texts: I am learning about transformers and in the equivalent circuit the magnetizing inductance of the excitation branch is supposed to represent the current needed to "set up" the flux in the core due to finite permeability of iron. However, this does not explain to me why flux needs to be "set up" to begin with. The voltage induced is not a function of the magnitude of the flux but rather the rate of change of flux. The flux could at one instant be zero and changing quickly and the same voltage would be induced in a winding as if the magnitude were larger with the same rate of change. This seems to be one of the biggest problems when analyzing "magnetic circuits" to me as there is a clear discrepancy in the duality with respect to maxwell's equations. The rate of change of magnetic flux would seem to be the "magnetic current" especially for energy conservation and duality for Faraday's law with Ampere's law. Can someone explain why there needs to be flux "set up" in the core and for that matter what the magnetizing inductance does.


texts: Make an RF transmitter: classic transistor oscillator or VCO module?

texts:
This question is about pros and cons of making an RF transmitter (eg in the FM band) in the classical way (eg. with a "transistor based" oscillator circuit, like this one which is very classic and simple ) or, instead, using a VCO module like this one.

About the first solution, making a transmitter with a transistor and a bunch of components, I know that most of the times, could be quite hard, the tuning of the transmitter: we have to make a precise coil, if we put our hand near the circuit the frequency will drift (also if we change the antenna length or position), and if the circuit is very basic, I guess that will also transmit some harmonics. Obviously I know that an oscillator transmitter could be more stable with some "trick": would be better make short connections (eg to avoid parasitic capacitance), we can put the circuit in a metal case (and connecting the ground to the metal case), provide a stable power supply, avoid the heating of the transistor and so on.

But I'm asking myself if starting with a VCO module would be more simple from the beginning. Taking again as example the POS-150 VCO Module I see that if I provide 7V to the V-TUNE pin the module will be tuned to 103.66 Mhz. So the main questions are here: a VCO module will assure more stability o will suffer of the same trouble of a classic transistor transmitter? Since the module is inside a metal case I guess that at least will not suffer of the frequency drifting if we put our hand near the module: but about the emiting power? Will also need a power amplifier on the output? The POS-150 claims an output power of 9.5dBm.
And just for starting to transmit a frequency, is enough just connecting the V+, ground connections, providing a clean VTUNE and connecting any kind of antenna? (eg a simple piece of wire).

Can someone explain me if a VCO module has some advantages and the correct ways to wiring it as transmitter? (will also need some external components, eg using some capacitors as filter, maybe on the power supply?)

Many thanks.


texts: What is the best website to place orders for electronics components online in the USA?

texts:
I need to start ordering electronics components and I am trying to figure out who to use. I want to pick one website to use for all my needs, so they need to have a diverse selection of components, competitive pricing, and relatively quick shipping.

I don't want to shop around to find the lowest cost parts, I just want a reliable company that I can rely on so I don't have to shop around each time I want to go online to order components.


texts: Evaluate signal power between two amplifiers

texts:
Let's consider this cascade of amplifiers:

Consider the intermediate node, and suppose there our signal has voltage Vx.
How can I evaluate that signal power (for instance to calculate the SNR, supposing noise power is known)?
In fact, Power is $$V×I = V^2/R$$, where R is ths load resistor. But the load resistor is infinite (and current is 0) because ideally the following amplifier has infinite input impedance.
Should I conclude that ideally there is no signal power? It seems quite strange. How can I evaluate the SNR in such a case?
I have often seen people using the signal theory definition of power, which is simply the square of voltage. But how can this analysis be effective if we don't consider the load resistor?


texts: Impact of "reference level" and "RBW" on the time domain signal in spectrum analyzer?

texts:
Two questions:

(1) What is the impact of "reference level" on the time-domain signal viewed on the spectrum analyzer?

[My attempt] Mean power level of a time domain signal would move up and down on the display? However, the envelope of the time domain signal would be same. Correct?

(1) What is the impact of "RBW" on the time domain signal viewed on the spectrum analyzer?

[My attempt] Smoothens the fluctuations of the envelope of a time domain signal. Is that correct?

Thank you in advance.


texts: Light bulb lights up in a fraction of time (blinks) using TRIAC-BT136 and MOC3021 (Solved)

texts:
I have several days with problems when assembling the circuit of the image (it is a light bulb that turns on when you clap). To briefly describe the operation of the circuit, when the potentiometer is completely to the left, the led and the bulb remain on. When lowering the potentiometer until the LED and the bulb turn off, when clapping, the pulse is received and the led blinks, on the other hand, the bulb should remain on.
As for the DC part (the LED) blinks when I clap, so that's fine on that side. The problem is that, (before reducing the potentiometer) when I turn on the circuit (5V and 220V) the bulb does not stay on like the led, but it turns on in a fraction of time (it blinks or tries to turn on). Below is a video of what exactly happens anyway.
Vídeo: here
NOTE:
In the video you will see that the light bulb blinks, turns off and then comes back and blinks. The reason is because I disconnected the 120V source, when I go back and connect it the light bulb comes back and blinks. So basically I plugged it in twice just for you guys to see that the DC part works normal, however the AC doesn't.

I have searched a lot and in many cases they recommend changing the resistance of the TRIAC-BT136 gate, which I have already done by changing the 100 ohms by 180 ohms (calculated using the TRIAC datasheet) and with a 330 ohms. This has not worked for me.

I have tested all the components and they are in good condition, I also bought another CD4017 because the previous one was somewhat loose, however it did not mean anything.

I have come to think that maybe the problem occurs with the MOC3021 but I do not understand, because in the end it triggers. Should I make a few changes to the MOC's 1k resistor?
UPDATE:

I tried with an incandescent bulb and the problem remains the same as with the led bulb.
I changed the 1k resistor from the moc3021 to 220 ohms (didn't work), then 270 ohms (didn't work, either).

SOLVED
The problem was neither the resistance of the moc, nor the micro, nor the type of CD4017 used. The circuit was well synchronized (AC and DC). The final problem was the use of jumpers. There were lines in which although they were conducting, due to any movement they were no longer conducting - I don't know if you understand me - the point is that the use of the jumpers did not produce effective connectivity in the circuit so I used utp cable and the circuit worked perfectly (Although the micro I had was a bit loose, I simply replaced it with another one and it already adjusted perfectly to the circuit).
Thank you very much anyway for the different ideas you gave me, I used them all and thanks to that I came to the solution which was quite simple haha.
If anyone has any ideas which they can contribute, it is really appreciated.


texts: What is the difference between the magnetic H field and the B field?

texts:
Wikipedia provides a mathematical explanation. Can I get the intuitive one? I'd like to, for example, understand a ferrite datasheet. These usually have graphs of H vs B, and the definition of permeability depends on understanding the relationship of H and B.

Also, I wonder: I was able to learn a great deal about electric fields before I knew what "fields" were. I learned about voltage and Ohm's law and so on, which a physicist might explain with a field, but which the electrical engineer explains with simpler concepts, like the difference between two points in a circuit. Is there a similar, simpler explanation of H vs B fields that is of more relevance to the electrical engineer, and less to the physicist?


texts: Build DC/DC (Buck) Converter using 555 timer

texts: I saw a design for a 12V DC to 5V DC buck converter using a 555 timer on http://www.simple-electronics.com/2011/10/12v-to-5v-converter-555ic-mosfet.html. Is this a good design to use towards my smps? I've been trying to design a 120vac to 5vdc (capable of 2amps) smps for a few months now and struggling with the pwm portion.


texts: Is there a difference between these two circuts?

texts:
simulate this circuit – Schematic created using CircuitLab

I am trying to apprehend the concepts of "ground" in electric circuits. There are some excellent answers on SE here on this topic and they have been very helpful. I am now quite comfortable with "ground" as a reference point. However, with the idea of using direct physical connection to earth in circuits, not so much. In simulators, for example, the two circuits above will give the same reading of current through the resistor. My question is, if I take two batteries, two bulbs and two one-meter wires and make two circuits as above, will their behavior be identical?


texts: How to drive a plain LCD panel (get it to work with DVI)

texts:
I have an old iMac G5 laying around I want to transform it into a second monitor, but without any extra software on the device, but by just controlling the screen panel.

I dissasembeld the iMac and found out that the screen panel is a LM171W02-A4 (M1)
http://www.beyondinfinite.com/lcd/Library/LG-Philips/LM171W02-A4.pdf

The datasheet tells me what every pin does, but I don't know how to deal with this information. Can I buy a board online that connects to the panel and has HDMI/DVI input, or can I build a cable myself to attach DVI to the panel?


texts:
Reading about Controller Area Networks and Ethernet standard, I cannot understand why there is a difference in the way the signal is transmitted. Both protocols use twisted pair cables to communicate, with mirroring signals, the logic state being determined as a function of the voltage difference between the two wires.

In CAN networks, CAN Low will range between 1,5V to 2,5V, while CAN High will be in the range of 2,5V to 3,5V.

In an Ethernet network, though, the signal will cross each other and the values will be the exact opposite of each other. So, when one cable will have +3V, the other will have -3V and viceversa.

Why did the engineers choose this particular methods and why isn't just one method used? What are the advantages/disadvantages of each?

Also, in a CAN bus, the wires will be terminated with 120Ohm resistors, to match the line impedance and ameliorate reflections and the end of the cable. I don't think ethernet cables have such terminations. If they are used, are they in the NIC's? If so, how do they account for different wire lengths?

Thank you.


texts: Unrecognized usb3.0 device using non-standard connector

texts:
I Have two PCBs,pin out define as follows ,the host pcb is A connector,and the device pcb is B connector.

I use the 1.25pitch connectors&USB3.0 cable to connect two boards,but the host board Unrecognized usb3.0 device. Cable is follow

Layout is follow

Host PCB:The TX-,TX+ traces about 25mm
             RX-,RX+ traces about 44mm

Device PCB:The TX-,TX+,RX-,RX+ traces both about 15mm


texts: Can adding a copper plane to the 2.4GHz antenna amplify signal strength?

texts:
Hello, I bought a 2.4GHz controlled RC car from a Chinese vendor.
Under the car chassis, there is a 30mm x 20mm copper plane attached.

Surprisingly, the customer's service team replied that
"it's antenna. 2.4GHz antenna amplification device."

I couldn't believe what I heard. So I'm posting this question.

Can that copper plane act as a 2.4GHz antenna?
Also, can this plane "really" amplify something?


texts: shift registers/d flip-flop memory states

texts:
I know D flip-flops retain a certain logic level(memory) but when they output(i.e. shift) this retain memory do they loose it?

for example:
lets say I have 3 d flip-flops connected as a serial shift register. And send an input signal of 1,0,1 in 3 consecutive clock pulses. The logic levels of D flip-flops will be D1=1 , D2=0 , D3=1.
Then stopped the input stream but keep on sending clock pulse. what would be the final memory state of these flip-flops be? 1,1,1 or 0,0,0

thanks in advance.

Edit: This is what the circuit would look like.

