texts: Capacitor Help -> Will stacking of dielectric and metal foil increase capacitance?

texts:
I'm new to this forum, so forgive me if I am missing something.

I am building a capacitor, and I want to know if stacking dielectric and metal foil will increase the capacitance, and if so

At what rate will it increase,
How should this be wired?
How should I stack it (such as metal/metal/dielecric/metal/metal or metal/dielectric/metal/dielectric or whatever I should do)

[EDIT] : I am using a dielecetric of paper, dielectric value of ~2. I can also use saran wrap.

currently my capacitor is 5 nano-farads, I want to know what to do to bring it up to 40 microfarads. Is this possible?


texts: Understanding CMOS performance and complexity for ASIC : 350nm to 45nm process

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I am trying to build an ASIC chip with the help of the MOSIS project. (They make it cheaper by combining multiple small project into a single fab). I have a choice between 350nm to 45nm, and everything in between.

My project consists of a implementing in hardware, the sha256 algorithm. I have 1 pipeline of gates that is performing the algorithm. This single pipeline has about 50,000 to 75,000 gates.

Ideally I would like to fit multiple pipelines on a 350nm process. I am not sure if 350nm is small enough for this. Where can I find information about the number of gates that can be expected to be put on a 350nm process to 45nm process, of 0.063mm^2

Also, what is the performance of each process. Each step of my pipeline has delays of less than 100 pico seconds. Can I get a fast clock of 80MHz or more on 350nm?

Thank you.


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Could you tell me how to find Vd and Vb in the schematic please? Is the PNP in saturation or linear mode?

I found Vb, with Vbe = Vb - Ve, then Vb = Ve -Vbe.
To find the mode of the pnp, I need to find Ib, and so Vd. But I don't know how to find it.

Thanks.


texts: How do a generate a clean, precise pulse wave electronically without jitter?

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I am trying to build a simple pulse generator circuit for electrophysiological stimulation purposes. It seems to be surprisingly difficult to generate a square/ pulse waveform where the pulses have precise amplitudes.
To generate pulses I have tried audio output from my computer, the digital outs from an Arduino, and a 555 monostable, and when recorded they all turn out with a bad case of the jitters (randomly varying amplitude).
Below are recordings taken straight from audio out of my computer into acquisition box. I have also tried using alternative generators such as an Arduino and a 555 and got the same jitter on everything.
My primary questions are what is causing this jitter, what am I doing wrong and how do I fix it? I need precise amplitude control. I have tried different recording devices and they show the same thing. 2) How can I get rid of overshoot? I have tried diodes for this and not had much luck.
Image 1: Original waveform outputted to audio.

Image 2: Signal (inverted) recorded by aquisition box receiving audio out from computer, showing jitter in amplitude and unwanted positive overshoot.

Image 3: Pulses of what are supposed to be equal amplitude with negative overshoot.


texts: Charging lead-acid battery in parallel with load - what if the system voltage goes above nominal, and how to prevent it?

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I have just purchased a 6V, 4.5Ah sealed lead-acid to power my arduino-controlled bicycle LED lighting system.

The battery is to be charged by the variable power provided by a hub generator, which has a rectifier/stabilizer (diode bridge + capacitor + zener).

Currently the hub-generator/stabilizer setup is being successfully used to power the LEDS directly (arduino is not in the circuit yet). At full load I have a consumption of around 0.45A @ 6V.

My goal, after incorporating the battery and the arduino, is that the system (arduino + LEDs) works "by itself" once turned on, in the sense that:

The system gets its power from the battery or the hub generator, whichever is "more active" at a given moment;
All the excess power provided by the generator and not consumed by the system will end up recharging the battery. The battery thus would be used in "floating" mode;

I believe this is a fairly standard configuration for this type of application.

My doubt is: The battery manufacturer recommends around 6.8 Volts for a constant-voltage (floating recharging regime between 10°C and 30°C), but my system is designed to work at 6V.

So it appears that, if I used a 6.8V zener diode (1N5342) to regulate hub voltage, I would successfully float-charge the battery, but could also be "over-volting" the system.

On the other hand, if I use a 6V zener (1N5340), as I am using now, I would not have enough voltage to charge the battery.

As a last confusing point, the open-circuit voltage of a fully charged battery of this model is around 6.5V, so even without being recharged, it is expected to "present" these 6.5V to the system, isn't it?

So, my questions are:

Should I be worried about this extra 0.8V if my system is expected to run on 6V? Considering that it's made up mostly of LEDs, I suspect this is not a big problem, but I'm unsure;
Suppose I absolutely needed to have strict 6V at all times, how would I float-charge the battery while the system is running without exposing the system to 6.8V? Is there something I could do, such as an extra circuit? Is there a standard way to do that?


texts:
On my sailboat the range of wifi and Bluetooth appears to be very much shorter than in my home - I can't figure out why.

ex1:
At home I can stream video with Miracast from my basement to a room upstairs some 25 feet away in spite of the thick concrete separating the floors. On my glassfibre boat using the same devices I can't make it work between the cockpit and the saloon less than 15 feet away and almost line of sight.

ex2:
At home I can reliably stream music from my smartphone to a Bluetooth device in the basement 30+ feet away with multiple brick walls in between. On my boat I get severe cut-outs when streaming between the same devices if more than 10 feet away in line of sight.

I do have many wireless devices on the boat (20 odd but not always on). However, I do at home too.

I've tried changing wifi channels - it does seem to have some impact but doesn't fix it.
I've tried powering off devices one by one - it doesn't seem to make any difference.
I then thought it was the metal walls on my dock that caused it, but it's the same when I'm on the water far from any external interference.
I've tried using wifi scanning apps on my phone to see what's going on. It indicates fairly good s/n levels (-60dB or better) on both ends but it does look like the streaming device stops transmitting from time to time.

My son had his Fusion AV unit replaced due to similar issues on his live-aboard catamaran. I got the old unit and it worked perfectly in my home but on-board my boat I have to be within 10 feet to stream Bluetooth reliably.

I've run out of ideas and my friend Google has let me down on this one.
New ideas are welcome.


texts:
When dealing with BJTs in an approximate large signal analysis, Vbe is often chosen to be 0.7 Volts (Given the component is operating in active mode). My question is: Is it possible to do the same for MOSFETs?

I'm asking this because I'd like to find an approximate expression for the output current in the following current mirror setup:

For the BJT case, I often saw the output current being approximated by (Vcc-0.7/R) so I was wondering whether a similar approach would be valid for the MOSFET structure.


texts: Specify user constraints (UCF) for Xilinx Platform Studio custom peripheral

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I've developed some IP using Xilinx ISE, and this required settings some multi-cycle path constraints in the UCF file:

NET "lowlat_result<0>" TPTHRU = "through_lowlat_result";
# ....
NET "clk" TNM_NET = clk;
TIMESPEC TS_clk = PERIOD "clk" 125 MHz HIGH 50%;
TIMESPEC TS_multipath_factll_result = FROM "FFS" THRU "through_lowlat_result" TO "FFS" TS_clk / 20;

I want to now utilize this VHDL code in a Xilinx Platform Studio (EDK 13.2)  custom peripheral.  There is no generated UCF file for the peripheral itself. Can I add one?

Or, do my constraints need to go in the main data/system.ucf file? I'm not sure of how the scoping works for net names in entities many layers deep.


texts:
Could someone break an ASIC?

If an ASIC is a fully customized, app-specific CPU, is possible to reverse engineer it?

I'd imagine the answer in general is no, since to me the only way to do this would be to keep firing inputs at the ASIC and see what it outputs. And if you don't have clear documentation as to what the ASIC expects as valid input, and what its various outputs imply, the ASIC is essentially a mysterious black box.

Are there advanced methods, tools, etc. that can be used to "crack" an ASIC?


texts: I am looking in to making a UAV quadcopter and I don't know how to calculate what ESC to use with the motors I have picked. I am looking at buying the HobbyKing Red Brick 10A ESC and the Turnigy Aerodrive SK3 - 2118-3100kv Brushless Outrunner Motor. Will these work together? Is it overkill? What battery would I want to use that will be light but have a long battery life? Is it the most efficient it can be for the price and application? If anyone has personal experience or knowledge in this all input and ideas are welcome.


texts: Vintage germanium transistors: How does this metronome oscillator work?

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I'm  trying to  restore and  learn from  a simple  metronome assembled by my uncle in the 60's. It has a  nice sounding beat  and  used  to  work until  very  recently  —  although unstable.  I've made  a  schematic from  tracing the  board tracks which is included below  without the power supply for simplicity.
Being a beginner myself, I cannot understand the disposition of Q1  and Q2. It  looks like the SCR  explanations I've seen around, but I'm not really  sure if they are there to work as an SCR.
I assume that the rightmost part  with Q3 and Q4 is just there to amplify  a pulse generated by the  leftmost part of the circuit, specifically coming from between R4 and C2. But how does this oscillator work at all?
The transistors are from RCA,  with SK3020 being a silicon NPN and SK3005  actually a germanium PNP. I'm  not sure if there are any particular characteristics of them that enable this functionality,  and I could  not find much  about their differences to modern silicon transistors.
Any pointers  or topics  to read about  in the  direction of understanding how this circuit is creating pulses is greatly appreciated.

Notes:

Added the voltages I'm reading now throughout the circuit.
The circuit was recognized by Spehro Pefhany as part of the RCA Hobby Circuits Manual, 1968, the original circuit is included in his answer.


texts: Reading current with YDHC SCT013 split core transformer and RPi or Arduino

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I've got a few split core current probes YDHC SCT013 that I used to use with an Open Energy Monitor module that has failed some time ago.

Now I'm looking at building a replacement power monitor myself but am unsure how to interface this power clamp? Should I just connect it to a burden resistor and measure the voltage over it with Arduino's ADC? What value should the burden resistor be though?
Also the output will be 50Hz AC - how do I measure that in some sensible way? Sampling fast enough? Or rectify it and smooth it with a big enough capacitor?
At the moment I'm not really looking at an exact Amps metering, let alone calculating RMS or true watts. I'd be more than happy to get some relative readings based on the load connected.
Any pointers how to do that?
EDIT: I have found a discussion and calculation of the burden resistors here. However still looking at solving the AC problem. Any ideas?


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Hi i am new to using transistors for signal amplification.

Can someone explain to me how to figure out the amount of current being drawn into the base of the transistor when it is in the common emitter configuration. ( see link below for circuit diagram).

I would also like to know what else i would need to do to create a crude Class A audio amplifier.


texts: Labeling requirements for equipment using off-the-shelf 900 MHz ISM radio

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Can anyone tell me or point me to an authoritative reference as to what external labeling is required for an industrial product that uses an off-the-shelf 900 MHz ISM band radio?

