texts: What happened to all of the Dynamic Signal Analyzers?

texts:
Decades back there were at least half a dozen instrumentation companies offering Dynamic Signal Analyzers (DSA's). Not Spectrum Analyzers, but rather Dynamic Signal Analyzers. The main differences being dual or multiple channel input and frequency ranges that went down to milliHertz. The DSA's were complete systems that would allow one to measure the transfer function of a servo system and analyze its stability margins in a matter of minutes.

I recall HP (Agilent), Onno Sokki, Bruel & Kjaer, Anritsu, and there were at least three others. But today there is only Keysight (Agilent spinoff) and Stanford Research System's 780 & 785, but the Keysight analyzers are the only viable ones for any serious servo work.

So where did this market go? Surely the demand has only gotten bigger with the rise of robotics work. I'm somewhat dismayed that development of new analyzers has not advanced beyond the HP35670A, which I consider the best DSA ever designed. Keysight still offers that model but the inputs are still analog. And no USB to get the data off.


texts: High Current PCB Design (polygon pour vs thick tracing)

texts:
I'm needing to design a PCB for power distribution. I have a 90W (5V 18A) power supply that will be responsible for powering 5 USB Type A outputs, each USB drawing up to 12.5W (5V 2.5A) MAX.
I'm used to PCB layout for low power digital electronics but this will be the first time designing something drawing this much current.
Am I just able to use a top layer polygon pour for 5V, and then the bottom layer polygon pour for ground? Or is there a reason I should have a thick trace (2oZ copper(?), thick width(?), solder on top of trace(?)) with each USB drawing off a main rail (like in the digram below)

I'm just trying to workout whether to trace or polygon pour to ensure my PCB can handle up a potential of up to 12.5A draw.
Thanks


texts: Is this notation for a single capacitor or a dual capacitor?

texts:
So Im trying to repair the indoor fan on our ducted AC system (2 weeks wait to get it replaced on warranty). Capacity has exploded. I replaced it with a similar cap (8uF 400v) and wired it the same as per the schematic however the fan still won't start.

Is the capacitor notation on the schematic indicating it is a dual capacitor? Or is it indicating a single capacitor with a junction on one plate? I can't find the datasheet for the original capacitor. Any advice would be great.

If I can't get a dual capacitor, how could I wire up two of these capacitors to have the same affect?

Or is it likely the fan is the problem?

Final question, how can I find the datasheet for the original capacitor?


texts: Simulation of 2D vs 3D electromagnetic waves

texts:
If you using a simulation tool that allows you to simulate behaviour electromagnetic waves in an environment. What differences are there in terms of doing the simulation in 2D vs 3D?

Does doing the simulation done in 2D necessarily mean your results (power of the EM waves) in reality i.e 3D will be less? If so then how do you estimate this loss?


texts: How do I decrease phase margin of an op-amp?

texts:
I have designed a CMOS op-amp circuit like figure

The problem is the phase margin is 79. How can I decrease phase margin to 60?


texts: Calculating FFT for only part of full frequency range?

texts:
Earlier I asked a question here about performing FFT at lower frequencies but still at high sample frequencies. I was under the impression that the FFT was inherently calculated at every frequency 0->(Sampling Frequency)/2 distributed in bins of width Fs/(2*N). But, looking at some of the answers I received, it appears that it is possible that Fs is only useful in determining the maximum frequency, which is Fs/2, but that it is entirely possible to, say, sample at 640 Hz but to only sample frequencies 0-64 Hz.

Yet, from what I've read so far on FFT implementations, it appears that the FFT in the examples I'm seeing, is being performed on the entire range 0->Fs/2, so I'm not entirely sure how to go about performing the FFT on only a portion of the maximum frequency.

Now, just to pre-empt this, I realize that somewhere along the line there is a high chance of some sort of misunderstanding on my part. I'm not entirely sure what I'm missing, but that's why I laid out my current understanding here and maybe somebody can properly explain why I'm perceiving that the FFT is only being performed on a part of the range, which I have the suspicion, due to the contradiction outlined above, is just an incorrect interpretation by me. Or maybe oversampling requires some sort of different logic that I was unaware of. In either case, I'm left a little confused so any help is appreciated.


texts: How do I determine the proper FM transmitter strength?

texts:
I want to build an FM transmitter that will transmit (on an unused frequency) from my laptop (near my video projector) to my receiver (about 20' away on the other side of the room). Then, I thought wouldn't it be cool to transmit music to the bedroom...again about 20' but with a wall in between. And of course, how about the workshop? about 1500sf, completely open.

How do I determine the signal strength that will meet these requirements:

maximum transmission distance perhaps 50-75' sometimes with a wall or two, but mostly without, but
weak enough to fall within FCC regulations for an unregulated xmitter.

I'd hate to solder something together that only transmits 5'.

Given a transmission distance, how do I calculate the power? does the power requirement change with frequency (e.g., 88.1mHz needs less/more power than 107.1mHz to transmit the same distance. Is there a rule of thumb for factoring in walls between trx and rx? or is that negligible?


texts: Connecting two wires to a DC 12v port on a controller board with 4 pads for a monitor

texts:
Sorry, the question was difficult to word. Basically I recently bought a controller board for a monitor and the DC cable I got wasn't correct. So until I get the right part, I just want to test the board and the monitor to see if they work.

When I turn it over, where the DC 12V jack is, there are 4 pads: 2x 12V and 2x Ground. Is there a way I can simply connect a red and black wire just to test?

[Here is an image to explain it further.]

All I want to do is connect a red and black wire, which I will connect to step up board, as this will be powered by USB, and supply 12V. (Don't worry, I checked all the amps, and voltages first, and please don't give any alternative ways of doing this.) I just don't want to go ahead and connect two wires and cause something to break.

EDIT: Which ones do I connect to? Both of the 12v and gnd? Or a specific one?

Many thanks.


texts:
I'm trying to design a filter that allows through a 1kHz sine wave, based on my university lecture notes I have the following transfer function for a multiple feedback band pass filter:

$$A(s) = \frac{-H\omega_0s}{s^2+(1/Q)\omega_0 s+\omega_0^2}$$ where \$\omega_0\$ is the center frequency and \$Q\$ is the quality factor.

I have calculated \$Q\$ to be 16.6667 (bandwidth of 60Hz) and \$\omega_0 = 2\times \pi \times 1000\$.

My lecturer has informed me that I can treat \$H\$ in the above transfer function to be a specification for the passband gain, I wish a gain of 0dB at the center frequency so I set \$H = 1\$. The problem is when I calculate my capacitor and resistor values using the provided formulas in my lecture slides, my frequency response is centered at 1000Hz, however it has a gain of approx 25dB (my chosen cap values are 100nF and R1 = 1.59k, R2 = 41, R5 = 64k).

How do I appropriately choose \$H\$ so that I have a gain of 0dB at the passband (aka 1kHz)?

I have attached the relevant info from the lectures below.


texts: What is the intended PCB layout for this Lumberg stereo connector?

texts:
I was intending to use the Lumberg 1503 02 3.5mm stereo jack connector on a PCB. After progressing some way through the design, I noticed that the pins for the connector are not on the bottom as I expected, but ~1.5 mm up the body. The rear pins also have a strange bend in them.

Based on the 3D model, I can identify three possible places where the connector could sit on a PCB:

I have highlighted the rear legs as they don't show up well otherwise.

From top to bottom, the green lines show possible PCB locations:

The PCB sits flush with the pins. This required a cutout for the body as well as the rear pins where they drop down.
The PCB sits flush with the lowest point of the rear pins. This required a cutout for the body and the front pins are in mid-air.
The PCB sits flush with the lowest point of the body. All pins are in mid-air.

Option 1 seems the only viable choice, but the datasheet makes no mention of a cutout, only standard PCB pads and holes for the locator pins.

What am I missing and how do I correctly design a PCB footprint for this connector?


texts: Vin: 2-36, Vout: 4.2. Should I use step-up, followed by step-down, or SEPIC?

texts:
My application has a small device, which draws about a watt, and is powered through a small dynamo, backed by a battery:

The dynamo generates 33 volts at maximum speed, close to L6902's max input voltage, and I can draw up to 800 mA from it.

A small micro is dedicated to observing the charge levels and commanding the DC-DC converter. The MCU tweaks the output current limiter of the L6902, the idea being that at low speeds less energy should be harvested - the MCU keeps the generator current roughly constant across the speed range.

The problem is that I cannot generate electricity at low rotation speeds, where the dynamo would supply < 8V, below the minimum input voltage of the L6902. Analysis suggests that the prime mover can in fact spend significant time at those lower speeds, where the dynamo will freewheel and the electronics would run off the battery only.

I'm thinking of ways to harvest at least a small amount of power at those lower speeds. One way would be to replace the current step-down converter with a SEPIC one. However, from what I've read, these are notoriously tricky to get right in terms of PCB layout, and usually take up lots of components and board area. Besides that, a SEPIC converter sporting such a wide voltage range (say 2-36 volts) is probably a very unwieldy one.

On the other hand, if I throw in some step-up conversion before the step-down regulator, a lot of shortcuts can be taken: like not using a dedicated chip at all!

I can easily wire a PWM output of the MCU to command a MOSFET for a crude boost converter. When I simulate the following schematic, I see that I can boost 3V to 10V at 400 mA output; there's some ripple in the 10V output, but the L6902 shouldn't care.

simulate this circuit – Schematic created using CircuitLab

The MCU will observe the dynamo voltage and adjust the duty cycle in attempt to keep the output at only approximately 10 volts.

I'm new to DC-DC converter design so I'm pondering on the workability of this idea, as there may be caveats I'm unaware of. Particular points I wonder about:

Switching frequency. I'm thinking of experimenting in the 100-300 kHz range, measuring what's most efficient.
Inductor parameters. I'll probably use the same as the recommended in the L6902 datasheet, which is 22µH, 180mOhm, 800 mA max.
MOSFET gate drive. I guess a MOSFET driver is a must?
What to do at fast motor speeds. I can probably just leave the MOSFET off, I will be getting Vout = Vin - Vdiode for the step-up part (of course, there would be resistive losses in the inductor, but those will be trivial at the low currents I'll need). Is this a reasonable thing to do, or should I design a bypass around the step-up part completely when the dynamo voltage is > 8V?

In the end, the question boils down to - whether I should really be scared of SEPIC or not? I can change the dynamo for a lower-voltage one and use a SEPIC IC; nothing in this design is set in stone.


texts: Using a depletion mode mosfet as a current limiting device

texts:
I have recently discovered the exciting world of depletion mode mosfets. Curiously, even in this document, I found nowhere that a depletion mode mosfet could be used as a current limiting/inrush current limiting device.
But this is strange, because what prevent us to use them like this:

or like this

(with a suitable heat sink of course) ?

