texts: RF microstrip track parameters calculation

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I am currently finishing the design of a board where there are two antenna microstrip on the surface of the top layer. I have a 4 layer PCB. I use FR4,so I suppose dielectric is 4.6. Thickness of the board is programmed to be 1.6mm, with the following stack

One is for GPS function and another one is for GSM function.

The manufacturer of the modules specify that control corresponding W and S of 50ohm coplanar waveguide. How do I calculate Track width  (W), separation to coplanar ground (S) ? I have saturn pcb software but I don't know if I can achieve this calculation with it ?

When answering, I would really appreciate if you can detailed by a simple 1-2-3 step process, how you process to perform the necessary calculation to determinate those parameters.


texts: Help on Schematic for ATMEGA64 and FT232RL

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I am relatively new to electronics and was trying to make a PCB with Atmega64 and FT232RL, similar to an Arduino. Pictures of my schematic are attached below. The wires in the top right of the FT232RL picture and the wires in the top left of the Atmega64 picture are connected (you can see the resistor and capacitor in both pictures). The power supply circuit is not included, but for your reference, it is exactly the same as the traditional Arduino power supply circuit. None of the I/O pins on the Atmega64 have been connected to anything yet- only the basic circuits for the crystal oscillator, overall microcontroller power, the UART bridge, and the reset button are completed. Mainly, I was wondering if my reset button circuit, connecting the FT232RL and Atmega64 was correct. If any other errors catch your eyes, please let me know.
Thanks so much for the help in advance


texts: Adjusting a fixed-voltage DC/DC converter's output

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I'm trying to get a 3.5V regulated DC rail from a 28V supply (...it's a weird voltage because the microcontroller's maximum frequency depends on its Vdd -- 4MHz at 2.7V or higher, and 8MHz at 3.5V or higher, and I'd like to run at 8MHz.)
I have a bunch of AP63203 chips laying around (datasheet: https://www.diodes.com/assets/Datasheets/AP63200-AP63201-AP63203-AP63205.pdf), which have a fixed 3.3V output.  Before I found out about the microcontroller's clock limitation, I was planning to use one directly.
But this chip has a feedback pin.  Normally this is connected directly to the Vout node (in between the inductor and the output capacitance):

simulate this circuit – Schematic created using CircuitLab
...and the VM1 voltmeter would be at 3.3V.  But I wonder.  If I connect it to a resistor divider, with the FB pin connected to the middle, shouldn't this drive the VM1 output to close to 3.5V?

simulate this circuit
I don't see anything in the datasheet that reads like the raised voltage on the SW or BST pin would be a problem.
One issue I do see is that the feedback voltage won't be quite 3.3V when Vout is 3.5V, because there's an internal voltage divider in the AP63203 to convert a 3.3V level at the FB pin to 800mV before comparing it to the internal 800mV reference voltage.  Depending on the input current on that pin, I'd need to modify the value of the 33k resistor, or get rid of it and simply connect a different-value series resistor between Vout and FB ... but I don't see any input current specified in the datasheet.  Does anyone else?  Could I derive it from other specifications?
My best bet might be to just get an AP63200 (...not a 63201, because the 63200 does PFM), or any other random high-frequency adjustable buck converter, and adjust its output to 3.5V.  But I'm trying to make what I have work, if possible.  (Plus the 63200 and 63201 only run at 500kHz, while the 63203 runs at 1.1MHz.  I like the better efficiency that the higher frequency gives.)
Is it feasible to adjust a normally fixed-output regulator like this?
Thank you!


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I'm using this preamp circuit for my electret microphone and then feeding the output to A0 analog pin of an arduino uno board. For some reason my serial monitor in the arduino ide shows the output at a constant 130 no matter how much sound I make in front of the microphone.

preamp circuit^

serial monitor^
This is the circuit I'm implementing.
https://www.instructables.com/How-to-Deal-with-Noisy-Neighbors/
my connections for the pre-amp part:- orange wire for output, connected to A0 pin of arduino uno. brown wire is the ground pin from uno, red wire is 5v pin from uno. electret mic green wire is +ve, white wire is -ve.
Thing is, I've implemented the same pre-amp circuit as the dude above, but for some reason the sound doesn't get picked up.
My preamp ckt below.


texts:
There are 3 types of dusters that I know of:

Microfibre
Electrostatic
Vehicular

AFAIK, the microfibre variant relies more on contact with dust than on electrostatic attraction, unlike the electrostatic variant. Still, I think there is plenty of potential for static buildup.
Which brings me to some of the exposed PCBs I have lying around, varying from a caseless desktop PC to various dev boards. What happens if you use a dust cleaner on them? On one hand, static is a known enemy of electronics. On the other hand, PCBs have lots of metallic contacts and traces, which might help dissipate any static before it builds to IC-destroying levels.
I have a strong suspicion someone already did some experimental research on this, but I can't find any.


texts: Eliminating power-on state changes caused by input signal fluctuations

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I have a circuit that uses several comparators to read an analog input signal and control some downstream digital logic. When the device powers up, the logic states fluctuate because the input signal takes time to stabilize. This behavior is undesirable for my application, so I want to eliminate the fluctuation. I've used power-on reset circuits to address startup transients in other projects, but I'm curious if there's a more appropriate method in this particular situation due to the behavior of the input line.

In the capture below, the sensor input signal is held at 0 V for about 7 ms when the power supply comes up. Because the discrete logic is very fast, it almost immediately outputs a logic HIGH due to the configuration of the comparators. Then, when the input stabilizes, the logic returns to a LOW state (which is what I want at power-on). I believe the 7 ms delay is due to a startup routine/delay within the sensor itself, as it occurs even when the sensor is disconnected from the rest of the circuit.

To solve this problem, I considered using a power-on reset generator to delay the downstream logic until the input stabilizes, but none of the chips I'm using have enable or reset pins, so the PoR would have to go on the main Vcc line. I'm not sure if that's good practice or not.

Alternatively, I could go with an analog switch or multiplexer on the input line to hold the logic in a known state, and then switch over to the sensor input after a set time delay using a simple RC circuit on the switch/mux control line.

Or, for an active solution, I could combine the switch/mux with a window comparator that latches when the input signal stabilizes to its nominal value (around 2.5 V) to ensure the logic waits until the input is at a known value. In my application, the sensor is mechanical and should always default to 2.5 V at power-on unless there's some other fault, so the window comparator would be an additional safety/interlock feature, but it's not absolutely necessary... just an interesting idea.

Is a PoR or input switch more appropriate in this situation? Or, is there another solution altogether that I'm not considering?

EDIT: As requested, here is a slightly simplified version of the comparator and logic schematic. (Excuse the unused inputs on the gates, but it was easiest for me to throw this together in LTspice, which uses one-size-fits-all gate symbols.)


texts: Changing to relocatable code for PIC microcontrollers

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I've come back to PIC programming after 10 years and I've been relearning everything. I'm looking at the section in the MPASM manual where it discusses relocatable code. And I've come to the conclusion that I'm puzzled to why absolute code is used at all?

Take this case:

        processor pic16f88
        #include p16f88.inc

.data1  udata      0x20
var1    res        1
var2    res        1

.reset  code 0
        pagesel    Init
        goto       Init

        code
Init:
        ....

        end

For all intents and purposes, isn't that absolute code?

So, from what I can see you can change the udata line and remove the 0x20. Then the linker will place it where it wants to. But you can override that in the linker script and specify an exact position:

section name=.data1 ram=gpr0

I'm mentioning this on stackexchange because it's rarely mentioned and it's the only reason one would ever use absolute code over relocatable (again, in my humble opinion).

While typing this, Stackexchange suggested this link which is a superb response and one of the few places I've seen the linker mentioned.

I do have a few questions though:

Can I use a dot to lead a section name? Like ".reset" above. I've seen it used but I'm not sure of its validity. In my mind its a way of keeping labels (Initial caps) and variable names (all lower) and section names (start with dot) in seperate "namespaces".
I'm puzzled as to the idata directive. If the data is initialised, who does so? Is there a code block I have to call to set initial data. I'd love to use this instead of setting initial data in an init section.
I want to use a large block of data for a buffer. I'm using a PIC16F1829 so I can use the FSR in a flat memory mode to point cleanly across banks. My issue is - how do I tell the assembler and the linker that I'm using, say, banks 3 and 4 for this purpose. If I use the keyword "protected" in the linker, do I have do use udata in the assembler? Or can I just pick some memory, put it in FSR and start writing?

And: Why on earth do books and tutorials (Gooligum excepted) insist on using absolute and why do lecturers keep using it? It does seems totally bizarre to promote absolute over relocatable long past its due date.

I realise this is opinion and might not be within Stackexchange's guidelines either but it's terribly important to know that relocatable code exists!


texts: Symbol vs. Word (Digital Communication Theory)

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So I'm trying to understand and link up the different chapters I've studied in a communications module. So here goes

I understand a Pulse Code Modulation System is made up of the following broad blocks

Analog Source goes to
Antialiasing Filter
Sampler
Quantizer
Binary Word Assignment
Line Coding
Sent through channel

Now I understand that in the Line Coding part, a pulse shaping filter is used. My confusion is that we usually refer to a small segment of bits as a symbol when dealing with the line coding part, but then what's the point of the word assignment (block 5).

What's the difference between a word and a symbol?


texts: How do I verify if a conductive mat is getting "Earthed"

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Explaining to me about electricity is like explaining to your Grand-Ma about it. So please be kind and gentle :)

I bought an Earthing Mat from "http://www.amazon.com/dp/B003RLOBOK". It includes a conductive mat to which I connect a white-wire whose other end goes into an earthing point on my wall. As long as a person's body is in contact with the mat, he is getting earthed.

But how do I verify/measure if the conductive mat is getting earthed correctly? (in effect I am getting earthed correctly).

I called up an electrician over to my house who demonstrated and verified that the white-wire (connected to mat) is getting earthed. After inserting one end of the white wire into the earthed socket, he touched one wire of a bulb (with 2 loose wires) to the other end of white-wire. The bulb lit up and he said that white wire is getting earthed.

But he didn't know how to verify the conductive mat. All he said that this looks like rubber and should not work.

I come with an almost zero electrical knowledge. So how can a novice like me verify if the conductive mat is working as it should.


texts: Driving an AC motor using transistor as a switch

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It's pretty straightforward to use transistor as a switch while working with DC voltage. But I am faced with a situation to switch on/off an AC motor (single phase).

Is it absolutely necessary to use a TRIAC or SSR? A stupid question maybe, but what would happen if I were to just make use of a BJT? Would it burn out?

