texts: Is it possible to have peltier plates within a few micron thickness range?

texts: Is it possible to make peltier plates of a thickness of a few microns . If not What device/material can be used in a thickness range of a few microns for cooling purposes ?


texts: Know any hardware for the PC to act as USB_device?

texts:
We manufacture electronic devices. Some of them has USB_host functionality. In order to test them for this functionality, we need another device (maybe pseudo device like PC) to act as the USB_device. Currently, we only support MassStorage class devices but we are not comfortable with the idea of inserting a USB memory to our device for Q/C operation. There won't be any feedback to our automation system and we want to be able to test other kind of devices.

Is there some kind of hardware that we plug into a PC and with its certain API, that device acts as a USB_device. We will have to implement the needed protocol by utilizing this API and we are OK with this.

Any chance ?


texts: Generate a model into Ltspice where we can adjust a parameter

texts:
I am trying to generate a subcircuit on ltspice. It is a first order filter where I would like to adjust the cuttoff frequency. I know that it is possible to do it on component but on a parameter ("param") I do not know how to do it.

I would like to set directly the param "fp" of the subcircuit. Does anyone know a way to do it ?
Have a nice day !


texts: Suggestions on soldering through hole large planes

texts:
I am small scale manufacturing PCB's I designed for high power actuator and LED control. It is 6"x8", 2 ounce copper and large power and ground planes, with no thermal reliefs. It has a section at one edge that is all SMD components, a large copper through hole buss bar that spans the entire length, and several through hole MOSFETs, and several through hole connectors.

So I have make 10 boards so far, and will be making around 5 a week. I use a hot plate for the SMDs, and that works great.

For the TH components, I use a hot air reflow gun, and use a soldering iron. This is not ideal. I have to put a lot of heat on it, and I struggle with cold solder joints if I don't get enough heat on it.

So, I am content with my method for the SMDs, as with a solder stencil, I am able to solder them quickly and quite consistent. For the TH components, I need a new method. I have a few options I've considered:

Use a IR preheater that goes under the board to heat the planes.
Same as 1, but with a forced air convection heater.
Get a larger spread nozzle for my hot air gun, and an articulating arm that can hold it to help heat more evenly.

Budget is whatever it takes, but I would like to stay under $1000 if possible. Let me know what you think, and if there are options I'm forgetting.

EDIT: I want to do this as correctly as can be done without large scale procedures, these are high power expensive boards, and don't want to take risks with how I heat it, like I feel like I may be doing now.


texts: characterizations Id (Diode Current) - Vd (Diode Voltage) IN4728A

texts:
I´m graphic the diode voltage and the diode current, this graphic would have to give a no linear graphic.

and my graphic is given this curve

What is my error?


texts: How should I wire this stereo jack for a mono plug?

texts:
I have two of these stereo jacks that I am planning on using to rewire some headphones that have had the original cable fail somewhere between the speaker and the end plug. Instead of bothering to fix the existing cable, I plan to replace the cable entirely but also give them the ability to have a removable cable. The replacement cable has 1x 3.5mm stereo plug on one end and 2x 2.5mm mono plugs on the other end.

What I'm not sure of is whether or not there is an optimal pole to resolder when using a mono plug in this (stereo) jack?

For anyone curious, the final product:


texts: How to toggle LED with button on dsPIC33 and dsPICDEM MCLV-2 devboard

texts:
I'm new to microcontrollers and the dsPIC33 and want to write a simple program before I get into anything more complex (even though this seems already very complex to me...). I am trying to toggle an LED on my dsPICDEM MCLV-2 development board using my dsPIC33EP256MC506 microcontroller. Right now, my code just makes the LED stay on without me pressing the button. Can anyone help me find whats wrong with my code?

If anyone knows of any sample programs that I can run and play with that would also be very helpful!

Compiler: MPLAB X

Programmer/Debugger: REAL ICE

Microcontroller: dsPIC33EP256MC506

Dev Board: dsPICDEM MCLV-2

main.c

int16_t main(void)
{

/* Configure the oscillator for the device */
ConfigureOscillator();
/* Initialize IO ports and peripherals */
InitApp();

TRISDbits.TRISD6 = 0; //set LED as output
TRISGbits.TRISG6 = 1; //set Button as input, port unknown

while(1)
{
    if(S3 == 0) { //start/stop switch
        uint32_t N = 21000000;
        while(S3) //debounce
            while(N--);
            LATDbits.LATD6 = 1; //make LED pin high
    }
}
}

user.h

#define S3  !PORTGbits.RG6  //S2 button
#define S2  !PORTGbits.RG7  //S3 button

#define D2  !PORTDbits.RD6  //D2 LED

#define DEBOUNCE_DELAY  30  //push button debounce delay, expressed in millisecond

/******************************************************************************/
    /* User Function Prototypes                                                   */
    /******************************************************************************/
    /* TODO User level functions prototypes (i.e. InitApp) go here */
    void InitApp(void);         /* I/O and Peripheral Initialization */


texts: Electric field in ionization area of a corona discharge?

texts:
I have a coaxial cylinder with a cooper wire inside which is corona discharge happening.
Corona discharge is happening after ionization in this coaxial cylinder. My question is about calculating E (electric field)and Q (Amount of charge) in ionization area!

Would really appreciate if your help is included the process before ionization (E and Q).
Thanks in advance for your help!


texts: How can a DC18V ~ 36V LED driver work with DC3.6V LEDs without burning them out?

texts:
I bought some slightly more powerful leds to build a hobby project and grow some herbs. The kit has 10 LEDs that have the following spec:

Power: 3W
Voltage: DC3.6V
current::700mA

It comes with a driver:

Output Voltage: DC18V ~ 36V
Output Current: 600mA

The idea is put 10 in series and drive them from AC with that driver.

My questions is how can it work without burning them out? I know about the voltage drop, but the first LED still gets a high voltage? They are only rated ~3V.

I "tested" one LED with 9V battery and it lighted up very bright and then it was dead. Was it because of 9V or was it because it drew that much current? What am I missing here, it looks like there is some very basic thing I don't understand. I have studied the OHM law and have built some simple things, but I'm out of ideas here.


texts: Discharge and charge rates of a capacitor - Comparing Energy Movements

texts:
This is a really simple question.  But I'm seeing some confusing behavior in an experiment I'm trying to make sense of.  So I'm trying to see if my understanding of theory is wrong.

Wikipedia says:  The coulomb (unit symbol: C) is the SI derived unit of electric charge (symbol: Q or q). It is defined as the charge transported by a steady current of one ampere in one second:

Ok so 1 amp for one second transports one coulomb, right?

So in other words, if I discharge a capacitor for one second at 1 amp and charge a second capacitor for one second at 2 amps from another power source, the final state outcome is that I put twice as much charge on the second capacitor as I discharged from the first capacitor, right?

If that is correct, then let me also ask something else:  The voltage is irrelevant to the measured energy expenditure right?  It doesn't matter if the first capacitor starts at 100 volts and discharges to 0 volts while the second capacitor starts at 0 and charges to 10 volts.  All that matters for computing the energy movement is the actual charge/amps.  Right?

Also, is there any kind of known condition where this doesn't hold true or something that easily trips people up?


texts: Op-Amp with Voltage Controlled Gain and Unity DC Gain

texts:
I have a car seat motor that I am driving via PWM and am aiming to measure its position by counting the minor variations in voltage across a current sensing resistor attached to the low side of a FET as the motor rotates. At higher duties the Vpp is significantly less (30mV) than those at 25% duty (4.7V). I currently tap the signal for measuring by a microcontroller ADC at two different gain stages to handle this, but desire to make this all happen in one stage with a variable gain circuit so only 1 ADC is needed.

Before I go into what I've attempted I want to state my primary question. How do I dynamically adjust the gain of my waveform to output a signal at a constant Vpp when my input Vpp ranges from 30mV to 4.7V?

I use a TI LMV344 op amp with rails on 0V and 5V. The motors are 12V.

Currently the circuit flow is:

Sensing Resistor Output
Diode voltage clamp to remove DC bias
High gain, non-inverting LPF op amp. Filters out 20kHz PWM signal
Diode clamp to reduce bias. I now know that I can put a capacitor between the resistor an ground on the gain portion of the above LPF
Sallen-Key LPF to further reduce 20kHz PWM signal. Low gain. This is where I tap for low duty signals as any more gain causes the lowest of duties to cause the current signal to saturate the op amp.
Diode clamp to reduce DC bias.
Another Sallen-Key LPF identical to the above filter, no tap. I really wanted to filter out that noise.
High gain, non-inverting LPF op-amp. Higher duty signals are tapped here.

The problem that I have run into is that at the highest duty, the Vpp output is low enough that its sometimes hard to make out pulses. At the cross-over duty, around 60%, the Vpp on the high duty side is saturating and the Vpp on the low duty side is too small.

My current attempt to solve this issue is to use the PWM signal used to drive the motor as a means of adjusting gain on a separate gain only amp. The gain is set to put the high duty signal at the desired Vpp. As the duty increases and inverted copy of the duty is filtered into an analog signal (represented by V3) and fed through a voltage follower connected to the inverting pin on the amp with the gain stage. But when I do this, the DC outputted in step 5 causes the signal to saturate at the op amp's upper rail when low duties are used. If I put a diode clamp between the signal from step 5 and the gain only amp, I can control the gain as I had hoped. When I put a capacitor between the gain resistor attached to ground and ground to reduce DC gain to unity and eliminate the need for the diode clamp, the gain is no longer controlled and the DC gain isn't unity. The diode clamp needs to be replaced since the various Vpp values need different offsets so they won't saturate.