To put flesh on bones, I have built a 800V, 10-20 mA PSU. I have a IXTY01N100D depletion mosfet, with 1000V breakdown voltage and 400mA current. It is not so easy to build a conventional inrush current limiter at this voltage. I wonder if I can use this transistor to limit the inrush current in the filtering output cap.


texts: For the circuit below, we know that kn = kp = 1.2 mA/V^2 and that Vt (V threshold) is the same for the NMOS and the PMOS. Does this mean that both MOSFETs are always in the same state.


texts: How can I test a microphone circuit with a test signal

texts: I have a microphone circuit very similar to below but I don't have a mic which is on back order.  I would like to test the circuit (and the processing that happens downstream) in the meantime.  Is it possible to hook up the electrical signal that comes out of an MP3 player (via the audio jack) to this circuit in lieu of the mic?  What other changes would I need to make?


texts: Let's say I have a square PCB with mounting holes near each corner and that the PCB will be mounted to an enclosure with 4 standoffs.  Is there a rule of thumb about how much tolerance I can have on the height of those standoffs?  If the standoffs are not all the same height, then the PCB is going to flex to some degree, so perhaps another way to ask this is how flat does a PCB have to be when it is mounted?


texts: How to wire together 3 power supplies for 3 different pd rails with the same reference 0v

texts:
How would I wire together 3 bench power supplies to get potential differences of +12, +24 and -6V, all with respect to the same 0V?
All 3 of the bench power supplies have positive, negative and ground terminals.

I've looked online and cannot find something similar, which I find surprising. If anyone could point me in the direction of any resources that can help me I would much appreciate it.

Thanks,
Steve


texts: Power source switching circuit with load as a voltage source

texts:
I want to design a power source switcher for Raspberry Pi Zero. Computer has to be powered from Li-Ion battery when no USB is connected and disconnect the bettery immediately when USB voltage is present.
Most of circuits I found require placing a diode between voltage source and a load - since one of the voltage sources is "inside" the computer I can't do that.
Crude representation of this circuit would be: (computer accepts both voltages)

simulate this circuit – Schematic created using CircuitLab
I'm pretty sure diode is not a right component to use here.
EDIT: I made a circuit that works in simulation, will it work in practice?

simulate this circuit
Older thread
My question is: Can I use reverse current blocking circuit using two FET transistors in this application? Like this one:


texts: Leaded Ferrite bead good choice for winding my own coils?

texts:
I have never designed directly with a ferrite bead:

pic here http://media.digikey.com/photos/Steward%20Photos/28L0138-40R-10.jpg

I want to wind my own inductor coils, and these seems useful for the fact that it has a ferrite core and some hefty leads coming out. I'd wrap my magnetic coil around the core and then solder the fine gauge mag wire to the leads. The final application would conveniently solder to the hefty leads.

My question is: Are the two leads part of the same conductor (a single wire fed through the ferrite core), or is there isolation between the two ends?


texts:
Why are high voltage power lines used? Electricity is generated at 11,000V...so is  that a potential at the generating station or potential difference across the ends of the power line?

And if it is a potential then I think we cannot apply the formula power = voltage*current.

I don't understand whether it is the potential difference or potential.


texts: Can an Integrated Circuit ROM ever be secured

texts:
This presentation which includes embedding public asymmetric crypto assets in a micro-controller on chip ROM suggests that there are, but I am sceptical.
Is it the case that there is nothing that can ever be done to hide the physical chip design from an examiner


texts: How to drive a 9V common cathode 7 Segment using Arduino and transistors?

texts:
I want to make a 4 digit timer with  9V CC 7 segment using arduino.
I tried the circuit below to switch the segments.

simulate this circuit – Schematic created using CircuitLab

The segments turns ON with 0V on pnp and 5V on npn transistor, I assumed 5V on PNP would turn the LED off, but it didn't. Is there any way I can switch the segment LED this way?


texts: Isolation transformer to reduce speaker pop

texts:
I have some computer speakers which suffer from the following problem:
when switches flip in certain devices in the house, like the thermostat on a radiator or the refrigerator, the speakers will emit a loud popping noise, caused (I believe) by changes in the voltage on the mains.

Would an isolation transformer between the speakers and the mains alleviate this problem?

If so, what capacity isolation transformer should I buy? The speakers are rated at 500W RMS (Logitech Z-5500). I've read that an approximate conversion of 500W to VA comes out to 500*sqrt(2) = 707. If I don't play the speakers at anywhere near maximum volume (certainly less than half the maximum), would a 600VA isolation transformer suffice?

Thanks for any assistance.


texts:
What do you think about converting pc power supply to bench power supply?
Is it ok for amateur use?

Edit: I thought it has some current limiting mechanism, but I see it doesn't.
It's big problem in my case.
I only need few hundreds miliamps on every voltage level. Can this problem be solved by some external current limiting circuit?


texts: Programming PIC 18F4550 using Bootloader

texts:
I was looking for simple boot loader which can program my PIC 18F4550 using uart communication. What I saw in all serial port boot loader program is, they are changing configuration bits especially LVP.  Is it necessary to set

  LVP=OFF (Turn off Low Voltage Programming)

in order to program flash using boot loader ??

Thanks I advance.

Update- Add Config Bits used by Boot Loader

Boot loader is used from this site

; CONFIG1H
CONFIG  FOSC = INTOSC_HS      ; Oscillator Selection bits (Internal oscillator, HS oscillator used by USB (INTHS))
CONFIG  FCMEN = OFF           ; Fail-Safe Clock Monitor Enable bit (Fail-Safe Clock Monitor disabled)
CONFIG  IESO = OFF            ; Internal/External Oscillator Switchover bit (Oscillator Switchover mode disabled)

; CONFIG2L
CONFIG  PWRT = OFF            ; Power-up Timer Enable bit (PWRT disabled)
CONFIG  BOR = OFF             ; Brown-out Reset Enable bits (Brown-out Reset disabled in hardware and software)
CONFIG  BORV = 3              ; Brown-out Reset Voltage bits (Minimum setting 2.05V)
CONFIG  VREGEN = OFF          ; USB Voltage Regulator Enable bit (USB voltage regulator disabled)

; CONFIG2H
CONFIG  WDT = OFF             ; Watchdog Timer Enable bit (WDT disabled (control is placed on the SWDTEN bit))
CONFIG  WDTPS = 1             ; Watchdog Timer Postscale Select bits (1:1)

; CONFIG3H
CONFIG  CCP2MX = ON           ; CCP2 MUX bit (CCP2 input/output is multiplexed with RC1)
CONFIG  PBADEN = OFF          ; PORTB A/D Enable bit (PORTB<4:0> pins are configured as digital I/O on Reset)
CONFIG  LPT1OSC = OFF         ; Low-Power Timer 1 Oscillator Enable bit (Timer1 configured for higher power operation)
CONFIG  MCLRE = ON            ; MCLR Pin Enable bit (MCLR pin enabled; RE3 input pin disabled)


texts: Problem I2C NACK in 3rd byte MLX90614 - Repeated Start

texts:
I am trying to read Melexis MLX90614 infrared temperature sensor through SMBus (I2C or TWK like protocol).

The protocol (SMBus) implement an special type of command or sequence called repeated start, that means we send a start condition without a previous stop condition.

I am using a XMEGA microcontroller using TWI libraries used in application note AN1308

In order to read the sensor data, I need to send 1 byte to write the address to read, and next read 3 bytes of data. For that reason is used repeated start.

The problem is I get ACK from 2 first bytes (write address and command write) but i get NACK when i send the address after repeated start condition

I have 3 captures from Oscilloscope:

General sequence

The repeated start condition appears OK, we have a start condition in the middle without a previous stop condition. The address is right and the command (address to read) also is ok (0b00000110 - 6)

The initialization of module is:

// ************** TWI Master config ****************
TWI_MasterInit(&twiMaster,
               &TWIC,
               TWI_MASTER_INTLVL_HI_gc,
               TWI_BAUDSETTING);

And the usage is:

    TWI_MasterWriteRead(&twiMaster,
                        MLX90164_ADDR,
                        bufferTX,
                        1,
                        3);

MLX90614 is 0x5A and bufferTX is a unsigned char array with a 0x06 in the first position. Also the baudrate is set to 100kHz

I don't know why i get NACK in 2nd address byte to read the data from sensor, the repeated start condition looks right. Also, the hardware configurations must be ok because I get ACK from 1st and 2nd byte

Thanks in advance


texts:
I am trying to get a small section of my PCB design to be ground-free as this is the advised layout given by the manufacturer of the component.

However, I believe that because there are components within this restrict area that are, or need to be, connected to GND, the restricted area fills with a ground plane that I do not want. Below are some related images.

The red line indicates my desired restrict area. Ideally I would like this area to be free from the surrounding ground plane and I will route the components that are required to be connected to ground manually with a few tracks.

Alas this does not happen and below is the actual result I get once I have 'ratsnested' the design.

As you can see, the area has indeed filled in with the ground plane, although it is a separate one to the main one, it is still an issue. So I would like it not to fill in at all!

Is it possible to do this on Eagle?

I need it because it is what the manufacturer recommends for the layout and it has proved problematic already without following there guidelines so I would like to rule out any possibility for problems in the future.


texts: Does using two Hall effect current sensors in parallel affect accuracy?

texts:
I am designing a circuit with allegro current sensor ACS770 for measuring currents up to +/- 90A.
I have 2 options :

use single ACS770-100B (100A Bidirectional version)
use dual ACS770-50B in parallel as suggested in :

Using Allegro Current Sensor ICs in Current Divider Configurations for Extended Measurement Range

Since my focus in on accuracy i am inclined to use option 2. However I cannot get my head around this : will accuracy increase , decrease or stay the same ? (resolution will be better obviously)


texts: Calculating the value of the resistance for controlling the speed of AC fan

texts:
i have an ac fan that i would like to control its speed
i am a bit new in this field so please bear with me

i had the idea of fixing 3 speeds with 3 switches one for each speed: (25%   50%    90%), and 3 relays each switch activates a relay and each relay wired in series with a resistance of a certain value so we have 3 speeds for every resistance (see the attached image)

i dont know the type of the motor (synchronous , asynchronus ,wound rotor...)

the motor have the following informations: 220 v , 50 Hz , 33W

i didnt make any mesurements (voltage,current..) when the fan is on

my question is how to determin the value of the 3 resistances if i want to fix the following speeds (25%   50%    90%)

thank you


texts: How to combine LTC2954 with TP4056 charging circuit

texts:
I'm new with electronics and I'm working in a personal project with ATmega328P-AU.

The project basics are and ATmega328P-AU powered by a LiPo battery and the battery is charged and controlled by a TP4056 + DW01A + FS8205A. Actually I'm using a switch to power ON and OFF and I want to change that using an LTC2954 (I chose it due the minimum parts needed at the end), but honestly I'm not sure where to insert it.