So the question would be do you need to constantly keep sending input 1 to D1 to keep it in logic 1? or can you just stop the input.


texts: Failing to get low quiescent current on 555 monostable

texts:
I put together the basic 555 monostable circuit, but found it drew a bit over 2mA when "off".
To an extent, this makes sense as the 555 effectively has a 15k resistor between VCC and GND. I thought that I could cut power to the 555 when it's off to drop to a really low quiescent current, so I put in the two transistors and associated components up above the IC in the schematic.
While technically a success in that this dropped the quiescent current draw, it only dropped down to 1.76mA. I took a look at a similar question and answer, and the only difference that I think I have in the power setup is that I'm using BJTs instead of MOSFETs. I looked up the datasheet on the PNP (a PN2907, but KiCad didn't have that) and saw the leakage current to be far less than what I'm seeing.
For testing purposes, I replaced the output sub-circuit on the right with just a resistor and LED for an indicator/dummy load. The test setup ran from a 5V breadboard power supply, though the final version is intended to run from a nominal 4.5V (three AA batteries).
Why is this still drawing milli-amps of current and what is the minimal change needed to correct this? (General critique is also welcome, though I intend to stick with through-hole and the 555 for the project at hand.)

Update: Adding the corrected schematic for the sake of others who may come looking.


texts: Torque, distance traveled and power consumed

texts:
I'm not good in math or physics in general. It's hard to me.

In a DC motor which from start to end take 1 unit of time with 1 unit of weight loaded is the same thing than 2 units of time with half-weight.

The reason I ask this is because I have an old car-window motor weak, I want to increase it's torque by halving a bit the gear.

It will have more torque, it will take more time to finish. But, does it consume the same power in the end changing one for another? If yes, I take a better approach.

I'm assuming normal condition with naturals losses everything has.


texts:
(Intro here, you can skip this for the actual question)

As a hobby project I'm building an audio amplifier. It'll be the amp for my "home theater". I only have a small room so there's no room for 5.1 speakers. And honestly I don't care for 5.1. So I want just a small stereo system with a mono subwoofer, or as they call it, a "2.1" system.

I have decent speakers, (Yamaha NS-50F pair, rated at 80W), and a subwoofer I built myself. Testing has shown that an LM3886 (68W max @ 4 ohms) is more than enough to drive it. So I went ahead and built a simple, triple amplifier.

The results were disappointing. Not even remotely enough "bass". So I built a small "bass boost" circuit (more like a "treble cut" and raise the volume). It was a lot better. But I missed the EQ.

I would like to build an EQ. An analog one would be relatively simple to build with a bunch of opamps. I want this controlled by a remote control so I'd have to replace the pots with digipots. But it starts getting complex, as I'd need:

Input stage/buffering
Equalizer
Low-pass filter for sub
Output preamp (LM3886 needs to be driven relatively high)

This is rather complex, too many ICs involved. Layout becomes critical, opamp noise starts adding up... and I'm simply not that good at analog electronics.

So I thought of just using a DSP. I'm more or less familiar with these as I've played with FIR and IIR filters in the past. Building an audio EQ and output multiplexer (stereo to 2.1) with a DSP would make things a LOT easier, less noisier and overall (in my opinion), better. Well, except maybe for ADC-DSP-DAC delay.

Is there a solution that has:

High quality (high SNR, low distortion) ADC with at least 24bit/96khz
At least 32-bit DSP core (floating point prefered?)
High quality (SNR, dist) DAC.
FREE development tools, or at least, unrestricted trial versions.
Comes in an easy to manually solder package (not QFN or BGA. QFP is fine)

Bonus features:

Extra inputs such as S/PDIF, I2S, etc. And multiple analog input channels (to save on the input multiplexer).
It's available as a cheap "ebay board"

I've found several options but not one that fully meets all these requirements. TI is not very helpful (their audio DSP site seems broken). Analog seems to charge $5000 for their software, and the "trial version" only supports one part. Cirrus Logic needs me to "contact my local sales office" to download their development software.

Seems so far the only realistic option is to just use an audio CODEC and a 32-bit microcontroller such as STM32F4.


texts:
I have the following circuit:

The MCP1402 MOSFET driver should be driving the BUK7Y13 N-channel MOSFET at 12V, but I'm seeing a much weaker signal which oscillates around 0.7V, preventing the gate from turning on the MOSFET.

The load being driving is just 3 LEDs and a resistor in series, as described here. I've tried both a full strip, and a short section with just 3 LEDs.
I have tried adding an additional 4.7uF polarized capacitor between 12V and GND, to no effect.
I have three of these circuits and they all exhibit the same symptoms, so it's not faulty components.
Even with no load (no LEDs) the MCP1402 gets hot to the touch, but I don't think anywhere near it's max temperature.
I had previously tried the same circuit but with a FAN3229 driver and no R2, but got similar results.

The FET has a gate charge of 5nC and the driver can put out 500mA - this seems fine to me, but the circuit is not working and I'm at a loss. I presume there's something I haven't understood about the use of a MOSFET driver but I can't see what.

Edit:

Here's an excerpt from the layout - there is a plane to the right of the right blue line which which is "SG" in both diagrams, connected to the low side of the LEDs. And the plane on the left of the left blue line is GND. The other two connects, PWM to control and the connection to the driver are clear.

Pin 4 is the gate as you can see, pins 1-3 are the source to GND and the tab/base is the drain to SG.

"With no load" means with no LEDS being driven by the circuit, and yes I have confirmed with a scope a nice 5V square wave coming in from my MCU, so the signal is correct. I should also add I do see a very, very faint flicker on occasion from the LEDs, as I would expect with the gate switching partially on.

Edit 2:

Having ruled out the obvious, here's the full circuit and layout which I didn't post before for the sake of clarity.

Polygons SG1, SG2 and SG3 are red(top)/blue(bottom) to right of board, connected with many (thermal) vias. 12V polygon is blue(bottom) on lower half of board, GND is blue(bottom) on upper half and red(top) on most of the board. Power supply is large desktop supply and MCU is functioning as programmed at 5V, LED1 is working, PWM to drivers is working, it's just signal from the drivers. Components were all recently purchased from Farnell.


texts: How to generate 2's complement of a 3-bit number using 3:8 active low decoder?

texts:
This is previous year problem of a competitive exam. I tried by self but i was unable to solve it.

Exact wordings of the problem:

  Generate 2’s complement of a 3-bit number (a2a1a0) using a single 3 to 8 active low decoder IC and
  AND gates.

My work till now : (Maybe my approach is wrong)

a2 a1 ao  y2 y1 yo
0  0  0   0   0  0
0  0  1   1   1  1
0  1  0   1   1  0
0  1  1   1   0  1
1  0  0   1   0  0
1  0  1   0   1  1
1  1  0   0   1  0
1  1  1   0   0  1

y2y1yo is required output .Now solve K map for each y2 , y1 , yo and write y2 , y1 , yo in product of sum forms .Notice that output of the decoder will be one of the max terms so we can some how solve using this approach .


texts: Altium Designer 16 - CurrentDate Special String Format

texts:
In previous projects, I used the CurrentDate special string, in the format YYYY-MM-DD (see the image below).

Opening the same project on a different installation of Altium, the format has been automatically changed to MM/DD/YYYY. Is there a way to change this format?

I'm unsure if I changed it in the past. If I did, I don't remember where this setting lives, and I can't seem to find it in the Altium documentation. Any help would be really appreciated.


texts: I'm looking at making my own USB cable for a project.  The primary issue I'm having is that I'm getting a lot of capacitance in my cable between D+ and D- (400ish pF) which is enough to throw off the signals being read by my pc.  Is there an easy way to fix this?  I understand this is an impedance matching issue, but I'm not sure where to begin with this one since the capacitance is between two input lines, not one line and ground which is what I remember from my electromagnetics course.


texts:
simulate this circuit – Schematic created using CircuitLab

I am working on a project with some 8-bit D-Flip-Flops (using CMOS logic), feeding the first output into the second, the second into the third, and so forth.  Only one of the D-Flip-Flop outputs should be on at any given time.

I believe I've set everything up properly, but there are two inputs to the first cell: the microcontroller, which can drive it arbitrarily high or low, and the cascaded output from the last cell, so it can loop indefinitely.

I didn't want to run into trouble where I was driving competing signals into this "bus" (I.E, low from the microcontroller but higher from the cascaded output), so I placed a diode (1N4148 IIRC) pointing from the source to the input pin of the D-Flip-Flop.  So to clarify, I have the following:

Microcontroller -> Diode -> Input pin
Final Output -> Diode -> Input pin

I figured this would help avoid problems.  Unfortunately, it seems to be doing something different.  Even when (and I've measured carefully) both inputs (the microcontroller AND the final output) are LOW, the input remains HIGH once it has been set high by either one of the inputs.

Why is this happening?  My initial guess it just the input capacitance of the pin holds that charge there, but I would think that would eventually dissipate (but it doesn't seem to, even after a number of uS (haven't tested it longer, but that's already too long for my application)).  When I added a pull-down resistor of 100K, it began working as intended.  I'd rather avoid putting more hardware (even just a pulldown), but I really want to make sure I'm understanding exactly what's happening before I make design changes.

Thanks!


texts: Protecting a switching regulator in a 12v automotive system

texts:
I'm using a MaxLinear XRP7659 as a 12v -> 5v regulator in my design. The circuit has an average power usage of 80mA @ 12v and a maximum usage of ~500mA @ 12v.
I have a 750mA fuse on VIN, along with a 100uF 63v capacitor and a common mode choke (both to clean up noise).
I am considering using a Varistor to protect the XRP7659 from destructive transients, but I'm confused about their specs.

Is the Varistor even the best way to deal with transcients?
The regulator is rated for an absolute maximum of 20v. This means that I should use a Varistor with a maximum clamping voltage of 20v, correct?
Why is it that certain varistors have a clamping voltage of 2x their rated DC voltage? In my limited experience, I haven't seen many regulators with that wide of an input range, so I have a I feeling that I'm misunderstanding something.


texts: LVDS signals having different ground reference with coupling capacitor

texts:
I'm simulating a LVDS driver connected to a LVDS receiver with a 100nF series coupling capacitor in between the +ve and -ve signal lines using the respective IBIS model of the same buffer. (DS25BR100 from TI)

Below is the waveform of the simulation

Right after i remove the coupling capacitor, the waveforms are back to the correcct differential pattern.

