texts: Isolating high voltage/high power electronics from low power electronics

texts: I understand that galvanic isolation is necessary to prevent shock and injury, but I don't understand when (or if) it is necessary to isolate the high voltage/high power side of a circuit from the low voltage control side. I feel like high power/high voltage switching can in some high load cases cause a large switching transients that can run through the power or ground lines and potentially harm the low voltage electronics. Is this correct? Should ADCs, microcontrollers, FPGAs, etc be galvanically isolated to protect them from high energy switching transients?


texts: Calculating pull-up resistor value for CD4078

texts:
How can I determine the proper value for a pull-up resistor that's being used as an input to a CD4078 when the datasheet doesn't mention anything about input impedance?  I'm trying to minimize power usage since my circuit will be powered by a battery.
The datasheet does say that the input current is +- 10mA, so should a 100K @ 5V suffice since that should provide 50mA?


texts: connect my rc car controller with my computer

texts:
I am new to hardware.  For my first project, I want to connect my RC car controller with my computer so I can control my RC car in my PC.

What kind of things (hardware, cables, tools, as well as knowledge) do I need to acheive this goal?

Is it useful if I have a breadboard?


texts: How to wire three 10W LED spotlights to one plug?

texts:
I have 3 10W LED spotlights that I want to attach to a wooden canopy to light my fishtank. They have live, neutral and ground. They look like this:

It requires AC 85-265V. I could easily attach each one to a three-point plug but that would look messy and I would need three plug-points.

I was wondering if it would be dangerous to instead wire all three of them using an electrical connection block and then use a single cable+plug like this?

I know the cable would need to be able to withstand the current needed by all three lights but I don't know how many amps it would pull (complete amateur). I have an extension cord that I would like to use the wire from, I assume this would be good enough since it has a bunch of plug-points and therefore can withstand the current?

Also, would wiring it like this affect the brightness at all?


texts: Is it possible to use a simple diode and pullup resistor to level shift down in one direction?

texts:
I'm working on a circuit that involves interfacing with a 3.3v microcontroller (ESP8266) and I'd like to be able to program it using my existing FTDI which operates at 5v. I'm new to level-shifting and looking around I see there are several different approaches. My question relates to a schematic I found for Adafruit's ESP8266 breakout, seen here: https://cdn-learn.adafruit.com/assets/assets/000/024/745/original/adafruit_products_schem.png.

For level shifting the RST and RX signals from 5v down to 3.3v, they simply use a diode oriented "backwards" let the internal pullup do the rest. It seems to work like this:

So my question is, is this a valid approach for unidirectional level shifting? Are there any pitfalls to doing it this way? I couldn't find any other examples of this approach in my searches so I'm not sure if this is just a "quick and dirty" way of doing it or if it only works in this scenario for some reason.


texts: Snubber Capacitor Voltage Rating in the Real World

texts:
What are voltage ratings for the capacitors inside the common off the shelf ac snubber networks, such as 0.1uF + 100 Ohm ?

It would seem that larger inductive loads can easily drive the capacitor voltage into the kilovolts. Is it ok because it only lasts a short time?

I am more interested in the real world practices than in theory. I don't know how many people in the field actually try to find or measure the load inductance and current to calculate the capacitor voltage before grabbing a snubber and wiring it in. Or is it common practice?

It is not obvious from datasheets what actual voltage ratings are on the capacitors inside those snubber networks. It is only stated for the networks themselves. And I have not taken one apart.

This applies as well to the numerous snubber examples on the web. Almost none mention capacitor voltage, only capacitance.


texts: I have an ATmega8 with a Nokia LCD 5510 connected to it. Everything works great on a breadboard and my next step is to move it to a more permanent board. My problem is that I can't program the ATmega8 while the LCD is also connected. I assume it's because they use the same SPI pins and that the LCD somehow interferes with the programming. How can I do this different so that I can flash the ATmega via ISP without unplugging the LCD?


texts: What is the proper name or part number of a 12V DC female car adapter with leads?

texts:
I've searched hobby sites like SparkFun, Digikey, BGMicro, and Jameco. I'm starting to wonder if I'm calling this item by the wrong name. What I'm looking for, exactly, is a 12V female car adapter with leads/wires or tabs I can solder.

I'm trying to make a bunch of 12V power supplies from 8xAA series connected battery holders putting out 12V and maybe 2000mAH w/Eneloops. I'd like to use these to power some car appliances I have, including some 12V, 0.25A max (3W) lights.


texts: DS1302 realtime clock - pulldowns required?

texts:
I'm trying to wire up a DS1302 realtime clock, one of these:

to a parallax propeller board.

The datasheet says (page 4) that pulldowns are integrated into each of the main lines (looks like 3 needed to drive this thing).

This post mentions that pulldowns are required, so that seems to conflict.

I'm assuming that what the datasheet says is that the pulldowns are internal and I can just connect these 3 lines directly to pins on the propeller.  Does that seem right?


texts: How to roughly know if a electronic scheme will fail soon and protect from it?

texts:
I am thinking of a farming project that includes using some board like Arduino, Raspberry Pi or Onion Mega (the list is not exclusive).

As the system will work with sensors and support life of its wards, their health will depend on the work of the whole chain of components.

I am surely going to keep the main board in a safe place, like, put it in a moisture- and temperature-proof case, and isolate contacts where needed, but I understand that these boards are more for education/experiments than for real daily duty. Also, there always a factor of defectiveness in the board coming from the manufacturer.

So, I wonder, if there is information about how durable the boards are and if they are suitable for 24/7 work during weeks/months?

How do I make sure that system has some more or less definite margin of safety and know the moment when I should replace it with a new one?


texts:
I am trying to make a PCB to control a Sensorless Brushless motor. I just wanted to know if it looks right. The IC I am using is a TB6588FG it has a 2.5A peak output current. I want to use it with this motor. I am going to use a 7.4V battery. The IC needs a analog voltage to change the motor speed. For this I am going to use a first-order RC filter(left side of schematic) to filter the PWM signal. The PWM signal will be supplied by a  microcontroller.

DATASHEET
SCHEMATIC DOWNLOAD


texts: What component is this and how can I test it?

texts: I'm new to electronics. What is this and how can I test it?


texts: How did scientists deal with electronics' problems before Kirchhoff and Ohm's laws?

texts:
Both physicists developed really powerful laws which still nowadays rule the electronic behavior of circuits.

These help us every day to solve problems, calculate circuit variables… but how did engineers do it before the said laws were discovered?

If alternative laws which would not be accepted nowadays were used before this, would this mean that the research done until the discovery of the laws was wrong? Did Kirchhoff and Ohm themselves rely on wrong theories to create 'the good one'?


texts: Confused with the output resistance of the CMOS inverter

texts:
I'm currently reading about the CMOS inverter from Rabaey Chandrakasan Nikolic - Digital Integrated Circuits 2nd Ed, it states:

I'm okay with the first part, but I'm not sure if I totally understand what it does imply (starting from therefore), in conciseness:
1- How does a path existing with finite resistance between the output and supply or ground help with the low output impedance?
2- What does it mean for the inverter (a digital circuit) to have low output impedance? In analog circuits like the common-source/common-drain amplifier it meant that it can drive heavy loads (e.g. a large capacitance or at high frequency)
3- How does it help make it less sensitive to noise and disturbances?
I have one more question that I would be also happy if I get the answer to, the book also states that because the high and low output levels are equal to supply and ground voltage respectively, we know that it has a high noise margin, does knowing the fact about output voltage levels alone help us talk about the noise margin because I don't it feel that it says enough?
Thank you :)).


texts: How do I calculate the peak output voltage of a capacitor differentiator?


texts: Differential input circuit design frequency issue?

texts:
The current design for this differential op amp scales down -/+ 10V 100kHz signal inputs to 0-3.3V for an ADC to properly read. Using a gain of .165, it adjusts -10 to 0 by adding a 1.65V offset, as well as adjusting +10V to 3.3 by the same offset.

The circuit works properly with sine waves, yet overshoots and has major delays with square waves at 100kHz as you can see below.

This is the current design and the op amp is a OPA340. I have already looked into adding low pass filters, and faster slew rate op amps, yet nothing is successful at higher frequencies.

Any advice would be greatly appreciated, thank you in advance!


texts: What causes 1000Hz (and multiples) electromagnetic interference?

texts:
When recording old analog synthesizers (different brands and models) I'm getting interference in the audio. This started suddenly about two years ago (I thought the synth I was using was malfunctioning, had it serviced, and even bought another identical one, only to find the problem persisting.)

I'm used to old synths picking up a lot of 50Hz (and multiples) mains hum, but this signal is exactly 1000 Hz and all multiples, up to above 20kHz. It's about 60dB below the signal level and 12dB above the noise floor (see image). It's not there if I unplug the synth, so it's not being picked up by the cable or my audio interface.

I'm guessing some other appliance is creating this interference, but when it started I hadn't bought any new audio or computer equipment or household appliance. It could be something my neighbours are using, but I'd like to have some idea of what to look for.

So, what kind of equipment or phenomenon could be causing interference at exactly 1000 Hz and multiples? Is this a typical problem? It seems like a strange frequency for any kind of wifi or other communications signal.

440Hz note with 1000Hz interference indicated in yellow

(In case this is relevant, the synths used are two different Korg MS-20's, a Korg MS-10 and a Yamaha CS-15, all between 35 and 40 years old; one of the MS-20's was recently serviced and had parts like capacitors replaced. Service manuals with circuit diagrams and part lists for the Korg MS-20 and MS-10 and the Yamaha CS-15 can be found online.)


texts: To use capacitor or diode in latching relay set-up? Which is better (less power loss)?

texts:
I’m building a circuit that involves the use of latching relays. In this circuit, the relay will switch between power supply A or power supply B, to my load.

To illustrate my case, let's say that power supply A is currently supplying current to my load, but I want to trigger a switch to power supply B. There are two possible implementations that I have thought of. I can use either capacitors or diode to ensure that my load continue to function in the event of a switch triggered by the relay. In the former, during the switching process, power supply B turns on, and both power supply A and power supply B will briefly overlap (thus the need for Schottky diodes for each, otherwise problems cause by competing DC power supplies ensue) before one is cut off by a relay, thus ensuring a smooth transition of power supply. The load remains unaffected. In the latter case, I envision a design where the (?)microsecond switch would be covered by a capacitor (or multiple capacitors) that ensures continual current delivery to my load, before power supply B takes over.

Given these two options, which should I use? I am thinking that in terms of power loss, diodes may cause more wastage than capacitors? Also, there might be abit of voltage drop if diode is used. Thus, I am inclined to use the capacitor approach. However, I am not very knowledgeable about this. I wanted to ask which would be the recommended option?


texts: Is it considered bad practice to put Vias on BGA pads?

texts: I am routing a Spartan 6 BGA, I have seen a lot of people place the via next to the pad, can the Via be placed on the pad if its filled before the BGA is placed?


texts:
I have some old Creative Inspire 6700 speakers with a dead amplifier. They are composed by four 8 RMS Watt speakers.