Here is the part of the schematic where I need to add the LTC2954:

I marked the place where I think I must insert the LTC2954 to keep the charging & monitoring the battery. Actually I power my ATmega328 directly with the VCC pin (3.7v - 4.2V).

Update...

I tried this and i wanted to use the INT and KILL signals to manage it with the microcontroller. I don't have any idea about he mosfet i need to use, the requeriments are +5v, 500 to 800mA and SMD, any help on choosing it and checking my schematic will be much appreciated. (i'm waiting for some parts in order to check by myself)

Thanks in advance !!


texts: STM32F439 CDC driver, is using UART required?

texts:
So, most of the examples use USB CDC driver and they bridge UART. I'm not embedded guy and learning the stuff one by one.
So, I understand UART... But I'm a bit confused how this bridging works. Is uart a virtual driver kind of thing or physical component inside the MCU.
How does this bridge of USB CDC driver work though USB and UART are components by themselves ?

I read this question, Does USB CDC always use a UART channel?

But I need more insight to understand this bridging. Please explain the bridging thing as well in details.

Because the confusion is UART itself needs pins configurations...  so pins are physical and how the bridging works.


texts:
I have no picture to show what my circuit is like, but I'll try to draw it and explain here as best as possible.
The circuit contains a NE555 timer, working in the astable mode with a frequency of 50Khz, 10nF charging/descharging cap, 230 ohm discharging resistor and 2300 +230 ohm charging resistor. It's powered by a single DC supply 15V. So far so good.
Powered by the same supply (15V), I have a flip flop circuit, which has no other connection with the 555 timer other than power supply ( which means they share the same ground and same +Vcc, and are not related in any other condition).
This flip flop circuit is made by transistors, and it's as follows :

The output is taken from the pnp collector, and the 11k resistor receives a pulse high to turn on, and to be turned off I connect by hand the ground through a wire into the npn's base.
The problem is: when the 555 timer is not connected to the 15V power supply, the flip-flop circuit works well as intended, but when the 555 timer is connected, the flip flop circuit goes wild and even by applying a ground voltage to the npn's base it doesn't seem to be turned off as the voltage in the pnp's collector stays high(about 14.5V). What could be taking place here? I really thought of many things but none seem to make sense once they are not connected in any situation but through the same ground and Vcc levels.

simulate this circuit – Schematic created using CircuitLab


texts: If I know how many millamps I'm drawing, and also for how many milliseconds, how do I calculate this to mAh consumed?


texts: Trouble with PUT circuit experiments in Make: Electronics

texts:
I'm relatively new to electronics (as a mechanical engineer, I had circuits courses... those were years ago now, but I'm not COMPLETELY ignorant), and wanted to take some of this quarantine time to learn more about a hobby I've meant to look into for years. I've had some issues with the experiments using a 2N6027 PUT in the Make: Electronics 2nd Edition book, specifically experiments 11 and 14. When experiment 11 didn't work; the pulsing signal that was supposed to be coming from the cathode of the PUT to blink an LED on and off in step 1 of experiment 11 wasn't working, instead just sending a constant signal and keeping the LED always on.

I thought that maybe it was something with the voltage divider across the gate pin of the PUT, since I don't have the exact 15k and 27k resistors that the experiment calls for, and used a few resistors in series to reach the proper voltage. I have 15k and 27k resistors on order now and have moved on in the book, to come back when I have those resistors.

Now, in experiment 14, there is another experiment with the same 2N6027 PUT. This time the resistors on either side of the gate pin are 1k resistors, so since I had 1k resistors I was hoping that this time the experiment would work, but... same result. Constantly on LED, no blinking/pulsing activity at all. Below are pictures of the schematic for the experiment in the book and of my breadboard, circuit is being powered with 6V as being recommended in the book.

Since I didn't have a 33k resistor, I'm using 3 resistors in series as you can see, total resistance is ~33.3k, I don't think that the extra 300 should be a problem, but I am new to this so let me know if there's any reason that would cause a problem. The other resistors are all within 50 of 1k, I've measured each one to verify this. I've tried multiple 2N6027s and all of them give the same result: LED comes on and stays one, while capacitor is charged for the duration, never discharging.

If anyone can see anything that looks wrong or has any troubleshooting ideas, please let me know... the fact that I can't get two separate PUT circuits to work leads me to believe that I'm just really doing something wrong. I'm more or less at the end of my rope with these, I've been screwing around with these PUT circuits for hours now and haven't been able to get the proper results... this seems like it SHOULD be simple, but I just can't figure it out. Thanks in advance!


texts: Trigger solenoid valve based on resistance

texts: I have a KUS SSS Water level sensor for my RV that I would like to have trigger a NO 12v solenoid valve to turn off when my tank has reached full (and ideally also sound a little piezo). The sensor ranges from 240 Ω empty to 33 Ω full. I'd like to trigger at about 50 Ω. I'm wondering what would be the simple circuit to make this happen?


texts: Driving LEDs / other small loads with a 74HC06 or similar inverter

texts:
I was recently reverse-engineering some firmware (and other bits) from a router, and spotted that the front panel LEDs were driven from a 74HC06 hex inverter gate chip rather than a proper LED driver.

A little confused, I pulled up the datasheet and found that the chip could drive as much as 35mA, which seems like a cool trick - you can strobe two low-current LEDs at once, save yourself a bunch of separate transistors, and drive everything from a single cheap IC.

After digging around further, I found other inverter and buffer gate ICs that can sink up to a couple hundred milliamps in a small package, with a lower cost than even buying a bunch of 2n2222 transistors. This seems absolutely ideal for driving small loads from a microcontroller.

Is this really a common trick? Am I missing something here? Anything tricky that I should be aware of?


texts: Shouldn't these headphone wires be insulated?

texts:
My headphones sometimes don't put out sound in one of the channels, so I opened them up and this question came to mind:

Shouldn't the 3 copper cables that connect to the mini-jack be insulated? One seems to be pure copper, I'm not sure how they changed the color of the other 2 to red and blue but it still looks like bare copper to my eyes.


texts: What do the C operators "&=" and "|=" do?

texts:
I've been working trying to read some C code and I've found some operators that I don't know:

What's the use of "&=" and "|=" operators when used for microprocessors programming?


texts: Fixing ground "open circuit" on printed circuit board

texts:
I was installing a RV roof vent fan and accidentally shorted it (connected it in reverse polarity).

The short seems pretty clean and I was able to manually confirmed that nothing else was broken by manually bridging the short with a piece of wire held in place.

I was wondering what the easiest way to fix this would be (I'm more of a software than an hardware guy)... I was thinking maybe I could just put a bead of solder where its broken?


texts: Input formula for 2 switching sine-waves (Heaviside eq'n)?

texts:
If we have 2 signal generators
1: \$\ 2sin(2 \omega t)\$
2: \$\ 3sin(5 \omega t)\$
being input to a selector switch that switches between the two continuous inputs every 0.5 seconds being sent to a low pass filter,

what would be my input equation to this filter?

So far, I have a rough idea that it would involve the Heaviside step function and represent something along the lines of:
\$\ 2sin(2\omega t)[U(t)-U(t-0.5)]+3sin(5 \omega t)[U(t-0.5)-U(1.0)]+2sin(2 \omega t)[U(t-1.0)-U(t-1.5) . . .etc \$

Is this about right?

Is there a general equation for such a system rather than writing a massive Heaviside equation?


texts: USB-C to USB-A 3.0 and USB-C for charging 20V

texts:
What is the connections configuration that I should implement to output a usb-C and usb-A 3.0 from a usb-C input? The input will be from a docking station capable of supplying 20V to charge my laptop. It can also be used with a usb-C to usb-A adapter to only use it as a docking station without supplying power to charge the laptop.
However, since the usb-C port to my laptop doesn't work properly, it can only be used as a charger. Therefore I would like to design a PCB that outputs a usb-A to use as a docking station and a usb-C to use as a 20V supply to my laptop. So far I figured out the connections if I had to achieve this separately. But I'm not sure how I can achieve this combined when CC1, CC2 and VBus are common to both outputs.


texts: How to read a port by a label in Mplab Harmony?

texts:
I'm more familiarized with MCC and with that framework is really easy to read a port we just need to give a custom name in pin module:

and after that in code:

DATA_IN_GetValue()

My question is how the same can be done in the Harmony framework because the label/name matters to me. I know we can read the ports with the overcomplicated function it has, but is there a way using the names?

I gave a name to the port here:


texts:
I have two comparator opamps which connected AND gate. I would like to change the output of the AND gate by changing the voltage on the 5k resistor with the Potentiometer.

I increased potentiometer value when the voltage at 5k was less than -0.5V. When the value at 5k exceeds -0.5V, AND gate output is high, so the voltage at 5k turned positive.

In this case I increase voltage at 5k above 0.75V by decreasing the value of potentiometer, but the output cannot be negative and it started oscillating.   What could be the reason of that?

Edit

I tried to create -1V + 1V on RV2 and R1 with feedback from AND gate output. But since the output of the AND gate is 0-5V, first voltage divider was used to reduce the range to 0-2V. 1V power supply(V3) was used for the -1V + 1V range. V3 for the first test, it will replaced with a voltage substractor circuit.


texts: Connecting LVDS signal from one PCB to another

texts:
I am tryin to connect LVDS signals on one PCB to another. I am using an FFC cable and am trying to understand if signal integrity would become an issue. The shortest FFC cable that I could find is 50mm and my signal frequency is 500Mhz. I also could not find the impedance of these FFC cables. I was wondering if there would  be any issues connecting these PCB's together using 0.5mm,50mm FFC cables.

Are there any other options to make connection between high speed LVDS signals on PCB?


texts: How do you control 130-size DC motors with an Arduino (seemingly 20A DC motors)?

texts:
I'm a little confused on specifications and limitations here...

I have 3 (130-size, I believe) DC motors I'm attempting to control with an Arduino. They are running off of a 7.2V NiMH battery pack, regulated by some simple switches.

Now, I know that the Arduino can't independently power motors. So, my next thought is using a transistor.

However, according to the guide I'm following, each motor (two motors?) will pull (continuously) 15A. I'm looking at the specifications of things like the TIP-120 and even the Arduino motor shield, but they only seem to be able to control 0.x mA - 1A per channel.

This seems like a lot of amps/a typo, but the guide continuously references these high currents (using 10A rated switches) - and when I try to research gates rated for such high currents, I get very expensive, very niche components.

Am I over-complicating or misunderstanding things? Does the voltage upgrade simply make things that much harder to work with?