Would like to ask why and how can I enable the waveform to have the same differential pattern while having the coupling capacitor. Thanks.


texts: how to calculate the Resistor for a mosfet so that the Vout 10 V is?

texts:
These value are given:

VDD = 15V
Zener voltage = 6.8V
Zener current = 5mA
Rs = 3kOhm

here is the link to the data sheet:
https://nl.mouser.com/datasheet/2/268/supertex_2n7000-1181251.pdf
I have calculated that R1 most be (15-6.8)/5mA =1.6kOhm but I'm stuck there.


texts: Photovoltaic systems - typical values of electrical current

texts:
SOLAR PANELS -> CHARGE CONTROLLER -> [shunt A] BANK OF BATTERIES [shunt B] -> INVERTER - AC OUTPUT
What are typical values (to give examples) of electrical current on shunt A (current in on batteries) and on shunt B (current out of batteries), and also at the AC output.
I know that this depends on the application, but I would like to have a better idea of typical values of current in these systems, what values can be reached?
This is for a energy meter project.


texts: Does using memory allocation API such calloc / malloc cause issues on ARM based boards ? I recently faced a issue wherein I used calloc (1024 Bytes) and this buffer was used across many functions in a single source file. I observed the output of a particular function varied randomly when calloc was used, but when I switched over to a fixed array, the issue never showed up. Hence I am wondering if calloc has got any limitations on a small memory footprint board.


texts: How can I vertically shift the voltage of a zero-centered signal such that I can read it with the Teensy 3.2's internal ADC?

texts: I have a sinusoidal signal with a frequency of 100 kHz. It's zero centered with a peak-to-peak of around 3V (i.e. from -1.5V to +1.5V). I want to be able to read the peak-to-peak voltage with one of the analog pins on a Teensy 3.2 MCU, but I'm unsure of how to shift this signal to the 0-3.3V range. I'm very much a beginner so I'm still a bit unfamiliar with the terminology. A basic explanation would be really appreciated.


texts:
I'm having trouble with a simple AND gate, using two 2N2222 NPN transistors:

For some reason, the base of the second transistor is high at 2.9V and I don't know what's causing this. I have verified that it isn't shorted to 3V and cut off the input to B so it seems the transistor is outputting the current. What could be causing this?


texts: How can I tell if I can power NFC chip passively?

texts:
I'm trying to figure out how to tell if I can power a particular NFC chip/microcontroller passively.  By passive I mean it needs no battery and can be powered by an NFC reader alone.

Many datasheets I read say they support ISO/IEC 14443 and all modes of NFC but don't clearly say anything about passive operation.  For example, here is a chip from NXP.

Is there any way to tell if I can power it passively?

Is passive operation always possible for ISO/IEC 14443 contactless communication?


texts:
I am reading the Adafruit Trinket tutorial here. It states that BAT+ is used for battery INPUT:

  If you want to power the trinket from a battery or power adapter or solar panel or any other kind of power source, connect the + (positive) pin here!

So I'm slightly confused by the Adafruit LED skateboard tutorial, which uses this pin for power OUTPUT.

My questions:

How can you use the power input pin for output?
Why don't the LEDs draw way too much amperage through the Trinket board?


texts:
I have a small circuit using a PIC18F14F50 microcontroller chip which is logging data into an external EEPROM chip over an i2c interface (which I can then read back later over the USB interface). One sample is recorded every 15 minutes and doesn't need to be particualrly accurately timed.

It's ok if samples are missed or mis-timed while batteries are being changed, but it's not great if the batteries expire and no data is recorded for several days until someone notices.

So I'd like to warn the user when the battery is low in plenty of time for them to replace them. The average current is under 2mA and I'm running in from 3 AA alkaline batteries in series to give 4.5volts so I'd expect them to last quite a number of days.

But I'm wondering how to detect that the battery is low? I presume the voltage will drop as the batteries reache the end of life. I'm thinking that this PIC has a 1.024v reference voltage so I can divide down the supply voltage and feed it to an analogue input and when the divided voltage drops below that trigger a warning.

But I don't know enough about batteries to know how well this will work? And I don't know what voltage to choose that would indicate that perhaps 10-20% battery life is left. Will that even work at all? Is there a better approach?

This doesn't need to be at all accurate, I just want to give a good warning in plenty of time without getting people to disard batteries that still have life left in them.

As my current usage is fairly constant, would a simple timer be reasonable if I can work out how long the batteries last on average and then pick 85% of that time before I give the warning? Or does battery life vary more than that?

Any thoughts would be welcome.


texts: Oscilloscope range affecting voltage reading

texts:
I am trying to measure the current usage of a device using an oscilloscope.
Every second the device turns on for a few milliseconds and then goes back to sleep. I need to find how much current is being used both when it is sleeping and when it is awake. I set up this circuit to help me read the current as a voltage across R1.

simulate this circuit – Schematic created using CircuitLab

I have found that the voltage range setting on my scope seems to affect the readings a lot.

Voltage Range ==> Reading

200mV ==> 1.76V

500mV ==> 4.39V

1V =====> 5.02V

2V =====> 5.24V

I can't see the sleep current without the 200mV range and I don't know which reading I should use for my calculations. Why am I seeing varying voltages and how can I fix my circuit?

Edit: Here is a picture of the waveform in question. this one is scaled to 500mV/Div because you can't see the top at 200mV/Div.


texts: Can i use 4.0 MHZ crystal oscillator instead of 3.5795MHZ for making DTMF decoder?

texts:
I couldn't find 3.5796 MHZ Crystal Oscillator for making a DTMF decoder so, I bought a 4.0 MHZ  Crystal Oscillator.

Will it have any problem using the 4.0 MHZ instead of the 3.5795 one?


texts: STM32F103: ST-Link doesn't actually update the firmware upon reprogramming unless I relaunch ST-Link

texts:
I've just got a new STM32F103 board instead of the F3 Discovery, can't get OpenOCD working, so I'm stuck with ST-Link for re-flashing. And I've spent 3 to 4 hours today trying to figure out why my firmware wouldn't work. Well, I just found out: everything works, but ST-Link will only flash once, and then won't update the firmware unless I restart the program, although success is always reported! Pressing "reset" on the board manually also has no effect. So:

Open ST-Link, program - OK; edit the code and rebuild hex, program - not OK. Fiddle with all the ST-Link commands including chip erase - still not OK.
Open ST-Link, program - OK; edit the code and rebuild hex, close ST-Link and reopen it, program - OK!

Doing menu -> Target -> Compare device memory with ***.hex also always finds no difference unless I re-run ST-Link. It's as if it is caching the .hex somewhere in its memory with no regards for its changes on the disk.

It's not that I can't be bothered re-run ST-Link every time, but what's going on? My pet project depends on STM32, I'm behind schedule, other people are waiting for me, and every time I have to make changes to the setup something new breaks. I need to improve my understanding of STM32 environment ASAP to avoid further problems.


texts: I've been wanting to expand my embedded skillset with ARM MCUs after spending a few months working with pic24 devices but I've hit a roadblock. I wanted to start programming ARM more "on the metal" without the abstraction layers that things like mbed provide, similar to how I would expect to program a pic and I intended to do this with MCUXpresso. The development board I am using is the FRDM KL25Z which has an mkl25z4 on it. I was expecting to be able to find a datasheet for the chip, read that and understand how to start controlling ports, peripherals etc. but I just can't seem to find that information anywhere. I have MCUXpresso correctly configured and have installed the SDK from NXPs website and have even got a flashing LED demo up and running but only have a vague idea on how any of the code works. What information should I be looking for to help me understand better what is going on? Do datasheets of ARM based chips exist just like PIC, should I be able to read and understand the datasheet in order to control peripherals just like pic etc? Any help would be great


texts: Differential equation to describe an RC circuit with a sine wave

texts:
In this image Vin is a sine wave , sin(ωt), and I am trying to get the differential equation that I will then be able to solve.
I am having troubles trying to find the current through the power supply and I no sure weather I am not taking the correct approach to solving this.


texts:
My project partner and I are working on making a rf-dc energy harvesting circuit capable of lighting an LED (even intermittently) or trickle charging a coin cell battery over a long time.
We are looking to use 2.4Ghz and 5 Ghz wifi bands to convert as much energy as possible using a Cockcroft-Walton voltage multiplier. I know that distance will be extremely low but we are more interested in showing it is possible than it being useful as of now. As many stages as necessary to power the led briefly, I think the minimum stages is 4-5. I have a dual band antenna 50 ohm impedance, schottky diodes, ceramic caps(various sizes), and access to a network analyzer to build a matching circuit. Supposing -20dbm or better is this possible?

How do I calculate the necessary capacitor sizes to use for the multiplier and the size of a load capacitor for instance to charge the battery? What is a good source for pcb for surface mounting that is better than fr-4?


texts: Easy way to define wire output multiplexers in Verilog

texts:
For the wire type in Verilog, I know that I can define a multiplexer as follows

wire a;

assign a = select ? 1'b0 : 1'b1;

And for reg's, I can do it as follows

reg a;
always @ (select)
begin
    case(select)
    1'b0: a = 1'b0;
    1'b1: a = 1'b1;
    endcase
end

Now my question arises - it's so easy to describe complex multiplexers using regs/always blocks/procedural statements. It seems so tedious to do the same with wires. What if I wanted to describe a very complex multiplexer driving a wire? Would my select? line be huge?


texts:
Hello I’m just a beginner and I made a simple circuit with a resistor and a capacitor with a led in between.

As I understand the capacitor just accumulates the energy but why is my led not going on?

When I get rid of the capacitor and simply connect the cable directly to minus it all works.


texts:
I am doing a question (I have broken the problem down to this sub-problem) which requires me to find the output resistance below:

I tried to do the small-signal analysis to find it by adding an extra voltage source and finding Vx and Ix. However, I'm stuck now. I can solve the problem if just ro2 was there, but the ro3 to GND is making it difficult to find the current Ix.


texts: Correcting for non-linear brightness in LEDs when using PWM

texts:
When driving an LED with PWM, the brightness (as I perceive it) does not scale linearly with duty cycle.
The brightness is slow to ramp up, then increases exponentially with duty cycle.

Can anyone suggest a rule of thumb to use as a correction factor, or other workaround?


texts: OTA / Common Base (CB) Transistor Circuit

texts:
I would like to fully understand the following schematic. Especially the nonlinearities are of interest. (Supply Voltage is +/-15V for both OpAmp and OTA)

It's an amplification circuit and the in going voltage is used to control the amplification via the OTA. However, I have trouble fully understanding the use of the transistor.

The applied voltage might be anything between 0V and 5V. this is then scaled with a resistor ([0,5]). The OpAmp applies a positive 0.3V offset and scales the signal slightly. (g = 1.02)

Sadly, this is where I drop out. I understand that the transistor is used as a common base transistor and that the offset (0.3V) is most likely used to get closer to the minimum 0.7V needed for a current to flow. I would like to know the dependency between the output of the OpAmp and the control current (Iabc) of the OTA. What is the correct approach of "calculating" the current at the transistors collector?


texts: What are the differences between Channel-to-Ground & Channel-to-Channel isolation?

texts:
I have the following questions regarding different types of isolation techniques:

What are the major differences between Channel-to-Ground & Channel-to-Channel isolation techniques?
Are all Ch-to-Ch isolated devices also Ch-to-Gnd isolated?
Is there ever a scenario where you would chose Ch-to-Gnd over Ch-to-Ch isolation given all else equal?
Do either of the two techniques reduce the effects of crosstalk? If so, how and which one is better?


texts:
I have a cheap ESD mat and wrist band which I use behind my desk with a computer/Arduino breadboard setup. However, my components are 1 to 2 meters away (since my desk is full).