I'm I able to use two of those speakers with TPA3110 amplifier like this: http://www.ebay.com/itm/2-X-8-Watt-6-Ohm-Class-D-Audio-Amplifier-Board-TPA3110-Mini-Stereo-Power-Amp-L3-/272226548195

I'm not sure if this is the correct community, so sorry if not.


texts: Where can I find an electric generator that produces electricity when spun?

texts:
I am fairly new to electrical engineering (I am much more skilled on software rather than hardware), and I am starting to pick up on building circuits and such.

I am attempting to design several of my own methods of power generation, however I do not want to build my own generator (the physical device).
For example: I want to build a set of bicycles that can be hooked up to a generator via a belt, but I want the generator that uses my spin from the bikes to generate the electricity.

Every time I search up generators for sale, it comes up with the portable gas generators. What retailers may sell what I want, or what better way do I have for searching for the generator?


texts:
I started reading schematics people make. I am not used to a bunch of voltage source dot and ground symbols. In high school physics, it's always loops from which you can tell if the circuits is parallel or series.

pair A

pair B

The reasoning in both cases is that the negative end of the battery is simply the ground.


texts: How to design a module that counts logic 1s in multiple inputs in Verilog?

texts:
For example, I have two inputs, whose value can be either St1 or St0. The changes of states are synchronous to the same clock, say 1MHz of frequency. I want to design a Verilog module that counts how many St1 have appeared in a certain amount of time.

For instance, within 5ms,

input A is 1 1 0 1 1

input B is 1 0 0 0 1

My problem is that when both signals are 1, how to make sure that the counter +2.

My first thought is just using a case:

reg counter;
wire [1:0] inputs;
assign inputs = {inputA, inputB};
always @(posedge clk)
begin
    if(reset)
        counter <= 0;
    else
    begin
        case(inputs)
            2'b00: counter <= counter;
            2'b01, 2'b10: counter <= counter + 1;
            2'b11: counter <= counter + 2;
        endcase
    end
end

But if we have 16 or maybe 32 inputs, is there a method better than writing a very long case?

An additional question is that if these lines are synchronous to clocks with different frequencies, how should we handle the case where multiple lines want to increment 1 to the counter at the same time?


texts:
Is reusing an electrolytic in a different circuit OK?
Is the heat from desoldering liable to change the caps performance?
Likewise going from lower operating voltage to higher, and vice versa?


texts: What is wrong with my USB Li-Ion charging circuit?

texts:
I'm trying to design my own PCB based off of this one:

My relevant schematics are here:

Their Q3 transistor DMG3415U-7 was going obsolete, so I used DMP2045U-7, which seemed to be a similar replacement.  As well as another regulator.

For the battery charger (U3 in the original schematics, U10 in mine), I wanted to use the MCP73831 variant (datasheet here), which includes these 3 status outputs:

So to read out all 3 possibilities from a microcontroller, I added the scheme with R12-R14 and D10.  The idea was that there would be a Vbus of 5V from the USB cable.  If the chip output STAT is low, the pickoff point would be 0V.  If it was high it would be 2.5V, and the diode would protect from any unwanted current flow between STAT and Vbus.  If STAT is high impedance, the pickoff point would be 1.6V.  So with an ADC at the pickoff point I could differentiate between all 3 states.  PROG is set to ground on the microcontroller pin it connects to.

I fabricated the board, and this is not working.  Firstly, the MCP chip doesn't charge the battery.  If there is USB connection but no battery, the Vbat output is 0V.  If both USB and the battery are connected, Vbat measures the voltage of the battery (say 3.5V), not 4.2V or another voltage used to charge at Constant Voltage.  I left it "charging" for 12 hours and the voltage never changed.

Secondly, the "STAT" output scheme is not working.  Measuring the voltages as Vbus, Vstat, and the pickoff point, the voltages measured with a multimeter in the different situations are as follows:

No Battery:

Vbus = 5V

Vstat = 3.86V (should be 3.3V)

Vreading = 2.82V (should be 1.6V)

"Charging":

Vbus = 5V

Vstat = 3.86V (should be 0V)

Vreading = 2.82V (should be 0V)

No USB, only battery plugged in:

Vbus = 1.46V (should be 0V)

Vstat = 2.5V (should be 0V)

Vreading = 1.95V (should be 0V)

I don't understand what could be going wrong.  Vbus and Vbat are direct connections to their sources otherwise, they don't connect to any other components not seen in the schematics.  Is there something wrong in the design?  Why would both charging and the status indicator not be working correctly?


texts: Gain vs. Directivity and effect of animal body to Antennas

texts:
My design works in a foresty area inside a collar of an elephant. These areas have at least -110dBm GSM strength (accurate ref. map linked) but, usually higher as I live in a small country where GSM coverage is easily provided.

Following is an excerpt from the datasheet of my GSM receiver

I am currently using a GSM antenna to receive GSM signals in harsh environment. But it may not be appropriate or the best suited. I'm wondering if I would have better reception if I chose an antenna with lower gain in my design.

Question 1: Does the gain of an antenna always increase with the decrease in directivity?

Question 2 : What type of GSM antenna is recommended for an application that can run in such low GSM coverage areas? What are the factors I should keep in mind to optimise this design to have higher possibility of connectivity?

Question 3 : What sort of an effect would the animals giant body have in the reception of GSM signals? If yes, what are the remedies I can do to reduce the impact of the same.


texts: Linking Android phone to motorcycle helmet comm set

texts:
I have a little mystery for you...

I want to connect my motorcycle helmet communication set to my Android phone, including the push-to-talk (PTT) functionality. This is a simple wired setup, not Bluetooth.

The communication set in the helmet is straightforward: two 32 Ohm drivers and a microphone. I made a cable according to the CTIA specifications for 3.5 mm headjacks at source.android.com. In the cable I spliced in a push button for the PTT function:

simulate this circuit – Schematic created using CircuitLab

(More about the resistor later) It can't be much simpler than this, right? Now the weird part:

Push to talk doesn't work.

The speakers are working; the microphone works fine, I can talk and record sound from it. Yes, I know ground is the 3rd ring, not the 4th (last). However, whatever I do, pushing the button does not activate the PTT function.

Of course I tested it with an off-the-shelf headset which works perfectly. I measured its characteristics: drivers are 32-33 ohm, microphone 1.13 kOhm and pushing the button shorts the microphone circuit.

The microphone in my helmet has a slightly lower DC impedance (around 890 Ohm) than the Android specification (>= 1000 Ohm), so I inserted a resistor in line with the microphone; I tried values from 100 to 1 kOhm, but still no PTT function. Electrically I cannot find any difference between the off-the-shelf headset and my setup when measuring at the 4-pin connector.

But, it even get's weirder. If I unplug the cable from the helmet (so no drivers or microphone, just the cable with the switch), PTT works. Of course there's no sound but the application reacts to the pushes.

And oh, I tested with two different Android phones by different manufacturers: the same result.

The only difference that I can possibly think of is that the microphone in the helmet might a dynamic type while the one in the headset could be an electret; but how to test that without breaking the headset open?

Could it be that Android phones put a low-frequency signal on the microphone line to detect one? But surely, a 1 kOhm resistor would be enough to fool that.

More info:

Mic open circuit voltage: 1.79 Volt (measured at the headphone jack)

My cable:
Microphone DC resistance: 0.90 kOhm
With microphone attached: 0.54 Volt
Button closed: 0.00 Volt

Headset:
Microphone DC resistance: 1.13 kOhm
WIth microphone attached: 1.32 Volt
Button closed: 0.00 Volt

Fixed 1 kOhm resistor: 0.58 Volt

So definetely a different voltage, which is not explained solely by DC resistance..


texts: what are the other 2 pins for in this old dc motor (Sankyo BFB9L11)?

texts: I received a box full of old electronic components and the pictured DC motor was in it (4 pins labelled as '+' '-' and 'P', 'P'). I would like to know what are the 'P' labelled pins for. Thanks in advance


texts: How is the -3.3VA voltage in this circuit generated

texts: I understand the +3.3VA, but I don't kown how the -3.3VA generated?


texts:
In wireless communication, we use a matched filter to suppress out-of-signal-space noise. After this filtering we do sampling. Otherwise, the power of noise is infinite (practically very large).

In short-haul fiber-optic communication systems photo-diodes are used for signal detection. Do we use a similar filter after the photodiode to get rid of the out-of-signal-space noise, before sampling?


texts: Standard/Specification for regular alkaline batteries

texts: Where can one find the standard specification for regular alkaline AAA, AA, C and D batteries? I mean, I know that different suppliers must have different battery capacity/property but there must be some standard that regulates this market. Eg.: maximum allowed current, minimum energy capacity, etc.


texts: Which component cannot handle the higher wattage?

texts:
First time posting a question, so hopefully I've stated all the required details.

As the title is not very specific, here is an explanation of my project. I'm making a revised version of the magnetic table lamp, as shown here:
http://www.instructables.com/id/Magnetic-table-lamp/

The electronics inside are shown in the schematic below. I use a W10M bridge rectifier (1.5A, 50-1000V), a CD263 capacitor (100V), 39ohm/1W resistors, 12V power supply and a LED 3V,0.15A.

Now here's my question: I messed up a bit with the construction of the cubes, which resulted in a high resistance and thus high voltage drop in between my cubes. I tried to fix this by switching to a 24V power supply, and 120ohm/3W resistors (a bit power-heavy, but a lower influence of the resistance between cubes).  However, things get smelly and I think a component is not suited for this voltage. Can anybody pinpoint what causes the problem?


texts: Name that thing... Circular 4-pin female connector

texts:
I've been asked to wire in some Octopod LED lights driven by a Pixel Drive 30 controller, but I can't work out what the connectors are between the lights.  I tried to contact the manufacturer but they've been taken over and the person I dealt with wasn't able to tell me.  This is one of the connectors I have...

Specifications are:-

4 equidistantly arranged pins
12mm diameter across the plastic part (I assume to fit a 1/2" male part?)
9mm depth to collar
Screw-fit casing

My behringher mx1602 mixing desk power supply has a similar connector in a 3-pin configuration.

From looking around it seemed to be an "Amphenol" connector used in vintage microphones and also power supplies.  My searches so far have been contradictory that the parts are rare as hen's teeth and very expensive but that doesn't fit with the use of a 3-pin variant in a relatively 'budget' piece of equipment like the MX1602.