Ultimately, my goal is to have the Arduino read all of the switches (which I think I can handle), do logic, and control output to the motors - that part I'm a little unsure of.


texts: This query is from my project on automatic motor switching of water tank. My question is that what should be the rating of switching device(relay or contactor) for single phase induction motor (2hp 8A class E) ?


texts:
Following diagram shows characteristics of typical telephone connection. (Insertion loss and Envelope Delay respectively)

I have been able to understand, that plots are due to dispersive nature of telephone channel, but i am looking for detail explaination for nature of given graphs.


texts: Is it possible to build a fake flash drive for the TV that is in reality a share drive?

texts:
Problem

I hate having to copy what I want from my PC to a flash or external drive and then stick it in the smart TV (which already has the ability to browse files on a flash drive) every time. I want the smart TV to always have access to a shared drive on my LAN.

Possible Solution

Is it possible to build (or assemble) a device or a contraption that masquerades as a USB flash drive for the TV, but it's actually relaying data from another place?

It could draw power from the TV's USB, and it's essentially a mini PC that makes the TV think it's a flash drive and I can browse files on the TV as normal, but on the other end of it I can remote into it via LAN (whatever OS that can easily handle this stuff), so I can tell it what to relay to the TV.

Is that at all feasible?
I don't think it's impossible, but is it doable at minimal cost? Does it actually require hardware manipulation or building, or can it be done/achieved with a mini PC and software?


texts: Why isn't number of loops included in the EMF equation?

texts:
The following is a snapshot from (http://www.electronics-tutorials.ws/inductor/inductance.html).

I understand the first equation which relates inductance, number of wraps, and current. But since EMF is equal to the derivative of flux with respect to time. Therefore if we take the first equation, solve for flux, and differentiate, we should still have the number of loops as a term in the equation.

Why is this not the case?


texts:
I want to make a device that can control a small solenoid valve for dispensing fluids. Basically a circuit which powers on and off the solenoid at different times to allow the fluid to flow.  The fluids will be gravity fed so very little pressure is needed. Most of the solenoid valves that I have found are like 100 dollars or more which is way too expensive for this project.

Does anyone know if there are any small inexpensive solenoids, or something similar, that would do what I want? I'd like the flow rate to be about 1 ounce per 5 seconds or somewhere around there but I can reduce the flow if it's more than that.


texts:
I'm currently looking to buy a lab power supply. But there's something I wonder.

We can adjust the voltage and the current.

Let's say I have a circuit requiring 9V and draining 1A.

What if I setup my power supply to 9V 2A ? I think the circuit will only use 1A from the two available and the power supply will warm for nothing but the circuit will not be damaged. Can you confirm this ?


texts: How to fool power supply that it has DC fan installed

texts:
I have a couple of server power supply units, namely HP DPS-1200FB. Those PSUs are working just fine (given their mileage) but the DC fans appear to be wearing out so I decided to replace them.

The original fan installed in those PSUs is a Nidec 40mm DC fan with four wires: GND, +12V, Temp and Rotation control.

When I was ordering replacement fans I explicitly asked for only two wires: GND and +12V because I prefer them to be running at full blast all the time.

When I install the replacement fans, the PSU runs for a couple of seconds and then turns itself off. My guess is it checks the RPM reading on the fan, does not get any data and thinks the fan is malfunctioning.

Is there a way to fool the PSU that it actually has the fan installed even though it only has two wires? I attached a picture of the original fan termination for reference.


texts: Finite state machine (FSM) that controls a memory block

texts:
I have to Implement a finite state machine (FSM) that controls a block
memory. The FSM receives two inputs, indicating ready when the memory is
prepared, read / write (r_w) indicating whether you want to perform a read or write and a reset signal. The FSM generates two variables, oe and we that are the "output enable" and "write enable" of the memory block.

So far I made the state transition diagram and the table of output variables depending on the condition but I'm not sure how can I design the circuit with it


texts: using ferrite beads khz region - advice?

texts:
I am operating some mosfets in the 50-500khz range, and wish to improve performance, reduce losses and very important reduce emi. I am using a resistor on the gate on the drive with a 12v zener and 10k resistor to ground/0v to try and adsorb transient voltages at the gate.

My question is, if i wish to permit 50-500khz operation / switching, but reduce emi and parasitic oscillations from the device, while maintaining fast switching, would i benefit from ferrites and would you be able to suggest some suitable options/ where to place (is it between gate drive resistor and gate?)

I Occasionally detect parasitic of multiple mhz that i wish to suppress.posting an exact schematic is not possible at this time but looking for advice anyway.

Thanks in advance

Edit: I'm really sorry for not posting a schematic when asking the question originally, main reason is that i don't have permission for what im working on at the moment but i work with a number of switching circuits in the khz region and was postulating about how one might stop ringing at the gate, while not slowing switching, after choosing fast components and suitable gate drive etc.  The question was general in that i understand a resistor on the gate of a mosfet can help provide some level of dampening, and routinely use them, but wished to know if a ferrite placed in the gate drive would be a good or bad idea in general to clean operation up more.

However to try and present something of a similar situation ive had a go this morning and dusted off an old mazilli zvs fly back driver from my tesla coil as i can switch it through a suitably sized inductor to achieve the same frequencies my circuit switches at and although the parasitics are slightly higher in frequency and amplitude in my test, they seem to occur in a similar fashion in that circuit too. I am scoping the gate and the source seperately and can see them occuring on switching. Although its a different circuit, my question, badly worded, was general as to whether a ferrite, placed on / inline to the gate of the fet would reduce ringing and emi? As a practical curiosity where i don't actually have any suitably sized ferrites in my parts boxes to test practically at the current point in time.

Link to a mazilli zvs (different situation but similar and somewhat exaggerated problem):


texts: AVRISP mkII. No comunication betwen programmer and device, after programing fuses

texts:
When I program my Atmega816au, I lose communication with the microcontroller after I program the fuses.

I can write and read the Flash memory with no problems, but only before I program the fuses.

When I program the fuses, the microcontroller becomes "useless" and I don't have access to it anymore.


texts: Choosing proper heat sink for a high power relay

texts:
I'm using this Solid-State-Relay to transfer 350 Watt:

Input: 45VDC x 10A
Output: 10VDC x 10A

The following is derived from it's data sheet:

  Maximum junction temperature 150 C
  Junction to Ambient 30 C/W
  Junction to Case 7 C/W

In order to keep it's features from changing because of a high temperature, I'd rather for it to have a maximum temperature of 50 Celsius degrees.
The ambient temperature is 25 C.

A simple calculation shows that a proper thermal resistance of a heat sink for this job is:
(50-25)/350 = 0.07 C/W which is crazy!!!

What do you suggest for me to do in order to keep the device below 50 C ?
Would it be unrealistic to use this kind of component for this kind of task?


texts: Question on DC analysis of BJT - Common Base

texts:
I'm trying to solve a question from my book. The answer for the question is given but I keep getting a different answer. I don't know if I'm doing it the wrong way or the book is wrong.

This is the question:
This is my working:

The answer is apparently 0.921mA but I get a different answer.

The question also asks for voltage gain and current gain. I did not attempt those parts yet since I got stuck on the first part.


texts:
I'm working with a high power LED(40W heat dissipation) on a single layer aluminium core PCB.To calculate the required heatsink it did the following:

\$P = 40W\$

\$Rjc = 0.6K/W\$ (datasheet)

\$Rcpcb = 0.77K/W\$ case to PCB. This is the thermal resistance of the isolation layer(MSC TC-Lam 1.3, 100µm)

\$dT = (Rjc + Rcpcb) * P = ~55K\$

In summer \$(Ta = 45°C)\$ this would require a heatsink with \$(Tjmax - dT - Ta)/P = (110 - 55 - 45) / 40 = 0,25K/W\$ which is hard to achieve without forced air flow(not allowed in the environment)
The only parameter I can change is Rcpcb.

Question: The manufacturer can mill through the isolation layer, but is there a way to connect(solder) the thermal pad directly to the aluminium core?
Are there any other ways to get the heat away?


texts: How can an electret microphone have a more or less flat response?

texts:
I've got two concerns. The first is that the voltage across the electret capacitor is proportional to \$\frac{1}{d^2}\$. For the voltage to be proportional to the pressure difference between both sides of the membrane, it would mean that the membrane would have to deform in the precise manner so that it would work, which I don't see how one could make that happen.

EDIT: \$C \propto \frac{1}{d}\$ actually, and not \$\frac{1}{d^2}\$. And since \$V=\frac{Q}{C}\propto d\$, the only thing to ensure is that the membrane behave linearly, which probably is the case as long as the movement is small enough.

The second concern is this circuit:

I really don't see why it should be linear, since \$I_d\$ is not proportional to \$V_{gs}\$.


texts:
In my project I use electret mic + opamp to capture audio, which is later used for speech recognition on a remote site. This works well when operates in a silent environment, but not when there is some interference that comes from another direction (for instance, a conversation near by).

I wonder how hard it would be to perform some simple analog voice cancellation by adding another mic + opamp a few centimeters from the first one (the device's total size is a few centimeters), in order to filter out audio signal that comes from the side and only keep the audio signal that comes from a source perpendicular to the two mics.

I tried to search a little and found some info about beamforming. However, I'm looking for a solution which is simple and cheap, and doesn't require digital signal processing.


texts: Circuit design using only NANDs and Inverters

texts:
So I'm having trouble with some circuit design for class.
We're given a truth table with 4 inputs and 2 outputs. I have karnaugh maps for the inputs and simplified my boolean expression. We have to design the circuit using only NANDs and INVs. For some reason I'm just completley lost on this one.


texts:
I'm trying to simulate the attached circuit in Proteus but i got the following errors after i made the branch attached to 32v tap of  the transformer.
[SPICE] transient GMIN stepping at time=0.00461295
[SPICE] transient GMIN stepping at time=0.00461295
[SPICE] TRAN:  Timestep too small; timestep = 1.25e-019: trouble with instance D3.


texts: How can I keep stable position of my drone? How can I detect bias of them?

texts:
I am just a little bit worried about my research because I feel stuck in one point and I can't find the exit door.

My question is about this:

I will design a drone and the professor wants that drone keeps its angles in one position. That is, roll, pitch and yaw angles don't change. How can I keep them in a stable position?  Or, how can I detect bias of them?  I am thinking about using IMU or MEMS-INS for this.

Am I on the right path?


texts: Can motherboard heatsink screws change the inductance of nearby traces?

texts:
I have bought motherboard and heat sink. The heat sink uses metal screws and the screw heads are isolated from the board with thin mica insulators. But the screws end up being above some traces on the board, thus changing the inductance on some printed wires. The board traces are specially curved like stairs to calibrate inductance and capacitance with each other, and I think these metal screws near them will change their impedance. I am not sure how much the screws of the heat sink will affect the motherboard but it is obvious that they will change the impedance of some of the printed traces.