I need to take off the wrist band and the ESD mat stays on the desk ... what is best? To roll my office chair towards the desk with components or to walk? The floor is wood and normally I wear rubber/leather shoes.

The risk I see is that components I pick up at the other desk can get static energy because of rolling my desk chair or walking to the desk (and picking up the components on that desk).


texts: Calculate induced voltage in a wire due to mains wiring

texts: I wish to calculate voltage induced in a short piece of wire of known length, due to mains household wiring carrying some current say 5 amps. My application is biomedical sensor wire and I can not use a shielded wire. my sensor wire is connected to a small battery operated circuit. so can       capacitive coupling can be neglected? Does this mean that the coupling is mainly inductive ?  How will the induced interference voltage vary with distance and orientation of my biomedical sensor wire from the mains wiring?


texts: Base addresses and offset values for registers, STM32 documentation

texts:
See the document here.
From page 193:

This table looks like stating that the base address for NVIC block is 0xE000E100.

The table below from page 208 states that NVIC_ISER0 register is at memory address of 0xE000E100, which is correct and validated by me in my code.

Now, from page 210:

This is the part things start to sound wrong to me: This makes me to think that, "hmm, ISERx registers are the first registers in NVIC block, so, if it is said to have an offset of 0x100, then it means that base address for NVIC register block is 0xE000E100 - 0x100 = 0xE000E000. But at this point, it conflicted with the above information which states(or at least I evaluated as so) that the base address for NVIC is 0xE000E100.

And finally, from page 219:

Which clearly states that both the base address is 0xE000E100 and NVIC_ISER0 has an offset of 0x100.
So, where am I wrong at?


texts: Why did my Ultrasonic Sensor HC - SR04 measured distance is less than half of the actual distance?

texts:
I was trying to test my ultrasonic sensor by measuring a distance of 10cm until 100cm and using an oscilloscope to look at the echo pin output signal. My oscilloscope is set at 0.5 time/div.

At first, my ultrasonic sensor couldn't work properly, but after some tweaking around, I can finally get my ultrasonic sensor working. But the strange thing was, the measured distance I got was always less than a half of the real distance value. For example, for a distance of 70 cm, I got 27.2 cm from the calculation. This is the output signal for a distance of 70 cm (3.2 DIV * 0.5 ms/DIV = 1.6 ms).

Basically, all I do is, I calculate the HIGH time by multiplying how many DIVs appeared and then I multiply it by TIME/DIV (I set TIME/DIV = 0.5 for all measurement). Then I multiply the time with velocity of sound  (340 m/s)and then divide it by 2. Because the HIGH time appeared in oscilloscope is the time to travel back and forth.

Distance = (T*Vsound)/2

Why did I got such a large discrepancy between the experiment result and the actual value? I've followed the standard procedure. I connected the Trig pin with function generator of 40 kHz frequency, the Vcc pin with 5 Volt, GND pin with ground, and the echo pin with the oscilloscope. Also my ultrasonic sensor is a brand new one, never used before.

So what possibly I did wrong?


texts: Differences between current sources transistor and current mirror

texts:
In this configuration

simulate this circuit – Schematic created using CircuitLab

if the two pMOS are equal, they provide the same drain current to both the branches: suppose that Vbias is chosen so that the drain current will have a certain (constant) value Ibias. Moreover, if a new pMOS is added and connected at the same Vdd and with the same gate potential Vbias, it will generate the same drain current as M1 and M2.

But often the current mirror configuration is used:

simulate this circuit

where the drain current of M1 is Ibias (and it is the drain current of any other transistor equal to M1 and connected in the same way).

I think that the two configurations (with appropriate Ibias and Vbias values) are equivalent.

My questions are:

is the second configuration the most common in CMOS circuits? I found it more often than the former;
if yes or if not, why?


texts: Affordable way to test frequency range of a 2.4GHz device

texts:
Does anyone know of a good/affordable way to test the frequency range of a RF device (e.g., Bluetooth module)? Not spectrum analysers since they're rather unaffordable. Are there relatively affordable tools for measuring the range? I heard about SDR, but AFAIK they don't do 2.4Ghz. How about RTL-SDR with downconverter, perhaps with something like this? Is it accurate?

How about HackRF?

Any help will be appreciated.


texts: What prevents semiconductors working below -40°C or so?

texts: Most devices seem to be characterised over -40°C to ≥85°C. What limits them to cold temperatures? Can an IC be damaged by keeping it too cold? Does this apply to other devices, e.g. diodes, transistors?


texts: Node Voltage: Why must I have to let unreferenced node to be going outward current?

texts: Why do I need to make V1, unreferenced node, outgoing current for i(a) to get the correct answer? why can't I follow the given current direction and use it to calculate the correct voltage at that node?


texts:
The question from my book : Is there any way to connect a light bulb to the phase lines connections, neutral and earth so that the RCD (Residual-current device) stop the current?

the answer is : Yes. Connect between any phase and earth.

My question : Why RCD does not stop the current when we connect the bulb between a phase and neutral?

Thanks


texts: Removing a piezo transducer from a reference design

texts:
I'm building a system which is intended to supply a microcontroller with a smoke-detection alarm. I'm currently intending to base the circuit on a Microchip RE46C190, which I can source fairly easily.

The datasheet has a typical-application circuit on page 21 which looks suitable for adaptation, but I need advice on how to remove the piezo transducer from the design (as I don't require an audible output; I intend to link the IO pin to the microcontroller). I gather that FEED will need to be tied to one of the rails (when not in test mode, anyway), but what should I do with pins HS and HB which are intended to drive the transducer? Can I simply leave then unconnected, and omit R3, R4 and C5?


texts: How can this PWM converter circuit be improved?

texts:
This circuit is intended to use a 1-10Hz PWM signal as input and produce a 1-10kHz 10A PWM output. It will be used for controlling the speed of a water pump: GP1352 The PCB will be ordered with (only) SMB components pre-assembled and will be potted once the SW has been commissioned. Thus keeping the heat low is important. I can only order the PCB with 1oz copper so heat from the traces is a concern as well. Therefore I am using 4 MOSFET's even though 1 should be able to power the pump alone. This way I plan to spread the heat generation out across the board to avoid hot spots. (The potting will be as thin as possible to allow the greatest heat transfer) The desire for low heat goes hand in hand with driving the pump to its full capacity as well.

I could explain the calculations and data sheet lookups I've used to arrive at this design, but the question would get very long and I think my intentions are clear from the description and the schematic. If anything was unclear I will elaborate in the comments.

So, how can I modify this circuit to better achieve my goal?

PS: This is my first electronic circuit design. Apologies in advance for the newbness, I'm doing my best.

Schematic updated 20191001 based on input from Brian Drummond and The Photon.


texts: How do current and voltage relate to load?

texts:
I think I've lost the plot somewhat on how current and voltage relate to the load in a circuit and I'm hoping for some really basic level clarification.  In fact, I'm not really sure how to ask the question.

For example, I feel like I had a decent grasp of a voltage divider circuit:

If Vin is 5V and R1 and R2 are 1K resistors, then Vout will be 2.5V and the current between Vin and ground will be 2.5mA, right?  That made sense to me.  In my head I described it that "the circuit is drawing the current it needs based on the power supplied and the load."

I made a nightlight for my kids with a photoresistor in a voltage divider configuration so that I could detect changes in light levels.  Because of the fixed resistor in the divider, the relationship between light and Vout isn't linear.  That made programming for different light levels more trial and error than deliberate.

Today I learned about phototransistors and saw in one datasheet where the relationship between light and current was linear.  That seemed encouraging, but I think it means my concept that the circuit "pulls the current it needs for the load" isn't quite correct.

This is their circuit for converting the current to voltage.  I don't understand what this means.  I mean, I understand that with a 10K resistor, .5mA would result in 5V out, but that sounds more like "the current is being pushed to the circuit and the load is creating the voltage."

But that doesn't make sense.  I can't put a 100K resistor there and have 45V, right?  So what would happen?  Does it just max out at 5V because that's my supply power?  Does the current drop accordingly?  How is the current not dependent on the load?


texts: Find impedance matching in a quarter wave transformer

texts:
I would like to know if there is a way you can find the impedance that has to be set between the load \$Z_L\$ when it is complex and the characteristic impedance \$Z_0\$ to have impedance matching without using the Smith Chart, since we are not allow to use it and all the methods I have search use it. It has to do something with the formula:$$Z_{in}=Z_1\frac{Z_L+jZ_1\tan\beta l}{Z_1+jZ_L\tan\beta l}=Z_0$$ and \$\beta l=(2\pi/\lambda)(\lambda/4)=\pi/2\$. The goal is to compute \$Z_1\$ and it seems always to be real.
The formula can be found in Microwave Engineering, Pozar, page 79, and with a scheme like this one:

also found in page 92, but the book specifies that \$R_L\$ is real.
The closest thing that I have found to my problem is this one:

but it uses the Smith Charts as it says so. In my problem \$Z_L=25-j175\$ and \$Z_0=36.11\$, giving a result of \$Z_1=\sqrt{75\cdot36.11}\$ but I don't know how that result has been achieved. Could it be related to a multiple media problem?


texts: What's the purpose of this checkerboard pattern?

texts:
This gigabit Ethernet NIC has a checkerboard pattern out of copper etched on the PCB:

Each square is electrically isolated. What's the point of adding these? I guess that the PCB isn't filled with a copper plane due to cost concerns, but why don't leave it empty then?


texts: What is the use of dual input, unbalanced output differential amplifier in an operational amplifier?

texts: Why do we use an unbalanced output Differential amplifier and not a Balanced one?


texts: BQ2407x Li-Ion charging circuit, what if Vin is disconnected?

texts:
We will use a Texas Instruments BQ24072 in our power board to monitor the battery.

-PoE or solar will charge
-Most of the time, circuit will work on battery.

When disconnection the Vin, one would assume the battery takes over.

datasheet p3 Vin voltage range between 4.35V and 26 V
datasheet p4 UVLO Undervoltage lock-out VIN: typical  3.3 V

This would suggest that everything stops working when Vin is too low.

Datasheet

Answer:
ok, datasheet p16, everything shuts down but battery is "connected" to out

UNDERVOLTAGE LOCKOUT (UVLO)

The bq2407X family remains in power down mode when the input voltage at the IN pin is below the undervoltage
threshold (UVLO).
During the power down mode the host commands at the control inputs (CE, EN1 and EN2) are ignored. The Q1
FET connected between IN and OUT pins is off, and the status outputs CHG and PGOOD are high impedance.
The Q2 FET that connects BAT to OUT is ON. (If SYSOFF is high, Q2 is off). During power down mode, the
VOUT(SC2) circuitry is active and monitors for overload conditions on OUT.


texts:
In Vivado, implementation of my projects can take a while especially if I use debug cores. What can I do to make implementation faster? I tried the "RuntimeOptimized" constraint and it made no difference. Is there an option for less optimization and faster compilation? If I debug nets as "data" only and not "data and trigger" will it make it faster?