I am trying to build an Arduino project which uses a DC motor following the steps in this Instructables article, but happen to have several AC motors lying around without any use.


texts:
I am not familiar with circuit analysis, although I can manage to solve basic circuit. However, I am currently stuck with a problem and I am not sure about the solutions.

If anyone could have a look at my  solutions I would highly appreciate it.

By using circuit logic I assumed D1 to be OFF and D2 ON. From there, we KVL and current division rules to find the total current I:

10.7 - I*R1 - 0.7 - 0.25I*R2 - I*R3 = 0 and derive I = 1.08 mA

From here we have the following:

V1 = 10.7 - R1*I = 4.22V
V2 = V1 - 0.7 = 3.52V
V3 = V2 - 0.25I*3 = 2.71V
V4 = V2 -0.75I*1 = 2.71V

We note that V1 > V4 therefore D1 is indeed reverse biased.

For some reason I am not sure about these results, this is my first problem of the sort.

Here is the problem:


texts: How is implementing FOC on SVPWM switching algorithm?

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I have that running SVPWM algortihm with no error. I tried to implement FOC algorithm that switching metod. But I failed. I measure phase currents (Ia , Ib , Ic) when low side switching time. And calculating
Iα=Ia  , Iβ=(1/√3)*(2Ib+Ia) clarke transformation and then Id=Iαcos(θ)+Iβsin(θ) , Iq=Iβcos(θ)−Iαsin(θ) calculating park transformation. This θ value is electrical angle that I got it from hall sensor information between 0 to 360 degree? Or am I wrong ? I set reference Iq and Id value . Then I used pid regulator. I used Vα=Vdcos(θ)−Vqsin(θ) , Vβ=Vqcos(θ)+Vdsin(θ) inverse park transformation . I think this θ value same with first park transformation θ value. Is there any wrong thing my progress ? Or it can be problem using Vα , Vβ in SVPWM algorithm?


texts: How do I find the mode of operation of a BJT circuit without a value for Beta? Is there some trick to this question?

texts: I tried finding the Thevenin equivalent of the input loop by using voltage divider to find Vb and Rb. And using Kirchoff's Voltage law on the input loop. But I'm stuck because there is no value for Beta. I also tried using simultaneous equations to work out if I could find the values for Ib and Beta but to no avail. I did assume the model to be active mode, I got stuck. Then I assumed it to be saturation mode and i still got stuck. Please help


texts:
My water heater element is rated at 3.6kW at 240V. To use solar power efficiently, I would like to use excess solar power (in a grid-tied arrangement) to heat our domestic hot water. Our electricity supplier only pays a pittance for exported power but still charges the full rate on any imported power, so the trick is to control the current to the hot water system (HWS) so that most excess solar power is consumed internally.
Would a heavy duty phase controlled triac be suitable? Would the large current switches cause problems? I do not know how the metering works, so this per-cycle method may not even register as a smaller average current. Ideally, the load should look like a varying resistance.
Would an approach like a switching power supply make sense? ie rectify the AC, then chop the current at high frequency, while protecting the supply side with large filters? I suspect this approach would cause EM noise unless carefully designed.
Are there better ways of controlling HWS power?
Motivation
The inverter connects on my side of the meter, but import and export are measured separately. I am trying to minimise the bill to the electricity company. To do that I need to use as much of the solar generated power internally, while being careful not to import power during a sunny day. Eg: when solar power in = 4kW, internal loads = 2kW, I want the HWS to draw 2kW. If I export power I get 7 cents per kWh. If I import power I pay 20 cents per kWh. The feasibility of the installation hinges on whether I can vary the load to match the generation.


texts: General Questions about PIC24 MCU Input and Output Pin Impedance, Voltage, and Current

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I'm having a mental lapse. Try and help me make sense of a few basic things concerning  microcontroller pins at the hardware level, please!

Correct me if I'm wrong… in the circuit of Figure 1 (see attached image), TRIGGER leads to a GPIO pin of a PIC24F configured as an input. When the MOSFET (P) channel is closed, TRIGGER (i.e., the MCU input pin) will be +3.3 V. However, when the MOSFET (P) channel is open, the MCU input pin attached to TRIGGER will be floating because the opposite end of the resistor is essentially disconnected, correct? If this is not the case, why?
Does a GPIO pin of a PIC24F configured as an input require a series current-limiting resistor as to not potentially destroy the pin from a given input? In other words, is one needed to make sure the impedance of the input signal is at a known value so as to know the current going into the pin?
That said, what if you were to connect an input pin directly to a +3.3V voltage source with no series resistor? No blown pin, right? The pin would only draw as much current as allowed by the input impedance (I think), which leads me to ask, what is the input impedance of an input pin? The PIC24F can sink and source 18mA of current. What I'm trying to ask is, what's the purpose of a series current limiting resistor to an input pin if the pin already has impedance and will only draw up to 18mA? It's not like the +3.3V will be conducted directly to ground through the MCU (because the pin has impedance), right? Maybe I have this all wrong...
Output pin question: I understand the purpose of a series current limiting resistor used for limiting current through an LED, as it could otherwise essentially become  a +V to ground short (high current through the LED causing it to overheat and break). But if an output pin already has some internal impedance which would limit current anyways, why is an additional resistor in series the standard thing to do? The pin can only source up to 18 mA - I assume this is governed by the pin's internal impedance. How would the pin be capable of sourcing any more current? Obviously I'm missing something…
Correct me if I'm wrong again… in the circuit of Figure 2, when the MOSFET (P) channel is open, TRIGGER is pulled low through the two resistors in series. When the MOSFET (P) channel is closed, TRIGGER will see +3.3V. No floating going on, right? Also, is the series resistor in-line with TRIGGER (1 kOhm) necessary? Or can I connect TRIGGER directly to the drain before the pull-down resistor (essentially directly to +3.3V)? This ties in with my previous question about series resistors with input pins...

These simple, basic questions have been gnawing at me for a while.


texts:
I feel like I have gone down a rabbit hole and came out knowing nothing. I understand this is a really basic question. My son and I are building a simple RC. It is using 4 1.5v (AAA) batteries in series. So if what I have gathered is correct that is 6v. What I cannot seem to figure out is what size wire should I get. I honestly thought this would be in the spec of the wire. Maybe I am not seeing it. I need a pretty good length and want to make sure before I go off and buy this.

I know there has to be a formula for this but what I am googling is not turning it up.


texts:
I'm trying to build a flyback circuit to charge a 1uF cap to ~300, but am having a lot of issues.  I'm just following the data sheet diagram for a 300V 3A charger (see pic below).
I've never been able to get an output voltage of more than ~150V.  And after moving things around, output voltage will usually be ~8V.  The layout I followed is a combination of the data sheet recommendation and conversation with LT tech support.  Components pretty much follow the diagram below.
I've attached a picture of my very unprofessional circuit to see if maybe someone could point out a glaring problem I don't see.  Other LT3750 circuits I've seen online are usually on actual circuit boards, but I'm not quite sure how to go about getting that done.  Maybe someone could advise?
It's quite frustrating to fail at making a proven design work.  Any help would be greatly appreciated.


texts: How to apply Thevenin's Theorem to this circuit?

texts:
I have been trying to solve this question with either Thevenin's Theorem or Norton's Theorem but I got stuck at finding the Vth .

Load Resistor is 5Ohm resistor in the middle .

I have removed the load and circuit became :

I calculated Rth as =(3+1+3+1)//4//4 = 1.6Ω

Simplifying the circuit :

Now I need to find the Voltage between points Req . But I don't know how to .

Thanks


texts:
http://physics.bu.edu/~duffy/PY106/ACcircuits.html

The voltage across inductor is V=IXL but from the graph this doesn't seem to be true so what does it show ? Same for Capacitors


texts: How to connect a capacitor (high pass 1st order) to a tweeter in series with a full-range speaker?

texts:
I've hit a bit of a snag with my stereo project.

I have a 2-channel amplifier from eBay, and I've been using it with 4 ohm speakers, one on each channel.

Now I planned to upgrade it with tweeters. I got a 3.9uF capacitor for my tweeters, thinking of connecting it in parallel. I got a set of tweeters of 8 ohms each.

I realized something.

Connecting my 4 ohm speaker and 8ohm tweeter (tweeter in series with a capacitor) in parallel, results in a net resistance of 2.67 Ohms and will cause a problem for my amplifier.

simulate this circuit – Schematic created using CircuitLab

It seems putting these two speakers in series will be better as it will give a net impedance of 12 ohms. But where/how can I connect the capacitor (as a high-pass filter) for my tweeter?

Any other way I could proceed with this?

I saw a method to do it in series:

But I do NOT have a low pass filter (I assume an inductor.) It would be better, because I don't have the time to procure other components :(


texts: Power Source Switching (my first circuit) -- will I blow anything up?

texts:
This is my first post and first attempt at electronics and schematics so please go easy!
GOAL: power 1A @ 12v Netgear ethernet switch (in a remote location) from any (or all) of three power supplies, and to failover between them. There is no special requirements other than to keep the switch powered up. Other devices at the location already failover between the three power supplies.  I am trying to rig up the Netgear for redundancy as well.  There is no particular concern about which supply is used... just want continuous operation.
LOGIC: I am trying to come up with a better plan than two DPDT relays stacked. OR-ing would probably be even better but makes me nervous.  So I have designed the circuit below using P-MOSFETS thinking it might be a tiny bit safer to try to keep supplies somewhat isolated. (Is this a bit like being somewhat pregnant?)  Using IRF9540 p-channel MOSFETS circuit is intended to failover from lower to higher numbered supplies.  For example, when Supply1 is active it pulls up M2/M3 gates for Supply2 and Supply3 to disable them.  So only Supply1 will flow. And then Supply2 if enabled similarly disables Supply3.  I thought the logic of P-MOSFETS was most suitable because it hopefully will be simple to use +12v signal from one supply to gates of MOSFETS controlling the others will disable their current flow.
COMPONENTS: Any specific components mentioned are because they are already on hand. Open to other suggestions if any of these are inappropriate.  Working from starter kits of components from Amazon. Parts on hand:
MOSFETS, Component Starter Kit, Shottkey Diodes, and these pre-made MOSFET trigger boards.
DISCUSSION: All of this is because I'm too terrified to try straight OR-ing (does that simply require Schottky diodes on the positive before paralleling them?)  I don't know if I need the flyback diode (or even if I did that correctly) or many other things but just trying to be cautious. I am hoping this switching will "break before make" or that diodes will prevent any "bad things" from happening with switching.
TESTING: This seems to work as desired on the breadboard but I have not yet attempted with 3 independent power supplies.  I will fuse the power supplies just before input into my circuit. I plan to tie all the negatives together and I think they already share a common ground.
OTHER ALTERNATIVES: (1) OR-ing the 3 supplies together with a Schottky diode on each positive. (2) stack DPDT relays that would remain energized most of the time. If power fails on a supply, that de-energizes coils and fails over to remaining supplies. This seems to offer best isolation and switching time is not a problem.
Thanks in advance for your advice and comments.
FURTHER READING:

How to protect circuits from reversed voltage polarity (YouTube)
Fundamentals of power system ORing (EDN)


texts: I am working with a TI PCM1807 ADC (datasheet: https://www.ti.com/lit/ds/symlink/pcm1807.pdf) and try do some signal processing on a FPGA. The PCM1807 output is I2S. I was wondering how to interpret this output. The datasheet says "2s complement". What does this exactly tell me? Has the sample to be treated as an integer or is there something more behind it like a special Q-number (https://en.wikipedia.org/wiki/Fixed-point_arithmetic#Notation) format?


texts:
Datasheet

Application Note

I'm working with the atmel m90e26 IC. Its energy is numerically pulse_based, but I do not know what the relationship between energy and pulse is in this IC. There's a  parameter named MC=3200 imp/kWh in the application note I attached it with the datasheet. Maybe this parameter is related to my problem.