I understand that the device itself may be required to have an FCC ID, but so far I have not been able to determine what labeling, if any, is required beyond this. The device is similar to this and would only be sold in the American market. While I don't think it matters, I am sending data only.


texts: Correct Wiring of 1 phase 220v Electrical Motor

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I am trying to install a single phase 220v electric water pump. I am fairly certain that it is wired correctly however the water pressure it is pumping out is absolutely useless.

I have attached how I have wired it:

It is a newly refurbished pump, so my first assumption is that I have messed it up.

As far as I am aware. The L and N should be connected to W1 and U1 respectively and then W2 should be connected to U1 (through the start capacitor).

Just some notes. The motor is running warmer than I would like? Im not sure what temp it should run at. But this could also be a result of heat not being cooled down by the water as its not pumping the desired quantity of water.

Here is the pump specs:


texts: A device that runs on AC current it's voltage inside is measured by always turning the multimeter's knob to AC voltage:same for DC right?

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I've bought a cheap multimeter and it's not automatic. I've to manually rotate the knob.

I live in North America. AC current is used in my home. Does this mean I can always measure voltage by turning the knob to AC voltage part(to appropriate measurement amount/unit) and measure voltage at two parts of the device's circuit that runs on AC current without burning the fuse of multimeter? or is there any exception?

When should I turn the knob to DC voltage? Is it when a device run on DC power source?

I saw electricians right away turn the knob to AC or DC for measuring Voltage and Ampere and figure this out without any problem.

So a device that runs on DC current it's voltage inside the device will always be measured by rotating the knob to DC voltage and that runs on AC current it's voltage will always be measured by rotating the knob to AC voltage. Is this true? Is this the general rule?


texts: Why would a regular converter not be able to charge iPhone and Samsung?

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I was looking around for a step down converter for a home robotics project, when I bumped into this one (image below). In the description it says

  Can not charge iPhone and Samsung cellphones; But can charge other phones.

Although I'm planning on using it to power a Raspberry Pi and not a phone, I was simply wondering: why on earth would those specific phones not be able to be charged by a regular 5V 3A power source? I mean; power is power right?


texts: How to Plot X/Y in Java Circuit Simulator

texts: Does anyone know how to select the Y variable when doing an X/Y Plot in Java Circuit Simulator? I tried many things and none have worked.


texts: Basic circuit analysis - diferential equation

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This is the circuit I got from an example in a book "Practical Electronics for Inventors", on page 48:

How can one understand that \$0=R\frac{dI}{dt}+\frac{1}{C}I\$ implies \$I=I_0e^{\frac{-t}{RC}}\$?


texts: Battery monitor gauge for embedded development

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For one of our upcoming projects, we have a battery pack consisting of 12 Energizer L91(Lithium /Iron disulphide AA Battery).

We divide this battery pack into three sets of 2 ,5 and 5. In order to have 3 voltage bus rails for the embedded system as the following.

Bus 1 - 3.0V
Bus 2 - 7.5V
Bus 3 - 7.5 V

Now as energy constraints are high for our embedded device, it is very essential to monitor these 3 voltage bus lines. Doing a research on the same, I came across TI BQ27500-V130. Going through the data sheets, I was not sure whether I can use this for the monitoring the bus lines in our case.

It would be grateful if you could give me an advice on whether I can use TI BQ27500-V130  for our application. Here are the constraints we are looking forward for the battery monitor we need to  use.

Consumes very low power
Has UART/spi interface
Estimate the remaining voltage on the pack.

I am looking for suggestions on what kind of battery monitors I can use for this purpose.


texts: Why isn't high side digital output stable?

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Our Advanced Drive Assist Systems(ADAS) project is based on Renesas RH850/U2A16 microcontroller.  We are using Infineon Technologies TLE75620-EST, SPI Driver for Enhanced Relay Control IC for driving loads.  Datasheet is attached.  We don't have any loads connected to SPIDER output pins.  We're not commanding digital output logic low or logic high.  On power up, SPIDER digital outputs pins are not stable.  They are toggling between logic high and logic low.  Attached is SPIDER OUT0_HS pin unstable waveform measured with oscilloscope.
When we stop code execution, output pin is stable.  Please see attached SPIDER OUT0_HS pin stable waveform.
Microcontroller communicates with SPIDER chip over spi interface.  Instead of stopping code execution, if we dynamically disable spi communications, would the digital output become stable?
Why is the digital output toggling? Microcontroller is using spi interface for control and diagnosis.  Are we sending something over SPI that's commanding the digital output to toggle?
How do I attach files to this post?


texts: How to reduce noise? (FlipFlop circuit creates lot of noise)

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I have this flipflop circuit and an sound detector circuit (amplifier + microphone). When connected to individual battery (NiMh) they work nice. But when connected to the same battery, the sound detector goes crazy. It looks like the flipflop is creating a lot of electric noise that reaches the amplifier.

My questions are:
1. Why an analog flip flop LED circuit creases so much noise? I expected this from digital circuitry not from a simple flipflop.
2. What kind of filter should I install to suppress the noise?


texts: Why does speed of DC motor increase when flux is reduced?

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I understand that from KVL

e = v -IaRa e=k(flux)speed

speed=(constant)*(V-IaRa)/flux

But physically what causes the speed to increase? What force causes the rotor to accelerate? In fact, physically, the rotor is moving because of field flux interacting with armature current's flux. So physically if I reduce one flux, the speed must reduce, since I have reduced the cause of motion as Toque is also depended on Flux.(F=Bil)


texts: High Voltage Nodes creep-age and clearance standards for electronics?

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I am trying to design with the NCV5183 with a 400V DC bus. I am trying to figure out the creepage/clearance standards i need to consider for high voltage layout and if the IC's pin to pin spacing is ok for a 400V application. Does the IEC60950 or any other standard define what spacing for the voltage that i am working with. Does this requirement only apply for spacing between high voltage nodes. Does it also apply to spacing between high voltage and low voltage nodes. If you check in the datasheet Pin 6 (HB) is next to VCC which will be at a much lower potential.

http://www.onsemi.com/pub/Collateral/NCP5183-D.PDF


texts: Determining the bit rate on a real-time USRP implementation

texts:
I'm transmitting a 16-QAM signal using an NI 2920 USRP. Here is a snapshot of the front panel that is seen (on LabVIEW) -

I'm trying to figure out the bit rate from the given details. The symbol rate is given to be 125k. For 16-QAM, each symbol must be encoded using 4 bits. Does this mean that the bit rate is simply 125k*4 = 500kbps? Do parameters such as the IQ sampling rate and samples per symbol make a difference to the bit rate?


texts: Proper way to demonstrate reverse recovery time of a diode using SPICE simulation

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After encountering a nice example from an answer of this question, I wanted to simulate the same  circuit in LTspice to compare the reverse recovery times of two diodes 1N4148 and 1N4007 by a 5V 100kHz square wave source:

If I don't verify/set Trise and Tfall for the squarewave i.e if I use the default settings, I get the following plots for diode currents I(R1) and I(R2):

The above current plots doesn't tell me anything.

But if I set Trise and Tfall as 0.00000001 which is the 1/1000 of the square wave period, I get the following plots for the diode currents:

As you can see the fast recovery time of 1N4148 can be seen very explicitly.

What is the proper way to check reverse recovery time in LTspice/SPICE? I mean what should be the rise and fall times relative to the squarewave period?

And how is that measured in real(the one we see in data-sheets)?


texts: Does a radio antenna need to form a closed loop to function?

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In either a radio transmitter or antenna, is the antenna and open end or a closed loop?
In electrical theory it seems that no open loop could achieve anything. But in physics a piece of metal exposed to radio frequencies might be expected to vary in electrical potential in a way that a sensing system (tuner) could be sensitive to.
Similarly with a radio tower, is the tower an open-ended conductor whose electrical potential is rapidly varied, or does the tower only emit radio waves when it conducts a current along its length?


texts: Can I drive a Low-Side MOSFET from a High-Side Driver?

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I'm working on a power electronics project where it involves driving 4 different MOSFETs, (3 HighSide and 1 LowSide). Rather than using a different IC for the LowSide driver, I am thinking about using 4 HighSide drivers to drive all the MOSFETs.

I wonder it would have any negative impacts on the circuit as would it damage the LowSide-MOSFET?

It kinda feels to me like that the HighSide driver has a higher part count to support bootstrapping when the LowSide driver needs much less and that's why a LowSide driver is appropriate for a LowSide MOSFET. Also I kinda observed that LowSide drivers are a bit cheaper than HighSide drivers. Are those really the reasons why a LowSide driver is preferred for a LowSide MOSFET?


texts: Help understanding switching voltage regulator (OKR-T/1.5-W12-C)

texts:
Looks like I need help understanding how to use the OKR-T/1.5-W12-C DC/DC voltage converter, b/c I just burned two of them. I am obviously doing something wrong, but I don't understand what.
Here's the part info:
http://www.digikey.ca/product-search/en?x=-989&y=-73&lang=en&site=ca&KeyWords=811-2782-ND
And here's how I hooked it up:

The regulator begins heating up rapidly and burns itself out. The first one lasted two days, the second one died in 5 minutes. Turning it on or off with the On/Off pin makes no difference to the heating process. The regulator does supply the expected +Vout until it dies.
P3 is a AA NiMH battery that I am trying to charge.
What am I missing?
EDIT 1:
Since the problem is not turning out to be obvious, I think it is time to update this post with complete info. Here's the schematic (I hope you can read that):

As you can see, I've added the capacitors and a constant current sink. The regulators continue to work for a minute or so and then break to the point where Vout just sits around 1V, not reacting meaningfully to Rtrim anymore. Vout does change when I change Rtrim, but these changes are tiny.
EDIT 2:
I'll also add the physical design picture, just in case there are any clues there:

EDIT 3:
I have implemented many of the suggestions provided here with a different buck converter IC, but still no luck! Details here: Strange oscillation in buck converter (AP3431)


texts: Color bands on a cheap resistor is confusing me

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I bought a cheap electronics components kit(for the first time, I'm a rookie electronics hobbyist) which came with some cheap resistors with no clear written specifications.

The resistor I am looking to integrate into my simple circuit is colored blue, and it has five color bands.

I don't want to say what color band is last or first(I don't know how to determine the order of the color bands) but the two outer bands are both brown, with there being three black bands in between them, again, making a total of five color bands.

What does all this specify? Does anybody know where I can get quality resistors(that are better documented and come with written specifications) at a good deal?
   And if I have this problem again, can someone please supply me with links that can instruct me on how to competently decipher resistor color coding and anatomy. Thank you.


texts:
I'm looking for unknown element U1, which fulfils the following requirements:

When power is ON, there shall be no connection between P1, P2, P3, and P4, i.e. replacing U1 with air would work. (Some nA leakage current would be OK.)
When power is OFF, electrons shall be allowed to flow from P3 to P2 (and not between other pins, but again leakage current is OK).
U1 shall not require its own power supply, i.e. it shall also work when the power supply is OFF.

Without requirement 3 I could use an inverter before the base of an NPN transistor to connect P2 and P3.