Here's that last paragraph as a schematic. The op-amps are LMV344 op-amps, not LMV324 as the illustration suggests. The input signal has a Vpp from 30mV to 4.7V depending on the motor duty.

simulate this circuit – Schematic created using CircuitLab

And here are two examples of the input signal. THe first is the current draw waveform at 100% duty and the second is the current draw at 25%  duty.

How can I get a variable gain circuit, amplify signals with Vpp between 30mV and 4.7V to around 4.7V, while avoiding saturation due to input DC levels? Thank you in advance. This has consumed me for the past month.


texts: high frequency noise from multiple feedback op amp

texts:
I've built a multiple-feedback low-pass filter with a TL084IN op amp. I've simulated the filter for the chosen R and C values using LTSpice and it looks like I was expecting: .

I've also assembled the filter in real life and checked the Bode Plot using NIMyDAQ. This time I get a lot of noise once the frequency goes past 1k, which is the part that I don't understand: .

Any ideas why MyDAQ's Bode looks like this ?


texts:
I have a camera from Imaging Source and it captures just one image for every external trigger pulse. But I want it to capture 3 images. Is there any idea of how to do it ?

The datasheetfor the camera DMK 23UV024

Steps executed so far:

Generate trigger pulse from a datagenerator and trigger the camera
Developed a LabVIEW program that can capture images on trigger
I have two different images to be captured for one single trigger, since the camera captures only one image for each trigger, it will create a confusion as to which trigger image belongs to which one. How can I solve this problem.
The idea is to capture 2 images based on 1 trigger pulse without any interference between the two images


texts: I have been trying to identify these 2 transistors online with very little luck. Not sure if they are obsolete but the PCB was bought in 2016.


texts: How to read the datasheet of a Digital transistor?

texts:
Could anybody please help in understanding the parameters of Digital transistor from its datasheet. Basically i need two parameters which decide the Maximum voltage for off state(0 state) and minimum voltage for the ons state( 1 state).

You can take the below datasheet as a reference
http://www.onsemi.com/pub/Collateral/DTC143E-D.PDF


texts:
I create one 4-layer board using Altium's PCB Wizard . By default, it set the plane pullback to 0.5mm, the keep-out area is 1.3mm from the board edge. That is, the top/bottom layer keep-out region is less then the power/ground plane, as below, the red layer are the power plane, and the blue one is the top layer pour.

Is it a good design considering EMC?


texts: 110V sewing machine plugged into 220V - DIAC blew?

texts:
Our 110V Brother sewing machine got plugged into the 220V side of our step down transformer. After a short pop, it does not turn on. I pulled the power supply board out and it seems like just an input fuse was blown along with the black component which I think is a DIAC from the symbol on the board.

The number on what I think is the DIAC is V102210 with ZNR above it.

Is the DIAC being used as voltage protector for the machine?
Would it be possible to just replace the DIAC with just a jumper? I just wouldn't have any protection next time. I removed the fuse and DIAC from the board.


texts: Degenerated signal at a logic level converter

texts:
I'm trying to pair a motor controller, and a bi-directional logic level converter to feed a microcontroller with a motor speed signal.
Some signals have already been successfully converted, but a digital out frequency signal of the motor controller still poses problems.
Here is a schematic (motor controller within the slashed line):

Observations:

Reading the signal between pin 10 (GND) and pin 18 (motor frequency) directly from the motor controller without being connected to the logic level converter is a clean, plausible frequency signal, alternating between 0 and 5 V.
When pin 18 is attached to HV1 of the logic level converter, the signal degenerates to a signal alternating between 3.8V and 5V with 0.435 VAC RMS (see scope below).
Supply voltage on LOW side of the logic level converter was measured to be 3.3 VDC (between LV and GND).
Supply voltage on HIGH side of the logic level converter was measured to be 5 VDC (between HV and GND).
If a constant 5 VDC signal is fed to the logic level converter on HIGH side, 3.3 VDC can be read on the LOW side.

Motor frequency is in the range 0..8000 Hz.
Question: Is there a flaw in wiring, or is the logic level converter inappropriate for the task?
I've already read this entry, but I was not able to relate it to my problem.


texts: How do I find the impulse response of the system given output and input signals?

texts:
I stumbled upon this question as I was solving my homework.
There is an input signal x(t).

and y(t) as an output signal.

My idea was to find the function of y(t) in terms of step function and then replace all step functions with delta Dirac function.

My question now is, do I treat step functions as the input impulse function disregarding all t's?
By placing  impulse function at T ,3T and 4T and letting it convolute with x(t), I can achieve the given output signal. But I would like to find it with the idea above. Thank you.


texts:
I am using pic16f887 microcontroller and using Hi-tech C compiler. I want to implement port pin's Array in Hi-tech but it is not allowing me to do so.
What is the correct way to access pin address with indexing, like we do in arduino.

i want array like

   bit * lcd[4]={RA0,RA1,RB0,RC4};

it gives following errors

arrays of bits or pointers to bit are illegal
constant expression required
illegal conversion of integer to pointer

It clearly means I cannot declare Arrays of Bit, what is the other way to access pin numbers via indexing in standard C style or any other compiler related trick.

In header files pins are declared in following manners

    // Register: TRISB
    volatile unsigned char           TRISB               @ 0x086;
// bit and bitfield definitions
volatile bit TRISB0              @ ((unsigned)&TRISB*8)+0;
volatile bit TRISB1              @ ((unsigned)&TRISB*8)+1;
volatile bit TRISB2              @ ((unsigned)&TRISB*8)+2;
volatile bit TRISB3              @ ((unsigned)&TRISB*8)+3;
volatile bit TRISB4              @ ((unsigned)&TRISB*8)+4;
volatile bit TRISB5              @ ((unsigned)&TRISB*8)+5;
volatile bit TRISB6              @ ((unsigned)&TRISB*8)+6;

My problem is that, I do not want to name the port I want to index them so that I could call them with their numbers like we do in arduino style

 digitalWrite(13,HIGH);


texts: I removed a photosensor from an OLD hp Inkject Printer. The photosensor is called "C8941-80018". I can't find any datasheet online. Does anyone know what wire color is what?


texts: Conducted EMI of buck converter is too low even without filter

texts:
I have simulated a 48 V to 12 V buck converter with LISN in LTspice. However, CM and DM EMI is way below CISPR limits. I want to simulate a real world converter. How can EMI be increased?
[2]


texts:
I am working with the ColdFire MCF5329. I have worked on other projects where the Ethernet function was a separate chip, namely, SMC. The SMC Ethernet chip has pins out for a 64 byte EEProm to store the MAC address.

Where does one store the MAC address when the Ethernet chip is integrated, as in the case of the ColdFire MCF5329 and when there appears to be no separate pins outs for a small EEProm?


texts: How to detect the presence/ absence of a PWM signal on a GPIO pin?

texts: I just want to set or clear a flag by detecting the presence or absence of a PWM signal with approximately >100 kHz frequency on a GPIO pin. I studied that a simple RC low pass filter can be used to convert the PWM signal into a voltage level and so it can be used as an external interrupt trigger for detection, but I am not quite sure if it works. Please let me know if there are better ways to do it (preferably in software). Thanks.


texts: What unit test framework can I use for a c based mcu project?

texts:
I'm thinking about how I can use unit tests in my mcu project,
and what frameworks I can use to simplify it.

Today I am using a stm32 with OpenOCD-jtag from a Linux pc,
where it is all controlled from a classic Makefile and crosscompiled with gcc.

I could create something myself, but if there is a framework that I can use it would be nice. (It is a bonus if the framework can output the result in a format that Jenkins/Hudson can read).

Is there a way to use a unit test framework with an stm32?


texts: Programmable Power Supply Design: Issues with variable load and voltage stability

texts:
TL;DR: How can I stabilize/regulate an output voltage coming from a DAC and use it to drive a load?
Long-time web-searcher/lurker, first time poster.
I've been designing an automated test station for work, and it's sort of turn into a pet project of mine that I spend a lot of time on outside of work. I guess that happens when your hobbies and work mix. Learning tons, but I obviously still have a lot to learn.
The point is to run one of our products through a series of regression tests. One of the requirements is adjustable (programmable) power. The only thing is, I designed this to simultaneously test n number of units (currently 8). So buying a programmable supply for each one is out of the question, not to mention space constraints. To that end I architected the system to have one main control board, which can issue commands to a theoretically unlimited number of "cards", which contain the hardware (DAC, latches, etc) necessary to remember the state the board told it to be in with regards to power level, adc level, inputs, etc...
I'm handling the programmable power section with a high-voltage 8-bit DAC made out of transistors. This can be anywhere between 0 & 90VDC. Typically 12-24V. This part works surprisingly well and is very accurate with ~100mV steps.
Check out the simulation link at the bottom of this post.
The resistor dividers are to prevent exceeding the max Vgs rating of the transistors while still keeping them in saturation.