What the relationship between energy and pulse is in this IC?


texts: Controlling a motorized ball valve and appliance with a float switch(es)

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I am trying to create some redundancies for a small commercial ice maker to prevent there from ever being a flood in my garage. The ice melts from the ice bin (which holds around 80lbs of ice) constantly and gravity drains from 3/4" PVC into a condensate pump a few inches away…  If/when the condensate pump fails, I plan to have a float switch open, breaking the connection at the DPDT relay and turn off the ice maker (to prevent more ice than what is already in the bin from being created) as well as close the newly installed inline motorized Taco zone/ball valve.  Any melting ice will then stay in the ice machine with the valve closed.   The Taco valve would also close in a power outage (being that the valve is N/C) so that the ice did not end up melting and draining with no power to run the condensate pump.
Planned install: The c & w/y terminals on the Taco valve would be wired directly to a 24V transformer.  The two end switch terminals on the Taco valve would be wired to one of the common and one of the normally open terminals on a DPDT Relay (which is controlled by a 24V normally closed float switch).  When the float switch activates (opens), the Taco valve would close. In the event of a power failure the Taco valve would close.  See crappy diagram I made below.
So I think I have that all correct, but was wondering if I should try to build in a 2nd float switch to prevent any chatter at the motorized ball valve and not sure if there would be negative consequences if the ice machine ever received 'flickering' power?    I think the situation I would need to worry about the most is an extended power failure that turns the ice in the bin to water...  When the power comes on, I fear the condensate pump would have trouble keeping up with a mass flow of water (although it is a 270GPH pump with 1G tank).  My assumption is there would be several 'trips' of the float switch as the pump worked to remove all the water.   My thought was installing low and high float switches on the condensate pump.  The ball valve would close and ice machine turn off when both switches were open and the ball valve would open and ice machine turn on when both switches were closed.  Not sure how that would be wired though???
My other thought, and this may actually be a better solution is to just use one float switch, but if the float switch ever opens it would essentially 'trip' the circuit (closing the ball valve and turning off the ice machine) and require a manual reset. This really seems ideal to me as someone would have to be present to inspect why the float switch was triggered...  I have absolutely no idea on how to best implement this (with my limited electrical expertise). I've seen latching relays mentioned from Google searches, but I am unfamiliar and not even sure if that would be the best approach.  Any ideas on how to accomplish this would be very helpful!!!
EDIT:
Normal state - Ice machine powered, NC motorized ball valve powered.
High float state - Ice machine no power, NC motorized ball valve no power.
Notes - Store the high float state if triggered.  After high float state is triggered, require a manual reset before the ice machine and motorized ball valve receive power again.
FYI: Ice machine pulls around 5-6amps at 120V.  Ball valve does around max .5 amps at 24V. Planning on also using the 24V transformer for relay(s).


texts: does my microwave oven have acceptable leakage?

texts:
I remembered that a microwave oven works on 2.4 GHz which is same as wifi frequency
so I did a test for the leakage for my microwave oven, I put the oven's door in front of 2.4 GHz wifi router(line of sight)  with a distance of 1.5 meters
I used wifi analyzer(android app), it gives -40 dBm when the door open and -60 to -65 when it's closed. I repeated the experiment many times and get the same result, the signal decreased by 20 to 25 dBm, which mean if oven work on 1000 watt it will be like a wifi antenna of 10 watts.
so is my oven have acceptable leakage?


texts: Limitations of Noise temperature of Antenna, Feeder cable and LNA

texts:
Read in a study guide: 'Since the noise temperature of the antenna and the feeder could not be reduced below a limit, noise temperature of LNA is kept as low as possible.'
I am trying to look for a definite answer why the antenna noise temperature and feeder noise temperature have limitations in their reductions? I have read that antenna elevation angle is a factor for antenna noise temperature with inverse proportionality. So can it be said as a reason, that as antenna elevation angle of earth stations are fixed w.r.t satellite's position in space its noise temperature can't be reduced a certain value?
So my questions are:

1) Why can't the noise temperature of antenna and feeder cable be reduced a certain limit or in other words its limitations?

2) Does that mean LNA's noise temperature can be reduced by some technique. Its certain even then a limit is there. What are its limitations?


texts:
To practise designing schematics (and possibly making it too), I have designed a simple AVR based blinker assuming it is already preprogrammed. The schematic is here:

I've seen many Atmega/arduino like schematics all quite different, some place the decoupling capacitor separately (as I have tried to see how it looked), brought the crystal down as I have to easier define the capacitors or even separate it in to nets all together.

The batteries here in this case are battery holders and have their own defined pcb size.

My main question would be: What would my schematic look like to a professional in the field? Ignoring maybe subtle things (PE is not GND? however is the only symbol that looks gndish) does it look like a schematic that is publishable?

I have considered putting the decoupling cap right of the battery holders, although was not sure whether to take away from that (4 columns of components!) or just add it in since it is very simple. What is your critique?

Update

I have completed the power supply, and cleaned up much of the text and connections (it is likely a thumbnail, you can view the image directly for larger.)

I believe I have fixed some simple things such as the pullup resistor.

I am unsure if the text should be anywhere specific (I had put it in the "info" layer as to not be green and made it in an appropriate place) and I believe labelling the power supply is all that is needed, as the mainboard is obvious.

I may need to try setting nets so the power supply is connected to the +5V rail, It may be already however there are quite a few ERC/DRC errors in the PCB view so I will look at that next.

I found as well I can export it as a monochrome image, and it removes all of the position indicators/grid and other noise. I am quite satisfied.

Is there anything that sticks out?


texts: MOSFET Ltspice determine some parameters

texts:
I am working on project for flyback converter using Ltspice.
Indeed, I have to insert the parameters for MOSFET inside the model but I have faced some difficulties to get the values from datasheet for these parameters:

Rd         Drain ohmic resistance.
Rs         Source ohmic resistance.
Is          Parasitic diode saturation current
Rb         Body diode resistance.

Kindly, please can you tell me how to get the values for those parameters from Datasheet. the component I work on it is STW11NM80.

I would appreciate your interest and your help.

Looking forward hearing from your side
Best regards


texts: Understanding Test Parameters on Datasheet (CL pF)

texts:
On Page 7 of the datasheet for M74HC590
It uses a CL (pF)
At the bottom of Page 8 is the test circuit which shows where the CL(pF) goes, in regards to a circuit diagram, but I don't understand that circuit diagram.  Is the D.U.T. the chip they are testing?
For context what I'd like to do when I get these chips is put 4 of them in series to count the amount of time it takes sound to go from one ultrasonic transducer to another with as high of accuracy as I can.
So I can calculate the speed of air traveling through a pipe so I can know the volume of air traveling through it, In the volume of 1-200 Liter per minute hopefully with a resolution greater than .1 LPM through a 1" PVC pipe.
I could probably go smaller but I am limited by the blower blowing the air to have at least 2 Kpa with a minimum of 200 LPM and I don't have any information on how the flow will drop as the pressure increases. So I'm worried if I go too small on the pipe I'll get to much of a pressure drop before I get to the outlet where I need that much pressure.
240 LPM @ 32k RPM 4.5A 0 Pressure vs At Zero flow 5Kpa of pressure 1.6A 36k RPM Is the blower output
Side Question


texts: Microcontroller Power Supplies and Power Sequencing

texts:
I am using this MCP5606S Microcontroller in my design. However, I am finding it difficult to understand its power Supplies. Then, I went to the Manufacturer website and downloaded the MPC5606S Reference Manual for better understanding of the Power Supplies. Unfortunately, I am not able to get clarity. In the Reference Manual, Chapter 40, Page No. 1227, they are talking about Power Supplies. Can someone explain me in simpler terms about the internal power or regulators that they mention inside the MCU. Like how to power them and which one should I power first. I am trying to design the power sequencing. So, if anyone can provide clarity, I would be really grateful.

Thanks.


texts: solar panels connected in series and parallel

texts:
Can I get 500 kW from solar panels using series and parallel operation?

If I connect 18 panels each of 250 watts 24 volts in series to get 415 volt direct current and 116 panels in parallel to get 1205 amperes, then combine it into series and parallel. Can i get 500000 watts from it ?
Since,
Power= Voltage*Current
(excluding all losses)
=> Power= 415*1205
=> Power= 518750 watts.

And after converting direct current to alternating current will there be a power change?

Since in electrical the above equation \$P=VI\$ is possible mathematically, is it also possible practically?


texts: state equation from given signal flow graph

texts:
I was solving a question in which I have to write state equations  from  given signal flow graph ,but I wanted to clear some basic doubts regarding general problem like this
I thought it can we solve by two methods
1.by converting given SFG into transfer function using Mason's rule and then converting transfer function into State equation

Write state equation directly (by observation) from given SFG

So my question
Is second method works always or it is unreliable in complex systems and we have to stick with 1st method although sometimes it is lengthy?
Or
there are some methods (other than method 1  that I mentioned) by  which we can directly Write state equations even for complex SFG?


texts: Nomenclature: How to describe this switch

texts:
I'm looking for a particular type of switch, however I don't know what it is called.

The switch I'm looking for is actually a bank of switches. When one of the switches is pressed, the others are depressed, such that the circuit is always closed, but each circuit changes the input source. It is the type in this product.