What element(s) can I use as U1 for achieving the named three requirements?

(Last time I submitted the question the text went away and only the circuit remained. Replaced the circuit by an image and try to submit again. And the I forgot D1 in the circuit, thanks to ariser for pointing this out!)


texts: relationship between nominal voltage and cross-sectional area

texts: Is there a reasonable approximation or some standard cross-sectional area that can be inferred from the nominal voltage of a transmission line? I'm only concerned with high-voltage lines, i.e. nothing at the distribution level.  I don't need something exact and even a relative measure of how the cross-sectional area will likely change between a 69kV and 118kV line, for example, would be good. I'm happy to assume the same material for all lines and any other simplifying assumptions that would lead to something reasonable.


texts: A confusion on two single-ended measurement systems

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Here is the link for two different measurement systems:

http://zone.ni.com/reference/en-XX/help/370466V-01/measfunds/refsingleended/

In RSE case, the AIGND is the point where all channels' grounds are connected.
This AIGND is directly connected to the measurement system ground.
I was having some offset issues and found out the offset comes from AIGND and measurement system ground's potential differences.

In NRSE case, the AISENSE is the point where all channels' grounds are connected.
But this AISENSE is not connected to the measurement system ground.

The company I contacted told me to try NRSE case to reduce the offset.

I have two questions here:

1-)Why in RSE case there is potential difference between AIGND and measurement system ground?(Why this wouldn't be an issue in NRSE case?)

2-)Why would one use RSE if NRSE would introduce less offset?(Does NRSE has some other disadvantages?)


texts:
Does anyone recognize where this is from? Manufacturer, model # etc. Found it hidden away in a cupboard, wonder if it's useful at all. Got a fuse, 5 relays, couple of LEDs(all soldiered ofc). Reverse image search didn't work and couldn't find anything on to help pinpoint more info

Thanks!


texts: CAN bus stuff error causes due to physical layer

texts:
I'm trying to diagnose the significant amount of bus "stuff errors" on my CAN network. Network is new and has not ran without these errors. Topology is as shown below.

18 Devices on CAN bus. 9 on each side, joined at din rail terminals.

Cable on the outside of dotted lines are this twisted pair
cable.

Cable on inside of dotted lines to din rail terminals is
this shielded twisted pair cable.

Dotted lines represent deutsch connector.

Bus length is roughly 20m - 25m

Bit rate is 500kbits/s

My question relates to the physical layer because I can be fairly sure software is working correctly.
Can any of the following things cause stuff errors on the bus?

Two different cable types
Sections of non shielded cable
A bad high or low connection to a device

Here is a picture of the CAN signals on a scope.

Here is an example of CAN traffic showing errors:
   355)      4916.3  Rx         0520  5  A6 0C 64 00 06
   356)      4919.6  Rx         0523  8  05 00 00 00 41 00 00 00
   357)      4919.8  Rx         0526  6  C0 01 08 00 08 01
   358)      4920.3  Rx         0525  6  A8 73 AC 0D D0 02
   359)      4920.5  Rx         0525  6  34 73 AC 0D D0 02
   360)      4920.7  Rx         0523  8  B4 00 00 00 40 00 00 00
   361)      4920.8  Error      0004  4  01 0A 01 00
   362)      4920.9  Error      0004  4  01 0A 02 00
   363)      4920.9  Error      0004  4  01 0A 03 00
   364)      4921.0  Error      0004  4  01 0A 04 00
   365)      4921.2  Error      0004  4  01 0A 05 00
   366)      4921.2  Error      0004  4  01 0A 06 00
   367)      4921.5  Rx         0523  8  10 00 00 00 41 00 00 00
   368)      4921.7  Rx         0523  8  62 00 00 00 50 00 00 00
   369)      4922.0  Rx         0523  8  1C 00 00 00 50 00 00 00
   370)      4922.0  Error      0004  4  01 0A 04 00
   371)      4922.1  Error      0004  4  01 0A 05 00
   372)      4922.2  Error      0004  4  01 0A 06 00
   373)      4922.3  Error      0004  4  01 0A 07 00
   374)      4922.4  Error      0004  4  01 0A 08 00
   375)      4922.4  Error      0004  4  01 0A 09 00
   376)      4922.6  Error      0004  4  01 0A 0A 00
   377)      4922.6  Error      0004  4  01 0A 0B 00
   378)      4922.7  Error      0004  4  01 0A 0C 00
   379)      4922.8  Error      0004  4  01 0A 0D 00
   380)      4922.9  Error      0004  4  01 0A 0E 00
   381)      4923.0  Error      0004  4  01 0A 0F 00
   382)      4923.1  Error      0004  4  01 0A 10 00
   383)      4923.2  Error      0004  4  01 0A 11 00
   384)      4923.3  Error      0004  4  01 0A 12 00
   385)      4923.3  Error      0004  4  01 0A 13 00
   386)      4923.4  Error      0004  4  01 0A 14 00
   387)      4923.7  Rx         0523  8  9C 00 00 00 4F 00 00 00
   388)      4923.7  Error      0004  4  01 0A 14 00
   389)      4923.8  Error      0004  4  01 0A 15 00
   390)      4924.1  Rx         0523  8  CC 00 00 00 41 00 00 00
   391)      4924.1  Error      0004  4  01 0A 15 00
   392)      4924.2  Error      0004  4  01 0A 16 00
   393)      4924.3  Error      0004  4  01 0A 17 00
   394)      4924.4  Error      0004  4  01 0A 18 00
   395)      4924.4  Error      0004  4  01 0A 19 00
   396)      4924.6  Error      0004  4  01 0A 1A 00
   397)      4924.7  Error      0004  4  01 0A 1B 00
   398)      4924.8  Rx         0525  6  86 73 AC 0D D0 02
   399)      4925.0  Rx         0525  6  28 73 AC 0D D0 02
   400)      4925.1  Error      0004  4  01 0A 1A 00
   401)      4925.2  Error      0004  4  01 0A 1B 00
   402)      4925.4  Rx         0525  6  4B 73 AC 0D D0 02


texts: Handling variable length commands with pauses in transmission

texts: I have my embedded system and I send many different commands to it using PC via RS232. The issue is that each of command consists of different amount of bytes. What is more there is possibility that the command will not be send at once . I wonder what is the good practice and  if there are any standards how should it be handled. Should I make all commands equal in length ?? Should I start executing command if it is possible even if not all information bytes of that command are yet sent or should I wait till all bytes of the command will be received by my system ?


texts: Manual override switch design with mosfet and DPTP

texts:
I want to design a bathroom light that automatically adjust color and brightness according to many factors (time of the day, people presence, mood, weather...) but I don't trust myself with electronics so I want to design a foolproof way to override my device so that I can normally switch lights.
Fort this design I would like to use two switches. The first switch is a dpdt that will activate the manual override, and the second switch will actually operate the light (provided override is active, otherwise it should not do anything).

Is it possible to build such circuit with commercial switches such that it will blend with normally used switches like in the picture? How are they called?


texts: Measuring a 2 cell 18650 battery from ATMega328P

texts:
I'm using an ATMega 328P (which will be running arduino code) as part of a project (a bicycle lighting system). It runs off of 2 Li-Ion cells, which both are step-up-regulated to 12V for the lighting, and run off of a linear VReg for the logic (the ATMega).

I thought it might be better to measure the voltage of both cells semi-individually instead of just getting a collective voltage for the battery. My plan was to measure the cell that is closer to ground using an analog-in pin, and then measuring the entire battery using a voltage divider, obtaining the value for the second one by subtraction.

I thought this may be useful if, for example, one cell in the battery fails, or was charged unevenly and starts to go dead earlier than the other.

Of course, I worry about frying the pin by directly measuring a battery, or causing an inaccurate reading due to something I hadn't thought of.

Is this even necessary? Would measuring the entire battery be sufficient? The individual cells have a protection circuit, so they should shut off if they go under the critical charge level. Is there an easy way to recognize from the battery voltage that one of the two cells is almost depleted that doesn't rely on them both being at the same charge level initially? They are individual 18650s (and at the moment I only have a 1 cell charger). Will state of charge imbalance cause any other problems not compensated by measuring each voltage individually?


texts:
This is an example calculating output resistance that drives the inductor.

Source:Linear Circuit Transfer Functions: An Introduction to Fast Analytical Techniques by Christophe P. Basso

What I am confused is why the input and output are grounded references so they are connected together here as indicated in the red circles?

For calculating output resistance seen by the inductor, should we only short the input 1 so the output resistance will be infinite?

Update:

Why not just calculate seen by the inductor as normal (short input voltage source and leave everything else remain the same as below?
So the resistance seen by inductor is infinity.

PS: Google book link - page 4:

https://books.google.co.kr/books?id=WGBFjgEACAAJ&printsec=frontcover#v=onepage&q&f=false

Or this online version:

http://dl.4mohandes.com/book/ba/Linear_Circuit_Transfer_Functions.pdf


texts: Looking for OP-Amp with good rail to rail performance, 5V to 0V

texts:
There are thousands of OP-Amps on Farnell's website, so I thought asking the stack-exchange community might be a good idea. I am looking for an OP-Amp for use in my project.

I currently have an OP-Amp, but it hasn't quite performed as well as I had hoped. The problem I have is that it won't drive its output lower than about 0.8 V and won't drive higher than 4.2 V. I am running this device from 0 V and 5 V rails.

The reason for the choice of power supply is to prevent signals outside of this range from damaging an ADC I am using. The ADC's analog input must remain within the 0 V to 5 V range.

I am processing audio signals, so other desirable things include slew rates of ~0.4 V/us or greater, bandwidth of 20 kHz or greater, and ideally in the standard pin arrangement for DIP 8 packages. (I call it a standard arrangement: VCC is pin 5, ground is pin 4, the output 1 is pin 1, v-1 is pin 2, v+1 is pin 3, output 2 is pin 6, v-2 is pin 7 and v+2 is pin 8.)

Is there anyone who knows of a device they could suggest? Any other advice would be welcome.

Edit: I should mention that I have found the device MCP6002, which I think would be an improvement, does this look like the sort of thing I might want to use?


texts:
simulate this circuit – Schematic created using CircuitLab

Being \$V_1=10\sin(100t)\$ and \$V_D=0.7\$V, it is asked to find the output potential as a function of \$V_1\$.

I made:
 $$-V_1+10\text{k}\Omega \times I=V_{\text{final}}=-10\text{k}\Omega \times I-5.7$$

and gives me \$9.9995\sin(100t)-0.000215\$.

However, in Multisim I got the following graph:

What is wrong?


texts: ADS1115 ADC input filter - active or passive?

texts:
I want to implement an ADC as part of my bachelor's thesis.
The datasheet of the ADS1115 show that there is no filtering done by the ADC chip before the multiplexer. As I read here, it is good practice to use a filter before the input.

