texts: Value of digital potentiometer when not powered

texts:
I have a circuit where upon startup, it selects a voltage source with a programmed current limit via a resistor. Though I want a uC down the line to change this when it first powers up to protect other circuitry. Therefore I want to use a digital potentiometer. The datasheet tells me the power on value but what is the value between wiper and terminal A when the power is off? I could place a "startup" via a transistor and then have the uC disconnect the resistor by influencing the transistor but I wanna save on these 2 parts if possible.
I am using this digital potentiometer: https://ww1.microchip.com/downloads/en/DeviceDoc/20001978D.pdf
This is my circuit I am about the finish up:

Edit to solve chicken and egg problems.


texts: Supply topology for microcontroller and ADC/sensor with noisy input/outputs

texts:
I am experimenting with a microcontroller project with a very wide-ranging, noisy DC input voltage at VCC. The controller processes a sensor input to the ADC and outputs a pulsed signal on all pins of a separate port. I need some advice on the best way to configure the system and microcontroller (ATmega168) supply (VCC/AVCC/AREF) to make the ADC and sensor as immune to all of the switching noise as possible.  I’ve drawn up 3 possibilities of the top of my head below, but not sure which, if any, is optimal for separating digital and analog noise as much as possible:

Possibility 1:

Possibility 2:

Possibility 3:

Currently I’m testing with both Vcc and AVcc powered from a linear bench supply (output 5.3V), and using a TL431 as 5V reference at Aref (similar to possibility 3).  A potentiometer is standing in for the sensor. Despite large capacitors between +5.3V and COM (4400uF total), the multiplexing currently causes a lot of noise on the reference output.  Below is a scope screenshot of the reference output, and this is without the switcher:

What is the best basic topology to supply this circuit? Any comments, recommendations or better ideas than any of these would be greatly appreciated.


texts: Is RESET* on the XMEGA disabled when using the PDI interface?

texts:
When PDI CLK is connected on the XMEGA (also the RESET*) pin, can this pin still be used to trigger a reset on the chip? If so, how does the chip tell the difference between PDI being used as a clock and a genuine reset signal? Every document I have found on this matter is somewhat vague about what happens to the rest functionality of the pin when PDI is used.

If my wording is vague, what I am basically asking is if the reset pin can be used to reset the chip, if the firmware on the XMEGA was loaded via the PDI interface. I have a project that needs to be able to be reset in the field, but I also want to use the PDI interface to load the firmware on it from the factory.


texts: Using one pot to control simultaneously different parameters

texts:
First, please forgive my lack of knowledge, as i'm a beginner in the matter.

I'm looking for a way to control with one pot different parameters. In context, i'm trying to control a Filter Cutoff on two different channels. Later on i'll add options for more filter types, so a Dual-Gang Pot won't do me much good.
Also, i'm trying to do it as analog as possible. No MCUs in the mix.

I've been lurking everywhere to find such a method, and so far, aside from possibly a digital pot (which would require some digital circuitry, adding more components on a already tight space), i just can't find anything.

Could you possibly help me with this ?
Thanks

Now understanding it is virtually impossible, best choice for now is to use as many Double-Gang Pots as needed, in my case 6 of those. Thanks anyways for your help :)


texts: How to switch a 700A 200V pulse for a coilgun?

texts:
I'm working on a coilgun and I need to discharge a capacitor bank through a coil to create a strong magnetic field. My coil has a resistance of 266 milliohms and when fully charged, the capacitors are at 200V with a capacitance of 4700uF total. This will result in a peak current of 750A (ignoring wire resistance and ESR of the capacitors).
Up until now I have just touched the wires together to close the circuit but I need to time the switching in a controlled way. My problem is that I have no clue what component to use to switch ~700A 200V. Of course the 700A peak is only for a very short amount of time and the whole pulse should last around a millisecond.
I have tried using 5x irfp260n MOSFETS in parallel, each MOSFET should be able to handle 200A peak so it would total 1000A when connected in parallel. Unfortunately one of the MOSFETS always dies after a couple shots (I did take care of the reverse voltage generated by the coil). I also am aware that connecting MOSFETS in parallel is generally not a good practice.
I have looked into thyristors but the inability to switch them off through the gate makes them useless for me. "Gate turn-off thyristors" looked interesting but I could only find really expensive ones (in order of hunderds of euros). IGBTs are known for being able to handle more current but I failed to find any that were rated for this kind of current.
Does anyone know a solution to switch 700A 200VDC for 1 millisecond?


texts: Calculation of a feedback resistor in an inverting shmitt trigger

texts:
This is taken from a frequency counter circuit based on a schmitt trigger comparator .
The frequency counter has a noisy immunity threshold of 100mV.
How would you calculate the Rfeedback resistor value and what is the purpose of an immunity threshold?


texts:
I am using pic controller with USB HID boot loader which will do a firmware update via USB and i have tested it successfully.If i add a blue tooth device(UART) and tries for a firmware update I trust it will fail to do an update.
In this case should i replace the USB HID boot loader and go for Serial Boot loader(UART) right.?

What should be done to make it compatible for both Bluetooth and USB?
Or is there any boot loader available that will do the job?
Smart phones/devices use update over air and USB right.?


texts: Why inductive reactance has two formulas

texts:
We know inductive reactance XL will have two formulas. One is XL = 2piFL and other is XL = V/I (Ohm's law). Why we have 2 formulas for inductive reactance.

Is the solution ( inductive reactance value) obtained from these two formulas will be going to be same or different ?


texts: Amperage in a USB AC-to-DC power converter

texts:
so it was my understanding that USB was standardized with 5 volts (V) at 1 Amperage (A), but I've seen wall adaptors with 5V and different Amperage including 1A, 1.1A, 1.5A, 2A, 2.1A, and as much as 3.3A before. Some of them had extra USB ports, but not all of them did. Does the higher Amperage increase charge speed? And if so, is there a standard tolerance of devices which charge via USB? For example, is 5V@2.1A "OK" for charging most tablets or phones, but >3.0A@5V could cause damage?

In addition, if Amperage is set by Voltage and Load, don't many computers pull more depending on what is being done?  I don't mean just Null-Operations (NOP) versus addressing, but whole sections of the machine might not be on / on stand-by if not needed. Would this mean the wall adaptor is rated by an average, not what it actually puts out?


texts:
I am trying to properly wire and then dim Cree LED tri-pods (3 LEDs on a disk).

The spec sheet appears to read that the way to connect 2 * tri-LED pods (6 individual LEDs in total) would be in series, incremented at 2.6v per pod (maybe LED). It is not clear about the pods at all.

Bench top test result only produce any light at all above 4v per tri-LED pod, with optimum at 7.8-10v in 'parallel' for two pods  LED info

Also, you would think that dimming these LEDs would be via PWM but my benchtop potentiometer demonstrates that lowering voltage is the way you dimm these units.

1) Can someone explain these LEDs pods to me, their optimum voltage and proper dimming?
I think my benchtop results tell the story, but I am very unsure.

2) With 7.8v being the calculated max, how bad is it to run them at 9v? There is a difference. I am sure there is some resistance in this circuit I am not factoring in.


texts: What is the use of a capacitor between Vdd and Vss (or Vcc and Vee)?

texts: I'm trying to make my STM32 communicate VIA Can. Therefore I'm making use of the CAN transceiver MCP 2551. In many circuits I've seen a 100 nF between Ground and Vdd. What is the reason for that? Here an example:


texts:
I just saw this picture about PCB 3D printing on a website, can it work in real life?
It's would be so cool, if it could useful in the real life.


texts: Question about flow with relay and capacitor (Make Electronics-Charles Platt, Exp. 8)

texts:
I'm a newbie working my way through Charles Platt's Make: Electronics (2nd Ed). I'm on Experiment 8 and I'm confused about something. The circuit looks like this:

What is supposed to happen is that when the button is pushed the capacitor charges before the power is cut to the button, it keeps the relay switched until the capacitor discharges. So the right-hand LED stays on for a few seconds before the relay switched back and the left-hand LED comes back on.
Platt notes that if the right-hand LED is removed, when holding down the button the left-hand LED will fade out over about a second before popping back on and cycling again, since some of the power from the capacitor flows through it.
What I don't understand is why the same thing doesn't happen when the right-hand LED is present. In other words, in the original circuit why does the left-hand LED wink out immediately instead of fading when the push button is held down.
As an experiment, I modified the circuit so that each LED had its own 470-ohm resistor. Once I did this, the left-hand LED would indeed fade instead of winking out. Can anyone explain this behavior to me? Thanks!

If it helps, here's the modified circuit on my breadboard, sorry for the crummy image quality:


texts: How to reduce a boolean function fast and easy?

texts:
I want to reduce the following function:

$$f(a,b,c) = (\bar{a}+\bar{b}+\bar{c})*(\bar{a}+\bar{b}+c)*(\bar{a}+b+\bar{c})*(\bar{a}+b+c)*(a+\bar{b}+\bar{c})*(a+b+\bar{c})$$

Now my method would be to reduce each 2 terms:

$$=(\bar{a}+\bar{a}b+\bar{a}c+\bar{b}\bar{a}+\bar{b}+\bar{c}\bar{a}+\bar{c}\bar{b})*(\bar{a}+b+\bar{c})*(\bar{a}+b+c)*(a+\bar{b}+\bar{c})*(a+b+\bar{c})$$

$$=(\bar{a}+\bar{a}b+\bar{a}c+\bar{b}\bar{a}+\bar{b}+\bar{c}\bar{a}+\bar{c}\bar{b})*(\bar{a}+\bar{a}b+\bar{a}c+b\bar{a}+b+bc+\bar{c}\bar{a}+\bar{c}\bar{b})*(a+\bar{b}+\bar{c})*(a+b+\bar{c})$$

$$=(\bar{a}+\bar{a}b+\bar{a}c+\bar{b}\bar{a}+\bar{b}+\bar{c}\bar{a}+\bar{c}\bar{b})*(\bar{a}+\bar{a}b+\bar{a}c+b\bar{a}+b+bc+\bar{c}\bar{a}+\bar{c}\bar{b})*(a+ab+a\bar{c}+\bar{b}a+\bar{b}\bar{c}+\bar{c}a+\bar{c}\bar{b}+\bar{c})$$

This is literally much effort for such an exercise

$$\begin{array}{c|c|c|c|} a&b&c&f\\ \hline 0&0&0&1\\ 0&0&1&0\\ 0&1&0&1\\ 0&1&1&0 \\ 1&0&0&0\\ 1&0&1&0 \\ 1&1&0&0 \\ 1&1&1&0 \end{array}$$

so now with DNF $$f(a,b,c) = \bar{a}\bar{b}\bar{c} \vee \bar{a}b\bar{c} $$


texts: TLC59116 (Y59116) maximum output current

texts:
I bought this IC (http://www.ti.com/lit/ds/symlink/tlc59116.pdf) to power a few RGB leds. I was under the impression that it could drive up to 100ma per channel, constant current. However in practice I can only get around 180ma total before it self shuts down.