Often I am changing small things in order to debug my firmware. I feel like this is the wrong way to do it, but I'm not sure what else to do when I get results different from those I simulated (I use ActiveHDL to simulate).

Is there a way to reduce implementation time if I made only minor changes?

Is it possible to improve my VHDL code to make things faster?

Thanks for any help.


texts:
I was looking at what goes into driving an LED strip from a microcontroller and i found this

https://electronics.stackexchange.com/a/67780/41661

which has this schematic

In the question the op states the PWM 3.3v is coming from a MCU but he never states what kind of MCU he is using.

I can see that R1 and R2 form a voltage divider that does almost nothing due to the massive difference in resistance and R1 should pull the line down when PWM isnt on and most of the discussion on the answer is focused on that but i dont understand how they came up with that value for R2.

According to ohms law 3.3v through a 27R resistor will flow 122ma which seems a lot of current, Arduinos for example can only supply 40ma to any one pin max and its recommended to stay below 20ma when possible according to this link. Now its entirely possible that the OP could be using a much hardier MCU than an Arduino but doesnt this seem like a strange assumption to make given that the MCU isnt specified.

I read the datasheet for the IRLML2502 supplied in the linked question and i couldnt find anything about how much current was needed to saturate the gate of the mosfet, though datasheets are still mostly greek to me.

Assuming the OP was using an MCU with similar limitations to an Arduino, wouldnt it make more sense to use a 180R resistor value for R2, allowing 18ma to flow at 3.3v or have i misunderstood something?


texts:
I have a schematic for a temperature controlled device which should operate at a particular temperature.

For that I am using an NTC, now I have done the math by hand but it is more efficient and effective to include a diagram and an LTspice simulation, how could I model an NTC as the parameters such as "B-Curve" and ABC for the Steinhart and Hart equations are the only ones that change?


texts: 3-Stage Shift Register using Blocking assignment in Verilog - Differences among simulators

texts:
Simulation of a 3-stage shift register using blocking assignment statement in Verilog gives different simulation results across simulators:

The RTL code is as follows:

`include "timescale.hv"
module shift_register
#(
parameter DATA_WIDTH = 3
)
(
input  wire  [(DATA_WIDTH-1):0] din   ,
input  wire                     clk   ,
input  wire                     rst_n ,
output wire  [(DATA_WIDTH-1):0] out
);

reg [(DATA_WIDTH-1):0] q1,q2,q3;

assign out = q3;

always @ (posedge clk or negedge rst_n) begin
   if(~rst_n) begin
      q1 = {(DATA_WIDTH){1'b0}};
      q2 = {(DATA_WIDTH){1'b0}};
      q3 = {(DATA_WIDTH){1'b0}};
   end else begin
      q3 = q2;
      q2 = q1;
      q1 = din;
   end
end

endmodule

The test-bench code for simulation of the above RTL is as follows:

`include "timescale.hv"
module tb_shift_register ();

localparam DATA_WIDTH = 4;

reg [(DATA_WIDTH-1):0]  din   ;
reg                     clk   ;
reg                     rst_n ;

wire [(DATA_WIDTH-1):0] out   ;

shift_register
#(
.DATA_WIDTH(DATA_WIDTH)
)
inst_shift_register
(
.din   ( din   ),
.clk   ( clk   ),
.rst_n ( rst_n ),
.out   ( out   )
);

initial begin
   clk   = 1'b0;
   rst_n = 1'b0;
   din   = {(DATA_WIDTH){1'b0}};
   #20;
   rst_n = 1'b1;
end

always #5 clk = ~clk;

always@(posedge clk) begin
   if(rst_n) begin
      din = 4'd15;
   end
end

endmodule

When functional simulation is performed using the above TB for the RTL (previously mentioned above) in ModelSim, the following waveform is observed:

The simulation appears exactly same as that of a 3-stage shift register using non-blocking assignment, where the output appears after 3 clock cycles and the input "din" appears at "q1" only on the next clock cycle.

When simulation is performed for the same RTL and TB using Xilinx Vivado, the following waveform is observed:

It is observed that the output appears at "q3" after only 2 clock-cycles and the input "din" appears at "q1" at the same clock cycle.

So, I am having 2 questions:

Although it is expected that for blocking assignment, the input "din" must appear at "q1" in the same clock cycle, why does ModelSim simulation shows that the input "din" appears at "q1" in the next clock cycle. Which of the simulators is correct?
How to model a perfect 3-stage shift register using blocking assignment statement in Verilog ? (which is synthesized as a 3-stage pipeline register and which, when simulated shows that the output at "q3" appears after 3 clock cycles).

Note: I am aware of the fact that blocking assignment statement should be used to model a combinational logic while a non-blocking assignment statement should be used to model a sequential logic. I am asking this question since, this was an interview question asked to me regarding implementation of a 3-stage shift register using blocking statement.


texts: Do you need to use different materials for a battery busbar?

texts:
I'm interested in building custom Lithium Ion battery packs out of reclaimed 18650 cells. I've seen several videos of people doing this and some of them use copper for the positive busbar and brass for the negative busbar.

Is there a particular reason for this?

EDIT: To be more clear, I'm talking about wiring up multiple 18650's together in parallel.


texts:
I'm trying to learn how to implement a 3V LVTTL interface using a Cyclone IV E (EP4CE10) FPGA. However, I would like to ensure that the input/output impedances of the IO is at 50R. I see that it is possible to achieve this In the IO Features guide here on page 7, providing I use column/row IO 4, 8, 12 and 16. However, I am confused as to what the actually means.

Presumably there are only certain IO that can use this feature, but I cannot seem to find which specific pins this applies to.

Reading the Cyclone IV handbook here on page 122 onwards, it talks about banks which I think I understand - but it doesn't tell me which specific pins this applies to - nor do I see anything about 'rows' or 'columns'. Furthermore I can't see how to actually ensure that the input/output Z can be set to 50R.

In short, how can find out which pins I can use and how do I set the impedance on the device?


texts: How to find the Nyquist-/sampling frequency of a Sigma-Delta-ADC

texts:
I'm looking at the datasheet of an Analog Devices ADC (AD7124-4) and can't understand what is the relevant sampling frequency to use as a basis for calculating the anti aliasing filter.
Is the relevant frequency the clock frequency of 614.4kHz?
Is it the maximum data rate of 19.2 kHz?
Or does it depend on the specific data rate I'm using?


texts:
I am a Verilog user trying to make sense of VHDL code of AXI4 Master bus functional model (BFM)

AXI bus master VHDL code

I have a few questions from the above code

What would block diagram of the code look like (how are components connected with each other)

Lastly, what is the use of FIFO? I mean to connect AXI master to AXI slave, can't one connect the appropriate signals directly as shown in the picture? What purpose does FIFO serve here and what if it is removed?


texts: Why is the sign of the voltage on this resistor positive in this example from my textbook

texts:
I am taking a circuits class and this example problem is really confusing me. I am asked to find \$ v_{o} \$ and \$ i \$ for the circuit below.

In their solution, the book starts from the 12 V source and traverses the loop clockwise. The last element in the loop is the 6 Ohm resistor. Since the current encounters the negative terminal first and moves from low potential to high potential, I figured the sign would be negative and the voltage for that element would be \$ -6i \$ making the final equation

$$
 -12 + 4i + 2v_{o} - 4 - 6i
$$

But they give it a positive sign. Why?

When they apply Ohms law in the second step they correctly assign the voltage a negative sign. Why do they not give it a negative sign when using KVL?


texts:
I'm new in electronics and I have a doubt. Recently I bought a 7 segment display to practice with Arduino, but I don't know how it works. I have searched at the Datasheet:

I suppose that my display is T because it is write in it "HDSP-N101" an I looked the first table of the Datasheet:

My question is:

I have to connect all cathodes to earth (because they are the negative part) with a resistance of 220 ohms?

And then, I connect the anodes to the pins of Arduino to create the numbers? Because there are 4 anode pins. With this 4 pins, how can I show a number?


texts: What is the difference between 7474 and 7479 ICs? How do they differ from 4013?

texts:
I am hobbyist and am looking to reduce signal frequency using D type flip flops. I have a circuit diagram for a 4013 IC but I would like to use a 74HC74 instead and I do not understand if it is possible.

From wikipedia:

7474 are dual D positive edge triggered flip-flop, asynchronous preset and clear.
7479 is a dual D flip-flop

Likewise the 4000 series:

4013 is a Dual D Type Flip Flop

I wasn't able to find a 74HC79 components however I was able to find 74HC74 and a 4013 IC.

From looking at the functional diagram in the specifications, they are essentially the same other then that one has CD [asynchronous clear-direct input (active HIGH)] and the other has RD [asynchronous reset-direct input (active LOW)] on the diagram.

I want to construct the following diagram using 74HC74 instead of 4013:

Could this be done using 74HC74? How would such a circuit be different? or can RD be connected to the negative wire just like CD?


texts: How to separate PCB antenna and SMA connector?

texts:
I am designing a prototype PCB for a Lora node.
It will have an SMA connector (J2) and a PCB antenna.
Switching RF connectors are not available in my area, so as an amateur enthusiast what is a good way to separate the antennas?
I have placed a solder jumper (JP1) before the PCB antenna as seen in the image below. Would it suffice or should I place another one before the sma connector too? Are there other, better alternatives?


texts: LDO selection in low noise amplifier application

texts:
Assuming a design case where an Ultralow Noise Amplifier like AD8331 is used. This amplifier has an input voltage noise of 0.74 nV/√Hz and input current noise of 2.5 pA/√Hz. The amplified signal will be digitized with a 24 bit ADC (Vref=3V) in order to perform an spectral analysis.

I have some questions regarding the selection of a suitable LDO for this application. I need to get 5V from a 15V source.

How would affect the selection of the following LDOs on the overall noise performance of the amplifier?

Example1:
Ultra Low Noise LDO: ADM7150
RMS Noise @ 10Hz to 100 kHz (V rms): 1.6μVRMS

Example2:
Low Noise LDO: LT1761
RMS Noise @ 10Hz to 100 kHz (V rms): 20μVRMS

Example 3
LDO: LM3480
RMS Noise @ 10Hz to 100 kHz (V rms): 150μVRMS

It makes sense to use an Ultra Low Noise LDO in this application?


texts: How to start with this ESC? Some simple questions

texts:
I'm building an autonomous boat for which I've been using a brushed DC motor. I now want to try my luck with a brushless DC motor. So I just ordered this brushless motor and I still have this ESC laying around (which I never used before).