I am currently trying to decide on what kind of filtering would be best for the ADS1115 inputs.
I read online from some people that passive lowpass filtering should do just fine.
I remember my professor stating in a lecture that active filtering in general is simply better than passive filtering.
In any case I would appreciate any input.


texts: In band diagram, why the Fermi energy (EF) is constant along the device?

texts:
In band diagrams of PN/PIN junctions etc. the Fermi energy level (\$E_F\$) is drawn as constant along the device (see image).

 (source)

Why is it constant? What does it represent?


texts:
I'm making a harness for a fan assembly. The wire gauge for the rig is 18awg but the fan assembly connector uses 22awg which means I need to adjust the wire size at some point between the two connectors. The fan rating is 115V, 400hz, 0.6A at steady state, and max 5A inrush.

Is it possible to downsize the wire mid-harness? If so, where at in the harness? I was thinking of downsizing 6in from the 22awg connector.

My understanding is that as long as the 22awg can handle the fan rating, downsizing wiring won't matter.


texts: Why LTspice is showing singular matrix error in the following inverter circuit?

texts: While simulating this circuit I am getting an error of singular matrix. Any advice?


texts: I am trying to measuring leakage current from motor and driver and identify which part contributes more leakage and then to improve it

texts:
From UL standard, if I only want to measure a part of device's leakage current to another part. I can just measure the Grounding wire. So I used a clamp on meter (0-10mA range) to clamp on grounding wires. In the cases below:

Ground the motor and driver together, and measure at driver side grounding wire to the power device.
I assume this will give me the total leakage.
Unground the motor and driver, and measure at the driver side grounding wire.
I assume this will give me the leakage of driver only
Unground the motor and driver, and connect a grounding wire from motor chassis to the power device grounding. Then use clamp on meter to measure on it.
I assume this will give me the motor only leakage.

But I found the sum of leakage of motor only and driver only does not equal to the total leakage. Does anyone know why? Or it is not the sum up relationship?
I used a AC power supply to do the testing. I found it gives way less leakage current reading than I use a variac. So I think the varic has some leakages too but I don't know if it is the AV power supply has some filters?
I used below connector to connect wires to the power device. Why do I get different reading on both side of the wires? I am so confused.

I am saying additional grounding wire is because the driver's power input only has line and neutral. The grounding wire doesn't go "on board". So I clipped it on metal chassis. Hope the new picture is helpful to understand.


texts: AVR: Pullup vs Pulldown on button input?

texts:
So I know the Atmega328p (What im using now) has Pull-up resistors available to be activated. And I know when reading input we could either make a button cause a PIN to go high or low....but is there an advantage to either?

Obviously making the button go to GND when pressed is easiest since there are Internal Pullup's available...but is there possibly an advantage to making an external pulldown and then making the logic level go high when pressed?

I seem to see the first (easier way) used more, but I was curious if there was an advantage to either one.


texts: When do you use a brushless motor driver and when do you use an ESC?

texts:
I'm trying to build a drone from scratch on my ARM microntroller on a Tiva C series development board. I know you need a motor driver(controller) to control a motor, but in the case of a brushless motor I'm seeing a brushless motor driver and an ESC (used in RC quadcopters). What's the difference and what should I choose (how difficult is it to interface with)? My goal is to make a PCB with all the components I need in the future to implement on my drone.

Here is the brushless motor driver I have been looking at:

http://www.robotshop.com/en/veyron-5a-brushless-motor-controller.html

Here is the ESC:

http://www.robotshop.com/en/lynxmotion-12a-multirotor-esc-1a-bec-with-connectors.html


texts: How to model Texas Instruments UCC28700?

texts:
I'm using Multisim in an attempt to simulate a flyback supply design reference by Texas Instruments that makes use of a voltage controller - the UCC28700. Multisim has no SPICE model natively nor does it exist for download at TI's website.

Does anyone have any ideas on how I can model it or at least get a approximate (even if ideal) substitute?

EDIT:

I tried to build more or less the same circuit as in the design reference but instead of using Texas' IC, I am simply PWM'ing the FET's gate. Of course this has the implication of not actually using feedback (the IC uses both voltage and current sensing techniques), which was the aspect I actually want to simulate and validate.

Still no progress. Insights, anyone?


texts: How to store modify and resend 4 bytes of data from an assembly coded dspic to that in a c compiler based pic18f

texts:
I'm using Xc8 compiler and pic18f.Im communicating with a dspic30f ;coded in assembly and receiving a 4 byte variable via i2c.

Task: I have to receive the 4 byte packet store,modify it and send
back to the dspic controller. Since I'm using xc8 compiler,I trust I
can store the packet as float only which consumes 3 or 4 bytes of
space.But the compiler converts the 3-4 bytes in to IEEE float
format of which I have only limited understanding.
Eg:If dspic sends a 4 byte value 0x0001ffff and expects pic 18f to
modify and send the value as 0x001f00ff. As the pic18 used xc8 compiler;I trust
the only way is to store the 4 bytes as float.But I have no idea how
to resend the modified float value in to the desired hexadecimal format?.

I would appreciate any valuable inputs or suggestions.Meanwhile I'll give an attempt to understand the float format in C compilers.
Any alternatives that can possibly make this happen will be deeply appreciated.
Thank you for your time.
Regards
Rookie91


texts: Why do block RAMs have synchronous reading instead of async reading?

texts:
I'm programming FPGA boards (Artix 7 to be exact) and I recently noticed that, in order to be synthesized into block RAM, an array of storage must have synchronous reading, otherwise it will only be synthesized into a register file.

Example of async read (can't become block RAM):

always @(*)
    rd_data <= mem[addr];

Example of sync read (may become block RAM if other conditions are plausible):

always @(posedge clk)
    rd_data <= mem[addr];

Why can't a block of storage with asynchronous read be a block RAM on Xilinx FPGA?


texts: How to connect linear power supply to an SMPS in series

texts: I have two small 12v power bricks, one of them a 3-prong 1.5A SMPS and the other a 2-prong 1A linear power supply. I don't know exactly what is inside the SMPS because it just came with an old modem, however I do know that the linear one is just a transformer attached to four diodes and a large capacitor. Can I just wire the positive SMPS to the negative linear to get a 24V power supply, or would that mess with the SMPS?


texts: How does this surface mount coin cell holder work?

texts:
Here is a schematic of a surface mount coin cell holder, taken from the datasheet:

Presumably after it is soldered in place, you just slide the coin cell underneath the central part, with the positive side down, and with the positive line underneath the middle part of the holder, onto which the cell presses down to complete the circuit. The mounting tabs give the negative polarity.

But a few things don't make sense.

Why are there little holes in the tabs, which presumably are the mounting points - won't this just reduce the strength of the mounting?
The 'gap' into which to slide the coin cell seems to be only 0.41mm high, which is surely ridiculously thin for a coin cell - is the idea that the holder stretches up to accommodate it?
If so, what size coin cell will it accept, and why isn't this specified on the datasheet?
Doesn't this method of operation mean that there will be a lot of upward force on the contacts?
How will this ensure a good enough electrical connection to the positive terminal, if there is no solder used there?


texts: Setting RNG (Random Number Generator) boundries

texts:
I am learning STM32F4 board. I want to get number between 0-15 using RNG. I can`t set boundaries to get that values.

Is there someone who has experienced with RNG or Can help me?


texts: Circuit Protection - Difference between two gas discharged tubes that are spec'd the same?

texts:
http://www.digikey.com/product-search/compare/en?returnUrl=%2Fproduct-search%2Fen%3FFV%3D90c000e%26k%3DGDT%2B500V%2B20%2525%2B5KA%2BTHROUGH%2BHOLE%26mnonly%3D0%26newproducts%3D0%26ColumnSort%3D-1000011%26page%3D1%26stock%3D0%26pbfree%3D0%26rohs%3D0%26quantity%3D%26ptm%3D0%26fid%3D0%26pageSize%3D25&part=495-1476-ND&part=GTCA26-501M-R05-ND

We are looking at protection for our new design. Upon doing BOM reduction exercises we discovered EC90X gas discharge tubes are $1.79 (Digikey Part Number 495-1476-ND). The ones marked new are $.50 and spec'd the same (Digikey Part Number GTCA26-501M-R05-ND). Can anyone find reasons why not to go to the 50 cent ones?

We also parallel a TVS SMAJ51CA in with the gas discharge tube.


texts:
I have tried this example code for sampling and FFT in MATLAB, but I have noticed that when the signal frequency becomes closer to nyquist frequency , some errors ( small frequency components near the given signal frequencies ) in the frequency domain begin to show up. Is there any explanation for this situation?

close all;clear all; clc;
freq = 100;
freq1 = 1000;
freq2 = 2000;
freq3 = 3000;
freq4 = 4000;
Fs    = 10000;
t = 0:1/Fs:1;

x = cos(2*pi*freq*t) + cos(2*pi*freq1*t)+cos(2*pi*freq2*t) ...
    +cos(2*pi*freq3*t)+cos(2*pi*freq4*t);
tempfft = abs(fftshift(fft(x)));
figure;
stem(0:floor(Fs/2),tempfft(floor(Fs/2):Fs));


texts: Ideal OP-AMP - why isn't output voltage zero?

texts:
Here is what I know about the Ideal Op-Amp.

The open loop voltage gain is infinite
The output voltage is given by the following \$v_o = A(v_+ - v_-)\$
Only with a negative feedback loop is \$ v_+ = v_-\$

My query is with regards to the negative feedback loop as shown below:

My queries are as follows:

Clearly, \$v_o = A(v_+ - v_-)\$ should still apply and since \$ v_+ = v_-\$, shouldn't the output voltage \$ v_o = 0 \$ always?
Since \$v_o = A(v_+ - v_-)\$ should still apply, is A still the open-loop voltage gain which for an ideal op-amp is infinity. Thus, would the output voltage always be infinity?


texts: Choosing output filter inductors for switching power amplifiers

texts:
Class D PWM switching power amplifiers use an LC filter at the output to filter out the switching harmonics:

Other than the inductance value, what properties are important for this inductor?  What types, specifically, are best?

Concerns would include distortion (from hysteresis/saturation of the core?), efficiency, EMI (toroidal shape, shielding), etc.

I think some of the important qualities would also be shared by inductors in switch-mode power supplies.


texts: Trying to identify varistor values off an ancient power supply

texts:
Was tricky to get a photo with the markings visible, but as best I can tell the markings read...

H L1
1502

...The scoring down the middle is from where I haphazardly removed the heat-shrink which was around the component

I have two which have blown and am trying to source replacements.
Would this be a suitable drop-in replacement? (closeup)

Thanks.

For reference, the components are off an old Motorola power supply (board is marked 1991 manufactured by a company named Astec) which is used for charging GP300 handheld radios. Charger output spec is 14V @ 10A (charges up to 6x radios at once).


texts: How to create this copper coil to withstand much heat

texts:
Hopefully this is not as off topic as it might seem.