Do you think that this is major problem and I should avoid this kind of heat sink?


texts: Material choice / optical properties for solar panel cover (glass/perspex/lexan)

texts:
First off I realise this is sort-of off-topic but this was the most relevant stack site I could think of...

I have a Bosch solar panel which was damaged by couriers, the glass covering was shattered but the panel underneath is fine.

So, I was just about to buy a sheet of something (probably standard glazing perspex) to replace it, but wondered what the optical properties of the solar panel/cells actually are - if putting the wrong glass or plastic in front of it could block certain wavelengths that the panel find most useful.

Any info greatly appreciated!

Edit to add: It's going to be mounted on a vehicle and I'd rather not use glass for that as getting hold of suitably toughened glass is not as easy or cheap as perspex/lexan/makrolon etc.


texts:
I want to know how can I enable the regulator in three different ways in correct way through the hardware. There is two PCBs in below picture.
PCB1:

24V input plug (user plugged)
16V battery
Charging circuit
small microcontroller
5V regulator
SW1 to turn on regulator and as input to uC

PCB2: Main PCB get power from PCB1
I would like to enable regulator pin if:

24v plug was inserted
SW1 pressed (doesn't matter if 24v plug or pcb2 is plugged) (uC keep it enable high after sw1 pressed)
if pcb2 attached to pcb1(doesn't matter if 24v pug or sw1 pressed)

I came up with below design but I don't know what to do with 24v plug or external board plug.
Note: Below schematic is for demonstration no P/N or Value is correct. Vsys is equal to 24V if plugged or if not is battery voltage.
MY Solution check this link

simulate this circuit – Schematic created using CircuitLab


texts: System clock reference input path for AD9544

texts:
According to the datasheet of AD9544, I have made the following schematic for the system clock input:
R1 = 150R
R2 = 330R

However, I discovered that my TCXO deliver an 0.2Vdd - 0.8Vdd output (https://www.mouser.fr/datasheet/2/122/ECS-2520SMV-1628252.pdf).
And when I observe with the scope, it seems that the level output is smaller than this (output current too high?).
The System clock reference input path specifications specifies that Input voltage must be 0.9V minimal for high level and 0.5v maximal for low level.

When I observe the TCXO output with a scope, I see 0.84V-2.3V (Low - HIGH).
When I observe the XOA input with a scope, I see 930mV-590mV (Low - HIGH).
I tried to put other resistor value as well and I observe the following value for R1=330R , R2=470R :
TCXO output : 0.86V-2.2V
XOA input : 976mV-544mV
Is there any resistor and capacitor adjustement for make the ad9544 works with this TCXO?
Best regards,


texts: How the negative resistance feature of tunnel diodes used in oscillators?

texts: Can someone explain how the negative resistance feature of a tunnel diode is used in oscillators with the help of this circuit diagram:


texts:
I need help identifying an SMD component it is a small(1 mm X 1.5 mm)  black part with an "O" written on top if it.
I think it is a Schottky diode for reverse polarity protection ?.

(Source, first part on codes beginning with O)

I have attached an image if that helps

The component in question is marked J2/J3 on the silk screen. Also, if it helps the image is of a remote control pcb.

PS: This is my first post so please let me know if i did something wrong :)


texts: How to safely build a hybrid battery module?

texts:
I want to create a hybrid battery module to start a car engine. I intend to use a supercapacitor bank in parallel with a normal car battery.

The bank is composed of 6 capacitors mounted on a balancing module (bought from Aliexpress) and has 16.2V (6x2.7V; 350 farads/capacitor). The car battery is a normal 12V lead acid battery.

I am concearned that by connecting the two sources in parallel these will discharge one into another. What safety precautions must I take? Would placing a diode between the two sources prevent mutual discharging? Can someone offer me some advices on how to safely proceed with this? Did anybody make something similar?


texts: Li-ion Swollen battery dangerous or not?

texts:
I have a Wifi AP and its Li-ion battery has swollen so much that its cover cannot be put in place over it now.

Its working but its backup time has reduced to 20%. I cannot put on the battery cover because of its bulge. Normally its mains charger is power-ON 24/7.

Is it safe to keep it working in this shape? Is their any recommendation as to when to replace a Li-ion battery? Is it possible that it blows up and catches fire?


texts: Using transistors to control a 555 timer in astable configuration

texts:
This is a condensed circuit used for hardware debugging purposes.
The goal of this circuit is to control the 555 timer with only three pushbuttons. I am using the 555 timer and resistors to simulate the signal source I will be using. This is not a high-powered system therefore I do not see the need to use relays.
When the button is pushed the microcontroller will receive a digital signal to turn on the LED. At the same time, this push button will be used to allow the 555 timer to produce the desired frequency. On a fundamental level, it is combining a simple push-button circuit with the 555 timer piano circuit only difference is that these buttons need to be shared.
To start I got all of the pushbuttons working with the Arduino. Then I connected one transistor to the 555 timers and the capacitor charged and discharged appropriately to give the desired frequency.
When I connected the other transistors shown in the circuit below, the capacitor charges but it does not fully discharge to create the signal for buttons 02 and buttons 03. However, button 01 still works.

Why this is the case?
Why does the first circuit work and the second one not work?


texts: How to light an LED with very low voltage and low current?

texts:
The goal is to demonstrate, visually (with a light of some sort) that power is begin generated, albeit very, very small amounts of power. What kind of set up could I use to light up an LED (or any visual indicator).

My power supply is incredibly small; about 0.1 volts and I'm not sure of the current, but consider it low.

I've heard of things such as a "joule thief" that could maybe allow me to light up an LED with very low voltage, but I believe that works by sucking current, which I don't believe I have enough of to do that with this very small power supply. Another option-- if my power supply is constant, but very, very small, can I use a capacitor somehow to store the small amount of energy trickling out of my power supply to then make an LED or other indicator light up (even just flash) once every few seconds or every few minutes?


texts: Full wave rectification with only an antenna input?

texts:
I am designing a receiving circuit and would like to do a full wave rectification of a sine wave signal received from an antenna. My problem is figuring out how to isolate the two ground signals of the rectifier. When the grounds are shared the rectifier works as just a single diode. Here is a schematic of my question:

simulate this circuit – Schematic created using CircuitLab

I believe that I can use a transformer with the antenna current through one winding and the rectifier on the output of the other winding but I would like to know if there are other options? Could I use an optocoupler for this? And is it possible to use an op amp with the ground of the amplifier as the input into the ?? node of the rectifier? Thanks for any help!


texts: I'm driving a TXB0104 translator from 3.3V logic on the B side, VccB is 3.3V, VccA is 2.5V, OE is on VccA. Both supplies are solid. It's on a breadboard. (https://www.sparkfun.com/products/11771). The A-side gave really bad waveform at 1.5MHz while there is no load on it. All 4 channels behave the same. Is this translator broken or just not cut out for 1.5MHz?


texts:
I am working on a balance controller for a robot. I have obtained a transfer function between the robots motor voltage and the robot pitch angle.
$$G= \frac{ -5.893e05 s^4 - 7.71e08 s^3 - 1.435e11 s^2 - 2.566e12 s - 7.683e09}{s^7 + 2418 s^6 + 1.317e06 s^5 + 1.977e08 s^4 + 1.312e10 s^3 + 1.796e11 s^2 - 9.658e11 s - 1.525e13}$$
The bode plot is:-

The system has poles and zeroes

As you can see, there is a pole on the RHP which means the system is unstable. There are no zeroes in the RHP. I plotted the Nyquist plot of the open loop system:-

According to the Nyquist stability criteria, I need \$N=P-Z = 1-0 = 1 \$ counter-clock-wise encirclements of -1 in order for the system to be stable. And this is not the case. In believe I can fix this if I add a PI-term to my system. I add a negative gain of \$K_p = -2 \$ and an I-term \$C_i(s)\frac{0.1s + 1}{0.1s} \$, so now my open loop transfer function is:
$$G_{ol,2}=K_pC_i(s)G(s) = -2 \cdot \frac{0.1s+1}{0.1s} \cdot G(s) $$
If I plot the Nyquist plot of the open loop system now I obtain:-

And it looks like there is one encirclement of -1, which should mean that the system is stable. I also found the step response for the closed loop system with unit feedback \$G_{cl} = \frac{G_{ol,2}}{1+G_{ol,2}} \$ and got this:-

To me, the system looks stable, but I just want to be absolute sure if what I have done is the correct procedure. Also, as you can see in the step response I have a steady state error of 45% or so. Is there a way to fix this, maybe adding another term to my controller?


texts:
I need help designing a power conversion circuit from 15V DC to 3.3V DC to power an ESP12E module (which can handle max 350mA, but actual usage will be 80mA).
I have tested a prototype with Wemos D1 Mini powered by 5V via AMS1117-5 voltage regulator (like this one) from 15V. It worked quite well, but the regulator running is at about 30℃ (with ambient temperature of about 22℃).
In the final design instead of Wemos D1 Mini I want to use ESP12E which uses 3.3V (with the PCB ordered from JLCPCB with SMD components assembled).
I was thinking of adding AMS1117-3.3 to step down 5V to 3.3V.
Are there better alternatives for this situation?
UPDATE 1: The source voltage is actually 15V and not 18V as originally stated. So AMS1117 coped because it's maximum allowed input voltage is 15V.
UPDATE 2: I ended up searching for 3.3V voltage regulators on JPCPCB, going through datasheets and found a few options. The short list is:

https://datasheet.lcsc.com/szlcsc/Diodes-Incorporated-AZ1117CH2-3-3TRG1_C108492.pdf
https://datasheet.lcsc.com/szlcsc/Changjiang-Electronics-Tech-CJ-CJT1117B-3-3-G_C164899.pdf

Will these do the job? Any advantages of one over the other?
UPDATE 3: I've checked the actual current draw of my prototype and it's only 80mA.


texts: Modeling a long single wire in a circuit?

texts:
I'm currently trying to make a model (equivalent circuit) of a long single wire  with a resistor and inductor in series. Is this a proper way to do it?

What I have done:

Calculating the resistance per unit length of a single wire
Calculating the self-inductance per unit length of a single wire

Is this a proper way to model up a long single straight wire? If it isn't, what is the proper way to do it?

Thanks in advance.


texts:
Is there a way of clearing a file in the petitFAT format?  What I came up with is this:

void SDerase(void)
{
    for(;;){
        res = pf_write("\0", 1, &bw);
        if(res || !bw) break;
    }
}

So this basically writes NULL characters to the files until it reaches the end.  It works fine, but it's a bit slow.  Erasing a 100 kb file takes roughly 1.5 seconds.  I will be using bigger files later, possibly a few megabytes, so this method would take ages.  Is there another method of erasing a file (.csv or .txt) with the petitFAT file system?


texts: Why won't this PC power supply run my BLDC?

texts:
I would like to power my Arduino and BLDC to be powered with an old computer power supply. My Arduino needs 5V and my 3 phase BLDC needs 12V.

simulate this circuit – Schematic created using CircuitLab

Details

I'm using a SLA5068 N-channel MOSTFET bridge. Datasheet Here.
My sequence is taken from the library AccelStepper--here is the homepage. The sequence has 3 steps; during each step, only one phase will be on.
The BLDC motor I'm using is one from an old Western Digital 500gb HDD. I can't find the specs for it, but I know it's rated for 12V because I looked up a datasheet for the motor controller chip that was on the board with it.