Maybe I misinterpreted the datasheet, and 100ma is the global maximum? Can somebody read it and tell me the correct interpretation, since I'm not really good in reading datasheets yet?


texts: I have a huge led matrix which will draw 3.1Amps of current. However I only have a 15v 1A psu> Would it be possible to use a transistor to amplify the current after I've lowered the voltage? Could you recommend such a transistor.


texts:
So in an application like this:

The coil of the motor will, by Lenz's Law, induce a very large negative voltage across its terminals (without the diode in place). Would this voltage be very negative at the left terminal of the inductor and very positive at the right? In this way the diode will conduct, but the negative voltage in this case would be directly connected to the power supply.

Also, how are the flyback diodes in this way utilized[L293 - H Bridge IC]:

It seems that the two left diodes will always be reversed biased, but what about the right-side two? Why are the left-side diodes even present if they are always reversed bias? It seems that the large negative voltage would forward bias one of the diodes to the right (whichever terminal is induced to a large negative potential), but what benefit does that have? Also, current flow back into the H-Bridge circuit does not appear very practical.

Perhaps I am looking at this all wrong.


texts: Can photocells (PN Juctions) be stacked?

texts: Can photocells (the PN junctions) be stacked (3) on top of each other (not just side-by-side) to let each PN junction produce electrical energy from the visible light, Infrared (IR) and ultraviolet light (UV)?


texts: How to implement OpAmp floating input protection

texts:
I needed a VCCS so then I simulated the circuit below in LTSpice and it worked great. I also designed the PCB and produced it, solder it and it still works great. But I have a big problem!

When the input (positive input of the opamp) is left unconnected, and the load is connected, the opamp hugs the VPOS or VNEG rails (arbitrarly!) and the output current goes to 2.35A (I am lucky that I put that current limiting resistor so the current will never go above +/- 2.35 ampers.

I think this is because of the input offset voltage of the MP38 and the fact that with no input since it will be open loop...it hugs the supply rail (I do not understand why sometimes it goes to V+ and sometimes goes to V-).

So my questions are:

Is what I said above the problem? or there is more to it?
How to prevent this kind of behaviour (possibly with some schematics
    please!)
What could I do better for this Circuit/PCB?

Would be this a solution (R1, 10k resistor pull-down parallel with input connector):


texts: How do you calculate RC snubber values for a discrete bridge rectifier

texts:
I'm working on a small linear power supply for an audio amplifier (home/hobby use) and I want to add an RC snubber on the rectifier diodes. I know this might be overkill, but I'm looking at it as an educational endeavour as well (I'll build a version with and without and compare results).

Looking at various sources on the Internet, I see multiple methods for calculating Rs and Cs, most of which share the same theory but give different formulas. Here are a few references:

http://www.cde.com/resources/catalogs/igbtAPPguide.pdf
http://www.hagtech.com/pdf/snubber.pdf
https://www.maximintegrated.com/en/app-notes/index.mvp/id/849

I managed to get the following data from the parts I'm trying to use

Triad F-345X trafo: 400mH secondary leakage (from vendor), 200pF interwinding cap (measured myself by shorting both primary and secondary and measuring capacitance across them)
Vishay HFA08TB60-M3 HEXFRED: Irrm 3.5A, dI/dt 200A/us, trr 37ns, Cj 10pF and L 8nH (if I'm reading the datasheet right)

Now, putting this all together, I take it I need an Rs of about 24k and a Cs of roughly 4nF. However, I'm not really sure about my calculations and my understanding of the matter...

EDIT: I've had another chat with Triad on the transformer and they mentioned leakage was measured on the primary. Since this is a 240 to 24V transformer, I can assume n = 10 so the leakage as seen from the secondary would be closer to 4mH. New calculations gave me more "normal" values - Cs = 620pF and Rs = 150R


texts: Door lock solenoid with finger print & Arduino Nano

texts:
Update - 22.01.2020

Here is my schematic.  I tried to use all of the comments guys below:

Should I use a fly-back diode as commented after I cleared the schematic? If yes, where?
Is it required to protect the Arduino or any part of the circuit in this diagram?
If the solenoid used 24V DC in this diagram, will 24V DC reach my Nano and damage it? If yes how to protect it?
Is the circuit protected from using both way to open the solenoid accidentally by finger print and the push button of the headset? If no how to do that?

Here is the post before update to the schematic:

I am a newbie to electronics, but I did read for a long time and search but this is my first circuit it may look easy for you but I need help.

Here are two schematics and I need them to be joined together with op protection and reverse voltage protection as well.

The project is a solenoid door lock I will add a finger print module operated with Arduino Nano to open it.

In fact, the solenoid is operated by normal doorbell intercom, so the project here is to make both ways to open the solenoid the fingerprint module and the intercom.

Please note:

The solenoid needs 1.8amp to open.
Reverse voltage protection due to the power will come to Arduino when solenoid opened from the intercom.
I have a TIP122 transistor if needed.
Arduino Nano will be used in the project.
Pin 9 or any will be used to send a signal to the transistor to pass the power required to open the solenoid.
Over 12V protection for Arduino Nano if dual input power source will be used.

The scenario:

Normal intercom button should open the solenoid.

Fingerprint module read the fingerprint
Arduino Nano received the data approved then send a signal from pin 9 to transistor TIP122 to open
Transistor TIP122 opens and passes the current to open the solenoid.
The finger print module goes into sleep mode if no activity for specific time.

Please try to consider the size of the circuit if possible need to be a small or good size to be placed behind the door of the house.

Edited 19.01.2020:"

I need to know how to connect these both isolated circuit to do one work which is open the solenoid without conflict with each other if both power used intermediately?


texts: Obtaining Q factor formula for RC circuit

texts:
note: It an AC RC series circuit

I'm trying to figure out why the Q factor formula for and RC circuit is Q = 1 / (wCR)

I know Q = 2pi * (energy stored in the circuit in one cycle) / (energy dissipated by the circuit in one cycle), however if:

energy stored = C * (Vmax)^2 / 2
and
energy dissipated = power(R) * T = T * (Vmax)^2 / (2R)

putting that in the formula for Q results in Q = wCR

What am I doing wrong?

Also, in a book(1) I've found that the energy stored in the circuit (the capacitor) is also Wc = (Imax)^2/(w^2 * C). Using this last formula, I can get the correct result for Q, however it is not explained where the Wc formula comes from.

(1) Book is "Electronic Circuits" by J.A. Edminister

Thank you for reading


texts:
I have been trying for a while to understand Coaxial Cable impedances for ham radio etc. use. I only know what it is not though.

Coaxial Cable does not measure the rated impedance from one end to the other
Coaxial Cable does not act like a load itself at the rated impedance, they may loose some power to heat, but they mainly carry the signal to the antenna (or whatever other load)

So, what is a coaxial cable impedance rating, and why can't I use a 75 ohm in place of a 50 ohm on the output of my transmitter?


texts:
For a low-current IC (< 1 mA) where I need to be able to switch it on and off, I'm connecting it directly to an Arduino analog pin. In order to ensure a stable voltage, I was thinking of adding a small capacitor across the IC. But I'm wondering if this might damage the Arduino? The max current draw allowed per PIN is 40 mA, and adding the capacitor would mean that there's almost a high current draw while it is charging, albeit only for a very small time. But I can't find out if such a quick high draw is allowed.

I tried to calculate how much the current will be the but the equations in this Wikipedia capacitor article are not immediately usable.

There's an equation for current, but it depends on the derivative of the voltage function. And the voltage function in turn depends of the integral of the current function. Hence there's many pairs of solutions to these equations.

What is the general practice/recommendation here. Would putting a 100 nF capacitor be OK? I also thought I could add a small resistor - so I would add a resistor between the Arduino PIN and the IC source PIN, and then have the capacitor still across the IC's source and GND. The resistor could be, say, 180 Ω which would limit the max possible current to 27 mA while causing only a voltage drop of 0.18V when the draw is 1 mA.


texts: Does the PID Controller (LOVE 16C-3) Need an External SSR?

texts:
My PID controller LOVE 16C-3 has a output of "relay".

Do I connect the output of the PID controller to the inputs of an external SSR?

Or is the relay already built in into the PID controller?


texts: Low PPM Tc Resistors for Voltage Divider circuit?

texts:
I have a voltage divider circuit that cuts an input voltage in half.  The half voltage is fed into an ADC.  I need this reading to be stable over temperature.  The resistors are 100K, but I don't think this matters.

Do I need to use resistors that have a low temperature coefficient to have a stable reading?

Or, because the resistors are the same value and have approximately the same temperature coefficient, can I use standard resistors?  The resistors will track each other over temperature and the midpoint will always be half the input voltage.


texts: As long as within the active region the collector-emitter junction is reverse biased, is there a purpose for which the collector must be doped? Moreover, not only that it is doped, but it is moderately doped, thus more than slightly doped like the base region.


texts:
As I develop my R&D project I decided to add bluetooth to the mix...  In the first stage I decided to use my own iMac as a transmitter and my iPhone as the receiver, and it worked great...

As I finish this early stage and start to think about field testing, well, I can't carry my 20' iMac around, so I would like to build a low-cost bluetooth transmitter.

My question is: Do I need something like a Arduino/Raspberry or there are "self-contained" transmitters?

Details:

The transmitter will be plugged into a reliable power source
The message being transmitted will be fixed and very short (20 bytes max)
The programming part is: while(true){ transmitMessage("myId",sleepInterval); }
The ideal answer here is something like: "Buy this guy here, download IDE X or Y or Z and here's a Transmitting Hello World Example"


texts: Multiple identical chopper drives in parallel

texts:
The DRV8825 boards from Pololu come as complete, readymade chopper boards with a current of up to 2.2A. However, I want to drive a bigger stepper motor, and happen to have a few leftover boards around.

Is it possible to get more current out of these boards bu putting two boards in parallel? If I were to do so (just to see if it works), would I be at risk of blowing a board?

EDIT: Datasheets:

DRV8825: http://www.ti.com/lit/ds/symlink/drv8825.pdf

Breakout board: https://www.pololu.com/product/2133

Don't have a sheet for the motor, as I scrounged it. Specs I know: 6A, 0.22 Ohm, NEMA 34.


texts: Finding if a value is among an array using a FPGA

texts:
I've been doing a lot of software engineering, and find myself intrigued by the hardware implementation of things to the extent that I'd like to port one of my recent algorithms to an FPGA.
Trying to teach myself FPGAs, which seems easier than it used to, but still leaves me in the dark for usual patterns/solutions. So here's my problem:

Say I put many (~100) "cores" on an FPGA which compute possible matches. Each possible match is a 64 bit value, and let's assume computing said possible matches is expensive (~35k clock cycles).

Now once the matches have been computed, I want to see if any matches a precomputed list of roughly 15k possible 64 bits values. The probability that a possible match is found being very small (~1e-8).

What would/should be an design to compute whether possible matches are found in my original list? I can assume that my original list is fixed (and presumably sorted).

In software, I've been using a binary search, but I'm wondering about RAM access in that case. If I had 100 cores each feeding one possible match every 35k clock cycles, it means that (assuming I had some kind of buffer available) I could have a binary search component as long as it'd take less than 350 clock cycles to see whether something matches (and assuming 14 comparisons for a binary search among 15k elements, that looks just about doable).