Some background information:

I've created the coil below to use as an induction heater from regular 230Vac household insulated wire. The coil is attachable to a commercial 2kWatts 230Vac induction cooktop. It works, the iron crucible lid up yellow hot. To prevent the insulation on the coil from melting I had it submerged in water, with a glass jar inside to prevent the water from reaching the crucible. But the setup is very impractical, the glass cracks due to the heat (differences?).

How can I create a coil with equal inductance and dimension that can withstand much heat and without shorting the wires (800°C or so)?


texts: Stepper motor Identification : Bipolar or Unipolar

texts:
I have the following stepper 35L048B2U in my possesion. I looked through similar questions, but could not find a satisfying answer. My motor have 6wires (would suggest universal), but on the digikey page and on the manufacturer one it tells me Unipolar. I am a bit mixed up here. I also tried to see if two wires (the common) were connected together but with no avail.

Do I have a universal or unipolar stepper?


texts: What happens when I suddenly stop the axis of an electric motor?

texts:
Suppose I have a simple circuit with a 9V battery that is connected to a DC motor, causing it to spin.  Then I suddenly squeeze the motor shaft between my thumb and fore fingers, and  bring it to a sudden stop.

How can understand what happens to circuit voltages and currents immediately after this event, as well as longer term?  For instance, if I hold the motor for a long time, will the battery continue to feed power into the system?  If so, will the power be more or less than when the motor was spinning?  Would the difference in power between the two scenarios be completely different magnitudes (i.e would something start burning?  if so, would it be the battery or the motor)?

Immediately after I stop the motor, will there be a large spike in something (current?)?  How would I calculate the magnitude of the spike based on the current prior to the event, number of windings, physical dimensions, time scale of the event, etc.

I just don't have a good mental model of how to think about motor behavior when they are in a "failure" mode.

Thank you!


texts:
For 3D CAD modeling, there is software called OpenSCAD which allows you to create 3D designs purely in code and then render them.

I'm wondering if something similar exists for PCB design where I could "write" a PCB, and then compile it to gerber files or similar which could then be sent to a fab site like easyEDA.

Edit:
I should specify that by "in code", I mean in some language with support for things like named constants, functions, looping, etc. For example, in OpenSCAD, I can do things like

  for(i = [0 : num_planks-1]) {
       translate([i * plank_w, bb_w, top_height]) cube([plank_w, plank_l, top_thickness]);
  }

and so by changing constants, I can quickly alter the parameters of a model.

What I'm trying to do is create a pcb for a keyboard, but I'd like to be able to easily tweak the layout without having to shuffle each keyswitch around by hand. Adding or removing a row of keys, changing the staggering of the rows, etc. It seems like these sorts of things could be easy if the board was properly described in code rather than in a graphical editor.


texts:
I'm trying to make a PCB which include a WIFI module to m.2 key e. For this I'm using a PCIe connection. As HF routing must follow some guidelines, however I'm strugling  a bit with the length of the tracks. The clock (1) is nearly 8mm longer than the TX track (2). (3) is the RX track. Can this blow up my signal if there is such a length difference between clock and signal trace?
By the way, I calculated correct impedance and checked if skew is close enough.
Stitch capacitor are not placed yet.
Here is guideline sheet for the m.2


texts:
I have a COTS solar battery charger that has a number of different LEDs identifying the battery level, if its charging, etc.  Its going to live in the shed, so 99% of the time no one will see its pretty array of lights.  Would it be OK to replace these LEDs with diodes and would it save any electric?
Thanks in advance.


texts: How to make an electrical connection to thin gold plating?

texts:
Hello fellow engineers.

I am trying to make an electrical connection with some gold plating.  The gold plating is shaped like a rectangle, with dimensions of 3mm x 1.5mm x 0.1μm thick.  Here is what the part looks like, it's quite small.

My procedure is:

Tin some 24 gauge stranded copper wire
Apply flux to the gold pad
Attempt to solder the wire to the pad

Every time I try to solder (using standard solder: 63% tin, 37% lead solder wire, flux core, 0.6mm diameter.  the solder I used), I end up with a failed connection within one second of solder flow.  What I mean by this is, all the gold seems to disappear, and I am left with an extra-tinned wire.  I think what happens is the gold is absorbed into the solder, as Wikipedia states here.

I am wondering, how do you suggest I make a reliable electrical connection to this part?

Edit 1

Per comments:
 - Tip: Metcal STTC-144, with a MX-PS5200 PSU.  I am not sure what temperature the tip is at during soldering.
 - Substrate: from the product description that the substrate is Si, with 0.3μm of SiO2, then 0.01μm of Cr, then 0.1μm of Au.


texts:
I'm working on a battery powered prototype and have discovered an annoying bug. When power is removed from the device by disconnecting the battery, the voltage on the 5V power rail will decay fairly quickly to around 2V but then will decay much slower. In fact, it will stay between 2V and 1V for around 30 seconds. If the device is restarted during that time (i.e. the battery is reconnected), one of the chips will go into a bad state and the device will malfunction. This is especially annoying because this is precisely how most people power-cycle the device.

I figure that there is still residual charge being stored in the decoupling capacitors on the 5V power rail, which is causing the device to sit in this range for a while until parasitic resistances slowly drain the capacitors. Could this be correct?

If so, is there a generally accepted way to best discharge those decoupling capacitors?


texts:
Hello I am using PIC18F26K83 and I need to use ADC module in it, in order to measure voltage value of a spesific pin. MCU clock frequency is 8 MHz. This PIC has 12-bit ADC inside of it. So my question is: How should I select the ADC clock frequency. I have seen that people say acquisition time must be at least 1.6 us.2 to 6 us is preferred. So I have 8 MHz system clock. Which makes 0.125 us. Fortunately I can divide this down. Now I have 2 questions.

I am not sure but I think for my MCU it takes 4 clock cycles for 1 operation. Should I consider this while I am trying to calculate the Tac? If yes then without any division period will be 0.5 us instead of 0.125. Then I can divide my MCU clock by 8 and I will get 4 us Tac. Does it sound correct?
In the datasheet there is a picture like this:

according to this image if I want to divide my Fosc by 8 I need to set this register to: 0b00000010 right? and 0b00000011 for dividing 16 and it goes like this. Is it the correct pattern? I just want to be sure. Thanks beforehand.


texts: Will 4 layer PCB isolate inner layers from moisture?

texts: I've never done a 4 layer board and am not familiar with the process of manufacture for them. Will the external layers isolate inner layers from water if say, I will be putting the board into water for long periods (months) of time?


texts: Are coin cells a suitable replacement for AA batteries?

texts:
I am currently using AA batteries in my projects but would like to look at cell batteries for my next project, due to their compactness.

Apart from the physical appearance, how do cell batteries differ from the more chunky AA batteries? (I am guessing the mAH would suffer for example?)


texts:
I'm designing a USB device that I want to be powered eintirely from a wall wart and have a couple questions concerning the power connections and ground loops.

1) If I connect the USB GND pin to the ground of the wall wart I should be safe from ground loops, right? My understanding so far is that the wart's DC output should be floating with respect to earth ground so I can safely connect it to the USB ground, since the PC's supply is earth grounded from mains.

2) If this is the case, can I just leave the USB's 5V pin unconnected?

3) Also, is the USB GND necessary? Would it be acceptable to only connect D- & D+, or is the USB GND needed for these signals?

4) In what cases would optical isolation be necessary? I see a lot of designs using isolation, is this necessary for all self-powered USB devices?

I've looked through other answers and other USB designs, but I'm not entirely confident yet and so some help would be greatly appreciated.


texts: One battery discharges faster than the other in my solar power system

texts:
So, I have solar power system and it is as follows:

2 AGM batteries each 100 Ah
2 solar panels, 24 volts, 250 watts each
a controller
an inverter

the batteries are connected in series to give a total of 24 volts and 100 Ah which in total is 2400 Watts. On the other hand, the panels are connected in parallel because they are already a 24 volt system.

Now when I first started using my system I noticed that the total daily charge is around 20-40 Ah which to me was not logical because I expect the batteries to charge around 60-80 Ah on a daily basis since I use the batteries as much as possible before my inveters beeps.

After a while I noticed an unexplainable degradation in the system performance so I did some measurements.

During the charging phase while in sun light I have noticed that the two batteries had almost the same reading which was around 13.8V. However, after using the batteries for about 6 hours, I have noticed that one battery was reading ~12.4V while the other was reading around ~8.2V.

So I turned off my inverter and after a while the first battery still read ~12.4V while the other read ~10V.

Now I want to know what caused my batteries to degrade and what can be done about it.


texts: Removing STM32F4xxx based HMI from CANBUS puts the network in BUSHEAVY state

texts:
I have a CANBUS with 3 devices on it. A PLC (CAN IO 14+, HAWE), a HMI (Barth DMA-20) and a 6 button CAN enabled button panel (Greyhill).
The issue is, when I remove the display from the network (without disconnecting power) to simulate a case of cable break, the button panel stops working as well after 30 seconds or so. While debugging the issue I noticed that the state of the CANBUS changes to BUSHEAVY during this period and this can be resolved only by doing a full power reset.
In my code, both the PLC and the HMI continuously send out CAN messages to communicate with each other.
What am I doing wrong here and how may I avoid the BUSHEAVY state? Or, is it a system limitation that I have to live with?


texts:
So I'm trying to make relatively a large square coil antenna that will operate at 125kHz frequency.

The width and height of antenna are 300mm (30cm) and wire diameter is AWG24 (0.51mm) and I'd like to keep number of turns pretty low (under 30).

To calculate inductance I entered antenna parameters to this calculator and came up with inductance value of 0.000731H (with number of turns being 22; width, height=300mm; wire diameter=0.51mm; permeability=1).

I then calculated resonant frequency with another calculator where I entered the inductance value I got before (0.000731H) and capacitance of 2.2nF. The resulting resonant frequency was 1.2550 Hertz which is only about 0.00125kHz, way below 125khz which I need.

Now to achieve 125kHz I could increase the inductance to 731H by making number of turns equal 22,000 but this idea doesn't seem to be very practical. Does anyone has any suggestions to solve this problem?


texts: Can I use a higher voltage rating when replacing capacitors?

texts:
I want to replace two capacitors in my LCD TV. The TV starting buzzing on dark colors, etc.

Now it started cracking and buzzing really aggressively so I opened it and found two bulging caps. I have disconnected the two internal speakers for now, which has killed the noise, but I need to replace the caps ASAP.

My question is this: When it comes to replacing caps, you can go to a higher voltage rated cap but have to stick to the same farad rating?

The bad caps are both  6.3 V, 4700 µF and i was thinking of replacing them with 16 V, 4700 µF but getting the better quality 105 °C rated one as the others ones are 85 °C rated.

Just wanted to double check before I damage my TV.


texts: Explanation for different Noise Signatures on Series Terminated Clock Line

texts:
In the picture below (taken from this youtube video), it is explained what the clock signal would look like depending upon the value of Driver and Series Resistance value compared to the transmission line impedance.