My searches for Amphenol seem to be a company that make an awful lot of connectors but I haven't been able to identify which model/part/description this part is in order to be able to even try to order one.


texts:
I would lije to perform a CRC or Checksum for the FLASH memory of my device, an AVR32UC3, this will be performed by blocks, so I'm thinking that the prototype can be:

uint32_t calculateCRC( uint32_t startAddr, uint32_t endAddr);

Do the contents of the Flash memory of the AVR32 have 32bit values?
If i try to do a FULL flash CRC the startAddr value would be 0x0 or 0x80000000?? (due to the program start of the AVR32 is in 0x80000000).
what could be the value for endAddr if checking the whole memory?


texts: Is it possible to create a voltage divider without resistors?

texts:
I'm prototyping a chromatic guitar tuner with an Arduino DUE and a piezoelectric sensor.

I was trying to amplify the sensor's signal and connect it to the Arduino's ADC pin. So I referred TI's SLOA033A.

That orange box, showing 1/2 Vcc, is my concern.

I'm using a 9V battery and TI's buck converter module to power the board and the Op Amps.

I created that 1/2 Vcc using a voltage dividing circuit and a buffer circuit.
I wasn't sure whether the voltage dividing circuit without the buffer can handle this.

In sum, these are my questions;

Since the Arduino DUE (MCU: ATSAM3X8EA-AU) cannot take negative voltages as an ADC input, that 1/2 Vcc is used to bias the sensor's signal to 1/2 Vcc, right?
As shown in my schematic, is the buffer not needed?
Lastly, are there alternative ways to create that 1/2 Vcc without this voltage dividing resistors?
I was imagining some kind of power IC or circuits that create 1/2 Vcc, but I failed to find one.
If the voltage dividing circuit is the cheapest way, then looks like I have no choice.

-Regards, David


texts: How can I estimate the minimum beta for this driver to work in hard saturation?

texts:
Imagine I build the below LED driver circuit where I know all the component parameters such as 2V LED forward drop and resistors and Vcc and Vbb as in the following diagram:

And if I only dont know the beta of the NPN transistor; how can we estimate the required minimum beta for hard saturation?

In hard saturation Vce will be zero? So Ic= 9mA.

Ib = 0.9mA.

Does that mean a beta of 10 suffice for hard saturation??


texts: Relation between crossover freqquency of loop gain and closed loop's corner frequency when feedback is not unity

texts:
In this Control Loop Cookbook from TI, in the red box the author said that the crossover frequency (indicated in figure 2) of the open-loop is same as 3dB down frequency or corner frequency of the closed loop.

However, I don't think this statement is correct with the specific case in figure 2. The statement is only correct if feedback factor Kfb is unity. But from the closed-loop gain, we can infer that Kfb is not 1 (Kfb = 0.5).

What do you think about this? Is the article wrong? In general case, the crossover frequency of open-loop fc(actually I think call it "loop gain" is more accurate) makes the closed loop corner frequency at Kfb*fc.


texts: Finding amplitude and phase response of an amplifier

texts:
I have a following problem, I have to find amplitude and phase response of an amplifier whose function is $$ H(s)={\frac {1}{s^2 + s + 100}} $$
I have solved simillar problems such as for this function $$ H(s)={\frac {1000s}{s + 10}}$$.
Where I got $$ Ф(jw)=arctg(∞) - arctg(\frac{w}{10}) $$ and $$ 20log|H(jw)| = 20log100 + 20logw - 10log(1 + (\frac{w}{10})^2) $$

Does anyone know how to get amplitude and phase response for the first function?


texts:
I have a no-name OCXO with pins marked by seller (VCC, GND, RF OUT, Vadj). I have checked its output frequency against rubidium oscillator using the following method:

I connected them both to different channels of the oscilloscope, set triggering on the rubidium oscillator signal and adjusted the frequency of an OCXO by connecting negative terminals of the lab power supply together (to get a common ground) and changing one channel voltage between zero and +4V. At about 2.5V (exact value doesn't matter for my question) frequencies seem to match.

Now, I'm looking for a way to provide an adjustable voltage reference to control its frequency when this OCXO is placed in some device. My first guess was to add some resistance in series, but I failed - current consumption of Vadj pin is way too low. I was actually unable to measure it with my Fluke 289 in microamps range.

My second guess was to use an adjustable voltage regulator, for example LM317 rated at 100 mA. My concern is - is this LM317 precise enough for the purpose I described (assuming I use precise and temperature-stable resistors for adjustment)? It has minimum load current of 3.5 mA which is far more than I'm gonna have, relatively high temperature drift and 0.1%/V line regulation.

If using LM317 for that purpose is not a good idea, I would be grateful for any better solution.


texts: Identifying electronic components in Robotale Electronics fans package

texts:
I am trying to figure out what the following components.

Is the blue component to the left a potentiometer?
I would guess that the two black cylindrical objects are buzzers? Is there any way to identify how much voltage/current can be applied on it?
The LED like object, with four pins seems to be a LED that is a RGB led? Is that correct?

Below, I've included some pictures.


texts: Best way to connect balanced audio line to ADC (with volume pot)?

texts:
Sorry for this more longish question: I'm currently collecting some ideas for my next project where I want to connect an external balanced audio line level signal to an ADC with differential inputs (like a PCM1804, not specifically though). I'd also like to have a volume pot to boost the signal if necessary.

I've looked accross the internet and found this circuit (an amplifier for a balanced line):

https://sound-au.com/articles/balanced-io.htm

Now this has two problems: First, it has fixed gain (I'd like to adjust that with a pot). If I understood correctly I'd have to change 4 resistors with one pot at the same time (I know of stereo pots but not quad pots) and as mentioned on the website the resistors would have to be close tolerance (which I'd guess is pretty difficult on something like stereo pots). Second, it doesn't output a DC offset which is required by the ADC.

From what I've found out the DC offset can be worked around by using an off the shelve solution like the OPA1632 which allows me to supply the DC offset voltage. This however also has two problems: First, I still don't have a volume pot in the circuit. Second the OPA1632 is relatively expensive at around $5 (am I too picky?).

One solution I could image is to convert my balanced input signal to an unbalanced signal, do the amplification with a pot, and then convert it back to balanced and then bias both outputs to my ADC's virtual ground. For the last step I'm not even sure if that's as trivial as connecting a capacitor in series of both lines and connect their outputs over a resistor to the bias voltage.

As for an attempt like above: Is converting a balanced signal to unbalanced back to balanced a silly thing? At that point I wouldn't even know why my ADC has balanced inputs in the first place. Is it common to have balanced inputs in audio gear but the actual "processing" is done with single ended circuits? I know balanced connections are useful for suppressing noise pickup on long wires (which I guess isn't such a big problem on a PCB).

I could also avoid doing the analog amplification altogether and do the amplification in the digital domain. However, if I we're about to set the gain to something like +40dB I'd obviously also boost my ADCs noise floor by that amount. Does it even make sense to avoid doing this digital amplification? Am I just going to amplify "analog" noise instead (I don't have that much experience with those kind of things)?

Does anyone have any idea which way I should go here? I can certainly understand good quality can cost money but if I can get 10x NE5332's or 10x TL072's for a single OPA1632 I'd like to avoid going for the more expensive part.


texts:
I'm currently learning about nodal analysis from a set of lecture notes. The notes are rather brief, and one question which occurred to me is whether it is possible for the admittance matrix to be singular.

That is, can we imagine a circuit that's physically possibly but whose admittance matrix is singular, so that we cannot determine the node potentials using nodal analysis?

It seems plausible that the answer would be in the negative, but I would like to see a formal argument. Note that I am not talking about issues with the admittance matrix being nearly singular, which might be problematic for numerical solution methods.


texts: I fried my multimeter while connecting it to AC

texts:
I just bought the multimeter "Multimeter Digital MAS830L" because I wanted to learn about electronics. INSTRUCTION MANUAL HERE.
Well, I've read the manual and it said clearly :

Alternative Voltage Measurement

Connect the red probe to VΩmA (200mA, 250V max FUSED)

Connect the black probe to COM (200mA, 250V max FUSED)

Setting on 600/200 V~

And then I just placed the red and the black probe in a European Power Point which has only two holes so it's pretty hard to miss something. And I'm pretty sure the polarity doesn't has to do with anything here because when you connect a device you can connect it both ways with the same result.
The first time (every device as much as I remember was off ?) and it measured Voltage correctly.
Second Time, the plug sparkled but nothing serious happened. But the tv was on in that room.
So when I did it the third time still with the TV on but on the other room, I've had a sparkle from my multimeter and the Plug together. The electrical switch from the room I was in turned off because of the fusions but I don't specifically understand why it happened.
I mean if I can not measure the Alternative Voltage with a multimeter from a Power Point, why does a multimeter has these kind of settings on it if it can not handle it ? Did I do something wrong ? I followed the manual's guidance.
I disassembled the multimeter , I saw the fusion and it was alright. I've seen the wire safe and sound in the glass (WHY ?) I changed it just in case with a 10A fusion because that's what I had at the time (but I wouldn't plug it anywhere dangerous), but still the multimeter was giving false values for almost every setting if not all of them.
I saw the board from the back and I saw a big black stain on the big wire circle where you adjust the settings with the plastic mode switcher. So that means that it will never work well I guess ? Because the copper on the board was damaged ?
If I did something wrong, aren't these things misleading for a newcomer ? Because I did what I was thinking was logical to do while following the manual's guidance. It didn't mention anything about Power Point plugs as much as I remember.
Thanks in advance.


texts: Bulbs on seperate circuits triggering third bulb

texts:
I would like to know if the following is possible, and if it is possible, roughly how the wiring should be done ...

I have 2 light bulbs (BULB1 and BULB2) connected to SEPERATE switches. I want to install BULB3 so that BULB3 turns on when ...

BULB1 is on, or
BULB2 is on, or
BULB1 and BULB2 are both on

and turn off when ...

BULB1 and BULB2 are both off

I have access to the wiring at BULB1 and BULB2, and no access to the wiring at the switches. BULB3 will have to draw power from either BULB1 or BULB2.

The idea is to add a light to a dark passage where there are bulbs on both sides, but none in the middle.

Thanks for any suggestions.


texts:
I have an LED light with a power supply that follows the ISO 60929 0-10V standard for dimming.  The manufacturer says "the power supply is current sourcing, and is roughly 0.5mA."

The following diagram is representative of this circuit.  The power supply (dimmable driver) is on the left, and the dimmer I would like to build (the controller) is on the right.

There are many analogue controller options available for a dimmer, but I would like to create a digital dimmer using an ESP32 and I²C.

This is where I'm running into a problem.  I've found a number of I²C controllable rheostats at DigiKey and elsewhere, but almost without fail their datasheets say the maximum allowable voltage across the rheostat pins is very close to the Vdd that supplies the rheostat IC.  Since I'm looking at a Vdd of 3.3V, the maximum allowable voltage is around 3-3.6V, which is completely outside the 0-10V range I need to control.