My questions:

Can I use this ESC with this motor?
How do I know what kind of PWM values I need to send to the ESC? Is that the same for all ESCs? Or is that a trial and error thing?
Is it possible to use the ESC to reverse the direction of the motor? Or do I also need to use an H-bridge for that (just like I do with the brushed DC motor)?

All tips are welcome!


texts:
I've been trying to figure out how to implement trig functions in my PicBasic projects.  I could use a lookup table but that limits my output.  I need to be able to use sin, cos, tan, and their inverses in order to do a time based calculation.

Should I just give up and start looking at programming PICs in C?  I've got a programmer and a couple of PICs next to me and would rather use these before jumping on the Arduino bandwagon, or would it really be that much easier to use an Arduino?


texts:
A common type of EEPROM used in computers is the Winbond chips, such as W25X10A, W25X20A, W25X40A, and W25X80A. The datasheet for these chips can be found on Datasheet archive.

It was not clear to me from the datasheet how to hardware protect the chip.

In other words, I want to disable the chip from being written, but not read at the hardware level. Is there any way to do this that is purely hardware based and does not involve sending data to the chip?


texts: I am a newbie and was hoping someone could assist me. Given the following schematic which takes a voltage of 12v and considers it off and a voltage of 2 volts and considers it on can someone tell me what changes would need to take place regarding capacitors and resistors (if any) to account for 20v instead of 12v? Meaning that when 20v is considered off and 2v is considered on.


texts: Need help in zero cross circuit by using op-amp

texts:
I worked on zero crossing circuit by using opto-coupler.Circuit is

It is working okay.Zero_crossing signal is

There is a 2-3 ms of signal loss is happening with 50Hz of AC signal.I don't want more than 0.5ms signal loss something like blue color signal below.

Is there anyway that I can reduce this loss.Any use of using op-amp?


texts: Can I get away with that poorly designed board?

texts: I am designing a board but space is not a luxury that I have at the moment, can I get away with that design or I must use a SMD resonator?


texts: Need help with LM317 voltage regulator circuit

texts:
I am new to electronics and not quite sure how to debug a circuit.
I created a simple regulated power supply circuit as following using LM317 voltage regulator.

simulate this circuit – Schematic created using CircuitLab

The circuit was working for last 1 day. Suddenly by mistake I supplied 19.2V input to the circuit. Ever since then the circuit supplies voltage but only upto a few volts like 3V. The range I get now is approx 0-3.3v, no matter what value R2 is set with. I need your help to identify what might have gone wrong in the circuit. I tried removing the capacitors and the LM7805 along with the voltmeter. Neither worked.

What are the parts I should test/replace to troubleshoot this circuit.


texts:
I want to continuously transmit the data on the UART2 of my dsPIC33EP512MU810

. UART2 Tx pin i am configuring it to Pin 51 of the controller which is RP99.

Now the UART output is being converted to RS485 using ST4485EB on board IC. 3 number pin of ST4485EB IC is connected with controller's 55 number pin which is RA2. I am making RA2 pin high to activate the IC.

My board also has a on board crstal TXC 4.00 MFC which is a 4 MHZ crystal.

Trying to configure the UART with baudrate of 38400 8 data bits, 1 stop bit, none parity and none flow control. Using the following code but not getting the desired result. Please help me out with this.

/******************************************************************************/
/* Files to Include                                                           */
/******************************************************************************/

/* Device header file */
#if defined(__XC16__)
    #include <xc.h>
#elif defined(__C30__)
    #if defined(__dsPIC33E__)
        #include <p33Exxxx.h>
    #elif defined(__dsPIC33F__)
        #include <p33Fxxxx.h>
    #endif
#endif
#define FP 40000000
#define BAUDRATE 9600
#define BRGVAL ((FP/BAUDRATE)/16)-1
unsigned int i;
#define DELAY_105uS asm volatile ("REPEAT, #4201"); Nop(); // 105uS delay

#include <stdint.h>        /* Includes uint16_t definition                    */
#include <stdbool.h>       /* Includes true/false definition                  */

unsigned int i;
#define DELAY_105uS asm volatile ("REPEAT, #4201"); Nop(); // 105uS delay

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <xc.h>
#include <float.h>
#include <libpic30.h>
#include <p33Exxxx.h>
#include "system.h"        /* System funct/params, like osc/peripheral config */
#include "user.h"          /* User funct/params, such as InitApp              */

/******************************************************************************/
/* Global Variable Declaration                                                */
/******************************************************************************/

/* i.e. uint16_t <variable_name>; */

/******************************************************************************/
/* Main Program                                                               */
/******************************************************************************/
int16_t main(void)
{

    TRISAbits.TRISA2=0;
    PORTAbits.RA2 = 1;

    RPOR8bits.RP99R = 3; // Assign U2TX peripheral to pin RP84
    RPINR19bits.U2RXR = 19; // Assign pin RPI16 to U2RX peripheral

    U2MODEbits.STSEL = 0; // 1-Stop bit
    U2MODEbits.PDSEL = 0; // No Parity, 8-Data bits
    U2MODEbits.ABAUD = 0; // Auto-Baud disabled
    U2MODEbits.BRGH = 0; // Standard-Speed mode
    U2BRG = BRGVAL; // Baud Rate setting for 9600
    U2STAbits.UTXISEL0 = 0; // Interrupt after one TX character is transmitted
    U2STAbits.UTXISEL1 = 0;
    IEC1bits.U2TXIE = 1; // Enable UART TX interrupt
    U2MODEbits.UARTEN = 1; // Enable UART
    U2STAbits.UTXEN = 1; // Enable UART TX
    /* Wait at least 105 microseconds (1/9600) before sending first char */
    DELAY_105uS
    U2TXREG = 'a'; // Transmit one character
    while(1)
    {
    }
}

void __attribute__((__interrupt__)) _U2TXInterrupt(void)
{
IFS1bits.U2TXIF = 0; // Clear TX Interrupt flag
U2TXREG = 'a'; // Transmit one character//comment this once testing is done and UART is working.
}

I can see the data on the PC terminal but its not 'a'. Tried different baud rate but none of them is giving me the result 'a' which I am sending.


texts: Can't use the Wake-on-Motion functionality of an MPU9250 with STM32

texts:
Hi there :) I'm trying to use the Wake-on-Motion functionality of this particular MEMS (MPU9250) with my STM32L152C-Discovery board: if the MPU9250 sense a motion, the INT pin will be high.
To achieve this I'm setting the registers as the datasheet suggests with the STM32 micro, handling also the interrupt, but it doesn't work.

Here is my main code(in main.c):

uint8_t interruptFlag;
int main(void)
{

  HAL_Init();

  SystemClock_Config();

  MX_GPIO_Init();
  MX_I2C1_Init();

  uint8_t MAddr=0x68;
  uint8_t buffer;

    if(HAL_I2C_IsDeviceReady(&hi2c1, MAddr<<1, 2, 10) == HAL_OK)
    {
      HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_6);
          HAL_Delay(1000);
          HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_6);
    }
    //register values
    uint8_t maskPWR_MGMT_1[2] = {0x6b, 0b00000001};//6b
    uint8_t maskPWR_MGMT_2[2] = {0x6c, 0b00000111};//6c
    uint8_t maskACCEL_CONFIG_2[2] ={0x1d, 0b00000101};//1d
    uint8_t maskINT_ENABLE[2] = {0x38, 0x40};//38
    uint8_t maskMOT_DETECT_CTRL[2] = {0x69, 0b11000000};//69
    uint8_t maskWOM_THR[2]={0x1f, 0x7f};//1f
    uint8_t maskLP_ACCEL_ODR[2] = {0x1e, 0b00000100};//1e
    uint8_t maskPWR_MGMT_1_new[2] = {0x6b, 0b00100000};//6b
    uint8_t maskINT_PIN_CFG[2] = {0x37, 0b00110000};//3a

    //writing the registers
    HAL_I2C_Master_Transmit(&hi2c1, MAddr<<1, maskPWR_MGMT_1, 2, 30);
    HAL_Delay(10);
    HAL_I2C_Master_Transmit(&hi2c1, MAddr<<1, maskPWR_MGMT_2, 2, 30);
    HAL_Delay(10);
    HAL_I2C_Master_Transmit(&hi2c1, MAddr<<1, maskACCEL_CONFIG_2, 2, 30);
    HAL_Delay(10);
    HAL_I2C_Master_Transmit(&hi2c1, MAddr<<1, maskINT_ENABLE, 2, 30);
    HAL_Delay(10);
    HAL_I2C_Master_Transmit(&hi2c1, MAddr<<1, maskINT_PIN_CFG, 2, 30);
    HAL_Delay(10);
    HAL_I2C_Master_Transmit(&hi2c1, MAddr<<1, maskMOT_DETECT_CTRL, 2, 30);
    HAL_Delay(10);
    HAL_I2C_Master_Transmit(&hi2c1, MAddr<<1, maskWOM_THR, 2, 30);
    HAL_Delay(10);
    HAL_I2C_Master_Transmit(&hi2c1, MAddr<<1, maskLP_ACCEL_ODR, 2, 30);
    HAL_Delay(10);
    HAL_I2C_Master_Transmit(&hi2c1, MAddr<<1, maskPWR_MGMT_1_new, 2, 30);
    HAL_Delay(10);

    //reading the register
    HAL_I2C_Master_Transmit(&hi2c1, MAddr<<1, &buffer, 1, 30);
    HAL_I2C_Master_Receive(&hi2c1, MAddr<<1, &buffer, 1, 30);

  while (1)
  {

      if(interruptFlag == 1)//if interrupt happens
      {
          //read a register
          buffer = 0x3a;
          HAL_I2C_Master_Transmit(&hi2c1, MAddr<<1, &buffer, 1, 30);
          HAL_I2C_Master_Receive(&hi2c1, MAddr<<1, &buffer, 1, 30);
          //set the led off and the flag to 0
          HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_7);//led off
          interruptFlag=0;//flag 0
      }
  }

}

also the Interrupt code(in the stm32l1xx_it.c)

extern uint8_t interruptFlag;//use the flag of the main.c
void EXTI9_5_IRQHandler(void)
{
    if(HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_5))//if the INT pin is high
    {
        interruptFlag = 1;//flat to 1
        HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_7);//led on
    }
  HAL_GPIO_EXTI_IRQHandler(GPIO_PIN_5);
}

As the register map datasheet says(in particular the INT_PIN_CFG register), the INT pin will stay high until the microcontroller reads a register of the MPU9250.
I also tryed the HAL_I2C_Mem_Read function in the while instruction, but i get the same problem.

I'm also monitoring the INT pin during the reset, and I noticed that at the reset, the INT pin goes low for few moments and then goes up, then the LED lights up, and the INT pin remains high.

I used the debug functionalities of Atollic TrueSTUDIO, and i putted some breakpoints in the interruptFlag = 1 line and in the line right after the if condition in the main. The code stops at the interruptFlag=1 line without problems, but the code doesn't stop at the breakpoint inside the if condition in the main.
It seems that it does not enter the if condition.