The video explains what the clock would look in each of the cases. I am trying to understand WHY?

Clearly, I am learning Transmission lines so any pointers or help would be helpful.


texts:
I want to use a relay switch with the GPIO on my raspberry pi 2 (40 pins).

I found the link below on google and it mostly makes sense, what I'd like to know is why do I need to use a transistor to activate the relay switch?  why can I not just wire it up directly?

http://www.susa.net/wordpress/2012/06/raspberry-pi-relay-using-gpio/

please keep in mind I am a novice with electronics.

Thank you :o)


texts: How does a Miller cap physically create a pole in circuits?

texts:
If we consider a single NMOS transistor (with its source terminal grounded) and a Miller cap (C) between its input (gate) and output (drain) nodes, circuit theory says that this Miller cap will be responsible for a pole.

If there is conductance G at the input of the NMOS, then the pole at the input will be: -G/(1+A*C), where A is the small signal gain of the stage and C is the Miller cap between input and output.

Furthermore, the miller cap also creates a zero because current at high frequency will flow straight through the cap to the output of the stage.

From a circuit point of view, I can understand this well. The Miller theorem states that the cap between the input and output nodes can be represented by an equivalent cap to ground with value A*C rather than C.
Because this cap goes to ground, this creates a pole.

However, physically, there is no path between the input (gate) and the ground that passes through the Miller cap C. So how can a pole be created? I understand Miller’s theorem, but the thing is, there is physically no path to ground through the Miller cap. There is only a path to the output. So physically, how is a pole created? How and where does the current flow exactly, and how does it make its way to the ground to create a pole?

If we note Cgs the parasitic capacitance between gate and source, there is a path to ground, which creates a pole, -G/Cgs. However circuit theory says that if we add a Miller cap between gate and drain, this will create a new pole that’s much more dominant than the one through Cgs. But to me Cgs is the only path there is between input and ground. So how else, other than by flowing through Cgs, can the current make it to ground through the Miller cap C and create a pole?

Edit

Forgetting about the maths for a minute, I’m just trying to visualise where the electrons go which result in a pole and a zero being created.
I would like to be able to intuitively interpret the meaning of poles and zeros and find a simple and rough way of approximating their value using this physical intuition.


texts: I wanted to ask question regarding voltage vs current mode for a feedback control motor . Will operating in current mode have any effect on our torque values provided that we are keeping the speed constant? The motor is a stirrer system i.e. stirring device for mixing  which gives us torque


texts: How do JBC calculate the power rating of their soldering stations?

texts:
I am having trouble understanding how a JBC power rating is calculated.
For example, this soldering iron uses the T245-A handle which uses the C245 cartridges.

The peak power is listed as 130W.
We also know that the station uses a 23.5V transformer, and the C245 cartridges are about 2.5 ohms resistance.
These stations work by passing full AC waves to the cartridge when it needs to heat up.
So, to find the power of the cartridge it would be
V=IR
I=V/R
23.5V/2.5ohm = 9.4A
P=(I^2)R
9.4A^2)*2.5ohm = 220.9W
So the calculated power of 220.9W is well above the 130W JBC says.
Does JBC just say 130W and never let the cartridge continuously draw above that by limiting the average power to the cartridge? Or perhaps I am missing something.
Edit
I should add that JBC stations do not use phase angle control for the heater.
They pass half or full waves of AC from the 23.5V transformer to the heater. When heating is required some AC will be passed and when no heating is requred nothing will be passed. There is no current adjustable current limit besides the resistance of the cartridge.
Also, JBC irons have a separate pin for the thermocouple, so the heating current is not passed through the thermocouple.
Source for image


texts: Make stun gun with Arduino as oscillator

texts:
    Hello. I've noticed that for creating "sparks" with an transformer I need an oscillator. I want to know if I can use arduino for this. I'm afraid of breaking it because of the high voltage that it would generate.

Here's my schematics:

    I programmed arduino to pulsate the current on pin D11. The current will open the transistor and the transistor will close the transformer's circuit and that will produce a voltage which will be stored in a capacitor.
   I've inserted a diode because I am afraid that the arduino will "burn". Is this safe(for arduino)? Are the schematics correct?  Or should I quit? (Sorry for my mistakes. This is not my original language)

EDIT
    The transistor is NPN. And the transformer's current source is the 10 V Battery..
    I don't want to use an "classic" oscillator because for me is hard to make one(from transistors) and I'm just a child so I can't buy anything from internet(for example a 555 timer).I got the arduino and the rest of the pieces from my uncle.


texts: Calculation of Rated Power for IGBT Module

texts: For an IGBT module with the following characteristics, how can we calculate the rated power? I mean how much is the rated power for this module?


texts: What (type of) sensor can detect odor of faeces?

texts:
"The Chemistry of the Smell of Toilets & Human Waste" has a really nice overview of the types of gases you want to detected if you're after building a toilet-clean-air detector.

Hydrogen sulfide (H2S) sensors like MQ-136 are available for as little as $20 but what about the other gases? Isn't there a sensor that detects several of those faeces gases?


texts:
I have a quick question regarding the ACS71020 chip. I am using SPI to communicate with this chip, and the iRMS value is represented as a "15-bit fixed point number with 14 fractional bits". My guess is that this means that the MSB equals 0 or 1, and the rest of the bits all represent a fraction of "1". So if you have 1 as your MSB and 630 (in decimal) for your 14 bits, your value is 1.0 + (630/2^14). Unfortunately, the datasheet explains that we need to multiply this floating point number by the max current that the chip can detect which is 30A. That makes no sense because why would you allow for values up to 60A to be reported since this 16-bit floating point with 15 fractional bits can equal 1.9999 at the highest end? Am I not understanding something correctly?
Thanks for the help
This can be found on page 27 of the datasheet.
Link to datasheet: https://media.digikey.com/pdf/Data%20Sheets/Allegro%20PDFs/ACS71020.pdf


texts:
I am new to AVR and microcontrollers and I am trying to get the UART working correctly on my Atmega68 chip. When I transmit data from my chip my PC terminal program receives them as weird symbols. I believe this is a problem with the baud rate but I am unsure how to fix it.

My F_CPU should be 1MHZ and the baud rate should be 9600. When I checked the fuse settings on the chip they were 0xdf and 0x62 which I believe is correct for a 1MHZ clock..

I am using a USBasp to program which has a jumper in position JP3 to reduce its clock speed - could this affect the uart?

I am using a USB to serial converter which I have tested using loopback.

My code is as follows, any help would be much appreciated:

void initUSART(void) {
    UBRR0H = UBRRH_VALUE;                 /* defined in setbaud.h */
    UBRR0L = UBRRL_VALUE;

#if USE_2X
    UCSR0A |= (1 << U2X0);
#else
    UCSR0A &= ~(1 << U2X0);
#endif

 /* Enable USART transmitter/receiver */
    UCSR0B = (1 << TXEN0) | (1 << RXEN0);
    UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);   /* 8 data bits, 1 stop bit */
}

int main(void) {
// -------- Inits ---------
    initUSART();

    while (1)
    {
        transmitByte('a');
    }
    return 0;
}

void transmitByte(uint8_t data) {
                                     /* Wait for empty transmit buffer */
  loop_until_bit_is_set(UCSR0A, UDRE0);
  UDR0 = data;                                            /* send data */
}


texts:
WinAVR seems to produce a lot of useless code, e.g. for following C method

ISR(INT0_vect) {
    TCCR1B = 0x09;
}

it produces (-Os)

PUSH      R1             Push register on stack
PUSH      R0             Push register on stack
IN        R0,0x3F        In from I/O location
PUSH      R0             Push register on stack
CLR       R1             Clear Register
PUSH      R24            Push register on stack
LDI       R24,0x09       Load immediate
STS       0x0081,R24     Store direct to data space
POP       R24            Pop register from stack
POP       R0             Pop register from stack
OUT       0x3F,R0        Out to I/O location
POP       R0             Pop register from stack
POP       R1             Pop register from stack
RETI                     Interrupt return

although

PUSH      R0            Push register on stack
LDI       R0,0x09       Load immediate
STS       0x0081,R0     Store direct to data space
POP       R0            Pop register from stack
RETI                    Interrupt return

should be sufficient. Because these extra commands take time, my question: how to tell the compiler to produce only the required code? Or is there a tool which can optimize the byte code directly?

UPDATE:
I've tried

ISR(INT0_vect, ISR_NAKED) {
    asm volatile(
    "push r0             \n\t"
    "ldi  r0, %[value]   \n\t"
    "sts  %[ioReg], r0   \n\t"
    "pop  r0             \n\t"
    "reti                \n\t"
    : // output
    : // input
       [ioReg] "M" (_SFR_IO_ADDR(TCCR1B)),
       [value] "M" (0 << ICNC1
                  | 0 << ICES1
                  | 0 << WGM13
                  | 1 << WGM12
                  | 0 << CS12
                  | 0 << CS11
                  | 1 << CS10)
    );
}

but the compiler complains:

c:\temp/ccjBxDFz.s: Assembler messages:
c:\temp/ccjBxDFz.s:30: Error: register number above 15 required

I've read a lot of AVR inline assembler documentation/tutorials, but can't get it to compile.


texts: Is RAM with read ahead (Look ahead) possible?

texts:
Is it possible to efficiently infer a RAM with "peek" ports apart from the usual standard ports?

A 32-bit x 4 RAM might have a peek port to peek at data just ahead of the current data being accessed by the read address. Approximate code would be...

assign peek = mem [ (rd_addr + 1) & 2'b11 ]; // RAM peek port (read).

apart from the stock RAM code...

reg [31:0] mem [3:0]; // 2D array.
always @ (posedge clk) if (wr ) mem [ wr_addr ] <= wr_data; // Write.
always @* rd_data = mem [ rd_addr ]; // Main Read.

It would be nice to infer a SINGLE block RAM with some extra (very simple?) read circuitry (ISE infers 2 RAM blocks). I guess this shouldn't require a true dual read port RAM (independent read circuits) or RAM duplication since the read addresses are always related (always 1 ahead). Is there an area efficient way of implementing the above in a typical modern FPGA ?

EDIT: Forgot to add write enable!

EDIT: This RAM is intended for video decoding. Example a stream of pixels received as 0x1234_5678 0x023_45678, 0xAAAA_AAAA would be decoded as 0x1234 (16-bit upper), 0x5678_23 (lower 16-bit + 0x23 from next, initial 0x0 is skipped), 0x678A_AAAA etc (0x45 is skipped). The decoding algorithm is derived from an LFSR that maps to the transmitter and changes for every pixel.


texts: How can I synchronize the framerate of two webcameras. Is it even possible?

texts:
Pretext

I am currently playing with stereo vision (two cameras capturing images simultaneously) for my robot hobby project. There are a few traits that is important when processing the images captured for stereo, and the most important of all is that images are captured at exactly the same time (also known as frame sync or genlock).