So, any idea? Is the binary search the way to go (and should it be modified? Using a heap to help with caching of RAM lines, or k-ary search? Looking at hashmaps or bloom filters for faster discarding?) Is there any "standard" way to do this kind of thing?


texts: How to use Esp8266 to communicate between Arduino and Raspberry Pi?

texts:
I need to read 8 sensor values from Arduino and send it to Pi through Esp8266. Also after reading these data my pi will give back 6 other values (integers) which has to be received by Arduino again through same ESP8266.
The values that are sent to Pi will be received by a python script and the 6 other values will also be ganerated by the same python script.
I am confused on what could be the best method to proceed with this. So, far I have settled on using the Esp8266 as a server and pi as a client. But still I believe there would better options. please guide me

I know RF modules will be an better option here but I am not allowed to use it.


texts: Where does the negative inductor current go during CCM at no load in synchronous converters?

texts:
As you all know, there are two primary mode of operation for dc-dc converters : CCM and DCM. At no load, the inductor current stops at zero at DCM. However, if CCM is enforced (such as Forced PWM), then inductor current can go to negative at no load or light load condition if the inductor ripple is large.
I had a simulation of a synchronous buck-boost controller at work and I saw that the current goes back to the input during negative inductor flow phase.
My questions:

Can I confirm that this is true and that if I use forced CCM, then my power supply would need to be one that can absorb this power during negative inductor current flow? If not, then where would this negative inductor current go?

Is this type of power supply common? Because there are quite a bit of synchronous converters that runs in CCM all the time out there

Thanks


texts:
I had some heated seats retrofitted to my car. I have wired them so that a 12 V ignition signal activates a relay and powers a bus bar which then powers the seats.
The switches are round ON-OFF-ON switches. So if someone leaves the passenger switch ON and I just get in and don't notice, the seat will always be on.
My query is: can a relay, latching relay or something else be put inline somewhere that will, in effect, reset the power to each seat?
This means that if you left it on and cycled the ignition, you would then need to go to OFF, then back to ON to get the seat to work on the rocker switch. This is essentially overriding the switches' physical state.


texts: FPGA(DE0 Nano) trying to connect with VGA but gets a Short Circuit

texts:
I am trying to connect my DE0 Nano FPGA to an display by using VGA.
The output ports of the DE0 Nano have a voltage of 3.3, but the RGB Signals of the VGA want 0,7 V so I used a voltage divider.

I found this pinout for the VGA:
Pin Connection
Ive got a simple program that the RGB Signals are constant "1", so that the screen should give me white. The RGB signals are 0,7 V when they are not connected to the screen. When i connect the cable to the screen a short circuit appears, and on RGB I've  got 0 V..

Red Signal > Pin 1
Green Signal > Pin 2
Blue Signal > Pin 3
H_Sync Signal > Pin 13
V_Sync Signal > Pin 14
GND Signal > Pin 5

Does anybody have an idea what i am doing wrong?


texts: Problem with LTC3872 Voltage Converter. Simulated results not matching with information provided in the datasheet

texts:
I'm trying to make a boost converter that takes an input of 3.7V and outputs 5V.  I found a chip that I think will work well, the LTC3872 by Linear Technology.

In the datasheet they give an example circuit which takes an input of 3.3V and has an output of 5V.  However when I tried copying that exact circuit in LTSpice, it actually decreases the voltage.  The resulting output voltage is 2.72 volts.

I've gone over the circuit several times and I can't seem to figure out any difference between the two so I'm thinking that there either is a problem with LTSpice or with the datasheet.

Is there something that I missed or am I doing something wrong?

For reference the datasheet can be found here: https://www.analog.com/media/en/technical-documentation/data-sheets/3872fc.pdf


texts: Why is my power supply behaving weirdly when I connect my RF amplifier?

texts: I have designed an RF power amplifier that operates close to 100 MHz and amplifies signals from 50mW to about 2W. Everytime I switch it on, the voltage on my lab power supply drops even though the current is within limits. It also makes a weird buzzing noise. I realised that the RF signal is finding its way into the power supply(2V peak-peak) inspite of the 1uH choke coil L2 and the decoupling capacitors C7 and C8. Is that why the power amplifier is behaving weirdly. If so how do I solve the problem? Also the problem only occurs if I connect the antenna. I am not sure why that is so too. Could it be because of some kind of impedance mismatch or EMI?


texts:
I found the guts of a paper shredder in an office supply store dumptster.  It's 120vdc. I'm clueless when it comes to anything that isn't powered by a 9v.  Do I need a transformer to power it?

I apologize for the amateurish question.  I couldn't get a good answer googling


texts: Measuring very dim light-- charged glow in the dark paint

texts:
I am not even a novice, but was directed here by several companies when they couldn't help me with finding a tool.
I am setting up an experiment to determine which glow pigments are brightest.
Full details of the controls and experiment is on ElementalBreakdown.com
I think what I am testing for is luminance.
The tool I need should be able to be granular down to at least .01 millilumens, if that's even the right unit of measurement.
The object I want to test is a small metal bead with various brands of glow paint applied over an adhesion primer and charged with the same light source.
I have sorted out a lot of details like making sure the actual phosphorescent (not an accurate term since the new paints use strontium aluminate or doped Europium) pigments are all the same size (50 microns).
So now I need to figure out what units to measure in and probably upgrade the cheap lux meter I have.
I don't have experience building electronics so would need a ready made tool or assistance.
Are any current tools sensitive enough to get accurate readings from a 50-80mm sized source at about 3 feet?
I'd like to take readings at several intervals like 5, 20, and 60 minutes.
Please help me if you know of such a tool or have advice on what and how to measure. I currently have samples from 5 of the largest companies all claiming to have the brightest product.


texts:
I am trying to drive this I2C LCD display with an ATxmega16A4U microcontroller.

Both devices are listed to work with I2C clock frequencies up to 400 kHz. The two devices are the only devices on the I2C bus.

However, working out the calculations for the pull-up resistor bounds gives some rather odd values.

Calculating the I2C minimum pullup resistor value:

\begin{equation}
R_{min} = \frac{Vcc - 0.4}{3mA} = 966.7 \Omega
\end{equation}

Looking at the uC datasheets, on page 92 lists the max pin input capacitance of 10pF.

However for the LCD, it has on page 8 something called the Capacitive load represent by each bus line labeled as Cb, and is listed at a max value of 400pF. I'm assuming I should just add this value to the 10pF uC input capacitance, but this seems really high and the calculations are wonky.

For example, when I try computing the maximum pullup resistor value for a 400kHz clock:

\begin{equation}
R_{max} = \frac{300ns}{10pF + 400pF} = 731.7 \Omega
\end{equation}

Am I misinterpreting the LCD datasheet? Obviously the max allowable pullup resistor value cannot be smaller than the min allowable value.

likewise, if I assume a maximum net bus capacitance of 400pF, I get:

\begin{equation}
R_{max} = \frac{300ns}{400pF} = 750 \Omega
\end{equation}

still under the maximum allowable value.


texts: How to get inverting amp in an electronics project with 1 battery

texts: I am trying to invert the signal from a microphone for a simple noise cancellation project.  I am using a 3.7V lipo battery, right now I am trying to use a single supply op amp (TLV2462), but don't know how to get the negative signal out.  I don't need much power/voltage out, I can boost power with a second stage, I'm mostly just concerned with getting a good inverted signal with 1 battery.


texts: Is an FPGA the best tool to generate a continuous flow of square pulses with arbitrary amplitude?

texts:
I need to generate a train of rectangular pulses, with positive and negative arbitrary amplitude. Ideally, I would like to have the generation electronics connected with a computer, and I would like to generate a flow of values that would decide the amplitude of each pulse.
(This is for a telecom project, so think of it as a stream of data, but I need to fine tune the amplitudes.)

Is an FPGA a good tool to do this?

The parameters are:

a rise time of 10 or 20 ns
a pulse duration of 100 or 200 ns
a repetition rate of 500 KHz or 1 MHz.
the max amplitudes should be +/- 1 V
the amplitude resolution should be of 1 mV


texts: What guarantees that RTL inverter is in triode region when the input is high?

texts: in this inverter my instructor says that if Vin is high, we need M to be in triode to have low voltage in the output. now I understand this but I don't know guarantees that it will be in triode. why doesn't it go to saturation.


texts:
The circuit diagram below is given in my book (written by Coughlin and Driscoll).

simulate this circuit – Schematic created using CircuitLab

Here it is said that, at the condition when \$ E_d=+2V\$, the output voltage will be \$V_o=+5V\$. But for an op amp, when the non-inverting voltage is higher than then inverting voltage, the output voltage will be \$+V_{sat}\$, which is approximately +15V.

Why is the output for this Op Amp IC (LM339) +5 Volts?


texts: Simple way to determine I/Q phase difference (positive or negative) without using FFT

texts:
I have a Doppler sensor with I/Q channels for detecting moving object. I need to also detect the moving direction of the object. Due to the limited power and flash memory of my MCU, I cannot afford FFT() or atan() or sqrt() functions.

In order to determine the moving direction of the object, phase difference between I and Q need to be determined (positive or negative). And the following methods are the ones I'm aware of:

FFT
x-correlation
atan(I/Q)
search posive slope of I and Q signal and determine the phase shift

The first 3 methods, I cannot afford them due to MCU limit. The last one is very sensitive to noise.

Is there other simple ways to determine the phase difference between I/Q is negative or positive ?


texts: What is the difference between \$V_{CC}\$, \$V_{DD}\$, \$V_{EE}\$, \$V_{SS}\$

texts:
I've seen lots of schematics use \$V_{CC}\$ and \$V_{DD}\$ interchangeably.

I know \$V_{CC}\$ and \$V_{DD}\$ are for positive voltage, and \$V_{SS}\$ and \$V_{EE}\$ are for ground, but what is the difference between each of the two?
Do the \$C\$, \$D\$, \$S\$, and \$E\$ stand for something?

For extra credit: Why \$V_{DD}\$ and not simply \$V_D\$?


texts: When conversing, what is a "big resistor"?

texts:
In casual conversation, what does "a big resistor" typically mean? Does it mean a resistor with a high resistance or a physically large resistor?