What is this switch called?


texts: I have a 4-20mA output. I need to turn an LED on when let's say 20mA is reached. I can obviously do this easily with a plc or an Arduino, but I need to do it as cheaply as possible. Is there a simpler way to do this? Can I achieve this with a BJT?


texts: Fluctuating ADC reading for 4-20mA pressure transducer input

texts:
I am working on a project of water pressure measurement, in which I used a pressure transducer which gives me output between 4-20mA current form.
I am using a 250 ohm resistor to convert current into voltage, and then I give this voltage to ADC of an Arduino Uno channel 0 (A0).
The ADC reading is continuously fluctuating up to 10 decimal numbers (ADC value varies + - 5 counts.)
I have also checked by connecting a multi-meter and measuring the sensor current reading for a particular pressure. The current reading is stable (does not even fluctuate 1 or 2 points.)
Also I have checked voltage value after 250 ohms +Ve and ground. The coonverted voltage is also showing very stable.
Why is the ADC reading fluctuating?
I am using an Arduino Uno, it doesn't have any changes in AREF, AVCC etc.
Please suggest effective solution.
My code is as follow..

const int analogInPin = A0;  // Analog input pin that the potentiometer is attached to

int sensorValue = 0;        // value read from the pot

void setup()
{
  // initialize serial communications at 9600 bps:
  Serial.begin(9600);
}

void loop()
{

  // read the analog in value:
  sensorValue = analogRead(analogInPin);

  // print the results to the Serial Monitor:
  Serial.print("Reading: ");
  Serial.println(sensorValue);

  delay(1000);
}


texts:
How can I drive this screen?

It's a 1920x1200 display from an old Dell Inspiron 6000 which is now dead, but the screen is great and I want to use it in a project. Is that a standard (either physical or electrical) plug, and does anything drive it? (either some kind of adapter from hdmi/dvi/vga, or directly from a newer laptop)

Any pointers would be appreciated.

Full resolution image


texts: Can I get the chip or electronic kit of a USB keyboard alone whithout the plastic case?

texts:
first of all, understand that I have a very basic knowledge of electronics.
I have a Commodore 64 case and I want to turn it into a USB keyboard.
My approach would be taking a keyboard appart and getting its internal electronics and soldering its pins to a custom made PCB.
But the problem is that all the keyboards I remember taking appart have chips which are connected to the membrane directly and there's no pins available to solder at least not by the hand soldering tool I have.
Is there any electronic kit to make this, or a keyboard chip alone?


texts:
I purchased a few fuses to get familiar with their workings, and I was surprised to see that the 100mA fast-blowing fuses I bought happily conducted up to 215mA (6V power supply, 10\$\Omega\$ resistor), where the filament just started glowing. I could reproduce this with a second fuse.

Am I gravely misunderstanding something here, or is this an issue with the fuses? They are Bel Fuse Inc. 5SF 100-R parts.


texts: Currents injected in the grid, connecting a wind turbine

texts:
I'm studying the connection to the grid of a wind turbine through a three-phase inverter.

Now I understand that , in normal operating conditions, in the connection to the grid, the reference for id component of the current (considering the Park transformation) injected in the grid should be set by the active power controller (the DC voltage controller), while the iq component should be zero. Therefore we guarantee unitary power factor, and zero reactive power.

Now my doubts come when we are considering abnormal conditions. I read that to guarantee fault ride through we should now have the reference value of id set to zero and the value of iq now different than zero and set by the grid current controller. Is this correct? Why should we zero the active power? To stop injecting active power in the grid? But why managing the reactive power, how will that help to reestablish normal conditions again?

TL; DR: I don't understand the role reactive power has to manage abnormal condition in the connection to the grid and why set the active power to zero.

EDIT: I've read this in the book "Grid Converters for Photovoltaic and Wind Power Systems" by Remus Teodorescu


texts: Finding depletion region without built in potential

texts:
I am trying to solve a problem as to find the depletion region's width of a p+-n-n diode. I am given the width of the first n region and the doping of both n regions.

Here is the problem:

I believe that I have to use some boundary conditions of the electric field to find out what it must be and then integrate the result to find the built in potential, but I am not sure how exactly to go about this.


texts: Why is a laptop power supply output voltage different from its battery?

texts:
I hope you will not mind answering. This question has long been on my mind.

Normally, the adapter output voltage is higher than that of the battery. In my laptop's case, the output voltage of the adapter (or charger or power supply) is 19.2V. (That .2V itself is also a big question for me. Is that so sensitive?) But the voltage of the battery is 10.8V.

My question is, why is the adapter output voltage different from the battery's voltage?

This is not about asking how it is regulated by the internal circuitry, but asking why.


texts: IC buffer like 4066 with 8 or 16 switches

texts: I have a computer and two monitors. I want to build a device so that I can switch between to monitors. I would use buffers (like 4066) and a microcontroller. Is there any buffer like 4066 with 16 or 8 switches? Because 4066 has only 4 switches and I have to use 4 buffers for each monitor.


texts:
Sorry it may seem stupid but I think my confusion is drifting me away from the solution so I wanted to ask.

I am trying to build a fixed RFID reader. But the project has some other complex work to be done, so I am using a mini PC as the main hub.

I need to connect an RFID reader through a port on the PC (there are RS232, Ethernet and USB) I am trying to select the cheapest solution for the reader module I have found. This is the RFID reader module I want to use but the thing is I am confused with the Fixed RFID readers with this module/the development kit and the RFID reader module.

Datasheet says there is a serial port on the module I have linked. If I just, say, connect this serial pins directly to RS-232 and use the API (which is compatible with the OS) will that be enough?


texts:
I am trying to put together a ray gun wrist gauntlet for my son's Buzz Lightyear Halloween costume. I think am going to do a little circuit with a big red LED and a 555 timer to make it flash (maybe a potentiometer to change the rate).

Is there a simple way to add a "ray gun"-like sound?  I'm not real picky about the type of sound as long as it's vaguely ray gun-ish.  Would a simple buzzer (with or without the on/off of the timer output) work?  Is there something better?


texts: How can I make the state diagram from the code in Verilog?

texts: How do I draw the state diagram of this state machine?


texts: Why connect the gate of a MOSFET to ground?

texts:
I was looking through the schematic for the Teensy 4.0, and I found that a transistor that sends power to the microcontroller for operating the usb connector has its gate connected to ground. This seems to make the transistor act as a diode, but I am confused as to why a diode wasn't used in this case.

Is there a reason a transistor was used instead of a diode?

Below are the links to the schematic/relevant parts and an image of the portion of the schematic I am talking about:

Schematic
Transistor datasheet
Microcontroller datasheet


texts: So when electrons leave the negative side of the battery and the voltage get lost across the resistors in the circuit ..how do the electrons lose their energy ? How do the electrons carry that energy that produces the electricity then they LOSE it in the resistor ?


texts: What does centertap transformer mean 26.4V 10A

texts:
I'm searching for a transformer for my battery charger unit EBL 264-3. Because the manufacturer SCHAUDT doesnt want to provide the informations regarding the elements in their units I have contacted a guy that repairs the units. He said that the transformer has 26.4V 10A on the secondary coil (centertap). Does this mean 13.2V - 0 - 13.2V ?

26.4V is a little bit off if I look at the schematics

Thank you

This is the charger EBL 264-3


texts: Op amp Adder circuit and positive voltages

texts:
Reading questions on converting negative voltages to positive ones it has left me with a question that I can't seem to work out. The circuit looks like this:

But you only have the one going to the inverting input.  My question is:

  When inputting a positive voltage it doesn't change/very slightly change. So do you have to implement something else for when the voltage is positive?

EDIT:
Image borrowed from Kortuk's answer here

                                R
                               ___
                       .------|___|----.
                       |               |
                       |               |
                       |               |
                       |        VCC    |
                       |         +     |
          R            |         |     |
         ___           |       |\|     |
 Input -|___|----------o-------|-\     |   Output
                               |  >----o----
                        .------|+/
                        |      |/|
                        |        |
                       ===      ===
                       GND      GND


texts:
I have a device that broadcasts BLE advertisments, I am trying to measure the RSSI level of the broadcasts on another device (I am trying to do indoor triangulation for location estimation)
When I measure the RSSI over time (when both devices are static and there is no movement inside the room over time) I can see that the RSSI varies over time

But when I measure the RSSI over time using another device, I can see that the RSSI is quite static

The room is the same, the location of the devices is quite random so I guess that this difference is not due to certain location of any of the devices,

Why is one device more stable than the other? what can affect the signal stability over time? (the caster and the environment are the same in both cases)

thanks


texts: Output of LM35 temperature sensor > 3.3 V?

texts:
According to the datasheet the maximum rating of the output of an LM35 is 6 V.

However, the output should give 10 mV/C and it supports upto 150 C, which results in 10 mV/C * 150 C = 1500 mV which is 1.5 V. In what cases it will deliver more than 1.5 V?

Update

I initially added a statement that the output should not be connected to a 3.3 V ADC. However, it seems this is not the case, still my question stays, how can the output be 6 V?

Excerpt from LM35 datasheet:


texts:
We use a buck converter to drive a resistive load with varying voltage/power. Now we detected a problem with load disconnection at high duty cycles where the driving mosfets and the flyback diode burn and the buck converter gets shorted entirely. I made a simplified simulation of our circuit to demonstrate the problem, the switch S1 simulates load disconnection after 5ms:

Here switching frequency is 50kHz and duty cycle is 90% and very high voltage spikes occur. When the duty cycle drops below ca 60% the overvoltage spikes do not show up anymore.

I know already from Buck converters- No Load condition that a synchronous buck converter would not have this problem and I've already simulated this and can confirm this. But synchronous buck converter cannot be used here anymore, we need to quickly fix this present solution.

The schematic shows some solutions we've tried:

Putting a high voltage TVS diode (VAR1), i.e. changing R3 to e.g. 1mOhm. This helps a bit but still we get spikes over 800V which would damage the components.

Adding a bypass (bleeder) resistor R4. But this does not help either until it is set below ca 20 Ohm, which is of course unusable in real application.

Of course in real application the load current is measured and when there is underload or overload the mosfet driving gets disconnected (not simulated here). But this takes at least 20 ms and cannot be made shorter. Here the damage happens within max 100 us from the point the load gets disconnected.

The question is of course, how to avoid this damage with minimum effort, cheap, low part count, space saving etc.