The power supply I'm using:

Behaviour

If I use the 5V for powering my BLDC, it works just fine (except I can't go very fast).
If I use the 12V supply, it works for a moment and then shuts off.

Things I've tried

Putting a 1K resistor from the 12V to ground. Also tried with a 570 ohm
Putting in a capacitor to ground.
Putting a fan from the 5V to ground so it has a constant load.
Putting a flyback diode in the circuit.

The most puzzling thing

This works fine with my computer fan, which is a BLDC that has a controller circuit built inside it; this leads me to believe I am missing something in my design.

Perhaps this is an important detail, when I use the 5V supply for my 3 phase BLDC, I don't hear any clicking, but when I use the 12V supply, I hear a lot of clicking and then it shuts down quite promptly.


texts:
I have this circuit below which has kp=200u,Vto=0.6,L=1u,W=10u,nmos transistor

Can anyone explain me how VS(voltage in source) becomes negative?Also I know that, in this cuircuit the the maximum voltage should be VDD and the minimum 0V.How this negative voltage appears.And one more question.I expected that this current (which produced by ideal current source) couldn't flow in the circuit because VGS


texts: Is a diode needed for this simple mini solenoid circuit?

texts:
I am building a mini pinball machine, which is about 10x22cm.  To drive the flippers I plan to use this 5v mini push/pull solenoid: https://www.sparkfun.com/products/11015 , along with momentary SPST buttons and a 5V 2A wall power adapter.

Those are the only electronic components in the machine. I am not using an Arduino or any other controller.  In this scenario, is it advisable to use a diode (or any other components) to protect the power supply?

If diodes or other components are advisable, I will be grateful if you could explain at a very basic level why they are needed and where they should be inserted into the circuit.  The schematic below is pretty much the current extent of my electronics knowledge.  I am interested in expanding my knowledge but find many of the technical terms used on this site overwhelming.

Here is the circuit that I have so far:


texts: Will an IC that requires an Oscillator work without one?

texts:
I have a PL2303HX and I just etched my board with a USB to Serial IC (PL2303HX). The problem is that it requires a 12 MHZ crystal but I don't currently have.

Just a side note, the IC is on the same circuit with the Atmega328. When I plug the USB cable the LED on pin 13 blinks once. (it means it's working.)

I tested the board but it didn't work but the PC showed a notification that an Unknown Device has been plugged. The problem might be from the circuit or from the crystal, so I'm just interested in knowing if an IC doesn't have a built in oscillator, will it work without one ?

Edit:
Actually it does include one but it needs an external one also.
"PL-2303HXD already has an integrated clock generator.
There is no need for the external 12MHz crystal oscillator used in HXA/XA PCB."


texts: How to make one of the CD4040 output pins reset another counter?

texts: Why does pin 4 (Q7) 4040 reset itself perfectly but not reset 4026? I would like the signal from this pin to reset the 4026 as well, but it doesn't. I also do not understand why this pin has such a low voltage of 0.5V? Why is the 4040 still resetting with this voltage? I just want pin 4 of 4040 to reset all of my counters. (For now, 4026 the reset pins are grounded)


texts: What is voltage level in DDR5 defined by JEDEC?

texts: Voltage level in DDR4 is 1.2 volt, will it be same in DRR5 also? Also how much maximum voltage fluctuation will be allowed?


texts:
I'm solving this high-school level problem, where I have to find the current through each resistor.

simulate this circuit – Schematic created using CircuitLab

There aren't any resistors in parallel or series, which could be combined, so I tried using Kirchoff's law for junctions and loops. The resulting system of linear equations doesn't have any solution according to Mathematica. \$I_0\$ is the current through the source, \$I_{15}\$ is an auxiliary current through the empty wire in the middle of the circuit. My resulting system of linear equations:

My questions are:

Is my approach to this problem right? Maybe I chose wrong loops. Is there any rule for which loops I should choose?
There are 16 unknown currents, I have 10 junction equations. Does it
mean I have to create at least 6 loops, to find all the unknowns?
If my approach is wrong, what is the first step or direction I should use to solve this problem?

EDIT: There are a few mistakes in the equations:

equation 3 is \$I_3=I_5+I_7\$
equation 15 and 16 don't include \$I_{15}\$ (there is no voltage change over the wire without any resistor)
With these changes, the system can be solved by satisfying \$\mathbf{A}^\intercal \mathbf{A}\vec{x}=\mathbf{A}^\intercal\vec{b}\$. However, the accepted answer shows a much better approach to this problem (the results are the same).


texts: How to dynamically adjust the load using a MOSFET for a battery discharge tester? All I need is to vary the gate charge of a MOSFET. For the final results I need to monitor the constant current profile.


texts: Control a dosing pump with raspberry pi zero w

texts:
Hi i have a few "Peristaltic Pump Dosing Pump 6V DC Motor" with the following specs:

DC: 6V
Non-load current: 100mA

So the idea was to control it with a L293D using the following scheme

Image source: https://business.tutsplus.com/tutorials/controlling-dc-motors-using-python-with-a-raspberry-pi--cms-20051

But replacing the batteries with the following battery eliminator:

Adjustable output voltage: 3-12 V (DC)
600 mA output at 3/4,5/5 V
500 mA output at 6 V
480 mA output at 7,5 V
400 mA output at 9 V
300 mA output at 12 V

Would that work or do i need to add some additional components?
Also what V output do i need to set the battery eliminator to?


texts:
I have an AC powered device, and a customer asks for exact leakage current. Current that can trigger a leakage current circuit breaker, so it's obviously something flowing through Y capacitors to the ground wire.

The question is, what is usually measured and what actually matters? Peak to peak? RMS? Pulse width?


texts:
I am working on a microgrid balancing algorithm.
The microgrid contains

buses/feeder pillars
uncontrollable generators
uncontrollable loads
grid connection
controllable generators
controllabe loads

The main goal is to maximalize power flow towards controllable loads using controllable generators and the grid connection.
Feeder pillars and buses have limits (it can be expressed as active power limit).
What would be the method to calculate how much is the max power that I can flow from controllable generators to controllable loads through the limited AC network components? (At this moment involving reactive power/frequency/voltage to balancing is not in the scope.)
If I could simplify the Microgrid network into a DAG (graph) is it valid (by Kirchhoff's circuit laws) to use max-flow, min-cut in some way on the network graph?


texts: How to determine the transform function of certain bode plots?

texts:
The answer to this question above is C, yet I only know that the anti-resonance and resonance are located at 8 and 11 Hz respectively.

Another example below to which the answer is B.

I appreciate any help on how to determine how to know what transfer function belongs to bode plots like these.


texts:
After some browsing I found transistor circuit very similar to my needs:
Understanding an 'ideal' diode made from a p-channel MOSFET and PNP transistors
Unfortunately its application is limited by the Emitter-Base breakdown voltage of used PNP transistors. Does anybody know similar circuits for 24V?
Thank you in advance.


texts: Differential Op-amp showing negative voltage on simulations

texts:
I am trying to determine if it is feasible to use an op-amp to interface a button 25 meters away. A user suggested this solution to me and im trying to explore it. He suggested to use a differential configuration to protect against common mode transients and false button presses. I tried recreating the circuit in proteus for simulation but i am getting weird results, i do not know if its proteus that is wrong or if its actually correct.

The circuit supposedly outputs 5v if a button is not pressed and 0v if the button is pressed
I am using a generic simulation model for the op amp. Notice the oscilloscope reading at the start you see a flat line at the beginning that is 0v. When a button is pressed it dips down to a - 5v but the voltmeter on the output will show 0v (not -5v like the oscilloscope). When button is released it shoots up to 2.5 volts and gradually go to 0v, but the voltmeter will read 5v, notice the leading point of the line where it is near zero but the voltmeter is at 5v?
Which one do i believe? Have i missed something? I have checked the schematic and it seems to match from other sources (example). The actual op-amp i plan to use is this.can i actually expect the proper voltages (0v and 5v) on the output of the op-amp in reality?
here is the op-amp property the one used above. I have actually tried using a model of an actual IC and the behaivor is the same where i am getting negative voltages on button press.


texts: How does trace/via clearance affect parasitic inductance if they go to the same net

texts:
After reading [Mike DeSimone]'s response regarding good decoupling and bypassing practices I kept wondering about distance between wires (wire = trace or net) .
[Mike DeSimone] comments that wires going to different nets should be as close as possible, but that wires that go to the same plane should be fairly appart.

If the currents in each of the parallel wires (I say "wire" to include both trace and via) are going in the same direction, then the mutual inductance adds to the self-inductance, increasing total inductance. If the currents in each wire are going in opposite directions, then the mutual inductance subtracts from the self-inductance, decreasing the total. This effect gets stronger as the distance between the wires goes down.
Therefore, a pair of wires going to the same plane should be far apart (rule of thumb: greater than twice the distance from surface to plane; assume the PCB thickness if you don't have your stackup figured out yet) to reduce total inductance. A pair of wires going to different planes, such as every example you have posted, should be as close together as possible.
··· Give the IC its own vias to power and ground, keeping opposing-net vias near each other and same-net vias farther apart ···

Now, all my designs have always been low frequency (<1MHz), but I recall having used, for example, more that one via to connect an MCU to a power plane. Or have used several vias to increase the maximum current of some traces that have to change layer, similar to this post. And I have placed them very close together (actually, as close as I could).
Could you please give me some insight on this matter? What is a good distance between vias or traces to avoid parasitic inductances?
I understand I can create a loop with two vias (perpendicular to my PCB), that is, if my vias are in series. But I fail to see how this can happen if they are in parallel or tie two unrelated components to the same net.
I have searched SE and googled, but found nothing useful to the matter of via clearance and the associated parasitics.

EDITS:

Fixed accidental cite to [Olin Lathrop] instead of [Mike DeSimone].
Changed question to include traces as well as vias (originally I only asked about vias).


texts: Power selection circuit for USB or DC Jack - both at 5V

texts:
I am designing a new board, where I need to detect if the DC input jack for powering the board has been plugged and then disconnect the USB power supply. I also need to detect it with the uC in order to enable some functions when I have a power supply.
The problem is that both of them are 5V inputs.