Or, is this just bad terminology that should be avoided?


texts: What "was" input resistance of this voltage-voltage topology amplifier before feedback?

texts:
I'm slowly working my way through understanding negative feedback in simple BJT amplifiers.  I'm studying this circuit here:

I read that one of the advantages to negative feedback in this topology is that it raises the input impedance by a factor of \$1+KA_V\$ (where \$K\$ is the feedback factor and \$A_V\$ is the open-loop gain of the internal amplifier).  I did a simple analysis of the input resistance \$R_{in}\$ and found that
\$R_{in}=R_B||R_{ib}\$
\$R_{in}=[(85k||106k)||(\beta(R_E+r_e)]\$
\$R_{in}\approx 45k\Omega\$
I was able to verify that this is the correct input impedance.  By simulating a test signal \$v_s=20mV\$, I measured the current entering the circuit at \$i_{in}=444nA\$, which checks out.
Here's the part that doesn't make so much sense to me.  If the negative feedback increases the input impedance by a factor of one plus the loop gain:
\$R_{in}=R_{in'}(1+KA_V)\$
What was the internal amplifier's input resistance before the negative feedback was added?  From my previous work with this circuit, I know that ...
\$K=(\frac{1}{A_F})-(\frac{1}{A_V})\approx 1\$
\$A_V\approx g_m(R_E) = 0.12 * (4000) = 480\$
\$A_F\approx 1\$
Plugging all this in, I should be able to find the internal amplifier's nominal input resistance \$R{in'}\$before the feedback network was added.
\$R_{in}=R_{in'}(1+KA_V)\$
\$45k\Omega=R_{in'}(1+(1*480))\$
\$R_{in'}\approx 93.6\Omega\$
For the life of me, I can't see how the internal amplifier could be analyzed to have an input resistance of 93.6.  I'm fairly certain my loop gain is correct as all those calculations check out in a previous question (here).
As an aside, I did try comparing this circuit to one with \$R_E\$ removed to see if that helped any (it didn't, I don't think).  I reduced \$V_{cc}\$ to a low enough level that my \$I_{CQ}\$ remained at \$3mA\$.  My input resistance fell as expected to \$R_{in}\approx \beta*r_e \approx 2080\Omega\$.  So, again, my analysis of input resistance proved out OK and checked out in simulation.  But adding the feedback resistor \$R_E\$ only increased the input resistance by a factor of around 21, not the expected 1 + loop gain factor.
Can anyone explain what expression for an internal amplifier's input resistance will work with the \$R_{IN}=R_{}in'(1+KA_V)\$ equation?


texts:
What regulations (if any) do I need to follow if wiring a 12 volt system (in the UK).
I was planning to wire up a garden shed / summer house to the 220v mains. I'm confident I could wire it safely and sensibly, but not being up-to-date on UK wiring regs I'm not sure I wouldn't miss something that might upset a bureaucrat should it ever come to be inspected.
To avoid this I'm thinking of installing a 12 volt system instead (100 watt solar panel, plus old truck battery). It's only a shed so realistically the most I need is power for lights, a laptop, mobile phone charger, maybe a couple of cooling fans for the warmer days and perhaps a drinks cooler.
If I went down this route, are there any UK regs I'd need to follow?
I'm an electrical engineer, I'm happy with the technical (and safety) side of the work, just looking for the regulatory side of the problem.
As far as I can tell, boaters and caravaners have to obey boating and caravaning regulations for the wiring. I can't find any general 12 volt wiring regs.


texts: Increasing the current to a solid-state relay?

texts:
I've got two strings of LED Christmas lights that operate at 120 V / 0.04 A (4.8 W). I'd like to connect them to this 5V solid-state relay:

Unfortunately, there's one small problem. According to the relay's datasheet:

Load current: 0.1 to 2 AMP

The lights only draw 40 mA, much less than the minimum 100 mA listed on the datasheet. How can I work around this problem? Is there some sort of device or circuit I can connect that will cause the lights to draw more current (without damaging the lights)?


texts: Mean Well power supply gives wrong voltage output?

texts:
I have the Mean Well PT-45B power supply (data sheet here). It has three channels, which should give 5V, 12V and -12V, as I understand.

Pin 1 and 4 or 5, and pin 6 and 4 or 5 should give 12V and -12V respectably (as of my understanding).

The issue is when I connect the power, and try to measure the DC voltage, I get wrong outputs.

Pin 1 and 4 gives -17V and pin 6 and 4 gives 7V (see pictures). There is a potentiometer to adjust the output somewhat, but If I adjust it away from center to the left or to the right, the readings get really jumpy (see gif).


texts:
I have a project where I'd like to convert a 0.5 V, 800 mA supply (a solar cell) to at least 3 V with as much efficiency as possible. I've seen DC boost converters, but all the ones I've seen are designed for a higher voltage.

Any tips on a good low voltage one?


texts:
In my project, we are using Li-Polymer batteries. We have LCD and high-power components which will generate heat. We have an enclosure in which battery and LCD and other hardware will be fitted. We are using a thermistor on the battery to monitor the battery temperature, and our battery charger will terminate the charging if the temperature exceeds 45 degrees.

As there are high-power components which will generate heat, that heat is affecting the battery and the charger is disabling the charging. Can anyone suggest how we can protect the battery from the surrounding temperature?


texts: Why does this IR receiver not receiving some signals?

texts:
I am trying to read some IR signals. There is a synchronizer emitting modulated IR signals. And my receiver must receive those signals and interpret them. Actually, there are only two different modulation:

signal 1

signal 2

I put a photodetector in front of the synchronizer and get these two waveforms on the oscilloscope. These are 2 signals that my receiving circuit should interpret.

So in overal, transmitted IR is something like this:

My IR receiver is this. It's datasheet is this.

This is the schematic:

output directly goes to microcontrollers interrupt input.

So here is the problem. Synchronizer, always transmit IR this way. Never changes. But my IR receivers output goes crazy most of the time. Some times it responds those coming signals like this:

and sometimes it outputs like this:

I can never tell! Why does receivers output varies like this? Received IR signals or their RSSI never changes, I do not move the receiver or the transmitter but receivers output changes in time. Can you explain why is this happening and how can I fix it?


texts:
I have a square wave being generated from a waveform generator oscillating between 0 V and 5 V.  The generator does not support negative DC offsets.  I need to shift this signal down to be centered about the 0 V value, i.e. oscillating between -2.5 V and 2.5 V (AC Coupled?).

What are ways of doing this?

(Forgive me if I mess up any terminology I'm a software engineer by trade.)


texts: NUL character in an ASCII-Based protocol over UART

texts:
I am developing a UART protocol based on ASCII encoding. Communication is between a PC and an STM32 board. Packet format is like this:
Packet: {STX,DATA,ETX} Where STX and ETX are 0x02 and Ox03 in ASCII.
Example:

STXHELLOETX in Hex would be: 0x02 0x48 0x45 0x4c 0x4c 0x4f 0x03

My question is where exactly is the position of \0 character in my packet? is it after ETX like this: STXHELLOETX\0 or after HELLO like this: STXHELLO\0ETX ?


texts: How fast is L1 cache of ARM Cortex-A9 in Xilinx Zynq-7000 FPGA?

texts:
I consider writing a small program for the ARM Cortex-A9 in the Xilinx Zynq-7000 FPGA, so the program will be small enough to fit into the 32 KB L1 instruction cache.  The data will also be less than 32 KB, thus can fit into the L1 data cache.

I expect it to be a very linear program, thus without penalty for branch misprediction etc.  Also I expect there will be no data dependency within the length of the pipeline, or that bypass will be able to provide the data.

Is the L1 instruction cache fast enough so I can get an execution speed of at least at least 1 Instruction Per Cycle (IPC)?

Is the L1 data cache fast enough so data load and store access will not have any affect on the execution speed of at least 1 instruction per cycle (IPC)?


texts: Why does the voltage drop when I connect an 8 ohms 1 watt speaker, specifically the source to the circuit is GPIO pin output voltage?

texts:
This circuit I am using to drive a speaker is acting strangely.
Case 1: When I connect the 3.3 volts source from the Nucleo board it works fine as expected (in terms of the sound.) When I check the voltage across source it is 3.1 to 3 volts. A drop of only .2 to .3 volts.
Case 2:  When I connect the GPIO output pin 3.2 volts as a source to the circuit, the speaker sounds very low. When I check the voltage at the GPIO pin it is 2.1 to 2 volts. It drops nearly 1 volt.
Why is it dropping so much voltage? Due to this speaker does not sound as expected.
What is the issue? Can I resolve this?
Edit: The GPIO is from a BlueNRG-1 chip.


texts: Measuring AC Current at High Voltages (up to 600VAC)

texts:
I've been looking at various ways to measure current for a while now, and am stumped on how to read high-side AC Current Measurements ohmically (no Hall Effect sensors). My initial thought was to use PNP and NPN BJTs in parallel (one of each), connecting them across a 0.1 Ohm current sense resistor (basically making a differential amplifier). I can't seem to make a circuit that works in this configuration, however, and differential amplifier ICs can't handle the high voltages I'm looking to measure (up to 600VAC). I've seen a op-amp from Analog Devices that can handle common mode voltages up to 600V, but am trying to make a circuit just from discrete circuit elements to start.

My question is mainly this: is it possible to measure high-side AC current with just a few BJTs and/or MOSFETs? My ideal circuit would do the following:

Vin=600VAC, 0.1Ohm current shunt resistor on the high side, Current=1 Amp AC.
--so--
V1=600VAC
V2=600VAC-(0.1 Ohm) * (1 A) = 599.9VAC

BJT circuit takes V1 and V2 as inputs, and gives 0.1VAC (V1-V2).

Thanks for all your help! The replies don't have to be an answer to the question, more trying to understand how something like this could be possible.


texts: Need help with simulating a 3-channel LED color organ in MULTISIM

texts:
I have been trying to simulate a LED colour organ in MULTISIM (literally) for hours. I don't understand why is it not working. My end goal is to get to simulate this on MULTISIM.
Here's the circuit I'm following:

and this is my attempt to simulating it on MULTISIM
The output I'm getting is like this:
The LEDs are flickering, which is not how a colour organ operating at single frequency works(as in the video shared above).


texts: At what point does the responsibility of the manufacturer end with regards to FCC/CE testing?

texts:
I'm curious as to when the responsibility of a manufacturer ends when dealing with emissions and RF testing, part of FCC and CE tests.

I repair TVs as a hobby and as business. I got a TV in from someone which would not power up most of the time. I found the soft-start circuit was stopping the TV starting, so I inhibited that. Now it works fine. But the PFC transformer makes a very audible whining sound, and the PFC bus voltage now measures 328V - when it really should be nearer to 390V. This tells me the PFC is not working (although the TV is fine with the reduced bus voltage) and so the TV probably wouldn't meet its emissions requirements. In this case, would the manufacturer be responsible for this?

Another example, an old Compaq power supply had a very odd "feature". When the 5V output was shorted, it wouldn't switch off. It would melt whatever was attached (including its own cable harness) and in the process make enough EM noise to cause an AM radio within half a metre to lose a station. Given that the 5V shorting is not a default configuration of the PSU, but it could happen, why is it covered in FCC/CE logos?

See, I am designing a power supply which might have an expected lifetime of 50,000-100,000 hours. But it won't last forever, that's pretty difficult to do. At the beginning of its life it would meet the requirements. But as it gets older, electrolytics degrade, ripple incrases, noise increases. Eventually, it won't meet the original requirements.


texts: Providing DC power with failover DIY for IP camera

texts:
I'm building a simple battery backup box for a 5V IP camera. I've got a few options for battery, sealed lead battery or a mix of portable LIPO style "USB" power bricks. I've seen boards built for security systems that supply power to the system via 110 to 12V DC while keeping a sealed lead battery charged then without interrupting power switch over to the battery when the power goes out. These boards are $70-$100.