I found another IC with two supply rails that looks like it might work, the MCP45HV31-104E but as far as similar devices in its product category there are very few, which makes me wonder if I'm approaching this problem from entirely the wrong way (I have a lot of software experience but very little electronics experience unfortunately).

So my question is am I looking at this the wrong way? i.e. is there a different way to hook up a "standard" digital rheostat (one with a voltage range near 3.3V Vdd) such that I can get the full 0-10V range out of it?

Or do I need something like the MCP45HV31-104E to implement a dimmer?


texts:
Fairly simple question but I couldn't find any instructions on this. I'm using an STM32G070
I'm interfacing with an ADS1231 which uses DOUT / ~DRDY on the same pin, and I'm wondering if there is a way to use the interrupt pin as an input as well. Essentially what I want to do:

Wait for a falling edge on the DOUT/~DRDY pin (currently configured as EXTI)

[Inside of the ISR:]

Disable interrupts on the pin
Use the pin as an input
Send out the 24 clock signals, reading the DOUT/~DRDY pin after each clock falling edge
Turn the pin back into an interrupt
Exit and wait again

I found an interesting answer in another thread, using the same part (https://electronics.stackexchange.com/a/339742/281491)

I would do it completely other way.

Set SPI2 MISO pin as GPIO input. Set the EXTI (falling edge) interrupt on this pin

In the EXTI interrupt - Disable EXTI, change this pin to the MISO AF, and initiate 3 byte DMA transaction (send 3 dummy bytes as you need to generate clock for the ADS).

In the DMA transfer complete interrupt change pin to the GPIO Input. Enable EXTI

Steps 2 & 3 will automatically repeat on every conversion.

Can anyone elaborate on how I would go about doing the bolded parts, or any other solutions?
Thanks


texts:
I have been programming CC3200 using code composer studio.
I know how to run the debugger on my device and run the the code successfully. But I can't figure out how to burn the code on my device so I can use the device independently.


texts: If the resistance of a shunt resistor in a circuit is acceptable, is there benefit to any other current measurement technique?

texts:
I am looking into using a shunt resistor to measure a current up to 30 A, that may be constant, or vary with a sine wave, square wave or even a PWM signal (up to 10kHz).
I understand there are Rogowski coils and Hall effect sensors, but if the resistance is acceptable for my uses, what other considerations should I be giving to the choice of current sensing?


texts: Different voltages for Single and Dual-supply (INA)

texts:
Since it doesn't matter for the Op. Amp. itself, the components presented as "single-supply" commonly relate to rail-to-rail input/output devices, which operate on lower total voltage supplies. If the input and output signals and their DC offsets operate within the limits, everything works fine regardless of the power supply (single or dual).
Since they are equivalent, "total" operating voltages are normally the same:

But in this INA datasheet, different values are presented:

At the page 20 of the datasheet there are detailed informations on input voltage range, including the Vref pin, but I could not relate this with the asymmetry in supported supply voltages. The difference is even higher for the AD8227.
If the reason for the different lower operating power supply voltages was a reliable Vref, it would be harder to use the INA with single-supply, and not the other way around.
Question: any idea on why can't this device work with ±1.1V?
References:
AD822 Datasheet
AD8226 Datasheet
AD8227 Datasheet


texts:
How do I find the resistance of a toroid or hollow cylinder that has been cut along a radius, that is, a straight cut from the center to the outer radius? The outer radius of the cylinder is ro and the inner radius is ri. The thickness is w. The resistivity is given is p. The general form of the resistance is p l/w, where l is the length. The cut is deemed very narrow.

Edit: The resistance is measured across the cylinder from the [exposed faces of the] cut portion.


texts: Interface of HC05 Bluetooth module and RF 433Mhz Module

texts:
I am trying to make an Android controlled toy car. Now the range of the bluetooth module is around 10 meters. However, to increase the range, I decided to interface the RF module with the Bluetooth (HC-05) Module. I have a TX and Rx pair of 433 Mhz. Basically, the app sends an integer value to the Bluetooth module. The Tx pin of the bluetooth module is connected to the Data pin of the transmitter.

On the Receiver side, I have connected the data pin of the receiver to the Rx pin (PIN 0) on the Arduino. This is the overall setup. I have attached an Image of the connections. It's my first time using Fritzing, so please dont mind the nasty connections.

I power the HC-05 and Tx pair using a separate 5V and the Rx using the Arduino. For the sake of the image, I have shown all of the components being powered from the Arduino. I am first testing the whole thing on an LED, so the code attached is that for an LED.
Below is my code:

int LED= 13;
char input;

void setup()
{
  Serial.begin(9600);
  pinMode(LED, OUTPUT);
  Serial.println(">> START<<");
 }

 void loop()
{
  if(Serial.available()>0)
    {
     input= Serial.read();
     if(input=='1')
       {
        Serial.println("ON");
        digitalWrite(LED, HIGH);
        delay(2000);
        }
     else if(input=='0')
       {
        Serial.println("OFF");
        digitalWrite(LED, LOW);
        delay(2000);
        }
     else
      {
      Serial.println("NO INPUT");
      Serial.println(input);
      }
     }

    }

Now, without the RF module, that is, when I connect the Tx of the HC-05 to the Rx of the Arduino (PIN 0), the above code works perfectly. However, when I connect the Tx pin of the HC-05 to the Data pin of the Transmitter module and the Data pin of the Receiver module to the Rx pin (PIN 0) of the Arduino, everything goes awry. Any suggestions on why this might be happening?


texts: Using Arduino to program Amtel AVRs via ICSP header

texts:
I have an Arduino (NG) board with an ATMEGA168 AVR micro. The board has a 6 pin ICSP header. Here is what I propose to do, please tell me if it is possible:

Remove current ATMEGA168 IC
Replace with a new AT AVR of similar series
Plug in the programmer to the ICSP header on the Arduino
Use avrdude software to program the AVR
Remove AVR and install in a socket on my project board and replace the original ATMEGA168 AVR
Continue to use the Arduino as normal

I have also thought about installing the 6 pin ICSP header on my project board so I can tweek the software with the chip in place. If I implement this part of the arduino circuit on my project would this be possible.

Schematic


texts:
I have a boost converter.

\$V_{in}\$ = 7V

\$V_{out}\$ = 14V

\$I_{load}\$ = 0.35A

While testing, I observe that as long as Vin<14V, I observed switching at the inductor switch node.

But, as I increase my input voltage, Vin>14V, I dont observe the switching at the switch node.

How come this happens with the boost converter, when I want the output to be constant 14V irrespective of the input voltage?

Could someone please provide some suggestions to overcome this and why this happens?


texts: How many active Bluetooth devices can I reliably detect in a single space?

texts:
I am engineering a low-cost attraction and hope to use Bluetooth device identification for proximity detection -- i.e. is guest A within range of static location X. Each guest will be given a customized mobile device (either iPod or Android based).

What is a realistic upper bound on Bluetooth device "density" before enumeration of all nearby devices becomes unreliable? For instance is having 25 active devices in a vicinity of a stationary Bluetooth-enabled PC too many in one place to detect reliably and entirely (all devices)? Is this too much congestion?

(To be clear: I do not need to establish connections. I only need to reliably detect the presence or absence of devices by name.)


texts: How to connect 2 thermistors for battery protection?

texts:
I'm planning to use BQ24100 for charging Li-ion cells connected in parallel.

Unfortunately, the cells have to be separated by few centimeters, so I have to use 2 thermistors. So, how to connect 2 thermistors to BQ24100, since the IC has only one pin for thermistor?


texts: Replace Expensive Transformer with cheaper alternative?

texts:
I have a range hood that has an expensive (IMO) transformer that has went bad.  Here is the link to the transformer that went bad: http://www.repairclinic.com/buy/1/14238-transformer-oem-5304464262.html

Does anyone have a suggestion on how I could replace this transformer with a cheaper alternative?  Would something I have around the house have a transformer in it that would work?  Could I buy something broken on craigslist and take it out?  Would Lowe's or Home Depot carrry something that would work?

As you can see it is a 120v to 12v transformer. And something went wrong?


texts: Understanding time-response of photodiode circuit (LTspice)

texts:
I'm trying to get an idea of the time response of a laser-gate I'm building; so, I wanted to do some basic simulations in LTspice based on this thread:

Adding Photodiode to LTspice

Attached below is my circuit and voltage response at the oscilloscope.

I'm confused because I figured the time response was going to be on the order of RC, ~10 ms for the given scope impedance and filtering cap, whereas this simulation seems to suggest it's only a few microseconds.

Is my understanding of the time response wrong? Or am I doing this simulation incorrectly? Thank you.


texts:
This is probably a basic question which i'm stuck with:

Why should there be offset at the input signals?

=> We have offset voltage of 1V on both the signals, when i remove the offset i get very weird result (result are given below)!

Weird result (without offset)

normal result (with offset)


texts: Sensor to detect movement of object on a horizontal wire

texts:
I am looking on how to build a solution to track movement of an item clipped to a horizontal wire. It has been suggested I could do with with an accelerometer and Arduino. I want to detect any movement, whether the object is rattled or slid. If slid, it would only move a couple mm at a time. The item on the wire is about 1cm width. It has a tag at the bottom so it's possible to attach something to it.
Am I on the right track with thinking an accelerometer is how I would do this? If so, would something like a 2-4g accelorometer do the job?


texts: Triangle generator circuit - supply rail error

texts:
I have a simple triangle generator circuit soldered and powered by 5V rails shown below. Verified by simulation and equations, it should output a 500kHz triangle wave a \$\pm4.2V\$. Instead, the only thing visible at the output is the power supply noise with additional high frequency noise at the peaks.

It seems like the issue is with the supply rails. The power supply is showing 5V but at the terminals on the board i'm seeing +1.8V for the positive rail and -3.2V for the negative rail. What is the cause of this and how is it possible for this circuit to bring down the supply rails?


texts: Understanding a Single Transistor Flyback Transformer Driver?

texts:
I've been watching a few analyses of CRT flyback transformer drivers and can't understand why the transistor would shut off. To my naive perspective, it appears that the transistor should never shut off due to the positive DC voltage applied constantly to the base. I'm aware that this isn't the case since transformers need changing currents to induce currents in their other coils. I'm aware that the coils have inductance which dampens current buildup and charges the inductor core, but I can't wrap my hear around the transistor region.

(Reference: https://en.wikipedia.org/wiki/Flyback_transformer#Operation_and_usage)

Circuit Diagram:


texts:
I have a motion activated circuit build with a spring switch (sw‑18020p) and powered by a CR2030 coin cell. Every time i "shake" the circuit, it turns ON for some seconds to grab some sensors readings and then turns OFF. Everything is insulated with epoxy so i don't have access to the components after i install battery.