Dedicated robot cameras with sync built in can be really expensive and so like many other hobbyists I want to leverage the price/performance found in mid to high-end consumer web cameras.

This works great for one camera but breaks down when working with stereo due to missing genlock. So I decided to see if it would be possible to hack a consumer webcam and retrofit a DIY genlock somehow.

I am a beginner in electronics, especially for high speed digital signals, but I can program atmel based MCUs. I happened to own two old logitech pro 9000 cameras, and I opened one up to peek inside (see photo below).

Questions

What I want to know is what I would look for in the board that could be used to retrofit/hack such a genlock?

My naive idea is that by simply disabling the oscillator crystal of one camera and connecting from the other, they would boot and operate at exactly the same clock and maybe this would also result in synchronized frames. Is this idea realistic? Why/Why not?

Any good ideas and suggestions are welcome.

Thanks


texts: Does fast one-day prototype manufacturing exist (with components, etching and pick and place under one roof)? What is the fastest possible?

texts:
We have different prototyping assembly houses, but cycle times are so long that engineers need to work on 2-5 projects in parallel.

The typical prototype assembly process is:

one day order process, panelization, quotes
PCB sourcing 24-48hours for rush orders (factory 2 hours away)
component sourcing, 1-4 days for most (in parallel with PCB sourcing)
PCB shipping half a day
optional stencils, no extra time
assembly scheduling (0.5-5 days)
machine and component setup
assembly of first prototyping 6 boards (0.5-2 days)
manual follow-up actions if necessary
exception management when necessary
shipping

When really pushing, it may be possible to get everything done in a week and half, but two weeks is more typical.

Is it possible for prototyping assembly as a service to happen radically faster? One day would be great as the overall goal. Given people's salary, context switching costs, overheads costs and opportunity costs from moving to the market faster, price is essentially irrelevant. Having an option of saying we need something and having it materialise without major project management overhead would offset all the reasonable costs.

Can a service like that ever exist? Does it currently? What is the shortest prototyping manufacturing and assembly cycle possible for assembly as a service?


texts: Brake Resistor in Regenerative Case for Elevator

texts:
I am trying to understand the switching pattern of Inverter and the Brake chopper while a 3-phase AC motor is in regenerative mode for example in Elevator case:

When its Cabin is full and it is moving downward OR
When its Cabin is empty and it is moving upwards.

In case (1) the Cabin is heavier than the counter-weight so it will accelerate downwards on its own.
In Case (2) the counter-weight is heavier than the Cabin so it will accelerate downwards on its own and Cabin will move upwards.

There are 2 things that I cannot understand so far:

How does the Elevator Controller differentiate that the motor is in Braking mode or Driving mode? That is how does the above two cases are detected? Is it that the Controller always assume that it has to drive the motor and it starts switching the Inverter in drive mode but if the motor currents are not as expected then it reverses its mode and goto the braking mode?
Once the Controller has detected (or decided) that the motor is in Braking mode then what is its switching pattern for the Inverter and the Brake-chopper? One possibility that comes to my mind is that all 3 HIGH side switches will be turned ON and all 3 LOW side switches will be turned OFF and the Brake-chopper will be turned ON until the ride is complete.

My understanding is very basic so far. Looking for its approval or corrections.

I am going through following sources:

Regenerative braking
4-Quadrant operation


texts: Overcurrent / short circuit protection for back to back mosfet ac switch

texts:
I'm trying to come up with a way to do overcurrent protection for the following circuit:

My first thought here was to monitor the increase in voltage drop over one of the mosfets (M1) and via a zener (D5) (that sets the cutoff level) activate a transistor that drains the gate. The zener is a 1.8V one and combined with the 1 voltage drop of D4 i thought it would cutoff at 2.8V which would be 3-4A for a irf740. But it's not cutting off anything.. any thoughts on how this function could be implemented into this circuit?


texts: 1977 GE 6RS20SP9B9 - what the heck is this component?

texts:
Ok so, ordinarily I'd not ask a "what is this" question, but this component really has me scratching my head - both at its function in the circuit and how it is constructed.  Anyone know what a GE 6RS20SP9B9 axial device, circa 1977, is?

The only datasheet I could find goes up to a 6RS20SP8B8. The *xBx series, according to this datasheet, seem to be "tunnel, vari-cap, and voltage-sensitive diodes."  Funny thing is, this device (along with a beefy resistor and cap as snubber) is directly across a 120vAC, 30A dual-SCR bus. So it is intended to be a MOV I believe, or at least perform the function of a MOV. Can anyone shed some light on this device and why it was used in the circuit?

Initial measurements (device was already falling apart) seemed to indicate it was slightly capacitive and slightly diode-like. The 19 little metal discs are coated in a blue/green substance. Some are more gray than others, possibly from wear. Measuring one of the discs inside with a Fluke 175:

vDC: 10mV / -20mV (variable on pressure and contact area)
Ohms: 170k / 15M
Cap: 0nF / 27nF

EDIT:

So I took @winny's advice and sampled one of the 19 internal discs and plotted I/V curves. Current on left, voltage on right.

A disc was cleaned with IPA. A tiny bit of the green color came off so it was washed quickly. But none of the "grey" was removed at all. To apply pressure to the disc and make contact to both sides, it was covered in paper and clamped in "helping hands" with the original leads.

Here is the resulting data:

The discs are definitely rectifiers, perhaps selenium. The "reverse" characteristic is mostly logarithmic, and testing the upper ranges was tricky as a strong positive temperature coefficient was observed. (Is this typical breakdown behavior for selenium?)

The "forward" characteristic is very diode-like, however shows a mostly linear response. Perhaps this could be improved by better clamping. "Forward" didn't seem to have a temp-co at all.

So... if 19 of these are stacked together, in an alternating fashion... then that would more-or-less make a high-voltage, avalanche-mode equivalent to a modern MOV!


texts: Questions about designing my own BLE-controlled LED device

texts:
This project is meant to get me familiar with designing my own PCB and working with lower-level components. I have experience with BLE using Arduino shields and BeagleBones, but I want to try building my own. After a lot of research, I think a suitable BLE chip is Nordic's nRF52833 SoC. An appropriate module built around this chip is Fanstel's BM833. Fanstel has an evaluation board, but the point of this project is to build around the module on my own.

I suppose my main issue is that I am having a lot of trouble finding helpful documentation.

My first question is, Would I need any other major components besides these:

A BM833 bluetooth module,
an ATmega328PB microcontroller to be the bluetooth module's master (I think I would have to burn the Arduino boot loader onto the microcontroller),
a 32.768 kHz crystal oscillator, and
an RS232 / USB to Serial adapter (strictly for programming purposes).

Is there anything major that I am missing?

My second question is, How do I configure the BLE module so that it is compatible with the ArduinoBLE library? I assume I need to upload some firmware, but I neither know where to get that firmware from nor how to install it. The only guides I see, such as on this data sheet, are for using the evaluation board, but I would really like to avoid that, in part because the board is kind of expensive ($40 + shipping).

My third (and last question) is, What would I wire between the BLE module and the microcontroller?

For communication between the module and the microcontroller: The BM833 pin functions table page 20 says that pins 31 and 32 (P1.01 and P2.02, respectively) are used as UART TX/RX on the evaluation board; the 328PB pin configurations page 15 lists pins 30 and 31 (PD0 and PD1, respectively) as RX and TX. Would I connect P1.01 to PD0 and P2.02 to PD1?

For VDD/VSS: The 328PB has 1 VCC and 1 GND, which is easy. However, the BM833 pin functions table above lists 11 grounds and 4 power supplies (although only 1 VSS, 2 VDDs, 1 VDDH, and 1 VBUS). Which of these pins would need power? Would all the grounds need to be connected or just the one labeled VSS? Should the two modules be wired in parallel or somehow in series?

Note

I've been researching this for about a week and am just about ready to tear out my hair. If this post has too many parts, please let me know and I will either break it up or remove parts. I also apologize if any of this seems very simple (which I am sure much of it is).


texts: Can I upload a 24V to 5V optocoupler schematic from a module I bought?

texts:
I have the schematic for an 8 channel 24V to 5V optocoupler board I purchased. It uses the EL817.
My input is an open collector input pulled up with 10K to 5V.
I can't drive it to gnd to trigger my input. It only goes down to 1.79V.
I would like to upload the schematic and my load if I can.
Thanks


texts: Using SPI to get higher sampling rate from ADC module vs using ADC on microcontroller

texts:
I am currently looking at a microcontroller, and I would like to use ADC on Arduino but found out that the Arduino has a limited sampling rate. Is it possible to us SPI communication with a separate ADC module to get higher sampling rate?
I don't have any circuitry right but I want to know if it is common to use SPI with a separate ADC module to get high sampling rate.


texts: Change of frequency in a capacitor when switch closes

texts:
I am studying an RLC circuit with a switch which initial position is \$a\$ as stated in the following image and with values \$R_g=5000\Omega\$, \$L_g=320H\$, \$C_1=31.66nF\$ and \$V_g=311\cdot\sin(100\pi t)\$:

The switch goes from position \$a\$ to position \$b\$ at \$t=0.41s\$, when \${v_c}_1(t)\$ reaches \$6000kV\$. The expression of the voltage across capacitor \$C_1\$ is the following one:
$$ {v_C}_1(t)=-6260\cdot\cos(314t)+11.4\cdot\sin(314t)+e^{-7.81t}\cdot(6260\cdot\cos(314t)+144\cdot\sin(314t))$$
 Using PSpice to plot the voltage across the capacitor \$C_1\$ gives me the following graph (it reaches Sinusoidal Steady State):

The Laplace equivalent circuit when switch is in position \$b\$ is the following:

Switch \${S_w}_2\$ is not important in this question. The expression of the voltage in the capacitor \$C_2\$ after computing it is the following:
$${{{v_S}_w}_2}\left(t\right)=117440\cdot\left(\cos\left(9.71\cdot10^5t\right)-\cos\left(1.09\cdot10^6t\right)\right)$$
Plotting voltages across \$C_1\$ and \$C_2\$ when \$t>0.41s\$ gives me the following graph (it is zoomed in a lot):

My question is, how is it possible that the frequency of the voltage that provides \$C_1\$ (since in circuit with the switch in position \$b\$, \$C_1\$ acts as generator) increases that way? Is it because of the coupled inductors? Why is it not the frequency of \$V_g\$?


texts:
I just experienced a big bang caused apparently by a short through my oscilloscope's ground lead, and wanted to see if you could shed light on the why this happened.

Yes I have watched Dave's video on the subject of scope ground leads, and was trying to be very careful. But obviously not careful enough. :-/

I was diagnosing a washing machine control board.  I wanted to view the tachometer output pin's status while in operation to see if it was working properly.

The tachometer (optical sensor) is powered by 13VDC, provided by an on-board power supply.