The only problem here is actually using that voltage to drive a load. Because this is a resistor network, it's really, reeeealllly sensitive to impedance changes. The best solution I've found so far is to use a double sziklai pair (simulation at the bottom of the post). This works reasonably well, and drives the load, but it has a few issues.

Small currents disable the pair and output voltage spikes to max. The device under testing can draw anywhere between 0.5ma & 500mA. I had to add a resistor (R1 in the next image) to make sure the transistors stay on.
Output voltage is wildly unstable. It's great when only drawing tens of milliamps, but when the current draw jumps up to 300-500mA, the output voltage can drop by 2 whole volts sometimes.

I could deal with this problem by using feedback to adjust the voltage continuously (I have a line for reading back the set voltage), but I'd really like to figure out a way to make this work without any trickery.
I've tried other methods to make this work, like LM317T regulator with digital pot for control, programmable bucks, but I can't find any combination of devices that will work both within the current draw and voltage levels.
So, with all the long winded stuff out of the way, is there a way to stabilize the voltage here or am I totally out to lunch with this design?
Falstad Simulations:

DAC

Sziklai pair


texts:
I want to add 2x UPS PowerWalker VI 2200 UPS 1200W in the next room.
Is it safe to add 2 Power Strip of 6M ? What Cord Gauge do I need ?

UPS page https://powerwalker.com/?page=product&item=10120094&lang=en


texts:
There is something I don't understand with protection diodes. I am talking about a series diode between the + and the load of the circuit to prevent damaging components when there is a wrong polarity on the supply, like this :

Normally the current through the diode grows exponentially with its voltage accross, with a forward voltage of 0.7 V (for example).

I understand that if there was no load, then there would be 12 V accross the diode, resulting in a very large amount of current which would quickly destroy it.

But when there is a load, and that the circuit is working properly :

Why is the voltage across the diode always 0.7 V ? I understand that all diodes have a forward voltage due to their depletion area, but I don't understand why if I supply the diode with a load behind, the voltage across the diode will always be 0.7 V and across the load 11.3 V. What sets this value ? Why not something else ?
If the load needs a current of 10 mA or a current of 1 A, then the current through the diode will be 10 mA or 1 A, and given its characteristic curve the voltage across the diode will be very different. It seems like a contradiction to the above point.

There is clearly something I am missing there, hope you could enlighten me. :)


texts: Ultra Low Power, LDO Enable from RTC vs. deep sleep MCU interupt

texts:
I have a question regarding optimising design for ultra low power consumption device. I'm trying to develop a remote sensor node that should measure and send data every few hours.

Currently I have an RTC (DS1337) that wakes up my MCU (ATMEGA328P) from deep sleep via hardware interrupt. While the sleep current is fairly low ( avg 76 uA), it is still a fairly large amount if I aim for a device to run in the wild for couple of years.

Could I instead, use the RTC to ENABLE/DISABLE the 3.3v LDO (MIC5404) thus shutting completely down the MCU and have the RTC runs on a separate coin cell battery? I think this is called power-gating. What will be the hidden disadvantage ?

Thanks!

RTC: https://datasheets.maximintegrated.com/en/ds/DS1337-DS1337C.pdf

LDO: http://ww1.microchip.com/downloads/en/DeviceDoc/MIC550x-300mA-Single-Output-LDO-in-Small-Packages-DS20006006A.pdf


texts: Saturation when using differential amplifier with op amp

texts:
I built an amplifier following this schematic:

And the gain is approximately 1000. When I use 10mV sine wave from a function generator, it works perfectly (it also work with other signals: triangle, pulse, square etc). However, when I get the input from electrodes to measure ECG (2 on each shoulder, 1 ground on the abdomen), it always saturates at op amp power voltage (10V). How do I fix this problem?


texts:
I have a system I built using a ADS1263 32-bit ADC that is measuring tiny biopotentials without much amplification (for a variety of reasons not under discussion) -- one very low noise instrumentation amplifier with a gain of 8, and a really low noise op amp to supply a Vref to handle bias.

At one stage, everything looked like it was going along swimmingly -- especially before building my 4-layer pcb, and then an issue popped up.

In the interest of rapid deployment, some compromises were made, the biggest being that I just mounted a Discovery board right on my main board.

The system spits uart to a PC via an FTDI USB cable mounted as a Virtual COM port (to save me time in working out my own USB stack until a later version-- hah!).  The FTDI cable also brings Vusb to the board.  It goes through a 5V to 6V DC to DC converter (isolated), which is then regulated back down to 5V and then to 3V with LDOs.  The 5V powers my Discovery Board, with power and ground going through ferrite beads in front of the board.  The UART goes through a two-way isolator, and then back to the usb power side of things.

Well, my analog side looks like its working fine -- but I can't see the biopotentials on a scope, as they're too small, even after my gain of 8 -- I need to sample them w/ the 32-bit ADC to be able to see them.

I'm getting a funky oscillation with a period in the seconds that has had me crawling up walls before late today. The input is shorted to generate this sample (amplitude is 32-bit signed int over a 5V range, and y axis is number of samples at 2400 Hz) :

It looks dramatic, and it is, in fact, problematic in my scenario, but the magnitude of that square wave corresponds to about 90uV at the ADC input (PGA gain = 32), and about 11uV at my amp input.  Until today, I've been looking for grounding troubles, etc., and couldn't for the life of me figure out what could be going on at that time scale that could be causing this.  Even though I'm filtering, I considered that if I had bad ground stuff going on, maybe I was aliasing, and this was the result.

In any case, during programming, and afterwards, the problem seemed to go away.  This confused me.  I thought that providing power to the board through non-isolated Vusb might have been getting rid of the problem.  Turned out I was wrong.

Then, late this PM, I noticed that LD1 on my Discovery Board was flashing red exactly in sync to my square wave!!!  Huzzah.  When I insert the usb cable to program it, the flashing stopped and went solid red, I guess when the on-board ST-Link resolved, and the square wave went away.  When I remove that USB cable, the light stays solid, and no square wave is apparent.

So, it seems like either that flashing LED or something else happening on the ST-Link is causing a few microvolts of sag someplace.

I suppose in the long run, I should really make my power scheme bulletproof, but in the short run I'd really just like to make the square wave go away by getting rid of the current draw that is presumably causing it.  I'd love some advice on how to reversably disable the ST-Link, or force it to shut up for a bit.  Perhaps just fooling it into thinking its been enumerated, keeping the LED on, is fine.  The best possible scenario is that I can do this from the TOP of the Discovery board, as that's my access without some dis-assembly.

If the action is irreversable, I can probably live with that.  I'd either kill a board to make sure I can move on with this, and maybe program it with another ST-Link, or just convince myself the problem is solved and then finish programming and just keep replacing the board.


texts: Making own Chromebook debug cable (SuzyQable)

texts:
I wanted to debug my chromebook so I was looking for SuzyQable which enables to activate debug features on chromebook. Unfortunately this cable is hard to get in my location so after noticing this https://chromium.googlesource.com/chromiumos/third_party/hdctools/+/master/docs/ccd.md#making-your-own-suzyq official google guide to make own diagnostic cable I decided to give it a try. At first I was a bit sceptical about it as the schematic diagram of SuzyQable (https://cdn.sparkfun.com/assets/9/e/f/8/2/951-00273-01_20180607_suzyqable_SCH_1.pdf) is far more advanced than what google is saying. However the hub seems not be necessary there. So I bought usb type A and C breadboards and connected pins exactly as described on chromium page linked above although with one caveat - I currently don't have 56K Ohm resistors so I connected in series:
56k Ohm = 22 + 22 + 10 + 1 + 1 [k ohm]

Once the whole setup is connected I measured voltage on CC1 & CC2 pins:

Voltage on CC1: Position 1 -> 4,81V; Position 2 -> 4,78 V

Voltage on CC2: Position 1 -> 0,44V; Position 2 -> 0,46V

Unfortunately after plugging it in the device is not recognizable as tty serial USB one, which should be visible under /dev/ttyUSBx

Obvious problems which I already eliminated:

They say chromebooks discover this debug interface in only on usb type c orientation so I already tried both, same effect.
I have usb to serial module (FT232R) I connected it to both devices (chromebook and Ubuntu host) and it was discovered as ttyUSB0 immediately. So this means both devices are serial capable.

Questions:

I wonder if the series connection, of 56 k ohm resistor, introducing voltage drop can be responsible for the issue?
Is the hub which is on sparkfun schematic really superfluous and can be ommited?
What voltage levels are needed for USB to be discoverable as serial device?

UPDATE:
Schematic diagram of my connection (according to chromium page)

Picture of real connections on a breadboard

My Chromebook model is: Acer Chromebook 311 bobba

PS: Chromebook sometimes log weird dmesg messages like:

"PDLOG (date here) P1 SINK (not charging) charger ?? 5000mV max 5000 mV / 500 mA"

Ubuntu on the other hand logs:

"usb usb1-port3: over current condition"
"usb usb1-port4: over current condition"

Yes I have no idea why it mentions two ports if I only tinker with one!

Thanks for any advice!


texts: Cleanest way to splice automotive wires in car?

texts:
I'm installing a remote car starter and it requires me to connect to the +12V and GND wires going into the OBD2 wiring harness.