Simulation file in Simetrix Elements 8.1 (free evaluation)


texts:
I am working with the buck converter AOZ1284 Datasheet
I want to get 5V with 12V in input so I chose R1=52.3k and R2=10k (Vout = 0.8 x (1+R1/R2) =0.8x(1+52,3k/10k)=4.984V).
Also I fixed L=4.7uH.
How do I calculate the value of Co and Cin (input and output capacitors?)
I found a section in the datasheet about the output capacitor but I don't know

the acceptable value for DLETA_Vo
the cut off frequency for the LC filter in the output


texts: Microbit - Control an LED that is powered externally

texts: I am trying to make a motion activated light with my Microbit. I have a 1W superbright LED and its clear the Microbit won't supply the current needed for this LED. So I'm using a 5V USB micro-B with a LD1117 for 5v:3V and a resistor to power the LED which works fantastically and is more than bright enough. My question is how can I use the microbit to control the LED? I want the brightness of the USB power but the control of the Microbit.


texts: Unsure about bulk capacitor value and type for custom PCB

texts:
I'm designing a custom PCB (90x90mm approx) which is using an ESP32 module to drive 5 dual channel H-bridge ICs (DRV8835) which control 9 miniature brushed DC motors (1A stall.)
The datasheet of the DRV8835 says to use an 'appropriate' bulk capacitor on the motor power input, they recommend an electrolytic capacitor close to the IC.
Power to my board is supplied by a 2S1P Li-ion (8.2V maximum.) I won't ever be driving all motors at stall, but I'm not sure on the exact maximum current use and duration. I could potentially be driving a few motors at stall for maybe a second or two (say 5A maximum current draw.)
I'm not really sure what value bulk capacitor to use. Pololu makes a breakout board for this IC and they seem to use a 10uF capacitor with a 1 ohm resistor in series for the bulk capacitor.
I suppose my questions are:

Roughly, what is the bulk capacitance this board needs?
The PCB height is constrained and aluminium capacitors may be too tall. If I were to use ceramic capacitors what additional series resistance should I add and why?
If I'm just using a single bulk capacitor at the battery input to the board it will be an inch or two away from some of the H-bridge ICs, is this a problem?
What's the worst that could go wrong if the bulk capacitance isn't right?

I'm a mechanical engineer and this is my first PCB design, apologies if these are silly questions.


texts: Disciplining a TCXO from a broadcast reference source

texts:
In the UK (and much of europe), a broadcast time and frequency reference is available in the form of the MST radio time signal. This is broadcast using on-off keying on a frequency of 60 kilohertz, to within one part in 10^12.

I'd like to use this signal to construct a cheap and accurate 10MHz frequency reference. My tentative plan is to construct a PLL, with a VCTCXO as the VCO component, and lock it to the 60KHz reference. That's the easy part.

However, I'm not sure how to approach a couple of other aspects of the solution. Specifically:

What's the easiest way to receive and amplify the 60KHz carrier wave, producing a clean 60KHz square wave output from the receiver?
How should I handle the periods during which the transmitter is not sending the carrier wave (which can last up to 500ms, at the beginning of each minute)? I don't want the phase comparator to decide the clock is way out of phase and skew the TCXO frequency during this period.


texts: How to know when to tune up a digital multimeter?

texts:
I have bought the multimeter with temperature measurement from the following website:

http://futurlec.com/Multimeters.shtml

Currently I use the voltage, resistance, and short circuit detection functions on it.

The short circuit detection function works fine. but now when I measure high resistance values over 100K, the results are inaccurate. For example, the 560K resistor was measured at 408 instead of 560 on the meter (I turned the knob to the 2000K setting). When I measured a 1K resistor, the meter reported 0.8 instead of 1.0 on the 200K setting.

All resistors measured were carbon film 1/4 watt with 5% tolerance.

One time when I opened up a multimeter to replace the battery, I noticed it had a fuse and a potentiometer as part of its circuit.

Would adjusting the potentiometer fix this issue? I mean the low battery symbol never appeared on the meter so I don't know if battery is an issue. Could I hack the meter somehow and measure something that could give me an indication if the battery is dying?


texts: Does an optically encoded dc motor count as a servo?

texts:
Up until now, i have thought that a servo referred to a very specific type of motor: one like this. However, i recently heard someone describe an encoded dc motor, like this one:
Is this in fact a proper servo? does the term "servo" just mean ANY motor that had a feedback system? (i think "closed loop" is the term)


texts: How did I survive a short hand-to-hand 230V shock?

texts:
About 5-10 years ago (can't remember when exactly), my father asked me to unplug a lawn mower from an ungrounded power outlet with no sunken part (the kind which had been outlawed by the EU for a few years by then). The outlet was in a corner, somewhat inaccessible due to a computer desk, so I reached over from the side of the desk and outlet (not the front) in a really clumsy way and tried to unplug it even more clumsily by trying to push my fingers between the plug and the socket. I had my other hand against the nearby wall corner, and all of a sudden I felt a current go through my arms and chest, from the outlet, through my left hand and arm, over to my right hand and arm, and into the wall.

After about a second, I managed to get my fingers from between the plug and the shock stopped. I had only 2 fingers in there, one against each rod, and apart from being impressed by the event and having an afterfeeling in my chest for about 15 minutes afterwards, I didn't notice any harm from the event. I can still work, cycle recreationally for a few hours, exert myself with moving stuff and life live like I'm used to in general. The only thing which might be a consequence is that I sometimes have a minor pain for 10 seconds or so in my chest muscles, but those are sporadically and not related to any particular activities, so I don't know if it is related.

Thing is, I always read and heard that such jolts are lethal. The surge didn't last long, but it passed right through my chest and wasn't mitigated in any way by any kind of barrier. And you often hear about people being killed by testing batteries with their tongue, which are only a fraction of the power of a domestic grid. How did I survive this incident?

In case it's relevant: I was around 16 years, a normally built male with no particular muscles or fat layers, in Belgium.


texts: dspic Timer1 Interrupts Occuring Twice as Slow

texts:
Maybe I'm missing something here but on a dsPIC33FJ16GS502, I designed Timer1 to toggle a pin at 200 Hz but when implemented, the frequency is actually 100 Hz.  I have the following configurations:

XT (HS): 16 MHz
FCY: 8 MHz
Prescaler: 64
PR1: 8 MHz / (200 Hz * 64) = 625

Here's the code:

_FOSC( POSCMD_HS & OSCIOFNC_OFF );
_FOSCSEL( FNOSC_PRI & IESO_OFF );
_FWDT( FWDTEN_OFF );

int main(int argc, char** argv) {

    OSCCONbits.COSC = 0b010;    //  HSXT no PLL
    OSCCONbits.CLKLOCK = 1;
    OSCCONbits.IOLOCK = 1;

    CLKDIVbits.ROI = 0;
    CLKDIVbits.DOZEN = 0;

    //  Set TMR1 Registers
    T1CONbits.TON = 0;              //  Shut off timer for configuration
    T1CONbits.TSIDL = 1;
    T1CONbits.TGATE = 0;
    T1CONbits.TCKPS = 0b10;         //  1:64 Prescaler
    T1CONbits.TCS = 0;              //  Use internal clock
    TMR1= 0x0000;
    PR1 = 625;
    IPC0bits.T1IP = 0x01;
    IFS0bits.T1IF = 0;
    IEC0bits.T1IE = 1;

    T1CONbits.TON = 1;              //  Turn on Timer

    TRISBbits.TRISB8 = 0;
    LATBbits.LATB8 = 1;

    while(1);
}

void __attribute__((__interrupt__, no_auto_psv)) _T1Interrupt(void){

    LATBbits.LATB8 = ~LATBbits.LATB8;
    IFS0bits.T1IF = 0;

}

If PR1 was set to 312, then I would get the 200 Hz frequency but according to my calculations, PR1 set to 312 would result in a frequency of 400 Hz.  I have no idea why I'm out by a factor of 2.  I'm pretty sure I'm configuring the registers right.


texts: Switch to stay ON until power removed (24V)

texts:
In my bathroom, I would like to install some 24v LED tape, some in a warm-white and some in a cool-white, that I can switch between at will. IE: I will turn on the circuit from the wall-mounted dimmer outside the bathroom and then select either the warm or cool LEDs via another switch. I then want the ability to switch from one to the other at will. This, I realise will be easy - Install a switch after the 24v transformer to alternate between the two.

However, I am curious whether a switch exists that will default to the warm-white circuit. So, for example, when I turn on the circuit at the wall the warm-white LEDs will be powered by default. I can then switch to the cool white however, when I turn off the power to the whole circuit at the wall the switch will automatically switch back to the default warm-white circuit so that next time I turn on the lights they are on the warm-white. Maybe some kind of self-powered relay? Electro-magnetic switch?

To add more complexity this will be after the 24v transformer that will be dimmable by PWM. If I have to I suppose it could be done on the mains supply with one transformer for each of the circuits.

So, to summarise: Default to circuit 'A' at power ON, switch to circuit 'B' after switch press, revert to circuit 'A' after power OFF.

Thank you in advance to anyone who may be able to help!


texts: How can I convert 0-5V to +/-2V using a dual supply op amp?

texts:
I have a 0-5 volt variable frequency sine wave signal source I am trying to convert to +/-2V.

I would like to preserve the frequencies 20Hz-20KHz.

I have a +5 and -5 volt signals I would like to use as power supplies.

How can I level shift this signal down 2.5 volts so that it is centered at 0, and amplify the signal by 0.8 using a dual supply op-amp?


texts: Is it possible to send sensor data over 10 kms using zigbee technology?

texts: my project is about rail track fault detection and interstation distance is around 10-12kms.  Sensor data need to be send to nearby stations and is it possible to do this with ZigBee module?


texts:
I'm picking up a weird bug with my 74HC595 Shift Register's latch pin (Datasheet).

What do I want to do?

I'm essentially trying to visualise the shifting of the bits with the clock constantly running, and varying the serial input. I want to connect a LED to each output pin, and then connect my input clock (555 timer) to the latching pin (RCLK) and serial clock (SRCLK). As far as I understand the output LEDs should then show the state of the shift register, but delayed by one clock cycle, as mentioned in this datasheet:

  If both clocks are connected together the input shift
  register is always one clock cycle ahead of the output register.

What is not working?

Connected the clocks together makes the shifting stop. Nothing shifts through. Not even in the shift registers, as I connected a LED to QH', and it never lights up.

The funny thing is that I could get it to work by unplugging the RCLKpin and letting it float. Then everything works perfectly, and I see my LEDs shifting. This is strange, as a change of state for RCLK is required for latching.

It even works if I place a switch on RCLK. Then I can see the latching only happening at the up and downward edges, as I expect.

But with the RCLKfloating shows the shifting bits perfectly.

My question:

Am I understanding how the 74HC595 chip works correctly? Is this intended behaviour?
Does the two input clocks need to be out of phase, as in the timing diagrams?
Could it just be EMI? It's built on a breadboard, but I put decoupling caps everywhere. Also, the speed I use never more than 2Hz, so I can't imagine that being the problem.