I'm looking for some kind of circuitry to prevent the device to turn ON, like for storing purpose. I was thinking of a reed switch inside and a magnet outside, so if i remove magnet it operate normally and if i put magnet back, i could store it without activating by accident.
The problem with reed switch is they are made of glass and break very easy, so i was looking for something more robust.

Anyone have a better idea?


texts:
I am trying to develop a BLDC motor ESC (electronic speed control) for motors in water. This means that the motors will be subject to more load (due to the water). I am going for the sensor less approach. I am initially giving it 35% duty cycle and looking for a specific '0' crossing in the floating phase. The waveform I get is shown below:

In the above image, the blue waveform denotes the float phase, whereas the yellow spikes denotes the areas/regions greater than Vcc/2 (in other words greater than '0' crossing).
Now, I measure the time the '0' crossing happens and double it. This doubled value is my new commutation time for the motor (the duty cycle, I keep it constant,though). This is shown in the fig below. It has no slope value

But, the moment I go for new commutation, it fails and the floating phase becomes a constant level. In contrast, when commutation it was a gradation (it had a slope).

Why is it so? I have detected the correct '0' crossing and it is a '0' crossing for that particular duty cycle. Why then does the commutation fail?

The reason, outright, I feel is thus. At 35% duty cycle, the commutation is occurring properly. But, the current required to rotate the motor is insufficient for the motor to drive the motor. But then that defeats the purpose of a '0' cross detection.


texts: How do I multiplex 6 x 4 bit ALU outputs?

texts:
I have an ALU that performs 6 functions, each function provides a 4 bit result. I want to multiplex these outputs so they can be selected with an op-code (selector bits of the mux). The only problem is there are no 24 in 4 out multiplexers, so how can I achieve this?

Thanks


texts:
A LCD display controller includes a 5 times DCDC converter. A circuit is needed to ensure that the in case of a fault in the display the 5 times voltage can not return to the CPU circuit in anyway.
The interface to the display will be +3.3V, GND and a (one way) SPI.
We have a solution with a Schottky diode, but could it be done in a smarter way with a fet?


texts: Problems with structures and unions in c

texts:
After many years I started for fun to program in C again. Now I have an issue with the use of structures and unions.

The declaration:

typedef struct {
    unsigned char   SOAKTEMP;
    unsigned char   SOAKTIME;
    unsigned char   REFLOWTEMPERATURE;
    unsigned char   REFLOWTIME;
    unsigned char   BAKETEMP;
    unsigned int    BAKETIME;
    unsigned char   COOLDOWNTEMPERATURE;
    unsigned char   COOLDOWNTIME;
    unsigned char   KP;
    unsigned char   KI;
    unsigned char   KD;
    unsigned char   CYCLETIME;
}EEPROM_DEFAULTS;

The initialisation:

EEPROM_DEFAULTS EEPD = {
                     170,    // SoakTemp
                      90,    // SoakTime
                     220,    // ReflowTemperature
                      30,    // ReflowTime
                      80,    // BakeTemp
                    7200,   // BakeTime
                      60,    // CooldownTemperature
                       0,    // CooldownTime
                      11,    // Kp
                       5,    // Ki
                       1,    // Kd
                       5     // cycleTime

};

To write and read this data into the EEPROM of the PIC16F18877 I need to split BAKETIME into a high and a low byte.

I have done this with a Union.

union{
        unsigned int Baketime;
        struct
        {
            unsigned char BakeTimeLowbyte;
            unsigned char BaketimeHighbyte;
        };
        } BT;

It works but I do not like the way I have done this.
I have tried in many ways to incorporate the union into the EEPROM_DEFAULTS typedef but without succes.
So my knowledge runs short after so many years.
Assistance would be nice.


texts: GL850 USB hub with or without capacitors?

texts:
I'm looking at two different USB 2.0 hubs which both use the GL850. This is Hub 1:

(source: mydigit.net)
This is Hub 2:

(source: mydigit.net)
Both take an external power source but Hub 1 uses four 220uF caps. Does anyone know why a cap is used for each USB connector in Hub 1 but not in Hub 2?


texts: Choosing output capacitor for power converting

texts:
In general, what is the best practice (mathematically) to choose an output capacitor for a boost or a buck converter?

In other words, could someone walk me through the design/decision making process for the output cap? I understand you have to consider output voltage ripple, but I'm not sure where everything fits in.


texts: Altium Designer 3D collision/distance problem

texts:
I'm using Altium designer 17 and I want to make a 3D layout of my board.
My only problem is that whenever I place a piece on the pcb, the component is flashing green and it says Collision. It Collision even if nothing is touching the pcb. Exemple this transfo:


texts: Is advisable to drive an LED matrix using a Shift Register+FET on High side and an LED driver on the low side?

texts:
Trying to find the most economical way to drive 60 leds (~20mA) for volume production.

Our main MCU doesn't have enough pins, so I2C or similar set up is needed and total budget of driving LEDS should be under $1.

Best I came up with is a 8-channel Shift register driving p-mosfets on the high-side and an 8-channel LED driver on the low-side.

Is this advisable or even a common thing?

The other method was a bit brute and RYO: use a cheap ATTINY ($0.40) and drive discrete FETS.


texts: Does the Northbridge Chipset IC have a "core" of some definition

texts:
Does anyone have any intimate knowledge of the design layout of the logic "core" found in the Northbridge chipset used in computer motherboards (desktop and laptops) ? This chipset is made by Intel and AMD respectively at the present.

Would it have just a single core or multi cores ? Where on die would this logic core be located near the top layer ? Could anyone tell me how does this core get executed or run on power on or reset of the device ? Where would the circuit code on die be located that executes this core and makes it active ?


texts: Role of Capacitor when switch is open in Buck Converter?

texts: in a buck converter, initially, when switch is closed, then capacitor charges and stores energy. But when the switch is opened, then Inductor current flows through thr free wheeling diode, but what happens to the charge stored in the capacitor?


texts: What happen with cells with different current rating put in parallel?

texts:
I don't understand how cells behave when connected in parallel.
So what if I have two Li-Ion cells: one ist "rated" at 15 amps (which means that the cell is able to discharge at 15 amps without problems , right?)
The other cell ist rated to 5 amps. Now assume both have appropriate same Voltage to connect them both in parallel. What happens if you connect a load which would draw 10 amps now? Would both cells try to discharge with the same 10A (and thus the 5A-cell would overheat and fail...), or would the current be spread up eavenly?
Is it actually forseeable at all what would happen, since it depends on the internal resistance of both cells, doesn't it? Does someone know what would happen?

Then another question: what if you put two cells of different capacity in parallel? Isn't the cell with the higher capacity supposed to give more current? Because the discharge curve of the high-capacity-cell is above the discharge curve of the low-capacity cell. So the high-capacity-cell would have to discharge more of its current until it decreases its voltage to the same level as the low-capacity-cell? So would that mean that the internal resistance gets lower with a higher capacity, is it proportional?

Hopefully my explanations aren't to confusing and hopefully there are people who are bothered by the same question :)
Thank you!


texts: Where can I find correct documentation of old floppy drive formats?

texts:
I have an old drum machine with an ancient proprietary 3.5" SONY floppy disk drive with no information on the device itself that I have seen. The performance is spotty and it's very picky about disks. The problem now is that it's seemingly impossible to find an authoritive answer on format or suitable replacements. So many companies made incompatible proprietary solutions, and of course they have all left the scene by now making future compatibility questionable.

It's a shame that it's possible to read ancient text from Egypt and Greece, while not possible to read a floppy from the 1980s. Does anyone know where I can start to get an answer to this?


texts: Best approach for sharing SPI bus across multiple sensors

texts:
I'm designing a few PCBs for a project:

Microcontroller PCB (SPI master)
Sensor PCB, where each sensor PCB has several SPI slaves on it.

In a full system, there would be 3 sensor PCBs directly plugged into 3 connectors on the microcontroller PCB. In certain scenarios, not all 3 sensor PCBs will be present.

My question is about best practices/approach for sharing a single SPI controller across all 3 sensor PCBs.  I'm planning to run the SPI bus at 20 MHz and the longest end-to-end trace length between the microcontroller and SPI slave will be  about 8 inches.

Some ideas I had:

Use a 'SPI bus multiplexer' to isolate which Sensor PCB is connected to the SPI bus at any given time, but haven't had much luck turning up results.  Was hoping to find something similar to a TCA9544A (I2C multiplexer).
Use 4-bit tri-state buffer on the microcontroller board for each Sensor PCB interface.  In this case, I'd have 3 of these on the microcontroller PCB.  Using the output enable to connect/disconnect a sensor PCB from the shared SPI bus.

Update:

Here's a diagram of what I'm trying to do:

I suppose I'm more concerned with signal integrity and EMI/reflections. I believe I have an understanding of the functional connection aspects.  How should I handle the inter-board connections, given that a sensor board may or may not be attached?  Should I use tri-state buffers at the interface?


texts:
The best clock divider is a PLL inside a FPGA. But the number of PLLs are limited. And sometimes using of counter to divide a clock is justified:
reg [7:0]counter = 0;
reg divided_clk = 0;
always @(posedge clk) begin
    if(counter == DIVIDER - 1) begin
        divided_clk <= ~divided_clk;
        counter <= 0;
    end
    else begin
        counter <= counter + 1;
    end
end

But the condition
    if(counter == DIVIDER - 1) begin

use logical elements in non-optimal way.
If we make another condition:
if(counter[DIVIDER_POW]) begin

we use less LEs but lose an accuracy of dividing.
Also we can find an optimal divider, then decremet the divider by one, then convert the divider to binary and make the condition from elements with one. For example the condition based on the divider equal to 50 looks like:
if(counter[5] && counter[4] && counter[0]) begin

The accuracy of this condition is the same as the first method. And it takes less LEs.
But is it possible to parameterize such condition?


texts: Is my answer correct to this non-ideal capacitor question?

texts:
In the picture there are two measurements. The one is of a single 10uF capacitor as shown in the picture. The other measurement is of the 3x 3.3uF capacitors in parallel as shown in the picture below it. These three capacitors in parallel have about the same nominal capacitance as the single 10uF one. In the plot on the right in the picture there are two traces, these are both impedance magnitude traces (there is no phase data.) The upper trace is of the 10uF capacitor and the bottom one is of the three in parallel.

It is clear that the impedance characteristics of the two are different, even though the size of the capacitance is about the same.

The equivalent cct of a non-ideal capacitor is a series RLC circuit.