I can cut the wire inside the car and then splice an additional wire but that doesn't seem to be very clean?

I know they sell "T-Taps" that bite into an existing wire to allow an additional wire to be connected but I've heard bad things especially since they aren't soldered.


texts: How to achieve high impedance input on OPAMP without sacrificing bandwidth

texts:
I was trying to simulate (In LTSPICE) buffer for ADC 08200 that would have 1Meg input impedance it is about to be used with standart oscilloscope probes. But I am having problem with bandwidth limiting. So far I have tried OPA354 and LMH6702 and both suffer from this pitfall.

What is correct way to make high impedance ADC buffer?

So far I have came to this as circuit with best result (as far as bandwidth goes, but it's having very high attenuation). I am simulating 1:10 probe with 9Meg resistor.

//Edit:

I have redesigned the circuit but I am having weird problem with simulation and I think that circuit should work but I am getting very small negative voltage out of OPAMP even thought it's supplied by positive rail only.

This is my schematic now:

Blue trace is output of OPA355 and green trace is non-inverting input.

R11 and R12 are used for offset adjustment. C5 is AC coupling capacitor (if used).

//Edit3:
Fixed model of OPA355 now, but I am having different problem.. on certain frequency it seems that there is some parasitic capacitance charging, but I have no clue where .. Same trace is for non-inverting input, output and inverting input...


texts: Im working on an Arduino project that involves receiving DMX with a MAX485 chip. The pinout of the chip has the 2 dmx pins labeled as A and B, but all the DMX pinouts have them labeled as + and -. What connects to what? Looking around, I have seen diagrams showing both ways. Which one is correct?


texts: If LED's have different bin codes, how can I know what I am buying?

texts:
I will start by confessing I am a hobbyiest engineer (ie: still in school) and thus am open to allegations my concerns are not terribly important.  However, I have this:

I was looking at page three of the binning codes for some Cree L.E.Ds (here) and a quick look suggests the maximum brightness ranges from "23" lm to "164" lm - though if you look at: page 5 of this, you might notice there is a much smaller range for the red ones I am interested in - 56.8 to 80.6. I'll assume this is typical, but significant...

I am in fact trying really hard to build a really bright bicycle light, so I much care about lumens per watt and visible flux.

Do real companies guaranteeing brightness in portable light have to calibrate their electronics to compensate for different batches (or even within batches), or wield their bulk buying power to get similar components?

Better yet, my supplier will simpler tell me what bin they happen to have. Is there a way for a consumer to reliably get ahold of a particular bin?


texts:
How can I calculate the total resistance of resistors combination between points a and b ?
I have already designed the circuit and added a 1 A current source between a and b.
For dependent current source I used component g (voltage dependent current source).

Solving node equations I was able to find Rab using Ohm's law .
According to my calculations V1 = 1.8282... V and V2 = 5.4545... V .
Rab = Vab / 1 = Vx

My question is how can I find voltage Vab = Vx ?


texts: Abnormal microcontroller circuit behavior when I connect SMPS

texts:
I designed a device that calculates current and power using a CT and an ATMega328P-AU microcontroller.

The board I designed was simple and I didn't account for noise cancellation on the ADC lines and AVCC and AREF. That being said, when I power the circuit using a transformer style power supply (Those brick style ones), my circuit functions well without any hiccups and I get proper current reading using the board I designed.

However when I power the circuit using those cheap Chinese 12V SMPS power supplies, the current reading goes all over the place and keeps the last read value even without any load; same thing happens when I add bigger filter caps on the power lines.

I suspect that the power supply has poor EMI protection and is causing my circuit to behave abnormally. Could it be due to me not including LC filters on the AREF and AVCC pins or both?


texts: Device/method for handling rapidly changing current demand in DC source

texts:
A circuit in my project uses rapidly switching MOSFETs to control current flow, and as a side effect, the current demand on the DC source varies rapidly.

The FET is switching at somewhere between 10kHz and 100kHz, and the current demand switches from 100A to about 150A every period at about that frequency. For example, this is a slightly less extreme example from LTSpice (ignore the small inductive spikes):

The DC source is a large 200V/1000A generator/rectifier from the 1950s, and likely can't handle any changes above ~60Hz. Is there a device or component I could add that could draw an essentially constant amount of current from the rectifier, but handle the rapid changes in load to maintain a constant voltage? A (very) large capacitor across the device could do it, but I'd prefer something a little more elegant and less likely to kill me (or at least advice on how to use something like that safely).


texts:
What things impact to range of FM signal? If I increse length of antenna would signal range increase?
I would like to increase the signal range of this project. Is that possible? Do I need more power or longer antenna? What kind of antenna is best for long range?


texts: Interpretation of the rating of a real transformer

texts:
The rating of a real transformer is 15 kVA , 2300/230-V then can we say that the primary rms is 2300 V or can we say that the secondary rms is 230 V or both.

To clarify further, suppose to solve for certain characteristics of this transformer like primary current and secondary current i use the equivalent circuit equation of the transformer referred to the primary side as:

Vp = aVs + Req*Ip + jXeq*Ip

Then what should i use for Vp or Vs in the above equation looking at the rating of the transformer.

In the above equation looking at the rating data given above is Vp= 2300 or Vs = 230 ?As mentioned earlier the transformer is mentioned to be real.


texts: AC/DC motor stall protection after the fact

texts: I am wondering if there is a circuit I can add to a low voltage DC motor or a 110VAC motor that will cut the power if the motor stalls.  I service coin op redemption games and on a few games these small AC/DC gear motors will jam and sit there and burn up.  I know about thermal protection but was wondering if there was something else simple that I can wire into the power leads of the motor that can detect a stall. Is there some type of fuse?? that would do this?  I did an experiment and jammed a motor while monitoring the current draw and it didn't make much of a difference. I would also like to avoid adding a optical wheel encoder type of thing because of the difficulty of mounting the device. One motor uses a Hall effect setup but it might be hard to mount it on other motors. Anything come to mind?


texts: Main aspect of circuit designing process

texts: As a electrical and electronics engineering student I still do not understand what we actually mean by designing a circuit. Are we just trying to shape signals using components or make sure specified amount of current goes through a particular element or there is somehing much more deep in this? We learn about solving circuits but not designing them for some purposes. So what is the catch here?


texts:
In designing a 3 Phase, 4 Pole, 24 Slot AC machine assuming a RYB phase sequence i am confused on the starting point of the blue phase. The calculations, table and diagram look like the following.

Calculations:

$$m = \frac{24}{3\times4} = 2 \hspace{0.2cm}\text {Slots per pole per phase}$$

$$\text{Phase Spread} = m\times\beta = 2\times \frac{180}{\text{slots per pole}} = 2\times \frac{180}{24/4} = 60^{\circ}$$

$$\text{Coil span} = \frac{24}{4} = 6 \hspace{0.2cm} \text{slots}$$

Now using the coil span and 4 poles we can create the slot table.

Table:

Representation of each Coil assuming a convention of current under north pole with a right arrow.

Diagram

simulate this circuit – Schematic created using CircuitLab

  Question: I understand how the red and yellow phases are wired, however the blue phase is confusing. Why is it shifted? Why are we not starting the blue phase at coil 3 and ending at coil 21 like the other two phases?

I understand that even though we are assuming a RYB sequence in the winding diagram the order in which the phases appear is RBY. I believe this is because when three phase is passed through the coils the order in which current is induced is RBY. This is best explained in the diagram below.

Is this why we are starting the blue winding in a shifted sequence?


texts:
A friend of mine asked me to help with thinking about a solution to create a RF communication between 8 robots and 1 access point. Not a lot of traffic, just to signal that the robot is (almost) at the end of his track and get some control information. once per few minutes. This is not very complicated and I was thinking about the nRF24L01+ chip with external antenna. We need a range of approx. 100 - 150 meter. LOS

the complex part is the following:
it is used in a field with solar panels, and we need about 4000 robots and 4000/8 = 500 access points.
The addresses of all the units needs to be unique but each access point needs to know the addresses of his own robots. (and these robots has to know the address of their access point)

I was thinking about a silicon ID (32bit) and use a kind of pairing during start-up. So all the units have address 0 during start-up, and after pressing a button on the Tx, he will send a message with his unique ID. The Rx will store that ID into EEPROM or SRAM. The Rx will answer a message with his own address and the Tx will store that one into his SRAM.

the cons. are that you'll have to "pair" 4000 units....
the pros. are that you have 500 "independent" networks.

Anybody can give me other/better solutions? Or some suggestions to my current idea?
maybe use xbee instead of generic RF radio chip?

Thanks in advance.

Regards,

Jasper


texts: Level Shifter, how to minimize power dissipated

texts:
In the above circuit used as level shifter, I would like to know if

Changing all Resistances by a factor of 10 would still give the same result. The reason I'd like to increase the resistances is to make sure that a minimal amount of current actually flows.
If R1 is really needed.

Any other level shifter which is more efficient using transistors/cap/res? I unfortunately am not from this background, so circuits using MOSFET goes over my head. However if some description is given, I'll be grateful.


texts: Controlling an output based on level of AC signal

texts:
This is my first post on this StackExchange after years of lurking, so please be gentle!