My setup:

My circuit is built on a breadboard, with the following schematic:


texts: Op amp circuit for logrithm calculation?

texts:
How does one design an op amp circuit which calculates the logarithm of the incoming voltage? I.E. if \$V_{in}\$ is the voltage at the input of the circuit and \$V_{out}\$ is the voltage at the output of the circuit, then the relationship between the two should be
$$
V_{out}=\log_{10}\left(\frac{V_{in}}{V_{ref}}\right),
$$
where \$V_{ref}\$ is some reference voltage such as 1 V.


texts:
I have a small boat and the main deep cycle battery is located just under a "shelf" like thing near the transom that acts as a cover for the gas tank and battery.  On one side, it is completely open (the bow facing side), but its essentially otherwise enclosed.  The battery is held in place with a plastic battery tray that is secured to the deck, and the battery is held down with a nylon trap and a buckle clip.

In the past, I've always released the buckle clip, maneuvered the battery out of the tray (there's NOT much room to work with, so its quite a hassle) and out from under the shelf in order to charge it.  Now, though, I'm thinking of getting an onboard charger that would have the leads attached to the battery permanently, and when returning home, I would leave the battery in place and just plug the charger into the AC outlet in my garage.  I know that ventilation is generally important when charging a battery, but my question is - is it safe for me to leave the battery in its tray under the shelf while charging?  Again, one side of the "compartment" the battery is in is completely open, but the "shelf" is directly over top of it (maybe two inches of clearance)..

I love the idea of the onboard charger that I would leave plugged in to charge the battery and then maintain it until next usage, but I don't want to do anything unsafe.


texts:
I am currently building a digital clock using the LM8560.
In the datasheet it says the maximum voltage at each Pin should not exceed +0.3V or -15V. The IC uses the line frequency of 50/60Hz, which is connected to Pin 25 from one of the transformers secondary windings. I am using a 2x 7V transformer with center tap.
But because its AC wouldn't the voltage at the input pin be +9.8V and -9.8V?
Is this ok to do so, or am I missing something in the datasheet?


texts: Impedance-matched antenna with an extra capacitor

texts:
I'm looking at the a schematic for an ESP8285 module, and I am curious about what they are doing with the antenna. The module is the PSF-B85 (by ITEAD: the version with a chip antenna). The antenna is used for the 2.4GHz WiFi/ISM band.

According to the ESP8285 datasheet (page 9 of the PDF), the antenna connection pin, LNA, has an output matched to 50 Ohms within the IC. So there aren't any matching topologies necessary for a 50 Ohm antenna.

In the schematic of the PS-B85, a 10pF, 50V capacitor has been placed between the chip antenna and the LNA pin. What is the purpose of this capacitor?

I can only guess that this would be a "blocking capacitor", but would it be necessary for proper function? Or is it a small optimization for the antenna?


texts:
I am programming for LPC microcontrollers (mostly LPC1769), for the past few months with success. I decided though to give STM32 series a try.

I just received a no-name board using an STM32F103C8 MCU like the pictured one.

I am using Eclipse to develop my firmware, where I have also installed the ST's plugin for ARM development. I program the chip through UART utilizing the factory bootloader. I have also extracted the CMSIS library from ST's Cube library, and I have included it in my project.

What I am trying to achieve: This board has an LED on PC13, and I am trying just to blink it. My project builds fine, and it uploads fine too.

The problem: Nothing at all happens at the board. I believe that the GPIO is does not even getting configured as output.

I have tried lots of different codes. Here is an example:

#include "stm32f10x.h"

int main(void)
{
    SystemInit();
    SystemCoreClockUpdate();

    RCC->APB2ENR |= RCC_APB2ENR_IOPCEN;

    GPIOC->CRH=0x33333333;

    while(1)
    {
        volatile int i = 0;

        for(i=0;i<0x40000;i++){
        }

        GPIOC->ODR ^= (1 << 13);
    }
}


texts: How to regulate voltage of transformer output for nichrome wire

texts:
I have a basic CNC machine for cutting EPS foam which uses about 9.5in/23.5cm long straight 28 gauge Nichrome wire as the cutting element. The nichrome wire is powered independently with a 220V-36V 5A rated step down transformer with a dimmer in series on the mains side. The CNC have no way of knowing the temperature of the wire.

Using this calculator, I found that I needed 5.2V at 1.6A (8.4W) to heat the wire at 600F/316C which is the recommended cutting temperature. But from my experience I found that supplying 2.5V - 3V AC (measuring across the wire with a cheap multimeter) is about right for cutting the foams. I am unable to measure the current or temperature while heating as I do not have the tools for those. Below are a few statistics of voltage and resistivity of the wire:

ACVoltageAcrossWire    WireResistance    Temperature
  0V                      2 Ohm             Cold
2.5V-3V                 30-90 Ohm           Good
  4V                   200-400 Ohm         Glowing

The problem with this setup is that - in my place, mains power is fluctuating very much causing the wire to unevenly heat up during cutting and is almost impossible to control with the dimmer as the machine is moving at 700 - 1000 mm/s. During a single cut, sometimes the wire would heat up too high that it eats up too much of the foam; and then the wire would be too cool that it would start dragging the foam causing lots of wastage.

I tried using a 12V 2A rated SMPS with an XL4015 buck converter (voltage and current adjustable) to power the wire. When I tested with a piece of 24 gauge coiled nichrome wire (about 10 Ohm), it worked fine. So, I tried it on the machine’s wire but couldn’t get it to work. The buck converter was very hot and is not working anymore. The machine supplier also told me that they prefer the transformer over SMPS as they had more problems with the later.

So, I was thinking, if I somehow get the output from the transformer rectified and regulate the voltage, it would solve my problem. But as I have very little knowledge in electronics, I don’t really have an idea how to go about it. I googled around for the designs or ideas, but couldn’t find anything that could fit my specific needs (apologize if I had missed any). I have a some linear regulators like 7805, 7809 & 7812, few LM317, TIP122, BT131-600 and other discrete components in my salvaged inventory. I would be very thankful if anyone could suggest a cheap & easy circuit for my problem.


texts: How can I render my 2.4GHz antenna directional?

texts:
With barely no knowledge in this field, I would like to render my antenna used with Bluetooth BLE devices more directional.

I tried to shield the antenna with different kind of metals with no luck.

Is there someone to point a way in order to render my antenna directional? Perhaps surounding with something?

Thanks


texts: What components do I need to display an analog DC current value on a 7-segment display array?

texts:
(See edit below)

Original Question:

This is the first PCB I've ever tried to build and I need a little help getting pointed in the right direction.  I've spent hours researching things and I think I'm finally to the point where I can ask an intelligent question.

I need something that senses current and does two things:

Outputs a 0-5V signal (proportional to the current) that gets sent to an external data logger.
Displays the current on a 3-digit 7-segment display.

This will be used in an automotive setting, so we're talking about 12-16V DC with up to a 30A continuous load that needs to be measured and logged.

I am looking at a Hall effect sensor such as the Allegro ACS770LCB-100B-PFF-T but I don't know how to display the current on the 7-segment array.  Do I need an ADC, microcontroller, both, or neither?  Is that Allegro sensor the right thing to be looking at?

Any suggestions on which types of components (with model numbers if possible) I should be looking at will help greatly.

Edited to narrow focus of the question:

How do I transform a 0-5V signal into something that a PIC Microcontroller can display on a 7-Segment display array?


texts:
Good morning All, I'm obviously a complete novice as far as 18650 and Li-Ion or LiPo batteries is concerned although I do have a reasonable amount of knowledge as far as Electronics design goes, however I have a few questions which I'm hoping someone Wise here can answer.

what is the difference between an enhanced BMS and a Protected BMS ?
If using unprotected cells (for argument sake we'll say 3s 18650 @2500mAh each can I use a 15 Amp BMS or does it need to match the (3x2500) 7500mAh pack ?
Can I use a BMS charger (once again for argument sake well say an Imax B6) to charge a single protected cell ? A Single unprotected cell?

I'm sure these sound like simpleton questions to the "initiated" however before I commit dollars in any significant way to this extension of my endeavours (I currently use NiMh batteries for a number of projects) I'd be extremely grateful for the answers to the questions that have arisen in my thinking But for which Google & Co seem to have NO answers.
Regards,
Leigh


texts: It is from an HP Pavilion x2 Detachable 12-b010nr 12" Laptop and I need to replace the connector, because one of the pins broke.


texts: Standard nomenclature for 2-row connector numbering schemes

texts:
Two-row connector blocks are ubiquitous in small-run and hobbyist PCB designs.  Pitches of 0.1" or 2mm are the most common, and there are all sorts of options for board-to-board or board-to-wire connectors.  The problem is that pin numbering schemes vary wildly.

Pin numbering schemes I've seen include:

DIP-style counterclockwise:
Zig-zag between the two rows:
Down one row then the other, but NOT counterclockwise:

In my experience, getting the pin numbers wrong is one of the most common sources of PCB heartbreak.  I've done a lot of wire patching to correct 6-pin header layout mistakes... and I've thrown away boards with 70-pin header errors.

My question is:  Are there industry standard terms for these (or other) 2-row pin numbering schemes?

I would love to have a short, reliable way to specify these schemes, to allow saying things like "We're using a 14-pin 0.1" header with zig-zag numbering" (or whatever).

Although standardized names with the broadest possible user base are (obviously) better, I realize that there probably isn't one true answer to this question.  I'd appreciate answers about how these schemes are named even within smaller subsets of the industry, as long as you're clear about the scope of use (e.g. "At company X we always called the second scheme 'shoelacing'").


texts: MOSFET gets hot in an Op-amp MOSFET-based constant current load build

texts:
I've made this schematic following the circuit steps in this site:

and after running the output with just 0.1-1A (which works ok according the input setting and current reading seems correct) but the MOSFET seems to get super hot and measuring the output voltage Vgs on the MOSFET, the comparator seem to be giving a low ~4Vgs max of the FET and probably not turning it fully on.

What should be done in this situation assuming not a lot of experience with comparators and such.


texts:
I am using a UART to communicate with RS232 on a Roving Networks RN-42 SM bluetooth module. I have the transmitter and receiver connected to a logic analyzer.

The issue that I am having is that my when i connect my uC's TX to the Roving networks RS232 RX, the logic analyzer shows that the TX line of the TX is 0'd. When I disconnect the RX of the roving networks module, it once again starts transferring data.

The images included in the links below.