I connected the oscilloscope ground clip to the 13VDC ground.  This is indicated in the schematic below.
I connected the oscilloscope lead to the tachometer input pin.
I did not disconnect the connector from the control board, but instead piggybacked the scope probe and ground clip into the back of the connector.

When I plugged in the machine's 120VAC power cord, BANG went the washing machine's on-board power supply.  The bang was definitely more powerful than I would expect from 13VDC, and let the magic smoke out of several SMD components around the PSU.   The oscilloscope was not damaged.

I simply cannot figure out why this connection created a short circuit.  Even if the 13VDC ground was isolated from the chassis ground, why would it be at a high potential difference from chassis ground?  That would seem dangerous.

I tested the electrical outlet to ensure it's wired correctly.

Thanks for shedding any light on this.

Schematic: (full manual here)


texts: Is a STM32F103 able to handle 74.25MHz from an image sensor?

texts:
So I have this project in my mind where I want to read pixel data from an image sensor via a microcontroller (e.g. STM32F103) and then display the image on a screen.

The image sensor I have in mind is the AR0103CS which is capable of max. 1280 x 960 @ 45 fps. I am aware that the Cortex-M3 is not able to handle 45fps but I am pretty sure that 1 or two pictures per second are possible.

Now there is a problem: The image sensor expects either a direct clock input of 74.25MHz or something inbetween 6 - 50 MHz (the AR0103CS would then increase this input clock to 74.25MHz with its own built-in PLL). In either case it is going to put out one pixel data (12-bit parallel) after the other in a progressive scan-line fashion at a rate of 74.25MHz.

I currently don't know if the STM32F103 is able to generate something above 50MHz as output clock (I think the GPIOs max out in high-speed mode at 50MHz)? Is there a way to route a timer to a pin which could then be used as the input clock?

Even if the STM32 isn't able to create 74.25MHz for the image sensor, I can still go with something lower in the range of 6 - 50MHz as the mentioned PLL will generate the necessary system clock for the sensor.

But in this case the Pixel-Clock-Output signal from the sensor (PXCLK) is still going to be 74.25MHz. This means I have to be able to read values from 12 GPIO pins at a rate of 74.25MHz for a short time frame (16.55ms to be exact).

The way I thought this could work is to create an interrupt for a specific GPIO which is in input mode and receives the PXCLK signal from the sensor. Every time the input value goes from low to high, an interrupt is generated.

In this interrupt handler I then read from 12 GPIO pins. In the 8-bit uC I worked with, the values of 8 GPIOs were combined into a single register such that one is able to read them in parallel. As the STM32 is a 32-bit CPU I don't know if there is a Port with 12 or more GPIOs which can be read in parallel?

Maybe there is other kind of hardware on the STM32 which is more high-speed because I assume doing this with GPIOs is not the best way possible.

Anyway, someone where who has more expertise with this controller and what it is capable of?


texts: "etching" transparent conductor on transparent plastic film or glass?

texts:
I've put the word etching in quotations as the method to get conductive tracks on a glass or plastic film might not involve a subtractive approach as with traditional PCBs of applying a conductive layer (such as ITO in this case) and then removing the unneeded part, but rather an additive approach such as printing or drawing the tracks on a transfer medium sheet and somehow transferring it to the glass or plastic (such as PET) film, etc. later, or printing/drawing directly on the glass or plastic film somehow.

Need two transparent conductors in an arrangment like this on a transparent plastic film. Such as ITO on PET. But it doesn't have to be ITO necessarily.

Of course for others it can be anything else such as this.

There are too many tracks and their size and their gaps are going to be sub milimeter, so hand drawing is out of the question.

Will be running few milliamps and about 8 VDC. Size of the whole film is going to be 10 cm x 5 cm max.

Since one may need to run dozens or maybe hundreds of tests with different widths, gaps and arrangments, is there is a way to print conductive material on a PET or similar transparent film at home, such as with a modified laserjet or inkjet printer, or a modified mini CNC? What can/should one use for the transparent conductive "ink" and the film and what should one use to get their drawing from a digital file onto real film/glass?


texts: Is it dangerous to run a permanent magnet alternator open-circuited? No current can flow so is all the power dissipated as heat? Is there even power generated in the inductive coils?


texts: Lithium polymer accumulators has 6 numbers on it. For example accumulator on the following image has 350830. What does this number stands for?


texts: If-Then-Else in a Behavioral Voltage Source

texts:
Can someone please help me modify this ISpice code so it works in LTSpice?
B1 2 33 V=V(23)-2 < 0 ? 0 : V(23)-2 > 5 ? 5 : V(23)-2
I've tried all kinds of things. Here is a simple test circuit and error code.


texts:
I have this task: When Vb changes, shall Vc change -4 time as much. Can you deside Re so this will happend?

can somebody please help me?


texts:
Is it possible to use some sort of sensors (or if anything else is better please tell) to obtain a football's position within the goal posts?

What I am trying to achieve is the position of the ball as a goal is scored. Then using that position (x,y) to plot.

I have little no experience with this sort of thing (software engineer) so just wondering if its possible. If so, I would love elaboration or research links.


texts: Is my understanding of output impedance for this transistor circuit correct?

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Im having trouble to understand the meaning of output impedance of an active circuit and in this case the emitter follower. I have read several information but yet failed to get the meaning. Im looking for an easy but correct definition.

If we call the output impedance of an emitter follower Zout. This is what I understand about the meaning of Zout: If we couple a variable load R and vary it, the output impedance Zout is then the change in Vce relative to the change in I R as I have drawn below?:

Is that the correct meaning of Zout in layman’s term? Definitions containing “Looking into” makes thing more complicated at the moment. If mine wrong could you provide such explanation similar to mine? Im completely confused and this is my maybe tenth time I struggle to understand.

The definition might be the inverse slope of Vce Ic curves but I need a more concrete definition showing also how it is obtained?


texts: How to determine the pinout of this connector?

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I am sorry for the potentially awkward question, but does anyone know how I can figure out how this 9-pin serial is wired, without tearing it apart?

Am I supposed to be able to see how it is wired by looking at it?


texts: C++ in Embedded Electronics - Literature

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Recently, we've been discussing the use of C++ in (small) embedded systems. As all examples from controller vendors I have seen in the past are tailored to the use of C this is basically what we've been using.

I would like to know if there is any literature which would get me started in this area. Basically I know C on Microcontrollers and C++ in "normal" PC environments. Yet, I would like to know more how I correctly map registers to my classes (or the other way round), how to deal with interrupts (or if there is anything special I need to know), which parts of C++ I may use (I will probably want to try to stay away from dynamic memory management, templates or exceptions) and so on. I am NOT looking for a general C++ start.


texts: How many sensors and devices can the 5V 1.5A pin of the Raspberry Pi4 supply?

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I want to power my 10 sensors (2 MyoWare and  8 FSR sensors) from the 5V pin of the Raspberry PI4.
The 5V pin provides as voltage 5V and as current 1.5A.
The one sensor needs 5V and a current 9mA.
Can I only  power them from the pin 5V of the Raspberry Pi and could the value current 1.5A  damage the sensors?


texts: What is the idle current draw of a charge indicator?

texts: What is the most energy efficient charge indicator for a 12v battery? how many mW does it use for every state of charge?


texts:
simulate this circuit – Schematic created using CircuitLab

My circuit is shown above - where I have the TXD pin of an ATMEGA connected to the RXD pin of a BT slave. Both devices operate on 3.3V - so far so good. However, because I needed to be able to access the BT slave from an external device, such as a PC through an FTDI connector, I have connected the TXD pin from the FTDI connector to the same line.

Questions:

I will be using the FTDI connector only for initial setup/test of the BT slave and the ATMEGA UART will not be transmitting at that point of time. As the ATMEGA TXD pin should be held high when it is idle, can I get away with the above circuit - i.e, would I be able to communicate with the BT slave using the FTDI connector without damaging the ATMEGA TXD pin? Would it be better (and work) if I add a 1K resistor in series with the FTDI TXD pin?
I can program/test the BT slave using the FTDI connector BEFORE I program the ATMEGA (both parts would be powered up though). In this case, would I be correct in expecting that the ATMEGA TXD pin would offer high impedance (UART not configured yet) and therefore there should be no chance of damage to the TXD pin?

Thanks.


texts:
I'm using LTC2263-14 14 bit pipeline ADC in my application. However, I'm completely confused regarding the input voltage range, reference voltage etc. It has a differential input with an internally generated voltage reference of 1.25V and the ADC generate a common mode voltage of VDD/2 which is 0.9V in my case. As far as I know, I'll should be able to digitize a differential voltage upto 1.25V, right?

However, from page 22 of the datasheet:

From the table it seems that when the differential input is 1V or -1V, the ADC hits its limit(2^14-1, 0 respectively). So what's the point of a 1.25V voltage reference if I can only measure up to 1V differential. From my understanding, the ADC should give a full scale reading if the differential input is 1.25V. Also I'm actually using single ended input (grounding AIN- and feeding the signal at AIN+). I'm using 2V input range and from page 18, it says:

From the above info, VCM-0.5V and VCM+0.5V, it doesn't seem to provide 2V range. Can someone clarify the above doubts?

Is it okay to drive the ADC with a single ended input, ignoring noise issues etc., and then do adjustments in software as necessary?


texts: MMBT2222 Datasheet doesn't mention maximum base current. How to calculate it?

texts:
The MMBT2222 Datasheet doesn't mention the maximum base current. How to calculate it? So that design should not exceed it.

I want to use it for switching in common emitter configuration; where the input is provided to base & output is taken at the collector. I want to convert 0 - 24V to 0 - 3.3V via transistor as a switch in inverter mode


texts: Obtain audio information from mic and play in MATLAB

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I am trying to make a basic VoIP implementation and I am stuck obtaining sound samples from the mic and playing the read data on a computer. I tried to sample the voice from the microphone and send it to the serial terminal using a very minimal code:

void setup() {
    Serial.begin(9600);
}

void loop() {
    int sensorValue = analogRead(A0);
    Serial.println(sensorValue);
    delayMicroseconds(122);
}

The delayMicroseconds(122) causes the sample rate to be around 8192 Hz. I also tried with a sample rate of 1000 Hz. The data plot obtained looks good, however, when I try to play it with the MATLAB command

sound(csvread('samples.csv'), 8192);

I do not really hear what it should be (I just hear random noise). I am attaching a graph of the obtained data and my microphone circuit. (I also tried subtracting the average from the array so the values are centered around zero, but no use).

Data Obtained:

Microphone Circuit:


texts: I'm using a Beaglebone black + BBVIEW 4.3 LCD Display + Datalogic Magellan 110i usb scanner. The scanner is connected to the usb host port but when I read a bar code the scanner goes down and then up again. The scanner datasheet says that during reading the current goes to a 400ma maximum so it should not be a problem to the USB host port. If I remove the LCD cape I have no power problems. The board is connected to an industrial adjustable power source 2.5A power source used for testing. Is the maximum current available in the USB host related to current for the LCD cape?