I would like to be able to enable an output (for example an LED) based upon an AC voltage from a split-core non-contact sensor like the following:
https://www.mcielectronics.cl/website_MCI/static/documents/Datasheet_SCT013.pdf

I want to detect when three to seven 50W incandescent bulbs (racing circuit start lights) connected to the AC supply are switched on and then off.

From my reading of that datasheet, the SCT013-005 and its voltage output siblings, all induce an AC voltage in proportion to the current flowing through the wire around which it is clamped (0-1V).

I would like to enable an output (for example a MOSFET in the below diagram) if the current flow in the clamped cable is above a certain (adjustable) level.

Since the amplitude of the signal voltage is so low, I thought to use an Op Amp with part of the feedback loop (R5) being adjustable with a potentiometer trimmer, however since I haven't worked with either AC signals or OpAmps before, I wanted to check my design was sane.

(It works in the circuit simulator, but I don't think that guarantees anything!)

D3 and R7 represent the hypothetical load. In reality, this would be the input of an optocoupler inside a piece of proprietary hardware.

I expect that the smallest load I will detect will be 2x 50W incandescent bulbs, with no other load on the mains supply cable, giving a mains current of 0.23A = (100W / 230V).

This should induce a voltage of 0.046V = (0.23A / 5A).
Picking round numbers, if I aim for a max gain of 100x then using a potentiometer (R5) with a maximum of 10k and an R3 resistor of 100 Ohms should give a gain of (1 + 10k / 100) = 101x gain, giving an output from the OpAmp of around 4.3V (or whatever the amp can drive, I don't expect I need a rail-to-rail part here), more than sufficient to drive the gate on a BSS138 or similar MOSFET.

In use, the operator would adjust the gain using the R5 potentiometer until switching the start lights on just enables the output.

A few more questions, should all that be sane:

Are there any caveats I should be aware of before I try building this?

Do I even need the diode D2?

Is it reasonable / correct to tie one leg of the AC signal to Ground?


texts: BNC splitter which separates ground and signal?

texts:
I'm a student doing research in a physics lab and we often have the need for a certain type of BNC cable splitter. This splitter has a BNC jack which accepts a single coaxial cable as input. It has two jacks for output. It routes the center pin of the input to the center pin of one of the outputs and it routes the shield of the input to the center pin of the other output.

To give an example, one thing we use this type of splitter for is to amplify a voltage (center pin) with respect to ground (outer pin) using a purely differential amplifier which takes two BNCs as input.

My questions are:
1. Is there a name for this type of splitter?
2. Is there anywhere that sells nice, high quality splitters of this type? We can homebuild them but it would be better if we can find a place to buy them from.

I've tried searching for this, but I haven't turned anything up. I appreciate any and all answers!

Edit: I should note that another thing we use this type of splitter for is connecting a two point resistance measurement from a multimeter to our breakout box. The multimeter has banana plugs and we want to connect the positive wire and the negative wire to different jacks on the breakout box (corresponding to different contacts on our sample inside a dilution refrigerator). It seems to me that a splitter like I described is necessary for this.


texts: Real time clock loses SCL I2C signal when backup battery is added?

texts:
I have a real time clock module in my layout (same parts as this module from Sparkfun: https://www.sparkfun.com/products/12708 ), when I have my system set up WITHOUT the backup battery, I am able to see the time and date on the serial monitor, but when I plug in the backup battery, the serial monitor immediately stops outputting this information.

I checked the SCL output of the DS1307 RTC module on a oscilloscope before the battery is added and I can see the master clock signal, but when the battery is inserted, this reading flatlines...

Here is the closeup board schematic (the RTC module is indicated by U9 (backwards text)):

And lastly the wiring schematic:
I can't add since my rep is too low, so just comment if you need it

If there is anything else I can provide to help debug, please let me know!


texts: Is there anyone who can do the following finite state machine problem with fewer states?

texts:
I encountered a problem about finite state machines in digital design which asks the following :

Design a sequential circuit with serial input X and serial outputs Z1 and Z2
which performs the following operation. Whenever the circuit receives a sequence 1100 on input it should output Z1 = 1 and Z2 = 0. Whenever the circuit receives a sequence 0101 on input it should output Z1 = 0 and Z2 = 1. Otherwise it should output Z1 = 0 and Z2 = 0. Draw the state diagram.

I found the folowing diagram. Is there anyone who can do this with fewer states?


texts: Generate unique IP/Mac from samd21 serial

texts:
We created 100 custom PCB around the samd21.

And I'd like to generate some unique IP/Mac addresses from the Serial number of the samd21.

In the datasheet they say the following

  Each device has a unique 128-bit serial number which is a concatenation of four 32-bit words contained at the following addresses:
  Word 0: 0x0080A00C
  Word 1: 0x0080A040
  Word 2: 0x0080A044
  Word 3: 0x0080A048
  The uniqueness of the serial number is guaranteed only when using all 128 bits.

And when I use the teensy 3.2 I use the following library: https://github.com/FrankBoesing/TeensyMAC

Any idea on how to achieve something like that ?


texts: Designing a prototype pcb in Eagle with other parts imported?

texts:
I am protyping a project with several boards like microcontroller, charger, booster etc. for my bachelor's degree in electrical engineering. Now I want to switch from my prototype board and etch my own pcb. I already know how to etch the pcb but I'm not sure how to approach the Eagle schematics.

I want to have every single board (charger, booster, microcontroller etc.) to be able to plug in to my pcb so I can just unplug them whenever I want. Is it then better to just create a new board and plug in the measurements of each board manually or would it be best to import the seperate boards?

I have the board -eagle files from Adafruit https://www.adafruit.com/product/259, https://www.adafruit.com/product/1903 and I am thinking that I could import them and make my prototype pcb from this but it seems difficult. What would be the best approach here?


texts:
I have a Nixie tube clock based on IN-12. I assembled the kit, it works great and it was great fun. But the tubes are just too bright in dark conditions.

I would like to modify the clock to be able to change the brightness. I have included the full schematic bellow.

I feel that a well placed potentiometer on the high-voltage power-supply (lower right of the schematic) could do the job.

UPDATE

I change the voltage, as expected, I got some non-uniform lighting. reprogramming the microcontroller is more work than I was willing to put in this project.


texts:
I've made a USB hub PCB using a USB2517 controller, but it's not working. When I plug it into the host computer, I get a "not recognised" message on Windows and "unable to enumerate" message on Linux.

I'm not able to identify the problem. The USB2517 seems to power on at first (current consumption goes up and 1.8 V at pin 25) and after the "unable to enumerate" message it powers off (0 V at pin 25).

You can see the schematic I've used:

You can find here the KiCad project with schematic and PCB layout: KiCad project. The idea of the PCB is to be an USB hub/power dispatch for a robot. Two batteries are plugged in - one to power the "logic" side (Arduino and STM32 boards) through the USB cable and one that is connected to power motors and actuators.

Do you have any idea what the problem can be?

Please keep in mind that I'm a computer science student, making PCBs only as a hobby.

Thanks for your help.

Update

I have to admit, I made some dumb mistakes. I'm not a pro in electrical engineering and I'm very grateful for your answers.

Following your recommendations and Microchip's reference design, I modified my schematic.

You can find the full schematic here.

Decoupling capacitors for VDD33 were present, but not shown in the previous screenshot.

I found these ESD diodes (CG0603MLC-3.3LEA) with a capacitance of 0.5 pF. Are they good for my application?

Do you think that my new schematic is correct? I don't want to make other mistakes.


texts:
I have a YT7B-BS battery in my motorcycle. My motorcycle doesn't start because the battery voltage is only 12.05 Volts.

The battery has the following inscriptions:

Standard charge: 0.7 A x 5~10 hours
Quick charge: 3 A x 1 hours
6.8 Ah (20 HR) / 110 A (CCA)
12 V, 6.5 Ah (10 HR)

I tried to charge the battery with an external hard drive power supply rated as following:

Switching adapter
Model SYS1298-1812-W2E
Input: 100-240 V ~ 1.0 A MAX, 50-60 Hz
Output: +12 V continous 1.5 A
Output power: 18W max

I have plugged the positive terminal of the power supply to the positive terminal of the battery, and the negatives to the negatives. After a 2 hours, the battery voltage is exactly the same: 12.05 V. The power supply is a little warm but not too much.

I plugged the motorcycle battery to my car battery for a few minutes and the tension went up to 12.5V, allowing my motorcycle to start (battery alone, no cables), so the battery doesn't seem to be dead.

Why isn't the power supply charging the motorcycle battery?


texts: What kind of motor would be better for mapping?

texts:
I have built a car like robot which goes around itself like many examples out there. I want to do mapping with its sensors.

The problem is if I use dc motor on wheels, can I detect how much it moved from starting point or should I use servo motor?


texts: Understanding the package drawing of a qfp

texts:
I am designing my very first PCB and there are a few things on the package drawing of my microcontroller that are unclear to me.

Why are the sizes expressed in fractions?
e.g.: 0,23/0,13 or 0,75/0,45. What does each element stand for
What do TYP and SQ stand for?

side question related to the previous one: I am looking for the length of a

is it calculated by: (16,10-12,40)/2 or  (15,90-12,40)/2?


texts: What is the maximum bitrate supported in the Can Bus?

texts:
i began reading about Can Bus for my final year project

i have to send a file to be flashed into the microcontroller using the CAN BUS .
I have found that the maximum bitRate that can be achieved is 1Mb/s but there is a lot of things to consider like the ack. time and the spacing between frames.