The answer I think is correct:

I think the answer is because inductors in parallel plays a role in determining the actual impedance of the capacitor. When there are 3 capacitors in parallel, the series inductance also come up in parallel. When inductors are combined in parallel, the net inductance becomes very small. When the net inductance becomes small, the net impedance also is small. This is why the impedance of the capacitors in parallel is slightly less than the single equivalent capacitor.

Please let me know if I am correct and if there is any additional information I have left out (like the role of the resistance.)


texts: If two iBeacons are too close to eachother, could their signals get confused for one another?

texts:
I have a simple question that I can't find the answer to. I am testing an app with some iBeacons, and I observe that one of my iBeacons never begins to range...the region is monitored, its just not being detected. When I look at console output the other beacons get detected, and then a few seconds later, another beacon gets detected, but it has the same UUID/major/minor/identifier values as one of the other locations already detected.

So all but one of the beacons get recognized and their states get determined. Then it appears that one of the beacons that has already been determined, gets determined again (same info). These beacons are somewhat close together (about a meter apart in x, y but on different floors (2nd floor and 3rd floor), and I'm wondering if one beacon signal could override another...which would be why I am seeing the info for one of the beacons twice. Otherwise I'm not sure why I can't detect this one beacon.


texts: What does these Verilog line of code mean?

texts:
I'm looking at this code: https://github.com/hgeisse/eco32/blob/dfd24eb13387f16b7da99a2285df023f446a676a/fpga/experiments/de2-115/memctrl-32/sim/memctrl-1/ramctrl/ramctrl.v

and I've found two lines of code that I don't fully understand:

          if (| count[13:0]) begin

and

  assign data_addr_out_of_range = | data_addr[26:25];

I know that the symbol |, means Bitwise OR and Reduction OR.
But I continue without understanding the meaning in those lines.

Thanks in advance.


texts: closed loop hall effect sensor operation

texts: I know that closed loop hall effect sensors generate a current in the secondary winding to oppose the flux in the core such that the net flux will equal zero. At this point the current in the primary is proportional to current in the secondary winding, however when the flux=0 will the hall effect sensor simply not switch off? Then secondary winding current will start to fall off therefore causing the hall sensor to turn on again i.e the output would be oscillatory?


texts: Current limit resistors for Optocoupler controlled Mosfet

texts:
Reading different design rules regarding optocouplers used as switch I have a question about the current limiting resistors R4 and R6

One aspect is the protection of the devices (e.g. ~200Ohm for a standard LED over a 3V voltage drop @ 15mA). How can I calculate the correct values?

For the 4N25 the forward voltage is 1.5V and my digital pin can produce up to 20mA => $$R_4 = (5V-1.5V)/20mA \approx 175\Omega $$
where for the Mosfet can switch logic input (5V) but I do not know which value describes the limiting factor for calculation of the resistor R6?

My attempt is with \$V_{GS} = 2V\$ @ \$I_D = 250\mu A\$ with following consideration
$$ R_6 = (5V-2V)/250\mu A) \approx 12k\Omega$$

Edit: the datasheets 4N25 IRLZ34NPBF


texts: what is the difference between these two configurations?

texts:
I can understand this circuit configuration:

But i don't understand when signal is placed in Qp's base.

In this configuration we don't have VBB/2 in the two base...
Sorry about my english and thanks in advance.


texts:
I sent in a function
$$T = -0.1 \frac{s+400}{(s+20)*(s+2000)}$$

> T = -0.1*(s+400)/((s+20)*(s+2000));
> bode(T)
> grid on

I was expecting the phase to start at -180 deg, but instead the MATLAB is showing +180 deg.

Is this an inconsistency or a conceptual thing?


texts: Capacitors in parallel vs. single capacitor

texts: The circuit below shows 3 capacitors in parallel on the input side, and 2 on the output side. Is there a reason for that? or would using a single capacitor (30uF & 660uF) make no difference?


texts:
I am confused by the current path of the Ćuk converter when it is at position one where the mosfet is conducting

The circuit analysis results in the two circuits below. What is the current path? Why is there current passing through capacitor C1?


texts:
I am designing a circuit to power a brushed DC motor. The motor will be given 24VDC, modulated with PWM. I would like to have an analog voltage sense capability for use with my Atmel ATmega328P @ 3.3 AVCC, with some room on top for a safety margin. This means I want both a voltage divider and a voltage averager (an RC filter).

As I have discovered (by reading Wikipedia), a filter is really a frequency-dependent voltage divider. If I know the frequency I will be using, I can design an RC lowpass filter—but instead of designing for 3 dB attenuation at \$f_c\$, I can design it for 10 dB attenuation at \$f_{PWM}\$. This is similar to this question, but I don't think I need R2, do I? See attached circuit diagram.

I calculated these values with the equation (from Wikipedia, again)

$$\frac{V_{out}(\omega)}{V_{in}(\omega)} = \frac{1}{ \sqrt{1+(\omega RC)^2} }$$

where

$$\frac{V_{out}(\omega)}{V_{in}(\omega)} = 0.1, ~~~ \omega = 2\pi 15625 = 98175 \text{ rad/s}$$

My questions:

Is this necessary at all? My idea here is that the voltage across the motor will not be exactly the voltage I expect based on the PWM, due to varying loads and back-emf, etc, so I need to measure voltage to use in closed-circuit feedback. Is this incorrect?
Am I going about this at all the correct way? Circuit design, value selection, etc?
Obviously this would be Very Bad for the ADC at 100% duty cycle, as there would only be the 24V DC component and the voltage is not divided. The max I am planning on is 60% or so. Is this likely to cause issues?
What advantages, if any, does Jeremiah Rose's circuit provide over this one, if the frequency is known and fixed? Besides the ADC protection at 100% duty cycle.

simulate this circuit – Schematic created using CircuitLab


texts: Compensating clock drift "by hand" - what have I solved?

texts:
Edit: I'm not actually looking for a solution, because short of syncing the hardware clocks (which I can't do) there isn't one. What I'm looking for is an explanation of where the magic -8.4ms I seem to have identified is coming from.

I have a hardware music sequencer (Squarp Pyramid), a laptop, a digital MIDI-triggered drum synthesizer (Roland TR-8), and an audio mixing console with built-in USB audio (Soundcraft Signature 12 MTK). Using my laptop with DAW software (Reaper), I record a sequence of drum beats from the TR-8, triggered over hardware MIDI from the Pyramid:

What I find is that the beat-markers in Reaper drift over time compared to the onsets of beats in the recorded audio - between 10ms and 20ms per minute of audio, depending on the BPM. This is expected, of course, but I'd like to reduce it as much as possible.

I don't have access to a reliable way of keeping the clocks in sync. The solution I'm working with right now is to use a slightly modified BPM on Reaper to compensate for the drift. For example, for 125BPM on the Pyramid, I set reaper to 125.02BPM. For 117BPM on the Pyramid, I set Reaper to 117.0382BPM. This reduces the drift to fractions of ms per minute of recorded audio, which I can live with - but I have to work out the drift by hand, and it's different for each BPM.

My method for determining the drift amount is as follows:

Record 10 minutes of audio with beat pulses at a particular BPM.
Align the onset of the 0th recorded audio beat with t=0 in Reaper.
Find the nearest Reaper beat marker to t=10mins, and measure the distance between it and the onset of the corresponding audio beat. This distance represents the clock drift over 10 minutes.

For 125BPM, the drift over 10 minutes is -95ms, giving me -9.5ms of drift per minute. \$\frac{60000}{59990.5}*125 = 125.02\$, so I set Reaper to 125.02BPM and the drift over 10 minutes becomes small enough to not be a problem any more. Unfortunately this has to be re-calculated for every BPM I set on the Pyramid. I figured out I can streamline this process by writing a C++ app that uses the RtMidi library to sample incoming MIDI clock pulses from the Pyramid’s USB output, calculating a rolling offset error to estimate drift from an expected BPM.

For 125BPM, the USB samples exhibit a clock drift of -1.1ms per minute, and I have to add a magic number of -8.4ms of drift per minute to match what I'm seeing when I line things up by hand in Reaper. I've tried this across multiple BPMs and the -8.4ms seems consistent (+/- 0.2ms). This method gives me reliable predictions for a BPM to use in Reaper to get the beat marks to line up with the audio, but the -8.4ms magic number is troubling.

Where is this magic -8.4ms coming from? I figure there are three clocks involved:

Pyramid (P)
My laptop (L)
The USB audio module in the mixing console (M)

I suppose that the tweaked BPM in Reaper needs to be based on driftPM (clock drift between Pyramid and mixer's USB audio). My USB capture method is giving me driftPL. The magic -8.4ms must then be driftLM. So driftPM = driftPL + driftLM.

Does this seem correct? It appears to work in practise but I feel like I’m stabbing in the dark. Is there an easier approach?


texts:
I'm planning to design a driver for VGA connectors, and for testing purposes I have an evaluation board of one CPLD. Concretely, the board is the Digilent's CoolRunner-II with the Xilinx's XC2C256 CPLD. But my intention is to implement the driver on a custom PCB with a smaller chip, let's say fo example the XC2C64A (random CPLD I've already found), to make the PCB cheaper due to the cost of manufacturing bigger surfaces.

Can I use the CPLD I have and then, once I have tested that the design works properly, tell ISE to synthesize it for smaller CPLD models to know which one could support the design? For example, to know if it has enough capability for the size of the logic or the design overflows it, so I could estimate which CPLD I should buy later.

Probably it's not the best solution, but it would be perfect for saving money if I don't have to buy evaluation boards for the other CPLDs. What do you think?


texts: Using all the taps of the transformer at the same time?

texts:
Let me clarify, I have a power transformer with 2x15V secondary (3 secondary terminals). I want to feed a full wave rectifier with 30 V (using the outermost 2 terminals), but at the same time I want to power a smaller circuit using 15 V (using the middle terminal and one of the others).

Is there anything that needs to be considered with this setup, provided I don't exceed the current ratings of the secondary? Is this safe?


texts: When designing a PCB, do you need to worry about the inrush/surge current or just the continuous/RMS current on the board?  Everything I have seen including IPC documentation is for continuous current.  Is the assumption that if you are ok from a temperature/trace width stand point, you will be ok for an inrush current?


texts: Is there any problems with driving a single 5mm LEDs off of a single or parallel 18650 batteries?

texts:
I want to drive one or two small (5 or 10 mm) white LEDs in parallel using one or multiple 18650 3.7vV Li-ion cells. The main reason I want to use the 18650's is, I already have them, they are rechargeable and have a pretty good mAh rating.

Is this as simple as putting a resister and a switch and I'm done? What about when the battery is drained and can only output 2.x volts? Will the light simply not light at that point and we charge the batteries?


texts: Altium overlapping room on top and bottom layer

texts:
I am trying to do a 4 layer PCB (The 2nd layer is Ground and 3rd layer is VCC). While I am placing overlapping rooms on top and bottom layers, then after placing the rooms, when I try to move a room on a layer, it moves some tracks and vias on the other layer as well. How to layout rooms / components in multi layer PCB this way? I mean I want to move the room on a layer without disturbing vias and tracks on the other layer.