DC power supply:

USB power supply and power selector:

I have a couple of conditions in this circuit:

DC Power not connected / USB connected / USB Host function OFF: In this scenario, the comparator outputs a low voltage which makes Q3 to be ON (p-channel) and this helps me have a clean 5V through this circuit.
DC Power connected / USB connected / USB Host function OFF: In this case, I want to disconnect the power from the DC jack from the USB, so current does not go into the USB connector. It shouldn't, since both of them are 5V, but stay with me. So, the comparator outputs a high voltage and turns Q3 off, disconnecting VUSB and 5V, and taking current only from the DC jack.
DC Power connected / USB connected / USB Host function ON: Now I want the device to be able to give power to the USB port, so I turn Q2 on with the USB_HOST_EN signal and power can flow from 5V to VUSB through Q2.

This circuit is a remix form the SparkFun SAMD21 breakout board and the typical power selector circuit that a lot or Arduino Boards use.

The problem I see is that when the USB is connected, the 5V from the USB can be found also at VJACK, so the comparator will always have its output at a HIGH state.

Q1 is a reverse polarity protection transistor. I thought of just putting a diode and that would solve all these problems, but I would not have 5V after the diode, but a 0.7V or more drop.

Also, since both the DC jack and the USB will have 5V, I thought the whole power selection circuit could not be there at all, and just join both 5V outputs, after Q2. But then the body diode from Q2 would also drop 0.7V when Q2 is off (Non host operation) and I would have less voltage than required.

Can anyone help with ideas on how to solve this?

Thanks a lot!


texts: Is it possible to measure Spinal Cord electrical activity over skin?

texts:
sorry if this is not the right place to ask this question.

I'd like to know the possibility and reliability of measuring electrical activity of spinal cord (specially the cervical region)

if it's possible do you know any research or project related to this, most of project I've seen is about measuring electrical activity of muscle contraction.

my goal is to decode the signals to control a virtual body. I'm a newbie if you have any information or resources regarding signal analysis that would be helpful

thank you in advance


texts: STM32: Is it possible to write data to flash memory by using system bootloader when write protection is on?

texts:
When I try to program with STM32 flash loader and if the write protection is on, it want erase all of the memory. Probably because of program drop the security level so MCU erase all of the data. But can I write a data without disturbing write protection and keep the piece of the flash memory intact?
Possible MCU: STM32f072xx or STM32f103xx


texts: I want to make a temperature controller, but the heating element didn't work

texts:
My schematic circuit from controller to heater (12V)

When I connect the heater, the voltage drops to zero.
When I try it in a simulator with a DC motor, it works:

This is my 12V heating element:


texts: Power on/off 30-50mA module with 3.3V Arduino-like GPIO

texts:
In my Arduino 3.3V project I have a problem shutting down a GPS module.
When it "sleeps" with a command, it comsumes 2mA which is way too much for my project. To my understanding I have to build a high side FET to switch the module ON/OFF.
Do I have to use a BC212B (PNP) transistor? Why is the current negative?
I read this problem for a high side switch:

"In that case, it'd be impossible to turn the switch off because VB (connecting to the control pin) would always be less than VE."

Since LiPo is 3.3V-4.2V and to my knowledge the pins of feather are ~3.3V this is a problem. Right? So, I do I need a MOSFET or an NPN like BC546?
I tried two diagrams, they are right?
Low side switch (I think not recommended)

High side switch (recommended but unusable?)

My setup
Feather 32u4 (max 10mA per pin) 3.3V
GPS module needs 20-25ma (let's assume 30mA) but in the future I may need to use a more hungry module ~50mA.
I want low power level like this guy.
My idea is to feed the transistor (BC549) from lipo battery 3.3V - 4.2V and to control the transistor with an output pin of the Feather.
If I understood the basic from transistors, the more current in base, the more current in output (device). I have to supply 0.1mA to have 50mA on output of transistor (worst case: cold), right?
In BC557B PNP specs the numbers are positive.
Questions:

Can I power ON/OFF my GPS module with a transistor?

What resistor to base for low consumption for 30mA scenario and 50mA scenario? 3.3K (30mA) and 1.1K (50mA)?

I read that I have losses with a transistor of 0.2V (or 0.6V?), so when my battery goes to 3.4 volts my module will it be problematic? I think it needs 3.3 volts not sure about 3V.

UPDATE: added all the components


texts: Is it possible to use msp430 with keyboard + LCD?

texts:
I'm trying to do an assignment for my class which requires me to use a keyboard as input through a microcontroller to a LCD screen, nothing fancy , I just need to show that when I press characters on keyboard , it will show on a small LCD. I tried to google it but couldnt find any tutorial or something close to that, only thing I found is http://www.youtube.com/watch?v=L1BXhAvQmaw or http://www.youtube.com/watch?v=xoMtwhj-zCg  which is exactly what I want to do.
I think I can combine codes from msp430+keyboard and msp430+LCD but my main problem is I don't know how to wire up the circuit or I don't even know if msp430G2553(pins and output voltage) is capable of doing this.
Any help?
Thank you.
P.S. I am using Energia.


texts: I am building a pcb board (18"L x 12"W) with infared diodes that will detect high speed @ a distence of about 1.00". Will the diodes pick up a speed of a metal object around 70 to 100 MPH?


texts: Monostable circuit with 1 hour high output

texts:
I want to build a monostable circuit (a circuit with one input as a pushbutton), that will output logic '1' when the pushbutton is pressed for one hour (with the least error possible) then go back to its original state of outputting logic '0' until the pushbutton is pressed again.
I know about the 555 timer, but I also know that it does not behave good with very high time periods like one hour, some have suggested using a TLC555 which is a CMOS version, but I am not sure if this is going to work.
What I found on the internet are circuits using 4060 with an astable 555 timer, if you could suggest a way to convert this into a monostable circuit I would really appreciate it, if not please suggest another circuit.
I prefer suggestions with discrete hardware components over the microcontroller suggestions in general, but if it is the most suitable solution, please share with me.
Thank you all in advance.


texts: Computing output resistance for zener power supply

texts:
I have a simple zener power supply, the schematic is below. My question is how to find the output resistance of the circuit?

I also have small signal model given, but I cannot get a proper result.


texts: Weird component in load cell Wheatstone bridge

texts:
While trying to repair a cheap digital kitchen scale, I came across this component (see picture below). AFAICT, this is 95% identical to the standard Wheatstone bridge interconnect for combining 4 individual load cells with 3 leads each; the red wires directly lead to the scale's controller. However, it has one additional twist: one of the red wires is connected to something below the white resin blob, and then continues to the controller. Unfortunately, even very carefully trying to remove a bit of resin seems to already have destroyed that component, I also removed something looking like Kapton tape with a trace on it. Before, the two leads going in and out of the resin blob measured about 65 Ohms of resistance; afterwards, it's more like 17 kOhm.

I already had sort of given up on the scale, so as a last-ditch attempt, I just bridged the mystery component with a bit of wire, but that didn't help either, the scale doesn't calibrate properly anymore.

But my curiosity has been piqued: can anybody venture a guess what that component is? I was guessing something like a PTC resistor to compensate for environment temperature, but isn't that the reason why these cheap scales self-calibrate on powerup, because you can save the temperature sensor?


texts: How can I map Body Diode datasheet params to simulink N-MOSFET model?

texts:
I would be interested on including the body diode effect of a NMOS transistor into the N-Mosfet that Simspace includes for electronics. However, the parameters that the Body diode in Matlab requires is not completely given in the datasheets.

Let's say that I have the following datasheet , where I can read

How can I translate these parameters to the ones shown in of Simulink block?

  Reverse saturation current
  Built-in voltage
  Ideality factor
  Zero-bias junction capacitance
  Transit time

Thanks in advance,

Kind regards!


texts: How to explain it? I understand everything until the last thing. I didn't find anything in Boolean algebra to this specific situation.


texts: Why should you use two resistors in parallel on an LED?

texts:
So I was looking over the Arduino R3 schematics and noticed this little design choice:

What is the reason for doing something like this? I mean it's hard to know what the designers were thinking, but maybe it was done this way to save space. Do you get any other benefits?


texts: Simple method to calculate output impedance of source follower

texts: Output impedance of source follower without Rs would be 1/gm. However, if you add Rs the expression becomes a little complex and the result is as in the image below. I know how to get the result with brute-force method. However, is the a simple way to get that expression taking advantage that we already know the output impedance of the circuit without Rs is 1/gm?


texts: How to manufacture cheap custom flexible circuit boards? (strips)

texts:
Let's suppose I need two long series of IR emitters and receivers to detect position of people along a hallway (corridor). I would use surface mount components to make the sensors less noticeable, and one series per side of the hallway. This is only the framework, no need to suggest improvements here :)

I could order custom PCBs online, but the thickness would be significant and I would have to run wires all the way to each PCB.

Another solution is to produce some custom plastic strips with metallic traces, on which I would solder directly the components.

Only one emitter and only at most three receivers would be active at the same time, the expected current consumption is 500 mA, at most 1 A (this if the IR emitters are pushed a lot), therefore metallic traces on plastic could work.

I have experience with the plastic circuit of the dashboard of my old ('90s) car and it was able to carry enough current to light the dashboard bulbs. I also successfully soldered stuff on it, without the circuit melting or deforming. See attached image (found online) as example of what plastic strips I mean.

However, I was not able to find any means to produce said plastic strips. How could I get them? I would need a periodic design, repeated over and over along the strip. I would say 10 mm width by 20 metres length (2x 10 m).


texts:
Most PCs don't have RS232 built-in anymore. So the only option is USB-2-RS232 adapters or RS232 PCI-E card. While I expected the adapters to output a low voltage it turns out most RS232 PCI-E card also just output +/-5V. In order to increase distance I need to boost the +/-5V to somewhere in the range of +/-12V. I did a lot of googling but all I kind find is TTL to RS232 (many outputting the +/-12V but my input is not TTL but +/-5V).

So how can I level shift a +/-5V signal to a +/-12V signal?


texts: How do I burn an ATmega328 chip via Arduino UNO as ISP?

texts:
I've an ATmega328 chip (without a bootloader), and I want to burn it with my Arduino Uno as ISP, so I can have a spare ATmega328 with an Uno bootloader.

I'm trying to follow the instruction in Using an Arduino as an AVR ISP (In-System Programmer), but there is a note that said:

  Currently, you cannot use an Arduino
  Uno as an ISP programmer because the
  optiboot bootloader does not support
  this sketch. A revision for this is in
  progress.