So , how can i know the maximum bitRate supported in the CAN BUS . It is possible to get 1mb/s as the maximum bitRate , how this can be accomplished.

The micro-controller i'm using is MPC 5748
Datasheet here

Any help will be appreciated, thanks.


texts:
What is the reason of using 10 kΩ resistor in series to the control signal? Is it related to the base current according to the NPN transistor's datasheet?
For example:

My CONTROL/GPIO is 5 V.
The maximum base current according to the NPN transistor's datasheet is 120 mA.

Does it mean I need to have minimum 42 Ω resistor?


texts: Function of ferrite core in the induction cooker coil?

texts: I wondering what is the function of ferrite core in the induction cooker coil? (In the other word why there are no ferrite core in traditional induction heater?)


texts: I have a very basic question about battery charging power. In a very simplified scenario, assume a battery with voltage 3.7 is connected to another rechargeable battery with voltage 3.2 which results in charge flow from the first battery to the second one with current 10mA. The question is, with how much power energy flows from the first battery to the second battery? I know Power=Current*Voltage but voltage of which battery?


texts: logic gates simplest square wave generator

texts:
Using CMOS technology, where tp=tHL=tLH=10ns, I need to make an simple circuit which generates square waves with frequency of 50MHz. I know that T=1/f = 20ns. I also have another formula that I found in a book and it says T = tHL+tLH = 10ns + 10ns = 20ns. I know how to convert logic gates to CMOS, but I don't know how to build this circuit using only logic gates, because of that frequency.
The simplest circuit that I know, is that: 1 NAND gate, with one of it's inputs x = 1, and another input y = feedback of output.

EDIT: If I have 50 Mhz frequency and I want to divide it by 2 so it will be 50/2 = 25, is that possible with the circuit that I designed below?


texts: 50 MHz Clock shifting from 5 V to 3.3 V and Bidirectional , possible?

texts:
I'm trying to design a circuit to convert a 50 MHz clock source from 5 V to 3.3 V. At first, I thought of using Sparkfun's level translator shown in the link below:

https://learn.sparkfun.com/tutorials/bi-directional-logic-level-converter-hookup-guide

However, the NMOS used there, the BSS138, has delay and rise times that are unsuitable for the 50 MHz clock signal. It has a delay time of 2.5 ns and a rise time of 9 ns when turning on. Similarly, it has a 20 ns delay and a 7 ns fall time when turning off.

I tried to look for solutions that are similar to the converter, but most of them don't seem to be suited for MHz signals. Some solutions show using ICs such as the SN74LVC8T245, but it's direction depends on the input to the direction pin, and the rise times seem unsuitable given the clock signal. Other solutions such as a resistor divider seem to work for lower frequencies, but I want to ensure signal integrity as this is a clock signal. Using a faster NMOS would be ideal and simplistic, and I can replicate the Sparkfun circuit for multiple lines, but what other solutions would be optimal for this fast clock signal?

EDIT: Since there has been some discussion regarding the need for bi-directionalaity, I wanted to explain a bit here. Initially, we thought that we could go with the level translator. One channel would be available for shifting the clock from 5 to 3.3 V, and the remaining channels would be used as needed for other purposes. But, due to the specs of the BSS138, it didn't seem reliable for our 50 MHz clock. After some discussion, being bi-directional is no longer a requirement, at least for the clock signal, so we're just focusing on shifting the clock down for now. I'm really sorry about mentioning bi-direction. Let's just forget about it for now. We plan for the clock signal to be stepped down, and then it should go into another module that accepts 3.3 V as an input. I don't know the load capacitance or impedance of the module, but when I find that out, I'll update here accordingly.

EDIT: So, after ignoring the bi-directional functionality, I think I may have found a potential solution: to use a buffer to step it down from 5V to 3.3 V while keeping signal integrity. I found some buffers that seem to work from TI, the SN74LV1T34 and the SN74LV1T126.

http://www.ti.com/product/SN74LV1T34/description

http://www.ti.com/product/SN74LV1T126/description

I imported the model of the SN74LV1T126 into LTspice and ran a simulation, hooking it up to 3.3 V and a 50 MHz 5-volt clock source, showing the output voltage with and without a load. Ideally, I would have liked to test out the SN74LV1T34, but there are no SPICE models available for it, so I'm just working with the SN74LV1T126. The image is shown below:

Here, I'm just showing one clock cycle so that I can measure the rise and fall times to see if it is within acceptable tolerances given the clock input. Judging by the sim, it seems to work well, but when under a load, it doesn't reach 3.3 V, but rather it falls down to 1.8 V. Since this is going to be hooked up to a module, it will be under load, so is there anything I can do to ensure it reaches the correct voltage?


texts: Why lithium ion batteries explode ? (Reason behind it )

texts:
I heard the reason for lithium ion battery explosion is lithium burns when exposed in air but Few days ago I pierced one of my batteries (10-20 holes) and it didn't explode , why ? It was broken phone battery (still works but %35 maximum capacity and 3.7v max voltage) .

Also I heard in somewhere ,  lithium ion batteries only explode when it's charged , is it true ?

The reason I asked because I have a lot of old & broken lithium ion batteries in my workshop and I'm collecting them in glass air tight jar so when I got enough time or batteries , I send them to recycling center for disposal.


texts:
I recently bought a DE0 FPGA board with GPIO headers.

The schematics shows that some of them are protected with BAT54S Schottky diodes.
Does it mean that if I input 5v logic level they will be converted to 3.3V and protect the FPGA or do I need to step down the voltage by myself?

What is the easiest-safe way of converting 5v to 3.3v ?


texts: Is stalling a DC Motor with rated current safe for the motor?

texts:
I know that stalling DC motor can cause overheat because of excessive current.
If i will limit the current to the rated current of motor, is there still issue to damage the motor ?
to be more specific I have 24v worm  geared motor and I want to stall it for 3-5 seconds with rated current. I think the gears will get warm, but how critical will it be for the motor.


texts: Passive Ethernet-over-coax converters... how do they work?

texts:
I just bought a pair of these passive ethernet-over-coax converters.  I was very skeptical, but they actually work!  I just can't figure out how... they do not require external power, coax only has one pair of conductors (inner wire and outer shield) and ethernet needs at least 2 pairs.  I hate to break them open - was hoping someone could point me to a whitepaper or other technical docs to describe the process.
I can't see any way around some sort of microcontroller that multiplexes the upstream/downstream channels onto the single coax pair, but where is it getting its power? I wasn't aware Ethernet (without PoE) could supply enough power to operate a mcu, but maybe?
Another thought: if ethernet transmits and receives at different frequencies, a couple of tight bandpass filters would allow multiplexing both signals onto the same coax pair and breaking them out on the other end. This would be a completely passive circuit requiring no power.
Thanks for shedding any light on this.


texts: How to select appropriate ferrite beads for power supply rails

texts:
I'm making a camera board using IMX225LQR image sensor. For this sensor you need 3.3V analog power supply and 1.8V, 1.2V digital power supplies. Also, the 1.8V power pins are close to the 3.3V analog pins. Thus I'd like to use ferrite bead to prevent noises in 3.3v rail generated by 1.8V digital power rails. But I have no idea what kinds of ferrite beads would be appropriate for this.

DC resistance : Should it be as small as possible?
impedance at each frequency: Should I look at impedances at 1Mhz, or 100Mz?

I'm going to use TPS62243 as 1.8V power supply. It's a switching regulator and has 2.25Mhz switching frequency. I wonder how you predict noise frequency, or if the 100Mz is general for noises in power rails.


texts: Low-frequency / DC circuits --- noise + decoupling issues

texts:
I'm using an AD8421 instrumentation op-amp, and I need to adjust the DC level of the output. As per the datasheet, the VREF input pin needs to be driven by something that asserts a voltage (low output impedance), and they recommend a voltage follower amp.  So, I'm doing just that:

simulate this circuit – Schematic created using CircuitLab

The 0.1uF caps were mostly out of paranoia/habit.

I'm wondering: do I really need bypass capacitors for this op-amp?  The op-amp is supposed to do a good job at filtering power supply noise/ripple at low frequencies, and this op-amp will not be subject to sharp transitions or any other high frequency signals;  at high frequencies, any other op-amp that would produce noise have their own bypass caps so that noise does not propagate to the rest of the circuit.

Now, speaking of power supply noise (since I'm using a DC/DC switching power supply), I then realized that the noise will directly leak to the output of the AD8421 through the input signal of the LF356.  I'm thinking I should replace the simple voltage follower with a low-pass filter at, say, 5Hz or so (e.g., place 10uF instead of the 0.1uF caps in the input circuit). However, the fact that the 8421 datasheet does not mention anything like this makes me wonder whether I'm being too paranoid? Any comments?


texts: How to test an RF crystal oscillator performance integrated into a Cellular radio?

texts:
I have a couple of reference designs with 2 different crystal oscillators integrated into it. These are cellular radio and can generate standard LTE QAM signals out of it. But I do not have access to high end equipment which can demodulate the signal for vector measurements. So I am looking for ways to test it using available spectrum analyzer (safe to assume it supports the test signal specs). Also safe to assume DUT control gives ability to transmit a known signal.