Here is my transmit code:

while(1)
{
    PORTC ^= 0xFF;

    transmitStr((unsigned char *)CMDMODE);
    _delay_ms(1000);

}

No connection to TX

Connection to TX


texts: What sensor to choose to track human presence indoors?

texts:
This is a hobby project about home automation. The idea is that of distributed system of cheap microcontrollers that take measurements, communicate, output data and control appliances.

One important task that this system should perform is detect at every room if there are humans inside (awake or asleep distinction would be a over-the-top bonus :) ). I am still at a loss if this is feasible. PIR-s? Webcameras? Microphones? Optical counters at the doors? Ultrasound?

Available processing power per sensor output: 5MIPS of avr instructions (8-bit RISC) for 3 seconds = 15 million instructions.

Typical usage scenario would be:

The apartment is empty (the system should know that).
The door opens and a group of 4 people enters the hallway. (the system should know that someone is in the hallway).
Two go to a room (the system should track their path by room, with a lag of no more than several seconds, plus know that there is still someone in the hallway).
, one of them returns, the other sits on a chair, (the first one is to be tracked. the system should also know in which room is the sitting person).
In the meantime the rest two wander randomly in a 2 x 2 meter area in the hallway (taking shoes off, hanging coats) (the system should know they are still in that area).
One goes to another room, turns the radio on and goes to sleep (the system should know that there is a sleeping person there).
Someone leaves the apartment and returns 10 minutes later (here the only requirement is that the system know that there are still persons inside).
The three leave (the system should know that there is still someone inside).
Much later, the sleeper gets up, wanders around for half an hour and then leaves the apartment (the system should track his position by room with a lag no more than several seconds, and know when he leaves that there is now no one inside).

I have no pets.


texts: What are limitations of Millers theorem for amplifier?

texts:
I mean to say that are the two circuits one original and other its miller/ drawn exactly equal in all respects or their are some difference in some respect if so please mention.

I am not able to think about any other parameters except current hain voltage gain output impedance input impedance and frequency response which I think are same for both original and it's dual.I want to know any other parameters important for small signal analysis and also if those parameters are same for original and dual circuits.

I know that Millers dual is a bit of approximated because gain used to calculate dual impedance is calculated by neglecting the Impedance whose dual is been found.

It will also be helpful certain cases where this approximation actually produce lots of error.


texts: Splitting a series voltage to power seperate devices

texts:
Good day all,

Here is the scenario. I have a 12v device and a 6 volt device I need to power.

Can this be safely/efficiently accomplished by using 2x4 AA battery holders and run them in series, making a connection in between the two packs to get 6 volts from the first pack to power the 6v device, while powering the 12v device as well by running it in series with both battery packs? This will drain the current on the first pack faster than on the second pack correct? Is this ok?

Thank you!

Edit for clarification:

My 6v device will draw 100ma continuously and be in use for only a few
minutes at a time, 5v is its minimum operating voltage. My 12v device will draw 330ma transiently, none when not in use, 12v is its minimum operating voltage.

I plan to use L91 lithium AA for maximum mah.


texts: I had given a few boards for manufacturing and this is how they’ve come back from the fab. Do I need to reflow these again? Would it be safe to do so? I checked and the pins are not shorted but what is that white substance around the pins? Solder flux?


texts: Combining Optoisolator and Relay into one I/O pin

texts:
I have a project that uses two microcontroller pins to control the input and output of an isolated device.  The LEDs are for status, showing when an input or output is enabled.

I'd like to save some I/O pins and I was wondering how to approach combining these together to use a single microcontroller pin?


texts:
So I have this device (Sim racing wheel) which is mounted to a carbon metal sim rig chasis which is on top of carpet. This sim racing wheel device is AC powered and is already grounded within the AC outlet. And a USB connection to my PC.
However due to some interference, it randomly causes my USB to lose connection and reconnect to my PC. So I was told I should put an additional ground to the sim racing wheel device.
So here I am not sure how to exact do that in my house? I know I have to probably run a ground wire attached to some metal area on the device but where do I find ground for the other end? And also is this safe to do??
Thanks for looking.


texts: Logic analyzer interference when analyzing SPI bus

texts:
I'm trying to analyze SPI EEPROM with a logic analyzer.
The logic analyzer is connected to the spi eeprom via ~20cm wires + SOIC8 Testing Clip (Only MOSI/MISO/CS/SCLK/GND are connected to the logic analyzer)
The circuit board that the SPI EEPROM soldered on works fine when not connected to the logic analyzer, however when the logic analyzer is connected the SPI EEPROM gets halted / stuck (prevents the PC from booting), which prevents me from analyzing the bus.
What might be the reason for that?
SPI Flash Datasheet (Its actually Gigadevice 25B64CSIG, but thats the closest datasheet I could find)
Logic Analyzer
Configuration:

Thanks.


texts: Off-delay timer with only a relay and an on-delay timer

texts: I'm trying to run two fans when there is a call for heat but I want fan 2 to shut off a few minutes later. I don't have an off delay timer however I do have an on-delay timer and a relay. I know it can work I just can't seem to figure it out.


texts: Antenna mounting confusion from Datasheet

texts:
I ordered a few samples of a particular antenna, because of the datasheet showed a rather peculiar layout - so I wanted to see what the actual component is and how it performs.

Antenna is Abracon's ACAG0201-2450.
Its datasheet suggests connecting it as such:

As I received the components I cannot see any 'dual' pads on the feed entry side of the antenna (left side of the antenna) to make the connection for the feed line and also GND plane - it's all the same pad on the component!

So what, I am supposed to short feed line to GND? Max confusing. Or maybe the datasheet talks bollocks?

Maybe someone more experienced on the antenna topic can shed some light on this?


texts: What is the common pin configuration upon microcontroller reset?

texts:
I have looked through two datasheets and user manuals now for two different microcontrollers (LPC2387 and STM32F4xx), and I haven't found (probably missed) anywhere where the initial state of the GPIO pins was described on powerup or after reset.

My question is not specific for these MCUs, but in general, is it most common for GPIO pins to be initialized as input-floating (high-z) upon reset? Is there a standard convention, or do different MCUs do different things, and one needs to read the datasheet/manual for each MCU one works with?


texts: Wireless power within a stainless steel enclosure?

texts: I need to transfer power wirelessly within a small SS tube that is not much larger than the diameters of the Tx and Rx coils. The coils are both inside the tube and are co-axial with it. Coils are 30mm diameter, although I'm also looking at 20mm coils with a max separation of 10mm ideally. Tube is about 40mm. Is this likely to cause a problem?


texts:
I understand that ceramics are good at ESR but would like to know if tantalum would suffice for my application.

Some 16 bit PICs require a >4.7uf cap (10uf recommended) low ESR cap for their internal regulator. The datasheet doesn't specify the type of capacitor but only says low ESR.

I have successfully used a 10uf ceramic cap with PIC24EP64GP202;
Can I use a tantalum cap instead?

Does DOM (Date of Manufacture) of the caps matter in this regard?

Does age (in-line use period) of a tantalum capacitor matter? Although I'm not going to use a used capacitor but would like to know this for curiosity.

Do tantalum capacitors age? Shelf life? In-use life?


texts: Can I burn out my multimeter's µA range by using a few mA of current?

texts: My multimeter only has one 400mA fuse protecting the µA and mA range (and a 10A fuse protecting the amp range.) Is it possible to damage the microamp range by feeding milliamps through it?


texts: Configuring PIC16F877A PORTA as digital output port

texts:
I am trying to use PORTA of PIC16F877A as digital output port. But somehow it does not seems to be working.

I am using MPLAB X IDE MPASM to assemble the code. Below is the code I am using to initialize PORTA -

banksel PORTA;
clrf PORTA;

banksel ADCON1
movlw 0x06
movwf ADCON1

banksel CMCON
movlw 0x07
movwf CMCON

banksel TRISA
movlw 0x00
movwf TRISA

banksel PORTA
movlw 0xFF
movwf PORTA

The LEDs at the output does not glow at all. What am I missing? I am not expecting RA4 to glow as I know it requires an external pull-up resistor but what about other LEDs.

Any help would be much appreciated. Thanks in advance.


texts: How to safely power a large LED strip project

texts:
I'm making an LED matrix with a board and 4X WS2811 strips (5 m length, 150 LEDs). Each strip is 45 W, takes 12 V and is 3.75 A. I have connected them in series and injected a 12 V, 60 W/5 A adapter for every strip.  It's powered by an Arduino Uno and all grounds are connected to the ground in the Arduino.
My question is, can this safely be power on from a single household outlet? I believe here in Canada each outlet can handle 15 A. So if this is true, is it unsafe to power all of these from a single outlet? The reason I want it to come from a single outlet is because I can turn on all adapters at the same time from the switch on my power bar.
If this is not possible, can the adapters be spread out from different outlets and simply turned on by connecting or disconnecting the Arduino?
I've attached a primitive schematic I made to the best of my abilities.


texts: Finding the Header Block in the Proteus symbol library

texts:
As the manual says...

  It is common practice to have on each sheet of a drawing a header
  block which shows details such as the design and sheet titles, the
  document, revision and page numbers, and the design's author. In order
  that you have full control over how this information is presented, the
  header block is defined as a symbol library entry called HEADER.

...but where is it?


texts:
I'm considering bying this LED strip for better lighting around the bathroom mirror, but I'd like to cut it into 1/3 and 2/3 and arrange them in parallel. Is that possible with the given parts? Electrically I mean, physically I'm quite capable of soldering and mounting.

I ask because I'm unsure what effect the parallel connection will have on the power supply and light output. I haven't bought the thing yet, but there are no relevant hints on the web shop page.


texts: For a MOSFET, does capacitive gate current only flow through to the source?

texts:
Everywhere states that a MOSFET has no current at the gate. However, this is not true since, during the time the gate capacitance charges up to reach the certain voltage threshold, the current is entering the gate capacitance.

My actual question:
During the charge-up time of the "gate capacitance", does the current only go to the source? (Meaning current enters the gate capacitance while charging and then leaves through the source for a N channel type?)


texts: UART communication not working with higher baud rate values?

texts:
I have a PIC32MX795F512L which is connected to 8MHZ crystal. UART program is working with 9600 baudrate value but not working with higher baud values like 115200.