So how do I do it?


texts: What causes "dead spots" in breadboards, where chips just don't work right?  My guess is that the plastic or backing metal is warped, so the holes don't line up right, or the metal is somehow tarnished and nonconductive.  In any case, can these be fixed?  The breadboards are part of expensive digital trainers and cannot be easily swapped out.


texts: VHDL elegant way of implementing a select with don't care condition in the input

texts: I am quite new to VHDL and I was wondering if there would be an elegant way of implementing a do not care condition with a select statement. It seems way to tedious to go ahead and list all possibilities for the do not care.


texts:
I would like to read out a sensor over SPI using the DMA. Since the sensor has some noise, I would like to take the average and so I need to read out the sensor several times. For this I decided to use the HAL_SPI_TransmitReceive_DMA() function, but it seems only to read out the sensor once. I think the problem is, because of the SS Pin, which is only triggered once in the whole reading process. How can I read out this sensor with the DMA, such that it only interrupts at the end of the read process?

Sensor AS5048a: (https://www.google.ch/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwjOqo-G5ODWAhXDCcAKHQk5DIYQFggtMAE&url=https%3A%2F%2Fams.com%2Feng%2Fcontent%2Fdownload%2F438523%2F1341157%2Ffile%2FAS5048_DS000298_3-00.pdf&usg=AOvVaw1kcnV9G51ORmSPkN1SUFSM),

(http://www.mouser.com/ds/2/588/AS5048-EK-AB_Operation-Manual_Rev.1.3-820438.pdf)

My code so far:

transfer_init:

void spi_getData(SPI_HandleTypeDef *hspi, uint8_t *tx, uint8_t *rx) {
    //tx containts the data after spi_prepare_tx_data and spi_get_tx_data
    if(spi_dma_complete==1) {
        HAL_GPIO_WritePin(GPIOA,GPIO_PIN_15,GPIO_PIN_RESET);
        HAL_SPI_TransmitReceive_DMA(hspi,tx,rx,SPI_SIZE);
        spi_dma_complete=0;
    }
}
void spi_prepare_tx_data() {
    uint16_t data16=SPI_CMD_READ | SPI_REG_DATA;
    data16 |= spiCalcEvenParity(data16) << 15;

    tx_data[1]=data16;//(uint16_t)SPI_CMD_READ | (uint16_t)SPI_REG_DATA;
    tx_data[0]=(data16>>2);
}

void spi_get_tx_data(uint8_t *tx) {
    for(uint8_t i=0;i<SPI_SIZE;i=i+2) {
        tx[i]=tx_data[0];
        tx[i+1]=tx_data[1];
    }
}

Rx DMA Interrupt:

void DMA1_Channel6_IRQHandler(void)
{
  /* USER CODE BEGIN DMA1_Channel6_IRQn 0 */
  spi_dma_complete=1;
  HAL_GPIO_WritePin(GPIOA,GPIO_PIN_15,GPIO_PIN_SET);
  //spi_getData(&hspi1,spi_tx_buff,spi_rx_buff);
  /* USER CODE END DMA1_Channel6_IRQn 0 */
  HAL_DMA_IRQHandler(&hdma_spi1_rx);
  /* USER CODE BEGIN DMA1_Channel6_IRQn 1 */

  /* USER CODE END DMA1_Channel6_IRQn 1 */
}


texts: Can I use 100μF and 47μF as input and output capacitor, respectively, for regulator LM7924CT?

texts: I have one LM7924CT regulator, but only have 100μF and 47μF capacitors at hand, can I use them? Would 47μF be too large for the output capacitor?


texts: How does a magnetic sensor measure the angular speed of a crankshaft? How does its spinning affect the magnetic flux?

texts:
I'm doing work to an electrical engineer graduation subject about the transducer. I'm studying the magnetic transducer just to understand how it works and I had a little doubt.
Let's look at the image first to be more clear:

As you can see the image shows a Hall effect sensor that measures the crankshaft angular speed.
I understood that when there's a significant magnetic field or flux sensed by the Hall sensor its output, in the case of a digital sensor, will be high, otherwise, it will be low voltage.
I reflected on the Hall voltage formula:
$$
V_H= R_H \cdot(\frac{B.I}{t})
$$
VH is the Hall voltage in volts, RH is the Hall effect coefficient, I is the current flowing through the sensor in amps, t is the thickness of the sensor in mm, and B is the magnetic flux density in Teslas.
In my point of view, only the magnetic flux is varying somehow in accordance with the crankshaft spinning, but I don't know how to explain it.
Could someone help me with this question?


texts: Break beam sensor to replace piezo transducer

texts:
I have a device intended to sound an alarm and flash a bright light when it detects a phone ringing (so you can hear the phone ringing in noisy environments like workshops). I want to repurpose it to let me know when my woodshop dust bin is full.

The device came with a piezo transducer as a sensor. It connects to the main device via a small cable wires to a 1/8” jack with two contacts. For my project I’d like to figure out how to swap in a IR break-beam sensor instead. Any tips?


texts:
I'm studying the Cortex-M3 of ARM. The problem statement reads:

  We're going to use a Harvard architecture with the following addressing capabilities: 32M words of code and 16-bit data words. The architecture can only address full words. The CPU has 16 internal general purpose registers and a Load & Store structure. With this information:

  Design the coding of each group of instructions, minimizing as much as possible the instruction size. The instruction size shall be a multiple of the word size. The different groups are:

  7 data transfer instruction, transferring data between memory and the internal registers, with direct addressing mode.
  5 data transfer instructions, transferring data between memory and internal registers, using indexed addressing mode.
  14 arithmetic/logic instructions to be executed between registers, being the destination register the same one as one of the input operands.
  14 arithmetic/logic instructions to be executed between registers, being one of the operands provided by immediate addressing, and providing the results in the other source operand.
  6 control instructions with inherent addressing mode.
  7 conditional branches with PC-related addressing, being the relative addressing of plus/minus 1M word

This is the proposed solution that I don't undestand:

Direccionamiento directo: Direct addressing mode.

Desplazamiento: shifting.

What I do know is that the address bus of the program memory has to be of 25 bits, the address bus of the data memory has to be of 23 bits and the data bus of the data memory has to be of 16 bits. It is stated that the data bus of the program memory has to be of 31 bits but I do not know why since Thumb-2 is of 32 bit, or maybe I'm mixing things?


texts: Whats the relation between AC power strip current rating and DC output current from the PSU connected on

texts:
this is kind of a noob question:

I have a power strip (extension cord from my wall AC outlet) that is rated for 250V 10A.
Over this power strip i'm connecting a power supply that gives an output of 12V 20A.

What's the relation between the power strip current rating and the PSU one?. I mean, how could you state the needed value for the power strip based the PSU current rating?

It's enough to just calculate the power consumption in Watts on the PSU (Vout * Output current) being lower than the one rated for the power strip?

(I'm not connecting anything else besides the PSU on it).

Greetings.


texts:
I have an old iPhone of which I want to reuse the LCD display. The thing is, I don't want to use it as an actual display but rather make a fancy lamp out of it. The question I have is how I can figure out which pins I need to put current on to make the screen shine. The idea would be to just have it connected to a simple switch to turn it on and off.
Is there any way I should go about doing this?


texts: Can I use this inductor in my boost converter circuit?

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I used TI Webench to spec out this boost converter circuit:

The design calls for an inductor that is marked as end of life.  Can I use this inductor instead?

My hypothesis is that they are interchangeable.  I think that if I boost from 3V to 5V with 80% efficiency, I should be able to draw 1.5A output by pulling 3.125A from the source.  The original inductor was rated at 7A and the new one is rated at 18A max.  Am I on the right track in my thinking here?

Also, the original had a maximum DC resistance of 14.7 mOhms.  I decided that the lower value was better here.  The new inductor has a DCR of 4.7 mOhms.  Which is better?  A higher or lower number for DCR?  Why?

Are there any considerations that I missed?  Will the inductor I selected work in this circuit?


texts: Simple high current alarm using transistor

texts:
simulate this circuit – Schematic created using CircuitLab

I need a suggestion to build a minimalist short circuit alarm.
With this diagram will light a LED easily. But if I replace with a Buzzer, it will not make a beep. My input voltage will be 12 Volts, alarm should be raised if current draws about 2 Ampere.

The R1 can not go further more Ohms, since I don't want too much current lost on the output. I tried to Darlington Q1, but the buzzer still won't beep.

Edit1: add the correct schematic. Sorry for the messed, this is my first thread on EE Community.

My main goal:
I want to have a simple high current alarm by using transistor(s) and to replace LED with buzzer. When high current occurs (>= 1A) it will have constant beep.


texts:
Just to clear things up. This is NOT a homework question, but it is lecture notes used as a practice exam.
I am trying to understand the 555 timer in oscillation (Astable) mode particularly the formula
$$t_l = R_bCln(2) $$ and $$t_h=(R_a + 2R_b)Cln(2) $$

I have seen the 555 Timer is oscillation where the Discharge port is either floating like this:

or shorting R_b like so:
EDIT: there should be a capacitor pinned to ground and the DISCH, THRES, TRIG pin in the photo below but I accidentally cut it off.

So by the formula that describes the time the oscillator is low,
$$R_b = 0 -> t_l=0 $$ which means there should not be any oscillation.
How can this configuration be an oscillator if the Rb resistor is missing?
Photo Cred: EE 409 Cal Poly Prof. Vladmir Prodanov


texts: How Does a Buck Converter Maintain a Constant Voltage?

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I don't quite understand how a buck converter works in terms of maintaining a constant voltage.
Let's say you have a 5V, 3A buck converter, but you hook it up to a 1K resistor (load) in series to give you a current draw of 5mA.
Now, let's say you start adding more 1K resistors in parallel to increase the current draw of the load(s).
What changes in the buck converter to meet the increase current demand?
Based on my understanding, there are only two parameters to play it here - switching frequency and duty cycle.
However, I thought that many buck converters have a fixed switching frequency, which rules that out as a possible parameter to tweak?
Part of my confusion comes from this graph shown in TI's power topologies handbook, where is shows the Imin and I max of the inductor current:

So my new hypothesis is that there is a part of the graph here that is not shown, which is the initial current rise from 0A to whatever the necessary current is to maintain the specified voltage drop.
To answer my own question, what would happen if we started adding 1K resistors in parallel would be that there is a single instance/cycle where the switch stays closed for a longer time to allow the current through the inductor to ramp up to the necessary value in order to maintain the specified voltage drop across the load(s). See my crude drawing below:


texts: Full wave rectifier vs full wave bridge rectifier

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What is the difference between the full wave rectifier and the full wave bridge rectifier? In other words what do we gain if we use the bridge? As far as I know both do the same thing while the bridge is using two more diodes making it more expensive.

Full wave rectifier:

simulate this circuit – Schematic created using CircuitLab

Full wave bridge rectifier:

simulate this circuit


texts: Why do Op amps need dedicated grounds to source?

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According to the author of this schematic the bias currents will not flow without a power supply-input signal common ground. I don't understand why the bias currents wouldn't just flow into the negative terminals of the voltage source even without a dedicated ground.
I would be really grateful for any pointers.