What tests can I do to compare the oscillator performance on the 2 reference designs using a spectrum analyzer? Phase Noise, Frequency accuracy, etc? And how to measure?


texts: I'm wanting to use a relay as a SPST switch, and I've noticed many designs incorporate a flyback diode. What instances are these needed and what are potential drawbacks, if any?


texts: What does a capacitor capacity really mean?

texts:
I am very new to electronics, and I am trying to use a capacitor to make my LED's stay on a little longer after I turn it off. I know that the voltage on the capacitor is the maximum limit of voltage it can take, and the fared unit of the capacitor is the capacitance, but that wasn't really clear to me, so I made a list of some stuff that I need to know to complete my goal.

Does a higher capacitance affect the time the charge is held?
If I had 5 100uf capacitors, and I connected them in parallel (which will give me 500uf), will it perform the same way as a 500uf capacitor (that was not combined with others)?
Does different types of capacitors hold charges longer than others?

Thank you all for feedback, help, and tips :)


texts:
I built a simple sensor board connecting a RFDUINO to two I2C components. A ADXL345 accelerometer and  a  MPR121  Touch controller. The board also includes an RGB LED, vibration motor and Li-Po charger circuit.
The I2C bus seems not to be working, and I cannot read the     register (using the wire library for Arduino) on  the two I2C.  If I connect a scope to the I2C lines (using some pads exposed on the PCB, see figure) I can see a 3.3v  but no activity on both SCL and SDA lines.
In a ealier breadboard prototype I used a RFDUINO shield and breakout boards for ADXL345 and MPR121 and did not present any problems.


texts: How to protect valve heaters from inrush during cold starts?

texts:
Some valves on the market today are rare and expensive.  GEC Marconi KT66's retail for about £300 /pair today for example.  Some others clearly show a bright flash as their heaters initially power up which is worrying when you see it for the first time.

One concern I have is that the traditional constant current approach may not be sufficient to initially raise the temperature of the heater element sufficiently.  I understand that some over current is necessary to begin the thermal resistance increase.  Without over current, the heater will just sit there and may not get sufficiently hot.  I'm not sure about this statement though.

One modern aspect of this question is that I'm not trying to be totally authentic with all of the circuitry.  Only the valves.  I'm prepared to consider any modern form of protection in what you might call a hybrid design.  An anachronistic design featuring relays or micro controllers would be fine as well as DC drive.

What modern or traditional means can be used to reduce the initial current /thermal surge on a valve heater to extend it's life?

NOTE.  A single small valve might require 300mA @ 6.3V RMS.


texts: How to safely discharge high voltage (> 42 V) capacitors?

texts:
I have a 1200 watt PC power supply (yeah that's for a gaming rig!). Unfortunately it's failing on me after about 3 years. As the guarantee is over and I don't want to have shipping costs, I want to open it myself and see what can be wrong. I have low to no experience with power supplies of this wattage and rating. So my question is, how can I make sure when I open the PSU casing, I am not going to kill myself.

Is it enough to just leave it off for few days? Maybe not, because I can see huge capacitors inside.

Maybe connecting it to PC and trying to turn it on without plugging it into wall socket could discharge the caps?

And a silly question, the huge inductors inside are not a threat while it's not connected to wall socket, right?


texts:
I'm trying unsuccessfully to make two Arduinos talk using SPI.

I found this great tutorial. The SPI Master send a constant string each second to the SPI Slave, which resends to the USART for depuration purpose. The problem is that nothing is printed on the Arduino's Serial Monitor.

The SPI Master is connected on a second computer and also sends the string to USART. The string arrives at the computer.

I tested all of Arduinos pins that I use and they're working (on both Arduinos).

My setup

Arduino Leonardo: SPI Master
Seeeduino: SPI Slave

Leonardo_________Seeeduino
(10) SS--------->(10) SS
(11) MOSI------->(11) MOSI
(12) MISO<-------(12) MISO
(13) SCLK------->(13) SCLK

The code used on the SPI MASTER:

#include <SPI.h>

void setup (void)
{
  Serial.begin(115200);
  digitalWrite(SS, HIGH);
  SPI.begin ();
  SPI.setClockDivider(SPI_CLOCK_DIV8);
}

void loop (void)
{
  char c;

  // enable Slave Select
  digitalWrite(SS, LOW);    // SS is pin 10

  // send test string
  for (const char * p = "Hello, world!\n" ; c = *p; p++) {
    SPI.transfer (c);
    Serial.print(c);
  }

  // disable Slave Select
  digitalWrite(SS, HIGH);

  delay (1000);
}

And the code used on the SPI SLAVE:

#include <SPI.h>

char buf [100];
volatile byte pos;
volatile boolean process_it;

void setup (void)
{
  Serial.begin (115200);

  // have to send on master in, *slave out*
  pinMode(MISO, OUTPUT);

  // turn on SPI in slave mode
  SPCR |= _BV(SPE);

  // get ready for an interrupt
  pos = 0;   // buffer empty
  process_it = false;

  // now turn on interrupts
  SPI.attachInterrupt();
}

// SPI interrupt routine
ISR (SPI_STC_vect)
{
  byte c = SPDR;  // grab byte from SPI Data Register
  if (pos < sizeof buf)
  {
    buf [pos++] = c;
    if (c == '\n')
      process_it = true;
  }
}

void loop (void)
{
  if (process_it)
  {
    buf [pos] = 0;
    Serial.println (buf);
    pos = 0;
    process_it = false;
  }
}

Is there something wrong on this project? How can I make it work?


texts: Can I use 9V battery to power up a cooler fan?

texts:
I am absolutely not an expert in electronics. But I have to make simple circuit: I need to power a cooling fan from a battery.

Right now I have a 12V cooler and 2x 9V batteries. There is no problem to power it up using only one battery, however the current will be too weak to provide sufficient RPMs (maybe even to start).

But using 2x 9V batteries gives 18V that is much higher than expected - I'm afraid it may burn this thing up a little.

As a solution I think I may use 5V cooler (if I can found such in a local stores), using 4xAA batteries (6V in total).

BUT: Some related forums told me that I am able to power up a 12V cooler using red & yellow wire and it's gonna give me 7V. As I am a bit far even from the electronics beginner, the main question is: is this statement correct and what may happen if I use 9V battery for 7V cooler?

Thank you in advance!


texts: actual formula for open loop gain in a non-inverting op-amp?

texts:
People keep only talking about assumptions where the open loop gain for a non-inverting op-amp is so high you don't have to consider it.

But suppose for a non-inverting amplifier that the open loop gain is something like 100. What would that mean for the resistances and input/output voltages?


texts: Code composer 6 linker file not placing variables

texts:
I am developing firmware on MSP430F2619. I need to store configuration information having 5 sections of 200 bytes. In order to read and write them independently I am trying to allocate 5 sections of 512 bytes each.

SEC_CALIB_1         : origin = 0xF200, length = 0x0200
SEC_CALIB_2         : origin = 0xF400, length = 0x0200
SEC_CALIB_3         : origin = 0xF600, length = 0x0200
SEC_CALIB_4         : origin = 0xF800, length = 0x0200
SEC_CALIB_5         : origin = 0xFA00, length = 0x0200

section_calib_1 : {} > SEC_CALIB_1
Section_calib_2 : {} > SEC_CALIB_2
Section_calib_3 : {} > SEC_CALIB_3
Section_calib_4 : {} > SEC_CALIB_4
Section_calib_5 : {} > SEC_CALIB_5

Then I am trying to place information structure using DATA_SECTOIN pragma

#pragma DATA_SECTION(Calib_Slot_1,"section_calib_1")
const Cal_Slot2_t Calib_Slot_1 = { 0x0011 };

#pragma DATA_SECTION(Calib_Slot_3,"section_cal_3")
const Cal_Slot3_t Calib_Slot_3 = { 0x0012 };

But only variable Calib_Slot_1 is allocated memory but not Calib_Slot_3

Program compiles successfully but during debugging it dose not variable  Calib_Slot_3 in watch window. Plus it dose not appear in map file also.


texts: stm32 uart issue serial monitor vs logic analyzer

texts:
I am writing data serial monitor via hal_uart_transmit and it works fine,
but when I monitor same serial bit pattern in logic analyzer I see extra two bits have the logic high state, why is that?

for example on the serial monitor, I get 5 in decimal,
in a logic analyzer, I get 00110101 it should be 00000101 isn't it?
not only for numbers, but I also got this issue for any string as well.


texts: Do bridge load-sensors follow linearity?

texts: I have been using four half bridge load-sensors. After forming a bridge, the output of the bridge is fed into ADC(ADS1230). I'm using this load-cell. From the output of the ADC, I want to convert it into KGs simply by 'Slope-method', assuming the output of ADC to be linear. I only have to be confirmed that the load-cell behaves linearly or not when the huge weight is subjected to it.