The RED is the top layer and BLUE is the bottom layer.


texts: How to read STM32F407xx Microcontroller Power Schematic?

texts:
I am working with an STM32F407xx microprocessor to analyze incoming signals generated by some hydrophones in a sonar system. At this point in time I am just reading through the datasheet and trying to figure out how the STM should be powered without all the peripherals for the sonar system attached (amplifier, filter, hydrophones, etc). I am having trouble reading the power supply layout provided shown in the diagram below.

[

(Taken from the datasheet, Pg 77)

My specific questions are:

What does 15 X 100nF actually mean? Why do I need FIFTEEN capacitors? Also how should these capacitors be connected? I know in note 1 underneath the diagram it says each power supply pair must be decoupled using filtering ceramic capacitors. But what does the notation 15 X 100nF + 1 X 4.7uF mean? Do I put 16 capacitors in parallel or what? I am so confused and I wasn't able to find anything on the internet related to the issue, probably because I don't know how to describe the issue that well. This same question applies to the other two highlighted capacitor sections that say 100 nF + 1uF. Again I assume they are in parallel but I'm not sure.
What do dashed lines mean in a schematic diagram? I know the large rectangle with dashed lines is supposed to represent the physical boundaries of the STM but what do the dashed lines to the left of the ADC right by VREF+ and VREF- mean? I found some information online where people suggested that the dashed portions are just optional but I can't be sure.

I've been trying to figure this out forever so any help would be greatly appreciated!


texts: I am using a large capacitor in one of my circuits and due to space constraints I can't keep it in the vertical position. Does anybody know how I can place it horizontally in the circuit in ISIS?


texts: Why is higher transconductance relates to faster transistor switch?

texts:
Here is a quote from this site:

  ...higher 'transconductance' - a measure of the performance of a
  transistor - than silicon transistors. The higher the
  transconductance, the faster the transistor can switch on and off.
  That means higher clock frequencies can be supported, and that lower
  core voltages are necessary.

The above bold marked argument shows up in Oxford dictionary under the example sentences as well:
https://en.oxforddictionaries.com/definition/transconductance :

  ‘The higher the transconductance, the faster the transistor can switch
  on and off.’

I know that the transconductance is the slope of Iout Vin curve. The steeper the curve the higher the transconductance of the transistor. But that curve doesn't have any time axis. It seems ∆Iout/∆Vin is about DC increments doesn't have anything related with time. Or does it? How is being faster switch can be related to higher transconductance?

There is no time in the below plot(Ic Vbe are DC values since they are capital letters, they are not instantaneous):


texts:
How does a precision half wave rectifier work? The one with a single diode.

When the input goes positive, the output of the op-amp is a large positive signal which turns on the diode and completes the feedback path. What I don't understand is  what happens to the initial output of the op-amp which was the signal multiplied by the large gain A.


texts: Assigning current direction in mesh analysis

texts:
Below is a circuit schematic of sources and resistors.
$$V_S=10V, R_1=50Ω, R_2=15Ω, R_3=5Ω, I_S=2A$$

Question 1:  Calculate the current i1 in amps that goes through R3 from left to right.
Question 2: For the same circuit, calculate the voltage across R3.

I used mesh analysis to solve this problem.  When I assign the current in the counter clock wise (CCW) direction, I get the correct answer.  But if I assign i1 in the clockwise (CW) direction, I cannot get the same answer.  It appears I am making an error when I use Ohm's law across R2.
When i1 is CCW, \$i_1\$ and \$i_s\$ are in opposite directions and the voltage is \$(i_1-i_s)R_2\$.  When i1 is CW, \$i_1\$ and \$i_s\$ are both in the same direction and pointing downwards.  So I thought the voltage would be \$(i_1+i_s)R_2\$.
But when I do this the answer is incorrect.  Can someone please explain why?  I think I should get the same answer no matter which way I assign the current.


texts: Visualize the Arduino PWM's output by means an oscilloscope

texts:
I'd like to visualize the PWM signal from an Arduino Uno board with an oscilloscope.
I'd like to use this layout:

Is this a safe connection?
In other words, might I have problems because the oscilloscope and tha PC's PSU share the same earth ground?
I need to connect the Arduino to the PC by USB cable because I need to run software from the PC to the Arduino.
Update:
I've connected the oscilloscope and it works fine.
When I change the duty cycle percentage (from 0% to 100%) in Matlab/Simulink I can see it directly on the oscilloscope.


texts: how to measure low frequency(50Hz) with atmega32 more accurately

texts:
I am trying to measure two AC source's frequency with atmega32, both will be around 50Hz. I already build the zerocrossing circuit using LM358, all I have to do with my atmega32 is to use the timer to read the square wave.until now i only manage to use the following simple method, which is to start the timer when the voltage on the pin is not zero, and stop the timer when the voltage reaches 0, then multiple the result with 2. I have to problems(questions) about this.
first, it is not really accurate, but it is really sensitive.I always got 52Hz instead of 50, but it can sense up to 0.05Hz change.
is there a better way to read the low frequency using atmega32?
second, I am having trouble reading to signals' frequency at a time. any suggestions?

int main(void)
{
  while(1)
{
   zerocrossingA();
   freA = frecalculationA();
   _delay_ms(20);
   zerocrossingB();
   freB = frecalculationB();
}

}
 void zerocrossingA(void)
{
  while(1)
{
      if ((PINA&(1<<7)) ==0 )
      {
            TCNT1=0;
            TCCR1B=0x01;
            break;
      }
      else
     {
            continue;
     }
}
while(1)
{
    if ((PINA&(1<<7)) !=0 )
    {
        TCCR1B=0x00;
        g1=TCNT1;
        break;
    }
    else
    {
        continue;
    }
}
}
 void zerocrossingB(void)
 {
    while(1)
 {
    if ((PINC&(1<<0)) ==0 )
    {
        TCNT1=0;
        TCCR1B=0x01;
        break;
    }
    else
    {
        continue;
    }
    }
     while(1)
    {
       if ((PINC&(1<<0)) !=0 )
    {
        TCCR1B=0x00;
        g2=TCNT1;
        break;
     }
    else
    {
        continue;
    }
    }
    }

    double frecalculationA()
   {
     k1=1000000/(g1);
     w1=k1/2;
     return w1;
   }

   double frecalculationB()
   {
     k2=1000000/(g2+1);
     w2=k2/2;
     return w2;
   }


texts: Reference material for mains-interfacing circuit safety

texts:
I've designed a simple switch/timer circuit for the following environment:

Residential installation for North America (technically only for Canada)
Single-phase 120Vac
Current of switched output device not to exceed 10A, typically <1A
Power dissipation of circuit itself is negligible (<<1W)
Circuit's power supply is an enclosed class-II isolated unit and meets UL60950-1
Circuit detects mains voltage through an optoisolator rated to 5kV
Output relay is an enclosed class F-insulated unit
Essentially one-off installation, not mass market production

As an absolute beginner in the area of electrical safety standards, where on the internet should I go to seek information on:

Whether this is UL/CSA-certifiable, and how I would go about doing that
Which safety standards apply
Detailed technical information on applicable safety requirements

I've already checked what I think is the authoritative source, but it seems to be behind a paywall. The same goes for UL standards such as 60950.


texts: Using differential and single-ended inputs simultaneously in a data acquisition system

texts:
Below is the wiring setup I plan to use:

Basically the black rectangle in the middle is this data-acquisition board which has 16 diff ended inputs.

The blue rectangle on the left is a six-axis force transducer which has 6 low level differential ended outputs and an analog ground AGND.

The red rectangles represents single-ended transducers. Since the daq board is diff ended, I plan to daisy chain the grounds of the single-ended inputs to the AI GND as in my drawing.

I don't care about the noise level much for the single ended transducers, but for the force transducers I have to use differential ended outputs.

So basically I need to simultaneously scan and log both diff ended and single-ended inputs by this board. AI GND is not connected to the building earth.

So far I tried hooking up all diff ended inputs with one single-ended transducer and didn't get any peculiar results and especially diff ended data is very clean i.e very low noise level. I also noticed if I also connect the transducers shield to AI GND noise gets even less.

In real I have to input five more single-ended floating sources as shown in my diagram.

Is there any problem in this way of wiring scheme?

Edit:

I decided to use all channels with diff input for better noise immunity instead of wiring the signal grounds to AI GND.

To use differential ended for the floating single ended inputs on the right, I'm planning to use the following red circled scheme:

They recommend it for differential data acquisition for floating sources.

Basically I want to create a balanced system for the floating inputs.

My questions are:

To obtain a balanced system the source output impedance of the floating sources should be equal, transmission lines should be shielded twisted pair(instead of a coax cable). These transducers like this one are single ended and are not fully differential. If they were I would not worry about their balance.

1-) Lets say I made a good shielded twisted pair cable for each transducer with BNC connectors to the DAQ in question, but how about the effect of the source impedance of the floating sources to the system's balance? I mean if the floating source's output impedance is 100 Ohm should I add a series 100 Ohm to the ground terminal of it to balance the wires? Do you measure that in practice or is there a rule of thumb?

2 I encountered two schemes for the diff inputs for floating sources. One of them they tie between 10k to 100k resistors between "each" signal lines to AI GND of the DAQ's amplifier as you see in the red encircled config above And I also see they tie this resistor only between the floating signal's low level input(or signal gnd) and AI GND. If I use resistors between or each wire to AI GND it will load the circuit(between 20k to 200k), but if I use one resistor config. then the balance might be an issue. Which one would be better in my case where the signals are DC-like signals?

3 And finally if I use shielded twisted pair cables should the all shields be wired to AI GND of daq device?


texts:
Currently I have this UPS power setup for my Router with the help of a DPDT relay so that the router works when mains power supply fails. The working principle of my project is real simple. Two separate power supplies are connected to a DPDT relay where one the power supply powers the relay coil and a battery. When the mains power fails the relay coil is no longer powered and switches to the battery supply. I used a relay mainly because it provides full isolation between the 2 power supplies.
My concern is that in my current setup the relay coils are always powered on when the mains in available which according to Omron, might lead to a contact failure or coil burnout in the long run.

So is there any a way to replace my relay setup with a more reliable component? maybe a Mosfet or SCR? Will the coil really get damaged?
I'm attaching the diagram of my setup

Edit:
So I went through the below suggestions and decided to change my setup into this new one which might be better than my first one.
These are the changes that I've made.