What am I doing wrong?


texts: What should this COM communication look like?

texts:
I am trying to rewrite a small utility tool for my bike computer Mio 105. Unfortunately there is not any API to do that, so the only thing left is reverse engeneering. So I have set up a USB sniffer and used orginal software to communicate with the device. I managed then to write a piece of code which was able to communicate too, the port was set up correctly, but there is a problem how it works. In original soft data is being transfered in bigger packages (up to 4kB) but in my code I had to read one byte by one. So here is the question: how to achieve something like this packages automatically?

I used Serial Port Monitor to watch a USB port.
Here's an example of data being sent:
https://pastebin.com/SdePj58x
When I manually open the port using this program I can see that RTS and DTR are turned on. Sending one particular hex code results in the same answer from device like given before. Is this communication somehow standarized or these hex-code commands are specific for this device and I need then to hardcode them inside my program?


texts: I want a solenoid that stays retracted and propels forward when current is passed through it. Is there a solenoid that does this? What is the difference between push and pull solenoid?


texts: NPN transistor as switch (actual voltage readings)

texts:
I started learning Transistors with this tutorial from the Sparkfun website. The tutorial is good and pretty easy to understand. So I decided to put my learning to the test and assembled a simple NPN transistor as switch. Here is what the tutorial states as the condition to toggle it between Saturation and Cut-off states:

Saturation: Ve < Vb and Vc < Vb

Cut-off: Ve > Vb and Vc > Vb

Below is the circuit I assembled on a simple breadboard to test these conditions in each state.

simulate this circuit – Schematic created using CircuitLab

It works as expected. The LEDs turn on in the Saturation state and turn off in the Cut-off state. But when I measured the voltages to see if the conditions are satisfied as per the tutorial, I can see some voltage readings don't obey the above conditions. I have noted down my readings below:

Saturation state:

Vbe or Vb = 0.62
Vbc or Vc = -4.92
Ve = 0

In the saturation state, the conditions are satisfied Ve < Vb and Vc < Vb

However in the Cut-off state, the readings are:

Vbe or Vb = 0.02
Vbc or Vc = -7.24
Ve = 0

In this case the readings doesn't hold the conditions (Ve > Vb and Vc > Vb). Actual Vb is still greater than Ve and Vc. Why is this happening? Did I miss anything here? Why do the actual measured readings seem to not be obeying the above conditions?

Besides these, in the Cut-off state where there is no collector current, I can still observe voltage drops between those LEDs connected to the collector terminal of transistor. Why is this happening? When current is zero, voltage drop shouldn't exist, isn't that true?


texts: Question about N-channel MOSFET turn on Voltage

texts:
I'm trying to understand a test result from a MOSFET-load switch circuit. The MOSFET tested after the load switch is DMN3404L, it's a N-channel MOSFET which has a typical Vgs around 1.5V. The load switch (MP5016H) has a Gate output which drives the Gate of the DMN3404L. In the test, the input of the load switch is 12V, the Gate output of the load switch is around 11.5V, since the source node of the DMN3404L is connected to the output of the MP5016H which is 12V as well, in this case, the Vgs is -0.5v, but the DMN3404L seems open which confused me. Is it supposed to be off because Vgs is <1.5V?
The I did a test to change the input voltage from 5V to 16V, it seems that when the input is below 10V, the output of the MP5016H Gate pin is higher than the source. When the input is higher than 12V, the Gate output is always around 0.5V lower than the source, but the MOSFET still seems turned on, because the voltage measured at the Drain is the same as the voltage at the source.
One thing I noticed is if there is no load at drain of DMN3404L, the voltage of the drain is around 0.7V less than the source, which seems that the MOSFET is off, but the diode is open, but as long as there is a load, the DMN3404L is turn on.
Here is the test diagram and results are attached below, I appreciate if someone can give me an explain why the MOSFET is on when the Vgs is negative?
Thank you,


texts: Relation between battery cell capacity & internal resistance

texts:
I'm trying to design a large battery pack, that should provide a given amount of power, with a reasonable amount of heat dissipations. To do so, I have three degrees of freedom:

indidividual cell capacity
number of cells in parallel
number of cells in series

Given an internal resistance, I was thinking of having a lot of parallel branches with cells of low capacity, in order to lower the current (and thus the heat dissipations in RI²).

However, I heard that the product of internal resistance times capacity is constant, meaning that internal resistance increases when capacity decreases.

Is that true? I could not find any confirmations on the net.
Is there a more accurate relationship between these two?

Thank you for your help!


texts: What are the names of these connectors in a schematic: an 8 pin connector and one labeled BU-BNC?

texts:
I am designing a PCB Schematic. I need to find the following two components. Could anyone please tell me which components are these?

8 pin labeled "X1":

BU-BNC labeld "X4" (I know the resistor and the GND, but I don't know the name of the connector.):

Also, I am making a circuit with 3 multiplexers, so the idea is to have the same VCC in all three of them. I added the VCC for one and copied it to the other two. Will the system automatically figure out that it is the same and connect the symbols together as a single network when I design the trace, or will I have to add some other component? The PCB I am referring to has this arrow, but I'm not sure:


texts: What is the use of GPIO Locking mechanism?

texts:
I came across this on one of the STM32 uC's reference manual and I really have no idea about the use case of this feature. I might be having a very narrow approach because I feel that it doesn't have any use case because the person who is coding for it will be taking care that he/she doesn't change the GPIO configuration at any random point of time.

That is what I feel and I don't see any practical use case of this particular feature but I really doubt because people at STM wouldn't have put something without any thought process. Can anyone help me?


texts: How can I calculate the maximum current a circuit needs?

texts: I want to add a fuse to a self-designed circuit, but for that I need the maximum current of the circuit. In this circuit I have some ICs, some resistors, some LEDs and some capacitors. When I want to calculate the maximum current for this circuit, is my approach correct so simply take the maximum current each IC wants (according to data sheets), and then add them up? Or do I miss something with this approach? Unfortunately the other answers (as far as I saw) are not valid for my problem.


texts: How to regulate voltage across capacitors

texts:
This is a charging regulator, and with over voltage regulation across Cload, which is used to provide power for up to 3ms in case of a power micro cut.

What I do understand in this schematic :

How the current limiting works with the PNP and PMOS, using the 10V zener to bias the gate
How it is necessary to have current flowing in the 33V zener to keep it in its breakdown region

Simulating, the current across D33V is 16uA when input voltage is at 72V, this allows to regulate the voltage across Cload at about 33.65V, which is D33V + the NPN's Vbe.

What I don't understand, and what I'd like you to help me with is why we don't just use a zener, and a series resistor to keep the current in an acceptable range?
I've tried to simulate such a circuit, using a resistor that would put the current through D33V at about the same as the current design (16 uA), and the zener can't regulate. It will only regulate across Cload when approx. 100mA is flowing through it, which is unacceptable in terms of power dissipation.
I don't understand the reason why it doesn't work.


texts: relay control with network and sms with main controller

texts:
I need this project for a melting plant.
There must be two relays in the control (connected to the device), so if one of them is in trouble, another will work to disconnect.
In the (current check) section, what part is there to make sure the relay is disconnected?
And in the temperature gauge, you have to set a thermometer to stop the relay in the event of an error.
In the (ether) section there should be a network module that connects to the micro and web server through the (main controller).
Please help me make this device.

Thanks to me (if you can submit a site or article too)


texts: How to optimize routes for prototype PCB

texts:
I've made a simple circuit design in EasyEDA, and I'm planning to implement it in a prototype pcb, like this one, just by soldering wires on the bottom side.
I'm not sure how to proceed in route designing, but allowing the software to auto-generate the routes for me. In case of EasyEDA, it provides options for tracing on different layers, but as I'm not going to order a pre-soldered pcb (with copper traces on both sides of the board), the result of auto-routing is not quite optimized for wires.
So, I wonder how to optimize route tracing when I just have the circuit design and a prototype pcb to make it work.

I'm open to correct the terminology used in this question since I don't have the proper background.


texts: Do we need to debounce the switch for key release

texts:
I understand that key debounce has to be considered either in Hardware (HW) or in software (SW) when we press a switch (to avoid make and breaks). Do we need to take care of key debounce even for key release? (make and break is possible even during release I guess).
But since we are considering debounce for key press actions (I am considering in SW), anyway we won't get key pressed output even if "make" is detected when we release the key.
If we go for hardware based key debounce (I am not hardware person), does it take care of both press and release conditions?


texts: Question about a short-circuited inductor

texts:
If an inductor is ideal then it has no resistance, but only an inductance, how does the short-circuit affect the inductor? Why would the voltage across it be zero?

I know that the 6H by mutual induction would cause a current to go into the 10-H inductor but how would it work if we assumed for just a bit that the 10H is alone


texts: Prevent Exceeding of Potentiometer Power Rating

texts:
I am using a 10k digital potentiometer to adjust the brightness of an LED.
However, I need to make sure that when I reduce the resistance on the pot, it will not exceed the maximum power ratings.

The max power the pot can handle is 473mW.

So using P = I^2R, we get Imax = 6.88mA.

The battery is 3.3V

From here I am stuck and unsure how to move forward with those values.
I have a circuit like this (10k, not 1k):

But according to this answer, that circuit seems to be called the 'pot smoker'
How can I make sure that I do not blow out the pot?
Is there a circuit I can create to put in between the pot and the LED?

Thank you!


texts: The fuel sending unit in my car operates within a range of 10-520 ohms. I want to replace this unit for one that runs in a range of 0-90 ohms. I'm assuming I will need something to compute the change, but I'm not sure where to begin as I'm not versed in electricity. Can someone help me out? Thanks in advance!


texts:
Given I have designed and produced an RF circuit with an output for connecting an antenna. I know this antenna has an input impedance of 50Ω. I now wish to measure the actual output impedance of my circuit, before connecting the antenna, to ensure that the impedance matches.

How do I actually measure the output impedance of my circuit?

And additionally, can I do this with hobby friendly priced equipment?

Update: I know the basic theory of impedance matching, but I have never understood how to actually do it. So I am really asking for input on the specific hardware and equipment to use, and how to perform actual tests.

The RF circuit is operating in the UHF range, and transmits about 10dBm, if this helps.


texts: Current limiting voltage regulator to power 12VDC fans

texts:
I'm building a ventilation system that will blow air into the back of our parked SUV.  Creating a plastic fan enclosure and installing the fans is no problem, but the electronics... well, that's a different story.

I have a 12VDC PowerStation PSX2 car jump starter for powering three or four Kingwin CF-08LB 12VDC case fans wired in parallel.

Online reading leads me to believe that I need to wire some sort of current limiting voltage regulator between the power supply and the fans, and it looks like I can easily buy that kind of module.  Unfortunately, I can't figure out exactly what I need - I don't understand the terminology used to describe the components I've found online and virtually all the posts here that deal with the topic use terminology that I don't understand.

I've got no problem putting an on/off switch and voltage regulator in an enclosure and doing the necessary soldering, but I sure could use some help selecting whatever voltage regulator I might need.

