2 days. I see no obstacles here.

While for the Arduino guy (like me) simplicity is very important, in full scale production cost control comes to the first place. And what we have for the MCP23008? Here's offer from Digikey, roughly $8,000 per 10,000 pcs: https://www.digikey.com/product-detail/en/microchip-technology/MCP23008T-E-SO/MCP23008T-E-SOTR-ND/739286

And here's for ATtiny404, roughly $4,300 per 10,000 pcs: https://www.digikey.com/product-detail/en/microchip-technology/ATTINY404-SSNR/ATTINY404-SSNRTR-ND/8594960

That means that for 10,000 pcs price difference is about $3,700. And 10k pcs isn't a breathtaking amount for a production device.

So the question is: what is the reason that such devices are not completely phased out by MCUs?


texts:
I am trying to find the value of a blown resistor so that I may replace it.
Its from a Circulation Booster V3 circuit board.
The marking on the board where the resistor lives is marked L1
It is green and can be seen in place and burned out in picture 1.
It is in close-up in picture 2.


texts: Digital voltage/current controller for DIY bench power supply

texts:
I'm trying to design a portable rechargeable bench power supply.  I have a 12V sealed lead-acid battery (WP7.2-12) which I can use as the main power source. These batteries are cheap and easy to source, and have reasonable power output specifications.

I would like to be able to digitally control the output voltage and current using a microcontroller.

I'm seeking advice for a voltage/current output controller which would be reasonably easy to interface with a MCU.  It needs to be digitally controlled (i.e. serial, SPI, I2C, 8-bit bus, etc), and should be able to provide two modes of operation:

Voltage output with selectable voltage and maximum current
(0-12V, 0-10A)
Constant current output with selectable current output (0-10A)

(Maybe these features need to be implemented as two separate circuits, using relays to connect the output to one or the other...)

Would an LED driver such as those referenced here be a good route for this type of controller, or would it be best to roll-my-own circuitry for this?  Any pointers/tips appreciated.

Obviously there are other components (i.e. overcurrent protection, battery charge controller, deep-discharge prevention, user interface, etc.) that must be implemented as well, but for this question I'm simply seeking a way to control the output voltage/current per the above.

Thanks!


texts: Can this circuit suffer from short-circuit?

texts:
I am preparing some circuits for children to be soldered in thumbtack technique. I found some that seem to fit my purpose. One of them is a siren. In the wiring diagram, I see that there's a line through two transistors that potentially connects plus and minus without any resistor (highlighted in red).

Here's my redraw of it:

simulate this circuit – Schematic created using CircuitLab

In that circuit, is there the danger of a short-circuit?


texts: Proper way to turn off PWM channel on STM32

texts:
I am using STM32F4 to drive a 3 phase BLDC motor and i'm using TIM1 peripheral to
generate 6-step PWM(complementary pwm) but when i change the configuration and i disable 1 channel it takes some time to go low which causing problems (you can check the photos in the links below )

https://ibb.co/fv3PGJ0
https://ibb.co/6sTsYDM
https://ibb.co/MkFLttv
also here is my configuration:

TIM1->PSC=0;
TIM1->ARR=800;
TIM1->CCR1=400;
TIM1->CCR2=400;
TIM1->CCR3=400;
TIM1->CCMR1 |= TIM_CCMR1_OC1PE | TIM_CCMR1_OC1M_1 | TIM_CCMR1_OC1M_2 | TIM_CCMR1_OC2PE | TIM_CCMR1_OC2M_1 | TIM_CCMR1_OC2M_2;
TIM1->CCMR2 |= TIM_CCMR2_OC3PE | TIM_CCMR2_OC3M_1 | TIM_CCMR2_OC3M_2 ;
TIM1->CCER |= TIM_CCER_CC1E | TIM_CCER_CC1NE | TIM_CCER_CC2E | TIM_CCER_CC2NE | TIM_CCER_CC3E | TIM_CCER_CC3NE ;//!CH and CH
TIM1->CR2 |= TIM_CR2_OIS1N | TIM_CR2_OIS2N | TIM_CR2_OIS3N | TIM_CR2_CCPC ;
TIM1->BDTR |= TIM_BDTR_MOE | TIM_BDTR_OSSR;
TIM1->CR1 |= TIM_CR1_DIR; // DOWN COUNTER
TIM1->EGR |= TIM_EGR_UG;
TIM1->CR1 |= TIM_CR1_CEN;

and this the code to change the config:

TIM1->EGR |= TIM_EGR_UG;
TIM1->CCER &=~ ( TIM_CCER_CC2E | TIM_CCER_CC3E | TIM_CCER_CC3NE);
TIM1->CCER |= TIM_CCER_CC1NE | TIM_CCER_CC1E; //AH + !AH
TIM1->CCER |= TIM_CCER_CC2NE;//BL

is there a way to turn off both complementary pwm at the same time


texts:
I want to know if the polarized capacitor has some advantage that they are used in some circuits?

For example, in a schematic of the BISS001 PIR controller IC, in some places, a polarized capacitor is used and in some places a non-polarized capacitor one.

Can I use a non-polarized capacitor with the same voltage and capacitance instead of these polarizing capacitors?

Reference Docs:

BISS001 datasheet
HC-SR501 PIR MOTION DETECTOR datasheet
Grove - PIR Motion Sensor or EasyEDA link

What I've understand from your answers is why the electrolytic capacitors are used, and why these are polarized.

But the designers of this circuit could have used a non-polarized capacitor or even polarized tantalum capacitors. Is it true? As the (Grove - PIR Motion Sensor) module uses polarized tantalum capacitors.

I want to know if the polarized capacitors are being used for circuit protection or is there any other reason (regardless of the type of capacitor.)

Is there a problem if these capacitors are replaced with non-polarized capacitors in these circuits?


texts: Input Resistance and Mid-band Gain of a CE-CE Stage Cascade Amplifier

texts:
I am trying to calculate the Input Resistance and Mid-band Gain of a CE-CE stage.

Here's what I got so far:

I am having some doubts regarding my calculations though. Mainly with the input resistance. Can we really ignore the second transistor when calculating Rin?


texts:
Hoping someone can help me with this project i'm working on. The thermode is made of a molybdeum alloy that gets heated by high current. Resistance of the tool is 0.3ohms it needs around 1000watts at 6v to heat the thermode. Its stated that the tool needed a " Pulse Transformer" to heat the thermode. My question is can a regular coil and core transformer be used instead? And what are the advantages using a Pulse transformer vs a coil and core??
Current transformer i have is a Microwave transformer rewound for
120v - 6v 900VA

Thanks

1


texts: Why gate capacitance in mos data dependent?

texts: I dont understand this page in my book. According to it , if voltage values at drain and source are inverted(to the gate input as shown in case 1), it has highest capacitance. how exactly is gate capacitance data dependent?


texts: Dummy Switches - Charge Injection and Capacitive Feedthrough

texts:
[R. Jacob Baker]

I have some confusion regarding a technique using dummy switches to compensate for charge injection and capacitive feedthrough.

How does M2 compensate for the charge injection of M1? When M1 turns off and 1/2 the channel charge flows to M2, how do they "cancel" if they are both NMOS devices?
How does the Cload capacitor ever get charged in the first place? M1 is being driven be one clock source and M2 is being driven by the inverted version of that. Then there's never a time when the two are both on together to provide a path to Cload? I understnad that the author said that the signal "should also be slightly delayed" but wouldn't cause more charge injection due to M2 now?


texts: Design of second order low pass filter using passive RC components and opamp

texts: I have an RC low pass filter connected to the non inverting terminal of the opamp. There is a feedback resistor from output of opamp to its inverting pin.Then an RC low pass filter is placed at the output of the opamp. So while designing the filter,should I consider these two low pass filter together as a second order filter and design or consider each RC low pass filter separately and design the filter.Which is correct to get the desired response?


texts: High gate pin current leakage on a p channel mosfet

texts:
I have added a P-MOSFET before my main circuit, between the v+ of the battery, and the Vcc main power line of the circuit, so that the battery stays disconnected and doesn't drain until I am ready to use it.
The gate is connected to the source of the mosfet with a 470k resistor. I would expect the Vgs to be 0 V until I pull it down with an extra transistor and an 'on' signal. However, without doing anything, the Vgs seems to settle at -0.3 V.

Here is the circuit. Any idea what is causing the leakage? Or is it a high frequency on/off oscillation? And how do I fix it?
Much appreciated!