I got rid of the 9V wall wart and now it's just a single 12V 2A wall
wart that powers everything.
Now uses a CC CV Buck converter with Li-ion charging feature to charge
batteries instead.
Added a 2 Series Battery Management Module with Cell balancer feature so
that I could now use 2x18650 cells for longer runtime and better voltage to
boost
Replaced the Boost converter with a Buck Boost converter.
Scrapped the Relay.

So, will my new setup work as intended? or is there any problem? or maybe place to improve?


texts: Not able to communicate with esp8266-12F using FTDI usb uart bridge

texts:
I designed a PCB based on MPU9250 IMU and ESP8266-12F and FT232RL uart-ttl bridge. You can see schematics for the usb to uart, and esp8266 circuits here.

When I researched about the uart part of the circuitry, I see numerous example mentioning FTDI USB modules and esp8266 bare chip programming. Therefore, I build my usb-uart circuit based on FTDI module and used FT232RL. However, I can not be able to program with using Arduino IDE NodeMCU flashing configurations. When I press reset button while holding gpio0 button I see following from serial port. I thought esp goes boot mode however I can not be able to communicate or upload the code. I want to ask what should I do in order to communicate with esp and upload firmware? I know I can not be able to provide enough information, however I am willing to share more if you ask.

This is what I get when I upload the code. It says "chosen serial port can not be found in attached board" and timed out when waiting for packet header


texts: Does current flow on an open transmission line?

texts:
Please take a moment to look at the diagram below:

The question is if the lightbulb will momentarily flash when the switch is closed. I think it will but I get the feeling I am wrong.

The reason why I think it will flash is because when the switch is closed, the transmission line wire electric potential should become the same as the electric potential found on the battery terminal and in order for that to happen, electrons will need to flow through the wire until electric potential balance is reached. As electrons flow through the wire, they will need to go through the light bulb filament causing the light to turn on.

By the way, I realize that the light bulb will not light up a room or that it will even light up at all, I am only using a light bulb here to illustrate my question and not mean to represent some sort of real life experiment.

Thanks.


texts: Confused with the time diagram and wiring for this SSI interface

texts:
I have an AEAT-6010/6012 10/12-bit magnetic absolute encoder and it has the following pin-outs:

Since it is SSI but not SPI I dont use the CSn output and leave it.

I supply 5V to the encoder and clock it between 60kHz up to 100kHz but I dont get any expected data at DO pin. When I observe DO by a scope it is just a very low level clock signal but not any data stream expected.

At one page it is mentioned that CSn is internal pull-up:

And unlike for a typical SSI this encoder also has a timing diagram for CSn:

When I measure CSn, it seems it is always 5V. Am I doing wrong by not using CSn here? Where and how should the CSn pin be connected? I'm really confused the interfacing of this pin and the function of it.


texts: So I have found the circuit for a band pass filter. I know its function and what it does, but I haven't understood yet why its components are placed were they are. Why are the capacitors and the resistors formed this way? and how their placement affects the form my voltage graph will have (square to sin graph)


texts: Exceeding Relay maximum switching frequency

texts:
I read in the datasheet of the DOLD OA5611 that the maximum relay cycles/s is 10 cycles/s.  Now I want to know what are the risks for the relay if I control it with a switching frequency more than 10 Hz. It's not specified in the datasheet what the conditions for the current and voltage for the maximum switching frequency are.

Otherwise i find in other relays datahseet that there is two values for the maximum operating frequency:
Mechanical max operating frequency which is 18000 operations/hour,
Electrical max operating frequency 1800 operations/hour @ rated load.
My questions:

What is the used maximum operating frequency to respect in the datasheet.
Can we exceed the Electrical max operating frequency if the relay is used with current and voltage less than the rated load.

From what I understood we can use the relay with frequency more than the Electrical max operating frequency if the used current and voltage are less than the rated load. But we cannot exceed the mechanical max operating frequency in any condition. am I right ?


texts:
I am trying to read data from a USB using CH376 module with PIC 18f4520 microcontroller.

The name of the file I am trying to read is "ABC.txt" and it contains "hello".

// Instructing module which file to read

SerialTransmit(0x57);
SerialTransmit(0xAB);
SerialTransmit(0x2f);
SerialTransmit(0x2f);
SerialTransmit('A');
SerialTransmit('B');
SerialTransmit('C');
SerialTransmit('.');
SerialTransmit('T');
SerialTransmit('X');
SerialTransmit('T');
SerialTransmit(0x00);

init_lcd();
lcd_string("fn");
function_int(RCREG);
DelayMS(1);

// Opening the File

SerialTransmit(0x57);
SerialTransmit(0xAB);
SerialTransmit(0x32);

init_lcd();
lcd_string("open");
function_int(RCREG);
DelayMS(2000);

if(RCREG!=0x14)
   {
    init_lcd();
    lcd_string("open not ok");
    while(1);
    }

 else
    {
        init_lcd();
        lcd_string("open ok");
        DelayMS(1);
     }
 i=0;

  // Setting to read 5 bytes

  SerialTransmit(0x57);
  SerialTransmit(0xAB);
  SerialTransmit(0x3A);
  SerialTransmit(0x05); // here
  SerialTransmit(0x00);

 i++;
 init_lcd();
 lcd_string("dl");
 function_int(RCREG);
 DelayMS(2);

 if(RCREG!=0x1D)
{
   init_lcd();
   lcd_string("dl not ok");
   while(1);
 }

 else
 {
    init_lcd();
    lcd_string("dl ok");
    DelayMS(1);
  }

// Reading

SerialTransmit(0x57);
SerialTransmit(0xAB);
SerialTransmit(0x27);

// It reads the first byte here, first byte is a waste byte i.e.
// it returns 0x05 (The number of bytes we want to read)

init_lcd();
lcd_string("0read");
function_int(RCREG);
DelayMS(3000);

// It reads the first byte here, i.e. H

init_lcd();
lcd_string("1read");
function_int(RCREG);
lcd_string("==");
lcd_data(RCREG);
DelayMS(3000);

// It is supposed to read 'E' here, but it still reads 'H'

init_lcd();
lcd_string("2read");
function_int(RCREG);
lcd_string("==");
lcd_data(RCREG);
DelayMS(3000);

// It is supposed to read 'L' here, but it still reads 'H'

init_lcd();
lcd_string("3read");
function_int(RCREG);
lcd_string("==");
lcd_data(RCREG);
DelayMS(3000);

while(1);

I am able to set up and instruct the module to open and start reading the file. But the problem is that I am stuck on the first byte. I cannot make it to read the second byte. How can I do so?

Thanks, I will really appreciate any help.


texts: U-Shaped Electromagnet Configuration for a motor?

texts:
I've been thinking about motor designs and where all the power goes for an electric motor, especially in terms of used/unused power. I noticed that in most motor designs, the neodymium magnets float either on the inside or outside of the motor as the rotor, with the opposite as either the AC or DC electromagnetic poles acting on the magnets.

However doesn't this waste potential force/power since the opposing magnetic fields aren't utilized? For example couldn't you take a U-shaped electromagnet and run a neodymium magnet through it's center so that all 4 poles of both magnets are utilized and potentially generating more force/torque?

Typical motor design with internal rotor:

Couldn't you run a flat neodymium magnet through this to utilize all 4 magnetic poles?

So you'd end up with a configuration like this, roughly speaking. This would be a design for an AC induction motor... Obviously you can add/remove poles/magnets as necessary, again, this is just an example.

The idea here is that by using a U-shaped electromagnet for your stator you condense the magnetic field, thus pushing more torque through the motor when the neodymium magnets on the rotor pass through the electromagnets.

Otherwise with conventional layouts the neodymium magnets on the rotor rotate on the outside edge of the electromagnets and it seems like you lose some of the magnetic force of the opposite that don't come in contact with the electromagnet.


texts: Vertical axis of the magnitude Bode plot

texts:
Why is the vertical axis in the magnitude Bode plot linear?
I am confused because i know that if we want to obtain the magnitude Bode plot of the frequency response, we take the decibel value of the magnitude of the frequency response, and since the decibel value is basically equal to multiplying the log value of the magnitude by 20, the vertical axis of the plot should be logarithmic. Where is my mistake?


texts: How to determine if TV is on by looking at yellow RCA monitor signal?

texts:
I have a U.S./NTSC LCD HDTV that has a yellow RCA monitor jack on the back.  Would it be possible to monitor this connector on an analog input of a microcontroller to determine when the TV is on or off?

Unfortunately, I don't have scope that will let me look at the signal from the RCA jack.  I think my microcontroller's analog port typically measures from 0 to 5V.  Would I need a scaling circuit, resistor, diode, or something other than just hooking a wire directly to the analog input?  (Yes, I'm fairly inexperienced on the hardware side, thanks!)

What danger do I pose to the TV?


texts:
I am making a KVM switch for a single USB port. I found a tutorial for this online, but I am concerned if there is any problem with hooking up VCC like this. Is that alright?

simulate this circuit – Schematic created using CircuitLab


texts:
I would like to be able to dynamically generate specific circuits for transfer to an FPGA. It seems I cannot amend the bit file directly. Can I generate the bit file from a schematic representation, something like transistor 1 -> transistor 2 -> transistor 3?

Background:
The goal is to hook up a genetic algorithm or other solution space explorer to an fpga, allowing it to explore different circuit configurations. The goal of this is to create a dynamical system exploiting non-linear properties on the fpga for use as a reservoir in a reservoir computing device.


texts:
I'm making a simple SMPS to create multiple isolated outputs to audio effects circuits.

I need to make a toroid pulse transformer which has one primary and
at least 10 secondaries.
These secondaries will be used in pairs to make 5 positive and negative outputs.

I've never wound my own transformer before so I have some basic questions :

Can I wind each 'pair' together. That is physically push two wires through the core together for each turn? Then use those pairs to create my positive and negative outputs? Will that have any effect on noise or galvanic isolation etc?
Can I safely wind my secondaries with thinner wire? The intention is that the primary will pass 3 amps, and each secondary will only be expected to supply 100mA or so. Is it safe to do that?
Will the transformer still work if the iron powder compound is not exactly right. So in an ideal world I'd be using a T130-3 (switching at 100KHz) But what if it's a T130-6 etc? Will it work, but just much less efficiently?
what would happen if I wound secondaries, on top of other secondaries? Would that work? So if I ran out of space on the toroid, could I just wind more secondaries on top of other ones? I appreciate that there'd be some difference in output voltage, but would those coils still work?
Sort of related to question 1. Would my negative secondary coils need to be wound in the opposite direction? And also, should my secondaries be wound in the same direction as the primary?

PS :

T130 core size : OD-1.3" ID-0.7" height:0.25" (roughly)
Type 3 iron powder (grey clear) : Carbonyl HP Permiability 35 80Khz-500Khz
Type 6 iron powder (white clear) : Carbonyl SF Permiability 8.5 (10Mhz up)