The USB battery pack bricks are nice because they regulate down to 5V built in. The one I'm testing now has a 19V power supply for charging and so far it will charge the battery while the camera pulls power from the USB connection. My concern in this configuration is that The battery will be in a constant state of use and charge while the camera pulls power.

I'm guessing the impact of constant use and charge will shorten battery life versus keeping the battery charged without use. So my goal is to find a way to connect two 5V sources, one is the factory 5V camera adapter, the other being the battery source and have it switch to the battery source when the DC adapter looses power without interrupting power to the camera. The battery has a built in charge regulator so while the camera runs off of the 5V from the DC adapter the battery will stay charged.


texts:
We have a typical USB 2.0 wall charger that has a USB A receptacle. Our charger has D+/D- connected together through a small resisor (<200Ω) to let devices know the maximum power is 1.5A/5V following the USB BC1.2 spec for a "Dedicated Charging Port" (DCP). Our charger is "dumb", it does not communicate with the devices.

Now we would like to modify the charger to use a USB C connector. We don't want to upgrade to the Power Delivery spec, we just want to use a different connector. We want to keep using the USB BC1.2 spec. I have done a bit of research and I have found that USB A to USB C cables add a 56 kΩ Rp pull-up resistor between VBUS and CC.

My idea is then to keep the rest of the connector circuitry basically the same and simply add Rp to the CC pin pulling up to 5V. Here is the schematic:

Would this work?


texts: Atmel ICE SAM connector pinout does not reflect the real pinout

texts:
Maybe I am just too slow, but I can't understand exactly how do you connect an ATMEL-ICE (6 pin connector, not the 10 pin) to a chip. I am using a SAMD21G (http://www.atmel.com/Images/Atmel-42181-SAM-D21_Datasheet.pdf)

I made a board, where I take the pins needed for the connection to the ATMEL-ICE. I am following this doc: https://github.com/femtoduino/femto-usb

As connection, I did connect all the ground  (pin 5,18, 35 and 42), and connected the power pins (pin 6, 17, 36, 43 and 44) to the power rail, which give 3.3V to each of these pin.

Then I have the pin 45 and 46, which are SWCLK and SWDIO

From the doc linked, the pin should be:

ICE SAM port         Microcontroller
Pin 1 3.3v           3,3v (main power rail)
Pim 2 SWDIO          SWDIO (pin 46)
Pim 3 GND            GND (main GND line)
Pin 4 SWDCLK         SWDCLK (pin 45)
Pin 5 GND            GND (main GND line)

But I do not see the green led on the ICE go on; also when I read the voltage in Atmel Studio, I see -3.2 in the target voltage; which tell me that the connection is not matching the right pins.

I am using the cable included in the ICE, using the SAM port as described in the document. The user manual of the ICE has so many different connections, but I can't figure out exactly the correct pins to start to program the microcontroller.

Looking for some advice about how to connect the microcontroller to the Atmel-ICE at this point; since the pinout on that document seems to be wrong.


texts: How can I use two TP4056 with four Li-ion batteries, but single load?

texts:
Need to connect and charge two Li-ion batteries in series.
I'm not sure if it is possible to connect and use two Li-ion batteries and TP4056 like this. Are they going to be balanced? Do they need to?


texts:
While looking around I discovered a demo of Toshiba's tactile feedback system here.  I assume that the display is set up to provide a small electrical current that has enough power so that our sense of touch can detect it.  Is this actually how this system works?

If so, what kind of current and voltage needs to be provided to be detectable by touch?  Would we be able to detect DC as well as AC?

If anyone has any references or source material on what the ranges of human perception are for this type of effect, I would appreciate it.


texts: How to find maximum coil current for relay based on nominal current value given in datasheet

texts:
As per datasheet for Relay (Panasonic: JS-M Series); all nominal values are mentioned for coil current, voltage & power dissipation. Based on these values how to estimate maximum values for current, voltage & power dissipation for relays.
e.g.
Nominal Voltage: 12VDC
Nominal Operating Current: 53.3mA
Nominal Operating Power: 640mW

This relays is designed for 12V system; (Automotive Domain); Can it be used for 24V systems?

I have checked this relay on 31.5V power supply. It was working fine without any damage. So I am not sure whether to use same 12V relay for 24V system or not.


texts: Op-Amp Design Resistor Values vs. Actual Values - Gain Calculation

texts:
I have created the following differential op-amp circuit with the aim of converting a 0-3.28V analog signal into a -10V to +10V output. I have calculated the gain required 3.28/20 = 6.1

From looking at differential circuits the gain is equal to the ratio of resistors used so I chose a 10k and 61k. However when testing the circuit I needed close to 74k to get the required output range. Can anyone explain why there is such a difference between the design values and the actual resistor values?

PS. The voltage divider in the top left is to provide the midpoint value 1.64V for the circuit.

This should really be added as a comment but need to add the link. I found a formula on the following website, maybe I misinterpreted it.

http://cnx.org/content/m13778/latest/

Clearly this is not the case, thank you for your explanation, it is by far the easiest to understand that I have seen so far.


texts: Why 3T APS pixel implements a NMOS reset transistor instead of a PMOS?

texts:
I'm very curious about why the 3T APS píxel sensor implements an NMOS reset transistor.
As it is well-known, we will have a voltage of Vdd-Vth during the reset phase. This situation will imply higher FPN, thus the initial integration voltage will be highly dependent on Vth.
If we replaced it with a PMOS transistor, we always would be reset to Vdd.


texts:
First off, please note that I am a hobbyist.

I have a couple of line level audio outputs that are picking up noise from a nearby 12v signal anytime it pulses. These pulses are translating into audible "ticks".

I am able to pick the noise up on my scope (each time the wave form is pulled down, that's a portion of the noise), but I'm having trouble identifying its frequency so that I can add a filter to my outputs to prevent that noise from entering my circuit.

How can I use the FFT data to point me in the right direction?

Here's an image of the noise and the FFT:

Here is a video of the noise as picked up by my scope, with the noise audible:

https://www.youtube.com/watch?v=xg_gBNa48d0


texts: How NAND Flash controllers erase single pages efficiently?

texts:
I'm working on some code to manage a NAND flash and I need to erase single pages, given that the smallest erasable unit is a block, the only solution I could think of is to:

Erase a reserved block
Copy the entire block to the reserved one
Erase the block
Copy the reserved block back and skip that page.

While this works fine (haven't tested it much but it should work in theory) it's obviously very slow, I was wondering how flash controllers, for example in USB sticks, handle erasing a single page efficiently ?


texts:
The Dynaco FM-3 tuner uses what appears to be a Foster-Seeley discriminator with one diode reversed, or, if you prefer, a ratio detector without the third coil and stabilizing capacitor. The Dynaco marketing material and user manual uses the term 'discriminator' consistently throughout.

I don't find this variant discussed in the RDH, or Cook & Liffey, which are my only FM texts of enough depth to cover this sort of thing. Does it have a name? How does it work? And what are its salient properties?

Schematic (also here):


texts: Right reasons for using a voltage regulator for DC motors

texts:
I read in an online book at https://www.learncse.com/images/Lessons/Lesson_14.pdf following reason for using a voltage regulator to power DC motors. While I understand the importance of using a regulator in certain situations, I am not convinced of the reason given. Please let me know if the following is correct?

The lesson as posted at https://www.learncse.com/images/Lessons/Lesson_14.pdf is to control a DC motor using an H-bridge and interfaced with an Arduino.

  One characteristic of the DC motor that is very important for the
  purposes of this lesson is the motor's  electrical  resistance.  The
  slower  the  motor  turns  the  lower  its  electrical  resistance
  and, therefore, the greater its demand for electrical current.

  Reason

  The reason this is important is that in these lessons the motors are
  powered by batteries. Batteries, in turn, have an internal resistance.
  As the resistance of a motor goes down, the voltage across the motor
  also drops as the proportion of the battery's internal resistance to
  total resistance increases. The result is all motors being driven by
  the batteries slow. To the observer, the DC motors just seem to be
  running rather poorly.

  Outcome

  To minimize that effect, this lesson uses a battery with a higher
  voltage than what was intended for the motor and a voltage regulator
  to maintain the voltage delivered to the motor at a lower but constant
  value. This approach works because the internal resistance of the
  battery impacts the voltage being delivered to the regulator, not to
  the motor.


texts: How to calculate net force from a Lorentz Force Density in Magnets

texts:
Consider a pair of solenoid magnets as shown in the figure. Based on the magnetic field (B) at each point and corresponding Current Density, (J), I can calculate the Lorentz Force density at each point as F = J x B. Since it is a solenoid (axisymmetric), if I consider, say YZ plane, I can get axial force density as Fz = Jx * By and radial force density as Fy = Jx * Bz for each discrete point in the coil.

From this Force density map( vectors at each point), how can one calculate the net force in each solenoid? My intuition was adding all the values in a face, and multiplying it with the area of the face will give the force in that face. If it is correct, how do I find the net force in the body? multiply it by 2 pi?


texts:
I'm curious is there ability to set STM32 to work as SPI Slave, without CS - just to rely on edges of SPI master's clock?
I want to interface it with ADF7021 which has SPI output(ADF is master) of Received data, but it doesn't have CS.


texts:
I'm trying to identify a component with the designation PJ2089 DZK. The PCB has a "Z" next to it so I looked around for zeners. However the closest thing to this reference was a 1N2089 diode. At this point I'm not even sure it's a diode as the cathode bar cannot be determined.
Any help greatly appreciated.
Kind regards.


texts: What are the advantages/disavantages on using CCM or DCM in boost converter?

texts: When should we choose continuous conduction mode (or discontinuous) when designing a boost converter?


texts: How does a circuit "know" the resistance?

texts:
This is obviously a very basic question, I'm pretty new to concepts of circuitry and so on. So, lets say you have a circuit with simply a battery, a resistor, and a multimeter measuring the current.

From my understanding, the circuit almost, well, knows(?) the resistance before any current travels. Obviously that's not really possible. But could someone shed some light on how this works? Thanks a ton.


texts:
I am trying to load an OpenWRT on a BCM963xx Router (SmartRG SR515ac), I managed to connect to CFE using a UART-USB, change the image server IP, but when I run the load command I get an error like this:
CFE>  r 10.20.0.16:vmlinux.elf
Loading ramdsk image 10.20.0.16: to address 0x00000000..
Loading 10.20.0.16: ...
Loading faile.: CFE errr -21
*** command status = -21

Using wireshark I can see ARP communication between CFE and the server, but no other traffic.
After some ARP retries the CFE gives up and return the error shown above.
Is there any reason why the router is not seeing the ARP replies and continuing with the TFTP load?
The router requests are padded to 60bytes but the reply are just 42 bytes long, could that be it? Can I force the arp table to add the padding to replies, either on Windows or linux?
CFE boot dump:
HELO
CPUI
L1CI
HE
CPU
L1I
4.1605-10.38-118.3
DRAM
----
PHYS
STRF
400H
PHYE
DDR3
SIZSIZ3
DIT
USYN
LSYN
MFAS
LMBE
RAE
PASS
----
ZBSS
CODE
DATA
L12F
MAIN

Base: 4.16_05
CFE version 1.0.38-118.3 for BCM963268 (32bi,SP,BE)
Bild Date: hu Sep  1 11:51:52 PDT 2016 (phanson@paulh-OptiPlex-9020)
Copyright (C) 2000-2015 Broadcom Corporation.