Following is the code:

#define FCY 72000000UL //PIC32 working on 72MHZ
#define FPB (FCY/2)    // Peripheral clock is half of FCY
#define BAUDRATE    9600 // Baud Rate Value
#pragma config POSCMOD=HS,FNOSC=PRIPLL //Using High speed mode with primary Oscillator
#pragma config FPLLIDIV=DIV_2, FPLLMUL=MUL_18, FPLLODIV=DIV_1
#pragma config FPBDIV=DIV_2, FWDTEN=OFF
int main()
{
  OpenUART1( UART_EN | UART_NO_PAR_8BIT | UART_1STOPBIT  , UART_RX_ENABLE | UART_TX_ENABLE, (FPB/16/BAUDRATE)-1 );
  while(1)
  {
   putsUART1("hello\n");
   DelayMs(1000);
  }
}

Is this could be the crystal not working properly. What other reasons can cause the UART not work with higher baudrates?


texts: Difference between Brushed ESC and Brushed DC Motor Driver (Controller)

texts:
What is the diffrance between a Brushed ESC (electronic speed controller) and a Brushed DC Motor Driver (controller)? they both do the same job, yet at different prices and look diffrent.

Example:

Motor driver datasheet: http://nvhs.files.wordpress.com/2013/02/datasheet-l9110.pdf

ESC datasheet: http://www.hobbywing.com/uploadfiles/sx/file/manual/HW-05.pdf


texts: In the realm of audio what are the differences between servo-amps and monolothic amps? Are there any performances criterion that might make one more favorable to another--gain, noise, ease of implementation, topology, THD, etc.


texts: Possible grounding issue - HDMI over CAT-6 electrical arc

texts:
I was recently asked to help with some A/V stuff at my church. The goal was simple: Display HDMI video from a laptop to two LCD TVs. Since distance was an issue, I purchased an active HDMI-to-Ethernet converter.

I've included a PDF diagram for reference: http://bit.ly/1L0JeHh

When I went to plug the 3' HDMI cable from the splitter to the first LCD TV, a huge electrical arc occurred when I barely touched the HDMI cable to the back metal plate of the TV. This fried the LCD TV and the HDMI-to-Ethernet converter.

I suspect grounding issues, but I don't know enough about HDMI to know if that could be the problem. How would I determine if grounding is a culprit here?


texts: Digital electronics - how does a circuit determine when some element (like adder) is done? (delay handling)

texts: Take for example a ripple carry adder, how does a circuit handle delays of some elements?If ripple carry adder starts working from some clock cycle, we can't expect that it will have correct results on the next clock cycle.


texts:
I've wired a set of WS2813 leds to a Raspberry Pi.  The led strip is found here: https://www.amazon.com/gp/product/B077J27Y4X/ref=ask_ql_qh_dp_hza
When I have this strip connected via the short cable/JST connectors that came with the strip all works well.  But when I connect an approximately 3' cable between the Pi and the led strip it no longer functions...just the first few leds light with a very random pattern (not as programmed).  I've removed the wire and soldered the JST connector back and the strip works fine again so I know the strip is still functional after my soldering skills were applied to it.  This is the wire I'm using...https://www.amazon.com/gp/product/B07SJGHMX2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I've tested the wire with a multimeter.  There is definitely continuity on all four wires.  I checked it with the continuity mode and resistance mode.  I've tested the voltage drop within the wire, coming out of the Pi it is approximately 5.2V and after at the input of the strip with the 3' wire connected it is about 5.1V, still higher than the required 5V.  There is a similar voltage on the DI and BI pins as well which is about .15 to .2 volts (I'm assuming this reads lower because the Pi is rapidly signaling these pins).
I'm just a hobbyist learning from the Internet and this one has me stumped...I can't find anything that can clue me into what is happening and why.  Your help is greatly appreciated.

As requested here are the wiring diagrams with two photos to show the actual circuits.


texts:
This question is inspired by Connectorless USB on a PCB. I saw a cool USB LED on AliExpress that can be inserted in either direction:

I'd like to build a board with a similar symmetric connectorless USB plug, but I am pretty sure the unused side of the connector will short out against the two tabs that I see on the inside of the metal sleeve of most USB Type-A sockets:

Since the AliExpress board works, I assume that a portion of its circuit handles the case where the +5V lead on the connector touches the sleeve. I bet that responsibility lies with the two diodes I see on the board near the connector.

If these assumptions are correct, would you please draw a partial schematic that shows the relationship between the diodes and the two sides of the connector? If nobody answers, I'll use a continuity tester on one of these USB LED boards to deduce the circuit myself, and then I'll post an answer. But I am a novice with electronics design, and I'd appreciate the expertise of someone who really gets what's happening in this circuit, rather than my own blundering observations with a multimeter.

And an extra bonus question: what is the function of the two tiny angled sections on the AliExpress board's connector that are absent on almost all other male USB plugs?

Do they do anything? Are they racing stripes?


texts:
I am working through setting up eclipse with openOCD to program a STM32VL discovery board using the following guide https://www.carminenoviello.com/2014/12/28/setting-gcceclipse-toolchain-stm32nucleo-part-1/ .

I have got all the way to the end but am stuck on trying to program it with the OpenOCD but I keep getting the following error:

GNU MCU Eclipse 32-bits Open On-Chip Debugger 0.10.0+dev-00254-g2ec04e4e (2017-11-10-11:53)
Licensed under GNU GPL v2
For bug reports, read http://openocd.org/doc/doxygen/bugs.html
Info : The selected transport took over low-level target control. The results might differ compared to plain JTAG/SWD
adapter speed: 1000 kHz
adapter_nsrst_delay: 100
none separate
srst_only separate srst_nogate srst_open_drain connect_deassert_srst
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections
Info : Unable to match requested speed 1000 kHz, using 950 kHz
Info : Unable to match requested speed 1000 kHz, using 950 kHz
Info : clock speed 950 kHz
in procedure 'init'
in procedure 'ocd_bouncer'

I am aware after alot of research there is bug with openOCD with USB3.0 but my device only has 3.0 ports...

I have using OpenOCD 0.10.0
My External tools configuration in eclipse is setup as:
C:\STM32ToolChain\openocd\bin\openocd.exe
C:\STM32ToolChain\openocd\scripts\
-f board\stm32vldiscovery.cfg

With my above .cfd setup as

#This is an STM32VL discovery board with a single STM32F100RB chip.
#http://www.st.com/internet/evalboard/product/250863.jsp
source [find interface/stlink-v1.cfg]
transport select hla_swd
set WORKAREASIZE 0x2000
source [find target/stm32f1x.cfg]
reset_config srst_only`

Has anyone else had any similar problems?


texts:
I can imagine problems of PCBs not fitting into their enclosures or misaligned screw/hole pairs. Are these type of problems common, especially with the dirt cheap enclosures?
I am planning to use one that has a "0.8 mm tolerance". It does not specify where exactly this tolerance comes in though.


texts: Arduino beginner LCD question - best way to connect to pins?

texts:
I just received my first Arduino kit today - it wasn't hard to make my first LCD chaser - woot!  Already I am on to better things.

I want to mess with the EL1602A LCD screen next.  What's the best way to connect to the pins?  They look enticingly solderable so that I end up with jumper leads hanging permanently off, but is that a good idea?

If not, what do people suggest?


texts: What does this IGBT data sheet mean by "transient" gate voltage?

texts:
I'm using IXGH45N120 to discharge some capacitors. The gate voltage is derived from the capacitor voltage, through some resistors and a zener. The circuit has worked fine for a long time, many hundreds of discharge cycles. We've recently had cause to look closer at it, and it appears the gate voltage is, at most, 23V when discharge starts. It drops to 20V within 150 mS.

The data sheet says the max continuous gate voltage is 20V. Max transient gate voltage is 30V.

I don't see any definition of what qualifies as "transient" gate voltage. I haven't heard any response from IXYS on the matter. Is there any way I can know if I'm operating within spec? Is 150 mS short enough to be "transient"?


texts:
I have a Windows tablet with a charger which crapped out. The old charger was 12V / 1.5A - fairly standard but it had a rare tiny pin connector. Rather than buy a new charger, I decided to cannibalise another 12V / 1.5A charger I had with a different connector. I snipped the wires on both chargers about mid way, and rewired them using a block of those plastic wire connectors surrounded by some insulating tape. Not pretty, but secure. The charger works fine.

Recently, I read that a cheap, two pin fitting LED bulb could be highly dangerous. Because the bulb can be inserted either way, the capacitive dropper which protects you from the live wire could easily be connected to the neutral, leaving the live unprotected. A 50/50 chance. While I do steer clear of these cheap LED bulbs, it got me thinking about my DIY charger.

Is there a risk that I've created a dangerous charger?
Is there a 50/50 chance the connector pin is live?  If so, is there a safe way
to rectify it or should I chuck it and just buy a new one?
Or, since the charger outputs 12V does it mean that it's safe enough?


texts: What are these unpopulated holes on the Arduino Leonardo?

texts: None of the pinouts online mention these holes next to the power barrel and LEDs. Are they connected to anything?


texts: Why does the UPS mode of an inverter have faster switching times?

texts:
Of all the sinewave inverters I have used, they contain a switch at the back labelled Normal and UPS. When you put the inverter in normal mode, there is some 40-50 ms switchover time, enough to make my PC reboot. Now when I put it to UPS mode, the turnover time is 8-10 ms according to the specs, the computer doesn't reboot, and the lights don't even flicker. But the only caveat is the input voltage is narrowed from 100V-280V in normal to 180V-260V in UPS mode.

So my question is, if the relay and the sinewave generator circuit is indeed capable of starting a sinewave within 8ms, why does the Normal Mode wait till 50ms to start the inverter circuit? Or is it that in UPS mode, the inverter circuit is always on and when main power goes off, it immediately switches over to the inverter output? In this case, the UPS mode will increase wear and tear of the inverter circuit, right, because it's always on?

Table from the Exide Inverterz GQP


texts:
I Need to design a Energy meter ( Single phase 240 Vac, 0.4 mA ) , its a industrial product with enclosure of IP 67. I need to design PCB for this product as per UL. I am new to UL procedure so please guide me.

Note 1) First Schematics and select all component, those are only UL Certified ?? what if some component are not UL listed, like resistor , capacitor , transistor,IC etc. will this PCB fail to get UL certificate.

Note 2)  In Layout follow the Clearance and creepage distance.

Note 3) Find the PCB vendor who make UL rated PCB,Send the PCB for manufacturing
Will PCB vendor will mark UL logo now on PCB or first PCB need to send UL lab to test and validate then in second interation we can ask PCB vendor to mark UL logo on it?

Note 4) If we need to send PCB for UL lab for certifiaction, Do we need to send bare board or assemble board or Full working unit.

Note 5) What Test lab people will run , Do I have to tell them what test need to run or do they run as per their process.

Note 6) What Standard need to follow to get UL rated PCB.

Note 7) How much designer involvement in getting UL rated PCB, should has to guide the PCB vendor for what material need to use or process.