The PowerStation jump starter specs:

Volts: 12
Peak Amps: 1000
Cranking Amps: 400
Charger Rating: 650mA
Polarity Reversal Protection: LED Warning
Battery Type: 18 Ah

The KingWin fan specs:

Rated Voltage: 12 VDC
Operational Voltage: 10.8 – 13.3 V
Wattage: 0.96 W

As I understand it, each fan will draw about 0.08 amps, so wiring three fans in parallel will draw about 0.24 amps.  If the jump starter's 18 Ah Battery Type means the battery has an 18 amp hour rating, it could theoretically power the three fans for 72 hours.

I'd really appreciate it if someone could suggest a brand and model number for whatever component(s) I might need to wire between the on/off switch and the fans, and also confirm that my understanding of the power usage is correct and I'll have no trouble using the jump starter to power the three or four fans for as long as five or six hours.


texts: Get some clarification about bias stabilisation with Emitter Degeneration

texts:
A textbook I use talks about the effects of adding \$R_{E}\$ in a common emitter amplifier. For stabilization of the circuit due to negative feedback

As the Device gets hotter, more collector current flows, VBE reduces which limits the increase in collector current

What I don't get in this is how when \$V_{BE}\$ reduces this causes a decrease in the collector current as from one of the equations in the textbook $$I_{c}=\alpha I_{E} $$ and $$I_{E}\ =\frac{V_{Bias}-V_{BE}}{R_{E}}$$.
From my rudimentary understanding if \$V_{BE}\$ were to reduce wouldn't \$I_{E}\$ increase which would case an increase in \$I_{C}\$ from the first equation.


texts:
I am trying to generate a random color RGB value -> light up RGB led -> wait for 5 minutes -> generate next random color -> fade from old color to new color.

For showing the color on LED I am using 3 channel PWM output on ATMEGA8.
For generating the random color I am using TIMER0 as seed value and then generating a random value according to formula return (unsigned char)(rand()/(RAND_MAX/255 + 1)); for the 3 channels.

Now since I want to show the intermediate colors as well (using PWM), here is what I am thinking of doing:

total transition steps = 500
time to show each intermediate color = 5ms
redStep = (finalred - initalred)/500 (same for green and blue)
for loop (1 to 500) : show color intialred + (counter*redStep)

My question being, is this the best way to transition between colors, to produce the most aesthetically pleasing colors (without any flickers etc)? Also any thought on the number of transition steps and hold time?


texts:
I am new in the automation industry, and now I am focusing on learning how to wire correctly analog inputs in detail, since last time I tried I damaged  the module input because of wrong wiring.
Here I have several questions about analog input wiring. They may seem pointless to you but I need these answers to fully understand analog input concept. It would be appreciated if you answer these questions.

When using 2 or 3 wire 4 - 20 mA current transmitter, does analog output wire (4 - 20 mA) always produce a current referenced to the power supply common? I mean, can we think this transmitter as a fixed voltage source and a variable resistor so the minus side of the voltage source is always linked to power supply common?
When using a 2-wire 0 - 10 V voltage transmitter, if the input module and transmitter are fed by same power supply, will just wiring the + terminal of transmitter to the + terminal of module be enough (by wiring " - " of the module and " - " of transmitter to common)? I'd like to know if the voltage produced by transmitter is always referenced to ground or can be any floating value.
The second question is valid for also for a 4 - 20 mA 4-wire transmitter. If both input module and transmitter are fed by same power supply, will just wiring + terminal of transmitter to the + terminal of the module be enough (by wiring " - " of module and " - " of transmitter to common)? It seems to me that a 4 wire transmitter output can be any floating value but what happens if we use same power supply for the module and the transmitter ?


texts:
I have a question regarding F-RAM I will be using the Cypress FM16W08 as an example. Here is a link to the datasheet: http://www.cypress.com/file/41731/download

I have recently used it as a drop in replacement for a Dallas DS1225 battery backed S-RAM that holds the calibration constants in a lab power supply. I was able to read the old S-RAM and dump the contents into the new F-RAM and it's working perfectly.

One thing confuses me though. It is my understanding that when a certain address in F-RAM is read the data at that address is lost. While in S-RAM the data remains after a read.

Since the equipment was not designed with F-RAM in mind and it's not writing the data back since it was designed to use S-RAM. Am I correct in assuming that F-RAM has internal circuitry to automatically write back to itself after a read?

On page 4 of the datasheet under the heading Endurance. I believe it vaguely refers to this operation as "a read and restore mechanism" but I'm not sure.

Thanks For Your Time.


texts: I need to know the power output needed for transmitter if I want that receiver catch this signal? In details, there is a tunnel 4 by 4 meters and a cars in it, cars have a receiver inside and transmitter on the tunnel upper floor. So, when car rides under the transmitter, receiver catches a signal. Is 22 dBm enough on 2.4 GHz frequency to go through car's frame? Antenna is just simple PCB.


texts: Selecting 3.3v or 5v to supply EEPROM by µC output

texts:
I am looking to select the power supply voltage to an EEPROM depending on the output of a microcontroller.

Basically I am building a universal EEPROM (flash) programmer, and I need to select whether to power the EEPROM itself by 3.3v or 5v.

I was thinking of simply using a couple of transistors to select one of the two power lines, and I can easily switch one line on or off, but can't for the life of me work out how to switch the other line to the opposite.

I could possibly use an analog multiplexer to do it, but I think that's probably overkill, and I'm not sure if it could handle the current anyway.

The output of the µC is HCMOS at 3.3V.

A typical EEPROM pulls typically up to 45mA or so peak.

I want to avoid having the two voltage rails on at the same time, but I am happy to have neither on during the switching.

Suggestions?


texts:
I came up with idea to create a simple keypad lock using this  ( Keypad Matrix 3x4 https://grobotronics.com/keypad-12-button.html?sl=en https://learning.grobotronics.com/el/2013/07/using-a-3x4-keypad/ ).

Now I want to brute-force the password using another arduino. So I connect some gpios from my attacking Arduino to the gpios of the victim Arduino.

In order to trigger the numbers I do gpio.High the 2 gpios from the reference table (second link) and then gpi.Low to close the connection. (I can trigger the button press with no problems by creating a short circuit between two gpios from the victim Arduino).

My problem is that I get something like a race condition (maybe some voltage leak) and also some combinations do not work.

So my question is. How am I supposed to connect the cables ? (Bare in mind that I have a resistor in every connection coming from attacking Arduino to victim)
Do I have to use some more components ? Why do I have "voltage leaks" ?

I am new in electronics and I come from a cs, software security background. Please do not hesitate to ask me for more info.


texts:
In documents and lots of online sources there is a formula as follows,
$$  Vdd = 3.3V * \frac{VREFINT_{CAL}}{VREFINT_{DATA}}$$
But I cannot get why CAL value is in the numerator and RAW data is in the denominator. I have this logic in my mind,
In the factory, producers used a preknown/fixed 3.3 V as Vdd and then they get this reference CAL value from ADC. But in reality, my Vdd may be different because of non-idealities. So I read Vref_int channel via my ADC and it gives me RAW. I get the CAL value by reading the device memory address provided by manufacturer. ADC reading and voltage level has a direct relationship. So, I conclude that;
3.3 V ------> CAL(from device memory)
 x V   ------> RAW(read from Vref_int)
Then, x * CAL = 3.3 * RAW
So, x = 3.3 * RAW/CAL  should be my formula to get my current Vdd value so that then I know that a maximum ADC reading (4095 for 12 bits reading for ex.) corresponds to x volts.
However, in the above formula it states that x = 3.3 * CAL/RAW.
Please help me with that, thanks.
My board is STM32F4-DISC.
-------------------- edit ------------------------------------
With all my thanks to the ones who answered, I now understood(I hope) what is going on and want to explain here in detail.
First, what is what :
VREFINT_{CAL} or CAL : The ADC reading of the manufacturer from Vref_int when an exact 3.3V Vdda is used (unitless, 12 bits integer)
VREFINT_{DATA} or RAW : The ADC reading of the user from Vref_int when the Vdda is unknown (unitless, 12 bits integer)
V_{DDA} : Kind of the voltage base for our MCU, when you give a digital high output then it should be exactly equal to Vdda (unit = volts)
Now,

1- In the factory, the manifacturer gets the ADC conversion data from
the Vref_int channel and stores it into a memory location as a
12-bit integer. $$  \frac{{VREFINT_{voltage}}}{3.3(V_{DDA})}= \frac{{VREFINT_{CAL}(stored\,value\,,CAL)}}{4095} \quad (1)$$
The logic is simple here, 4095 for 3.3V and CAL for Vref_int.
2- When you want to calibrate your voltage level, since you don't know
your exact voltage base level, you read the Vref_int yourself and
get another ADC conversion value(RAW), let's call it $$VREFINT_{DATA}$$
Then $$  \frac{VREFINT_{voltage}}{V_{DDA}(unknown)}= \frac{{VREFINT_{DATA}(measurement\,of\,user\,,RAW)}}{4095} $$

Since $$VREFINT_{voltage}$$ is fixed, replace it with its equivalent from eqn. (1).
Then you can see that the equation yields to $$V_{DDA}(unknown) = \frac{3.3*CAL}{RAW}$$
Finally, you can use this Vdda value as your voltage reference(base) on your calculations.
This edit may include some mistakes, please let me know.


texts: can a 1.68A fan be used with a 500mA power supply? (at less fan output)

texts:
So i was wondering if i could use this certified UL power supply that is rated at 500mA for my fan that runs at 1.68A load. Will it cause problems? OR does it just not power on (i think thats what its going to do)

it may be helpful to reference what the power supply is designed to do if more amperage than its able to output is demanded

it is of course, inefficient, if it does turn on. I mean this as an experiment.

thanks

EDIT:
it's an older AC adapter for something i no longer have.
this is a link of its data information, it lists some protections. Searching google i was unable to find a corresponding datasheet. https://www.amazon.com/PK-Power-Adapter-SCP41-120500-Transformer/dp/B06XJC5362
it is a SCP41-120500 Class 2 Transformer Power Supply 12VDC

at any rate, i chopped the end off of this power supply, plugged it in and used a multimeter to check its voltage output. It is reading at 16V? i am using the multimeter correctly.


texts: Sleep current of automotive device increasing over time

texts: I have something like a tire pressure monitor. It is battery operated. I haven't done automotive before and it is a whole other world besides consumer. I put in all high temp components (i,e, 40-125C vs 40-85C). I can't really find much info on what happens to IC and components in a high temp, high mechanical stress environment. My question is: my sleep current when I install is low uA, but a few months later it cam become 1 mA without changing anything. Is there a descriptive cause of what happens? I wonder about the ceramic caps (there are no tantalum or electrolytic). Do they develop fractures causing greater leakage of current?. I don't see anything on the web about what happens. If I knew, I could justify spending more on problem components I identify.