Boot Strap Regster:  0x1fffbf
Chip ID: BCM63168D0, MIPS: 400MHz, DDR: 400MHz, us: 200MHz
Main Thread: TP0
Memory Test Passed
Total Memory: 26435456 byts (256MB)
Boot Address: 0xb8000000

HS Srial flash device: S25FL128, id 0x0118 sector 64KB size16384KB
Flash no used for uxiary Fle System
Board IP addres                 : 10.20.0.101
Host IP address                 : 10.20.0.16
Gateway IP address                : 10.20.0.1
Run from fash/host/ttp (f/h/c)  : c
Default host run file name        : mlinux
Default host flash file name      : bcm963xx
Boot delay (0-9 seconds)          : 1
Default host ramdisk fil name    :
Default ramdisk store address     :
Board Id (0-0)                    : 96316
Primary AFE ID OVERRIDE           : 0xfffffffe
Bonding AFE ID OERRIDE           : 0x00000000
Number of MAC Addresses (1-32)    :1
Base AC Address                  : 3c:xx:xx:xx:xx:xx
PSI ize (1-128 KBytes           : 128
Enable Backup PSI [0|1]          : 1
System Lo Size (0-256) KBytes    : 0
Auxillary Fil System Sie Percent: 0
Main Thread Number [0|1]          : 0
Serial Number                     : SR515AAxxx-xxxxxxx
WLan Feature                      : 000

** Press any key to stop auto run (1 seconds) ***
Auto run second cunt down: 1
External swich id = 53125
web info: Waitig for connection on socket 0.
CFE>
CFE>
CFE>
 Port 3link UP

CFE> r 10.20.0.16:vmlinux.elf
Loading amdisk imae 10.20.0.16: to address 0x00000000..
Loading 10.20.0.16: ...
Loading failed.: CFE error -21
*** command status = -21


texts: VLSI: RC Modeling of a digital CMOS circuit

texts:
The simple RC-model for mos transistors in digital circuits, brought in CMOS VLSI Design book by West-Harris is like this:

But in other sample of book a 3-Input nand gate modeled like below:

When I modeled the circuit using basic model, I noticed that there is a missing Capacitor at highlighted node. There should be two parallel capacitors: one among Source-Body of B, call it Csb(B) and other one among Drain-Body of A, call it Cdb(A).

Since both of them assumed to be grounded they should lead to a 6C capacitor at highlighted node.

What I want to know is that depicted model got typo errors or I missed something in my considerations?


texts:
I have a BLDC 3 phase 8 pole motor, with hall effect sensors, most other three phases motors have 1 wire for each phase U , V , W however this motor has two for each phase(these do not include the separate hall effect sensors, of which there are 5 as expected). Does any one know the reason for this, I have attached the motor specification sheet.

Best Regards

JW


texts: Understanding the effects of frequency on appliances

texts:
Recently I was thinking about a generator project and realized that is beyond my current understanding of AC power. I have been doing some research since but I am really having a hard time understanding the frequency part of AC power sources. From what I understand the frequency of an AC signal is the number of full +/- voltage cycles in a signal.
To make discussion simpler lets consider an A/C generator that is driven by a constant 1500 RPM. If that generator has has 4 poles this would result in 50 Hz, since there are 6000 magnet switches every minute, which is 3000 full voltage changes a minute which is 50 changes a second.
Now lets assume I have the same sort of generator (size, etc) but it has 12 poles like an usual car alternator, it will produce 150Hz AC power. At this point I am really wondering why any appliance would care. If you consider it within a full second nothing really changes, there is the same amount of time in positive voltage and negative voltage as if it would be running with 50Hz. It just switches three times more often.
Why exactly do A/C appliances care how often the voltage inverts with A/C power sources?


texts:
How can I chain two level shifters in a multi-master I²C system?

The following picture shows the I²C bus. Due to low-voltage to the masters, the A side (low-voltage side) of the level-shifter needs to be connected to master and the B-side (high-voltage side) is connected to the slaves.

Bus architecture:

With TCA9517 device, we see a swinging or bouncing behavior on the bus, when either master sends a zero to the bus.

Are there alternative I²C level-shifters to solve this problem?

Edit:
It's not required that master 1 can communicated to master 2 or reverse. Both masters are using the slaves at the 3v3 bus.


texts: What are the real world limitations of using a transistor as a switch?

texts:
I have a circuit where a 5.055V 2.17A (MAX) DC circuit is supposed to be switched using a 3.404V 0.99A(MAX) DC source.

Theoretically, 3.404V 0.99A between base and emitter should allow quite a large current to pass from collector to emitter, but when I am using BC548 B type (Min theoretical gain 200X) as my transistor, the Collector-emitter current that I am actually getting is only about 1.34A.

Of course, BC548 is not designed to handle that high level of current. So I replaced it with TIP31C O Type (Min gain 20X), but something strange hapened with the TIP31C. That transistor is passing at least 1.63A between collector and emitter even when there is nothing connected to base and therefore no potential difference is going on between base and emitter.

simulate this circuit – Schematic created using CircuitLab

Admittedly, I do not know how to read all the parameters on a transistor datasheet, but even the BC548 did not break down at that voltage, and there is no OFF characteristic mentioned on the TIP31C datasheet at all.

Not only that, even after applying the 3.404V 0.99A potential difference between base and emitter, the collector-emitter current is only going up to 1.72A.

Is there any theoretical explanation behind this strange behaviour?


texts:
I'm having a little suprise with timer interrupt on update event. I thought that if timer is configured to count up, update event will occure just after the overflow, i.e. when CNT will become equal to zero. According to figures 103-105 from reference manual.

But that doesn't seem to be the case for some reason. I tested it with this simple code:

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

// tick frequency in Hz
const uint32_t tickFreq = 1000*1000;
const uint16_t timPrescaler = SystemCoreClock / (tickFreq ) - 1;

TIM_TimeBaseInitTypeDef timBaseStruct;
timBaseStruct.TIM_Prescaler = timPrescaler;
timBaseStruct.TIM_ClockDivision = 0;
timBaseStruct.TIM_CounterMode = TIM_CounterMode_Up;
timBaseStruct.TIM_Period = 5;

TIM_TimeBaseInit(TIM2, &timBaseStruct);

TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE );
NVIC_EnableIRQ(TIM2_IRQn);

Then in the irq handler:

void TIM2_IRQHandler(void)
{

    if(TIM2->CNT != 0)
    {
         TIM2->CNT = 1;   // <----------- and I put a breakpoint on this line
    }

    TIM2->SR = ( uint16_t ) ~TIM_IT_Update;
}

I don't have anything else enabled, no critical sections, just an empty while loop.

I also have an .ini file for debugger, so when I stop the execution, all timers are also stopped.

Now the interesting bit.

When I debug in the Keil Simulator - execution doesn't stop on the breakpoint.
But when I debug on the board - execution stops on the breakpoint and I can see that TIM2->CNT is equal to 1!

It does appear to be connected with tick frequency, if I make it a thousand times less, breakpoint doesn't stop the execution. But what the hell, it's just 1 MHz; CPU is clocked on 72 MHz!

Now I wonder - is it a bug in the simulator or in the hardware? Or I have simply misread something and timer is not initialized properly?


texts: What happens if you put a capacitor in the wrong direction for a short time?

texts:
I have a 6300uF capacitor rated for 50V. When I connected it to my circuit I put it in the wrong way. After a few seconds I realized my mistake and switch off the circuit. I want to know if any damage have been done to the capacitor. It is not bulging and it did not explode.
Edit it is applied to a 13v 10 amp max supply. It is a aluminum  Electrolytic capacitor Panasonic.
Datasheet:http://industrial.panasonic.com/cdbs/www-data/pdf/ABA0000/ABA0000C121.pdf


texts:
reading some of the capacitive sensing IC datasheets around, they always recommend an isolation overlay over the sensor pad.

Like this:

I'm wondering, why not use the actual PCB as overlay?

like this (sorry for the bad photoshop):

Please note that I'm not just going to determine the "touched/untouched" state, but the actual amount of touched area (by measuring the actual capacitance).

I've done some experiment with MPR121 sensor and some copper tape on a blank PCB material, and it works pretty good, but I'd like to hear some opinions before I'm going to make some actual PCBs.

Would that be as good as using a proper overlay?

Update: I've read that FR4 (the PCB material) should provide almost the same isolation as acrylic and other plastics, so I think it could work


texts: What causes "positive feedback" in audio amplifier

texts:
I am currently using an audio amplifier to make a presentation.

However, sometimes mid presentation the audio amplifier will go into a "positive feedback" mode where the sound coming out of the amplifier gets increasingly louder and louder until it suddenly drops off.

At first I thought that my voice was too loud which causes the amplifier to hit the saturation limits. However, that does not explain why the sound volume gradually increases, also does not explain why it suddenly drops off.

  Can someone explain to me what is causing this phenomenon and how do you prevent it?

Feel free to use circuit or control theory I have rudimentary understanding of it. A diagram will be most helpful.


texts: I want to connect a signal in a .v file to a top level pin assigned in the pin planner but I've no idea where to start. I've looked at several guides but as a C programmer this is all quite alien to me.


texts: Hall sensor doesn't switch back when I move the magnet away

texts:
I am currently working with hall sensors and I found this difference between two sensors:

The first one changes voltage when I approach and move back the magnet.

The other one changes when I approach the magnet, but needs the other polarity of the magnet to turn back to its original state (and it has a little circle on the flat side.)

I can't seem to find the keyword in order to make sure the next ones I buy are in the same category as the first one, maybe "latching" is the word I want to avoid?


texts: Can you put transformers in series to get higher voltage?

texts:
I was looking for the answer and found this related question: Wiring transformer output in series to get twice the voltage possible?
But the answers don't seem to address what I was imagining. I am thinking of connecting the secondary coil of one transformer to the primary coil of the next, but the only information I can find talks about hooking the secondary of both together either in parallel or series. Am I making any sense?


texts: How to import PSPICE Model into Orcad Capture?

texts:
Can someone tell me how to add PSPICE Model in Orcad Capture and PSPICE simulator.

] have downloaded LM239 PSPICE model from texas instrument site, the file they are providing is "LM239.5_1".

While running the simulation I had an error "ERROR(ORPSIM-15108): Subcircuit LM741/NS used by X_U5 is undefined" and have no idea how to resolve it.


texts: Atmel ATMega8 doesn't hold "HIGH" state of PB0 and PB1

texts:
I'm new in microcontrollers and I wrote simple program that set HIGH state at PB0 and PB1.

#include <avr/io.h>
#include <util/delay.h>

#define F_CPU 8000000L

int main(void){
    DDRB |= (1<<PB0) | (1<<PB1);
    PORTB |= (1<<PB1);
    PORTB |= (1<<PB0);

    while(1){}
}

The problem is that my avr can't hold on HIGH state and connected leds are blinking. Where is the problem ?


texts:
is there any way how theoretically determine the current consumption of ultrasound piezo transducer?

I only know impedance for res freq = 50 ohms and excitation voltage around -170 V.

Does the Ohms law work in this case?

Thank you.


texts:
I'm struggling to identify the origin of the IC in the attached image. I believe it is a rebadged HP/Agilent part:1826-1488, ADC CMOS 12-BIT 20-PIN. can you tell from the logo who makes it then I can try to track the original part number and perhaps find a replacement part if no longer in production.

it's in a HP system power supply (HP 6624A).


texts:
I've been using Vivado HLS (High-Level Synthesis) for the last months and making designs for a Xilinx's ZedBoard.

Now I will probably have to work with a FPGA from another vendor and I don't know if I can still use Vivado HLS to convert C to VHDL. I mean, it generates VHDL code which should run in any FPGA but for example the AXI interface isn't Xilinx's specific? So, can I use Vivado HLs to produce VHDL code for any FPGA?

The reason why I'm asking this here -  and not directly to Xilinx - is because I need a relatively fast answer, so please don't downvote this.


texts:
Hey so I am stuck over this question:

The first part is simple. Since \$\sigma=0\$, therefore \$\alpha=0\$ and \$\beta=\omega\sqrt{\mu\epsilon}\$. \$\epsilon\$ can be found by referring to the datasheet of the board.

What I don't get is the second part. If \$\alpha=0\$ then there should be no attenuation because the factor \$e^{-\alpha x}\$ reduces to 1. Am I right to understand that the electric field will have the same magnitude of 5 mV/m after 50 meters?.


texts: Turning remote control signal into audio

texts: Is there a way to convert the IR signals from remote controls (for TV's, DVD players, etc.) into audible sound signals? There is a good circuit online, but it uses the CA3237E which is obsolete, so now I'm stuck. How would you demodulate the IR signals? With a 4046?


texts: How to design a 2nd Order High Pass Butterworth filter with a gain of 6 dB?

texts:
I have been trying to design a 2nd order filter with a gain of 6 dB (or 2 Av), using the following Sallen-Key Topology.

I have calculated R1 and R2 to give me a desired cut-off of 1.6kHz and this part is working fine. I am however not managing to get the gain up to 6 dB.

Following the example from this book, page 450, using the Butterworth co-efficients for Second-Order Filter Parameters α = 1.414 and b = 1.0.

Calculating: R4 = 2 - α = .586 ohms

Calculating: R3 = 1 + .586/1 = 1.586 ohms

This resistor ratio is providing a gain of 1.586 as per the Butterworth coefficients. Thus my circuit looks like this:

The frequency response looks like this:

The above image may not be too clear, however the cut-off freq is as desired, however the gain is not 2 AV (6 dB) but 1.586 AV as per the above calculation. I would gladly provide more information if necessary.

How can I alter the above equations to provide a gain of 2 Av while using the Butterworth coefficients?


texts: M.S. Math to Engineering Ph.D : Mathematics in Electrical Engineering

texts:
I have two Bachelor's degrees. One is electrical engineering and the other one is mathematics. I am studying mathematics (partial differential equations) in the graduate school (Master course) now. But I want to study electrical engineering later (for Doctor's degree). So I have a question here.

Would you tell me a field(or major) in electrical engineering which is deeply concerned with mathematics?


texts: Calculating reliability of a parallel redundant system

texts:
I'm trying to calculate the reliability of a system that has proven to be a bit more complicated than I thought. Here is the block diagram for the system:

Every single component in this diagram is a Line Replaceable Unit with a mean downtime of 2 hours. If any of A-F fail, that's a failure for the "subsystem" indicated by the dotted line. The entire system will successfully work as long as only 1 of the dotted line, A-F, "subsystems" has failed. Because of the mean downtime of 2 hours, if two of the dotted line subsystems fail within 2 hours of each other, the system fails. This subsystem highlighted in green is not particularly difficult. What's throwing me off is the inclusion of components G1 and G2, routers that fail when either A (UPS) or B (DC power) fails. This makes up the subsystem highlighted in red. The entire system fails if both routers (components G1 and G2) fail, within 2 hours of each other of course.

Basically, I thought that the reliability of the whole system can be calculated with Bayes Theorem which would give the reliability of the system as:

Reliability of green subsystem * probability that G1 and G2 do not fail

PLUS

Reliability of red system * probability that another of the dotted line subsystems does not fail

PLUS

reliability of red system * probability that the other red subsystem does not fail

Unfortunately, I think I'm vastly misunderstanding Bayes Theorem and maybe the system as a whole. Can someone lead me in the right direction to how the inclusion of these G components affects the system reliability? Maybe I just need to re-read up on Bayes Theorem?

Thanks!

****EDIT****
I've simplified the diagram a little bit and I think it moves things along a little bit.

With this diagram (note modified lettering) I was able to determine all possible failure cases, 11 to be exact. The logical expression for whether it passes or not is: ~[(~F & ~G) v (~D & ~C) v (~D & ~E) v (~C & ~E) v (~B & ~C) v (~B & ~D) v (~B & ~A) v (~B & ~F) v (~A & ~C) v (~A & ~E) v (~A & ~G)] which gives the possible failure scenarios: (X, Y)=pair of failed components resulting in a failure.

(F, G) (D, E) (C, E) (C, D) (B, F) (B, D) (B, C) (A, G) (A, E) (A, C) (A, B)

So now my issue is definitely just a matter of Bayes and making sure not to double count.


texts: How to do IMU and camera "sensor fusion" tracking?

texts:
I have some 50ms latency cameras on hand and an gyro+accelerometer+magnetometer 800Hz IMU. I would like to know how exactly I should do a sensor fusion of such an IMU and camera to fix the positional data from the IMU positional drift. I'm not able to find much resources online.

Reason I don't want to go with just camera is the latency of 50ms with it.

The optical markers for the camera can be LEDs, ORB-SLAM data or AruCo markers which I currently use which add another few ms latency to the camera tracking.

Maybe there is even an existing library or documented implementation I can use?

Thank you.


texts:
In my application, I want to generate -9V/50mA from 12V Input.
What are options available?

I have come across few options as below:

1) http://www.ti.com/lit/an/slva257a/slva257a.pdf

Buck regulator to generate -ve output by changing OUTPUT and GND pins.
For such low load current, possibility is that it will operate in DCM mode.

2) Dual Pump Charge Output
http://www.farnell.com/datasheets/9917.pdf

I need IC which will take and generate -9V.


texts: Why are RMS values considered DC equivalent?

texts: RMS is defined as the AC equivalent voltage that produces the same amount of heat or power in a resistor if the same is passed in the form of a DC voltage to the resistor. But shouldn't the power in AC change continuously due to change in voltage and current and hence producing varying power in the resistor as opposed to the DC circuit where a constant power is generated. I am confused so please help me.


texts: LDO transient performance enhancement circuit understanding

texts: For the following LDO circuit, how does the transient performance enhancement circuit sub-block in green color works ?


texts: Detect movement direction of container elevator arm with contacless sensors generating signal for GPS/Modem

texts: Container Washer Truck: So I want to  generate a brief signal "Analog In" 24V for my GPS/Modem to send to backend once (with GeoLoc and Timestamp) when the elevator arm moves UP and passes contacless sensor A first, then contactless sensor B. No signal when it moves down past B and then past A. When the arm moves down again past B first and then past A no signal is generated. After going past A downwards process needs to be at original situation again.  What's a simple most robust way? Microcontroller or relay fine, which? 24V vehicle, 2D movement only, can be three sensors,too but contactless. (No budget for RFID tags etc.)


texts: Jumpers within diode through-holes in a PCB

texts:
I'm designing a keypad and I may not need to use diodes so I was thinking to use open jumpers within through-holes.

In case I need a diode I can still solder it otherwise I can bridge the jumper.

Is this a safe thing to do?


texts:
I am in the process of laying out coils for a Axial Brush less Motor. My question is - without taking turns or power into consideration. Are there any design ratios - which should be attempted. When seeking to a design a motor which is not specifically bias for torque or speed? I understand this may be a little iffy because PMs come in different strengths. But in general - are there any ratios or "rules of thumb" which one should consider for a balanced motor?
Such as PM diameter = coil inner diameter. PM surface area to coil surface area. PM diameter to Coil wall thickness etc. Or Coil Field to PM field?
I am about to start winding coils for a motor - and thought I would ask first before committing. As I am new to all of this. Below is a link to a 2-d drawing of the current pairing I came up with. The coils are 10-12mm tall. The PM is 30mm Diameter. I drew A - then realized the PM didn't fit well so I drew B. After drawing B - I now think I should get a PM that is slightly larger?
Full size: https://ibb.co/xLPGbzD


texts: What did my professor mean with this: gain-bandwidth product

texts:
After trying to ask multiple times my professor what he meant with this I still don't get it.

Basically I have an inverting amplifier with a specified gain-bandwidth product of 0.6 MHz.
Now as I understand we have that the gain-bandwidth product is calculated multiplying the closed-loop gain with the bandwidth.
Now the closed-loop gain is calculated with the ratio of resistances and it corresponds to 20 in my circuit.
Therefore the bandwidth is 30 KHz.
Now my professor tells me that the closed-loop gain must be in decibels in that formula and therefore it should be about 23 kHz. I don't get why the closed-loop gain needs to be in decibels in this formula, can someone please explain me?


texts: In the beta multiplier reference circuit, what is the function of start-up circuit? Can we use the beta multiplier without the start-up circuit?


texts: ADALM Mk2 Scripting environment not printing to console

texts:
I have a ADALM MK2 module.
I am trying to do Scopy scripting.
I have a script test.js with only one line:
printToConsole("hello")
nothing prints,
any ideas?
(i call the script with Scopy --script test.js)


texts: Spec'ing an always-on alarm/tracker for a car battery

texts:
What is the specification of a standard car battery (e.g. of a 2008 Jetta)?

Say, I want to connect an always-on alarm or a tracker to the electrical system of the car.

Is it likely to deplete the charge of the battery such that I won't be able to start the car?  Are OEM batteries or the always-on circuitry in modern cars protected from this kind of thing?

Also, suppose the device I want to install has its own backup battery, and specs of such battery are provided, as well as the time that it's supposed to power the unit for.  Considering that car batteries should supposedly never be fully depleted in order to remain capable of holding the full charge and of powering the starter, how would I do the math to calculate how many days I can leave the car undriven for?  Once driven, how long would it take for the battery to recharge?


texts: Can I modify this bluetooth keyboard to only have a certain keys so I can carry it around?

texts:
I'm trying to make a bluetooth remote shutter release thing for Androird and iOS. I asked about doing it from scratch but everyone thinks it's too ambitious for a beginner, so I gave up on that

Few days ago I acquired a bluetooth silicone keyboard that is still functioning(tested it with iOS and Android; able to get both phones to take pics)

My question is now, can I modify the board or he circuit so I only keep the buttons I want so I can carry it around? the keyboard is attached in the link

(for iOS it's the Volume Down key, and for Android it's the Enter key)

thanks for the advices and tips!


texts: Can I add an audio jack to a digital audio board?

texts:
Can I use the preamplified audio signal on an iphone only microphone (Tascam iM2) to add an audio jack?

There is already a USB 5V input which perhaps powers the preamp, and a volume control where I can perhaps intercept the audio signal. Is it too difficult?


texts: How this capacitor discharged by leakage of the diode in peak detector circuit...?

texts:
The text says:
"When Vin is high the diode is FB and capacitor charges up to peak. When Vin is low the diode is RB and the capacitor tends to discharge. The reason given for this is the diode leakage currents.."

But i don't understand one thing that is that as we know that the leakage current of diode is the current that the diode will leak when a reverse voltage is applied to it and the leakage current is entire function of the reverse bias voltage applied to it...so why the text tells us that this leakage current of diode is responsible for the discharge of the capacitor...??

or if i am interpreting it right then it might be inferred as that the diode due to its leakage current provides a path for the capacitor current to discharge and get dumped in the op amp....??


texts: Wiring LED driving lights powered from two separate switches and a common power source for two mode operation

texts:
I need to wire a total of four LED driving lights (12 volt, 40 watts  per light) that I need to control as two pairs  (2 left lights / 2 right lights), with each pair switched by two different means, using the same power source (the vehicles' 12 volt system).
To explain a bit more, the lights will be used in two different modes:

In mode one (normal) they are operated in pairs using a typical switched relay circuit with power supplied via an auxiliary fuse box connected to the vehicles battery;
In the second mode (emergency) the lights again will use a typical switched relay circuit via the fuse box, but this circuit  includes the addition of a "wig-wag" LED alternating flasher relay (2-channel 240 watt / 120 watt each channel) which would then connect to a common lighting harness used by both the "normal mode" circuit and this second "emergency mode" circuit.

Sorry if this is completely confusing, but being new to this sort of thing I'm unsure how best to describe my problem and more unsure that this will even work without damaging some or all of the components.
I've been told to "use diodes" without being told the necessary particulars, such as what kind of diode and where.
Thanks in advance to anyone that can help!


texts: For switching 220VAC, is a specific coil voltage and coil resistance better than another?

texts:
Is there any reason why I might choose an EM-relay rated at coil-voltage of 24V or 12V, over one rated at coil-voltage of 5V, all other specs like contact max. current, switching voltage, life etc being same. The only other difference in specs that I see are coil resistance, and contact material.

Most of the circuit schematics I found online, seem to use 12V relays, and very few use 5V relays. Given that low coil-voltage rated relays have lower coil-resistance, I'd only believe that one wastes lesser energy in switching and holding the relay, by using the 5V one, compared to the 12V one.

PS> By default I might order the 5V part, as I have quite a few 5V power supplies at hand, and none rated 12V. But if there's a good reason to use 12V EM-relay, I don't mind. Both parts (5V/12V) cost same.


texts: Different library for STM32 without interrupt, with interrupt or DMA?

texts:
I am an OO programmer, and since some time I'm spending time (as a hobby) with an STM32.

For a hobby project I'm using a shift register (74HC595), and LCD. For both I wrote a class to easily construct and use it.

Both are based without interrupts/DMA, so the methods are very simple (actually for the shift register there is only one method: ShiftOut(uint16_t data)).

But I can imagine later when I want to use the shift register in a more challenging program, that I want it to use interrupts or even DMA.

Since I don't have much experience with embedded libraries, and also cannot remember seeing it before, would it be better to split a library in 3 classes (one for without-interrupts, one using interrupts, and one using DMA) or an 'all in one' solution?

The advantages for combining:

Just one class
No repeating code (most 'business logic' will be equal)

The advantages for splitting:

Better performance (no need to check what manner (none, interrupt, DMA) is used)
Less code (no checks which communication method is used)

Or I could make an abstract base class and create classes for non-interrupt, interrupt or DMA deriving from it (but that will be a performance hit for every function).

Since I mostly don't see the 'split' solution (but sometimes see different classes made by different people) I wonder if it would be useful.

Also as a side question, I'm intending to pass everything what is needed (so e.g. needed I2C or SPI port, GPIO pins). I'm not sure if I can pass easily callbacks for interrupts/DMA settings, as this is set by CubeIDE and doing that manually without CubeIDE seems a bit overwhelming right now. Can I expect problems passing interrupts/DMA functions?


texts:
I have bought several DC Buck converters for my home-made 3D printer. I'm running a 24V PSU, but my fans are Noctua (12V) ones. So i want to convert 24V down to 12V. And the Voltage output works fine. however after several minutes the module gets really hot to the touch. Up to the point that it is not touchable with your base hands. Is this 'normal'?

The unit I'm talking about is this one: https://www.aliexpress.com/item/Hot-sale-Mini-360-DC-DC-Buck-Converter-Step-Down-Module-Mini360-4-75V-23V-to/32825363837.html


texts:
Question: Find the complete expression for i(t) in a series RL circuit with source \$Vsin(\omega t)\$.

simulate this circuit – Schematic created using CircuitLab

So to attack this I thought to bring out the ol' ant trusty Laplace tranform.

The final eqn I get is

\$ V \frac{\omega}{s^2+\omega^2} = (Ls+R)I(s)\$.

which becomes \$ V\omega \frac{1}{s^2+\omega^2} \frac{1}{(Ls+R)} = I(s)\$.

Can someone suggest a good method to move forward from here? I've tried fraction decomposition but I just can't move forward :(


texts:
I tried to connect via Atmel studio 7 to a ATSAMD21G18 to change the NVM user row (need to change BOD). I thought I could do it without having to write code. I connected via J-link fine but when I tried to write to flash I lost connection with the device. It will not connect anymore as if it's bricked. According to datasheet the flash section needs to be erased first before programming. Shouldn't there be a warning from AS7 ? What happened and how can I get the device working again ? Below is a picture of the connection.
Related issue I found explains how to write to flash using J-link via command console which I'm not very familiar with and commands seem outdated.link


texts: Problem with USB mini-B surface mount right angle connector

texts:
This question is about the advisability of continuing to use a USB mini-B right angle surface mount connector in my pcb designs.

On occasion we see one of these connectors peel back or delaminate off the pcb. Immediately the question is asked, why didn't you use a through hole connector?

If they are so problematic why are they being sold by many of the major connector companies.

Are other pcb designers experiencing this same problem?

Is a  through hole replacement for this connector the answer?

Mouser Part #:  538-67503-1230


texts: Problems driving a universal motor with triac

texts:
I have a router, Dewalt DWP611. The controller unit burnt out, so I wanted to make something simple to control it. I made this circuit:

My motor is 110V version and I am using 200k potentiometer instead of 500k.

The motor spins, but brushes spark heavily and it uses much more current than it should (around 4-5 Amps instead of less than one). When I lower pot setting, it starts rotating with bursts, also with heavy sparks.

What am I doing wrong? I identified the motor as universal motor with series winding connection, which should run on AC or DC. I know that factory controller uses soft start, which I don't.

I have 2 units, both run the same way. See the videos, low and high rpm:

Low RPM

High RPM

Both units were burnt the same way, after long CNC job (14 hours) and a lot  of aluminum debree. I think debree was filled and stuck inside. I opened and cleaned everything, internals look good now.


texts: Analog Switch IC controlled with logic input

texts:
I want to brake the connection between 2 traces on my pcb if i need to.
the input is 12v (cars voltage 12v-14v) from the cars brake signal and the output goes to my device that uses the brake signal.
i want to be able to cut this connection so the device does not receive the brake signal anymore.

I tried to use the MAX4544 but i don't know if this is the best solution.
the problem i have with below schematic is that when COM gets 12v V+ goes from 5v to ~8v.

Maybe there is a better way to do this different ic or schematic.

I already have a opto coupler to sense the brake signal to my MCU.
Maybe its better to use this digital signal to drive a mosfet to output the 12v to device and use a analog switch to cut the digital line to the mosfet.
But i would lose the safety part to have it NC.

my knowledge it not this extended so i am
looking forward to suggestions and idea's


texts: rfp30n06le MOSFET not outputting current

texts:
I have a rfp30n06le (N channel MOSFET) that I'm trying to power a brushed motor with.

The source is connected to ground of a 1 cell lipo battery.
The drain is connected to the negative side of the motor.
The gate is connected to a 3.3v pin of a microcontroller.
The battery is reading 4.04v
The +bat to drain is reading 4.04v also

When I hook the motor up to the positive end of the battery, the bat+ to drain reads 0v, and the motor doesn't do anything.

When I change the gate voltage to the 4.04v from the battery, the motor starts turning slowly, and the bat+ to drain reads 1.5v.

It seems as if the MOSFET isn't allowing much current through, but increasing the voltage allowed more current to flow. This makes me think that the gate to source voltage needs to be higher for the MOSFET to allow enough current to go through.

Am I reading the data sheet wrong? shouldn't I be able to use this MOSFET with a gate-source voltage of 3.3v?

rfp30n06le datasheet https://www.sparkfun.com/datasheets/Components/General/RFP30N06LE.pdf


texts:
I bought a small DIY infrared emitter today, but two of the LED's are missing.
The data sheet for the LED's is also missing.

The schematic is like this (a bit bigger):

Power source is 12V.

There are 3 LED in row followed by a 100Ω resistor.

Lets say L5 and L6 are missing. Is there a way to calculate a new R2 without knowing the U and I of the LED's?


texts: Do Germanium BJTs have lower impedance than Silicon BJTs?

texts: What brings this up is the fact that Germanium has a higher electron mobility than Silicon(as well as lower barrier potential) and does that translate to greater admittance(including susceptance)?


texts: What is the most amazing PCB artwork you've ever seen?

texts:
Have you ever looked at a PCB and burst out laughing?

Have you ever looked at a PCB and said "Wow, that is amazing"?

Have you ever seen a PCB that artistically expressed criticism of society's treatment of the poor?

I'm focusing here on the PCB itself as art -- rather than, say, some large artistic installation that may have light, sound, motion activated by some PCB.

(I hope a question focusing on artistic style rather than functionality isn't completely off-topic for chiphacker.
I was inspired to post this question after seeing the amazing artwork that endolith mentioned in the Chiphacker "Best licenses for Open Hardware" question ...
and seeing
The Best CD case insert... ever.
)

EDIT:
Wow, that's a lot of amazing artwork. I wish I could give everyone a prize for telling me about each piece of strange and wonderful artwork.


texts: Tektronix P6015 Replacement Potentiometer Considerations

texts:
I’ve acquired (saved from the landfill) an old Tektronix high voltage probe, model P6015. The probe body and cable are in decent condition, but I discovered two damaged potentiometers in the compensation box (R3, R5), one of which had been previously replaced with the wrong value.

I managed to locate a copy of the original manual, and it indicates the following ratings for each:

I’m looking at sourcing comparable replacements, and there are plenty of options that can be made to fit mechanically into the previous location. I’d like to know if there are any considerations I should make based on the original circuit / age of the device, or if a standard 20% or lower tolerance potentiometer will be adequate?
I appreciate any suggestions from the community.