texts: STM32 HAL_ADC_Start() ends with HAL_ERROR

texts:
I'm new to microcontroller programming and I have a problem I can't solve.
I am using STM32 Nucleo board L4R5ZI and I try to read the analog value on one of the pins, and then use the ADC to convert it and send it to the PC using the UART.
But when using this code, I only get a "0" in my PC. It looks like the HAL_ADC_start() function returns HAL_ERROR. Do you know what it could be?
I hope that you understand, English is not my native language :)
ADC_HandleTypeDef hadc1;
UART_HandleTypeDef hlpuart1;

...
uint16_t raw;
char msg[10];

HAL_Init();

SystemClock_Config();

MX_GPIO_Init();
MX_LPUART1_UART_Init();
MX_USART3_UART_Init();
MX_USB_OTG_FS_PCD_Init();
MX_ADC1_Init();

    while (1){

      HAL_ADC_Start(&hadc1);
      HAL_ADC_PollForConversion(&hadc1, 100);
      raw = HAL_ADC_GetValue(&hadc1);
      sprintf(msg, "%hu\r\n", raw);

      HAL_UART_Transmit(&hlpuart1, (uint8_t*)msg, strlen(msg), HAL_MAX_DELAY);
      HAL_Delay(5);
    }

...
  hadc1.Instance = ADC1;
  hadc1.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;
  hadc1.Init.Resolution = ADC_RESOLUTION_12B;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  hadc1.Init.LowPowerAutoWait = DISABLE;
  hadc1.Init.ContinuousConvMode = ENABLE;
  hadc1.Init.NbrOfConversion = 1;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.NbrOfDiscConversion = 1;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc1.Init.DMAContinuousRequests = DISABLE;
  hadc1.Init.Overrun = ADC_OVR_DATA_PRESERVED;
  hadc1.Init.OversamplingMode = DISABLE;

EDIT 1
I find out that HAL_ADC_start function return HAL_ERROR in this section of code:
while (__HAL_ADC_GET_FLAG(hadc, ADC_FLAG_RDY) == 0UL)
    {
      /*  If ADEN bit is set less than 4 ADC clock cycles after the ADCAL bit
          has been cleared (after a calibration), ADEN bit is reset by the
          calibration logic.
          The workaround is to continue setting ADEN until ADRDY is becomes 1.
          Additionally, ADC_ENABLE_TIMEOUT is defined to encompass this
          4 ADC clock cycle duration */
      /* Note: Test of ADC enabled required due to hardware constraint to     */
      /*       not enable ADC if already enabled.                             */
      if (LL_ADC_IsEnabled(hadc->Instance) == 0UL)
      {
        LL_ADC_Enable(hadc->Instance);
      }

      if ((HAL_GetTick() - tickstart) > ADC_ENABLE_TIMEOUT)
      {
        /* Update ADC state machine to error */
        SET_BIT(hadc->State, HAL_ADC_STATE_ERROR_INTERNAL);

        /* Set ADC error code to ADC peripheral internal error */
        SET_BIT(hadc->ErrorCode, HAL_ADC_ERROR_INTERNAL);

        return HAL_ERROR;
      }
    }
return HAL_OK;

It is part of function ADC_Enable() which is used in HAL_ADC_start(). Condition in while() is still TRUE that means, a timeout occurs later.
Still don't know how to solve it.


texts: How does feedback in power supply work considering output change delay?

texts:
I'm designing an SMPS with a PIC microcontroller, but this question applies not only for SMPS but to linear power supply too.

I set a desired output voltage in my microntroller and then I perform some simple calculations to set an estimated duty cycle that will give me the desired voltage. But this is not exact and output voltage can change when load is applied so I perform and ADC read every 200uS to detect if the output voltage is the voltage I want.

The problem is: let's suppose I want an output voltage of 32V but my current output is 30V so to correct this I start increasing duty cycle and at the same time measuring with the ADC, but, If I increase the duty cycle, the output voltage won't rise automatically, it will take some time due to output capacitance, so, when I perform a new ADC reading the output voltage is still low and I will increase the duty cycle AGAIN because I think my output voltage is still incorrect, but the fact is, it is increasing slowly. At the end I will detect an output voltage above 32V due to the over-increased duty and will start decreasing the duty cycle and the same will happen, so I will have an output oscillating between a maximum and a minimum constantly.

I know I could for example, change duty, wait 20mS and now read the output voltage to give some time to voltage to rise, but this will decrease power supply performance in a transitory. So, how is this problem solved?

This way of thinking makes me guess that linear power supplies like LM723 or any other should face the same problem, am I right?


texts: Simple Circuits- negative voltage vs current flow

texts: Say I have a voltage source of -5V. Does the fact that the voltage is negative impact which way the current flows? It seems like a silly question because from what i've already researched I don't think it has any impact.


texts:
I am not sure whether to call it a probe on my schematic diagram or is it something else.

I have ATmega328P checking its two digital pins whether both have been connected to the ground. When floating, these pins are HIGH. The only time that it becomes LOW is when it senses the ground through a detachable conductive material that has 3 terminals for the two digital pins and the ground.

Is it considered a probe? What should I call it in my schematic diagram?


texts: What is the name of this kind of connector where you stick a whole board in to connect?

texts:
An example of the connector type I'm looking for a name for can be found on this board:

It's the big box. You stick a board in to it with strips of exposed copper to connect. It also seems similar to how video game carts and USB work.

I'm looking to get my own version of this connector to interface with some old logic packages that I found.

These boards just have pretty common logic packages on them and they look like one plugs the whole board into something. I would like to design my own board to do this, but I think I need a part like the one on the adafruit board.


texts: Good replacement for 74HC573N Octal Trans D-Type Latch?

texts:
Does anyone have any recommendations on what to use? I suppose any 5V, reasonably broad temperature range (automotive application) latch would work, but if there's something people like, I'm game!
I don't need to be pin compliant as I'm spinning a new board.

-------Edit:
I should add that the few places which DID have the exact part wanted well over $20 each for them, making them the most expensive part of the project by an order of magnitude!

That said, the advice to just switch packages (I was keeping the socketed 20 pin DIP in order not to scare off a customer who just wanted "more of these cards I ran out of") seems to be the way to roll, and the parts are totally reasonable as suggested by answers here.

Thanks everyone for the help!


texts: Light up an LED with an NPN transistor in active low?

texts:
I have a circuit which is turned on at a logical zero. I would like to have a LED indicating this circuit is on, but I only have NPN transistors at this moment, which conduct when there's a logical one on its base.

Is there a way to "emulate" the behavior - i.e. that when there's a logical one, the LED isn't lit up, and when there's a logical zero, the LED is lit up - without having to use a PNP transistor?


texts: How do I simplify microcontroller-based prototype into a sensible production-like circuit?

texts:
First some context: I'm an IT person by trade, and I dabble in electronics as a hobby. I have rather limited experience - apart from some toy circuits I've only made a single "production" quality installation, a lighting system for a display case. On the toy front, I've done some simple Arduino and ARM-driven circuits. In general, I'm not that eager to resort to coding, as this is something I'm already familiar with, and I'd like to learn something new :)

Now for the question itself: I'd like to do more practical circuits, similar to the light setup I've mentioned above. Solving practical problems is a great source of motivation for me. Problem is, while I can sort of work out how to implement what I'd like to achieve, I have tremendous problems with picking sensible physical components to put in the final assembly.

For example, I have an RF-controlled (433MHz) socket. I got a simple circuit working, with a pushbutton triggering an Arduino to send the right command via RF transmitter to toggle the socket on and off. I'd like to make a permanent "production" version of this circuit now, one that doesn't include a whole big Arduino shield. Heck, probably the AVR itself is an overkill for "press button, pipe 24 bits over RF" solution.

Another example: a magnet-triggered LEDs like these. Getting a prototype that uses a reed switch to go from "wave a magnet" to "toggle LED" is simple. Trying to achieve the same effect in a tiny surface of plastic model part sounds next to impossible for me.

In short: drawing circuits is all fun and games, but how do I get from "that's a working prototype that has way too many cables and PCBs" to "that's a sensible implementation that's not an overkill and fits within the space allotted"? And without practical experience in this matter, it's hard to get that practical experience - I literally have no idea what kind of simple building blocks I have at my disposal, and what constitutes an overkill.  On the other hand, perhaps going with a micro-based solution is cheaper/simple than trying to work out something without a microcontroller just for the sake of it?

I guess this question can be condensed to: What do I read on to avoid slapping a microcontroller everywhere? :D


texts: What dangers are there putting power through RCA connectors?

texts:
I've had no luck searching Google for terms like RCA power connector, other than a passing reference on Wikipedia. I have plenty of RCA connectors, and tons of wall warts. I've got a small LED desk lamp that I want to power with a wall wart instead of a battery, but I don't have any female connectors that the wall warts plug into.

So my thought was to use an adapter and change the end to be an RCA connector. If I'm putting a few volts and maybe 500mA or so, would there be any problem as far as the RCA
 connectors go? Obviously I'll need to reduce the voltage for the LED and I'll have to deal with those concerns, but if there's any problems with the connector I'll just try to find some standard connectors.


texts: How to calculate appropriate value for noise-removal capacitor?

texts:
I'm still figuring out analog electronics with my waveform generator project. It has a 9V power supply that I split into +/-4.5V rails with an op amp virtual ground (the subject of an earlier question). The +4.5V side powers an ATmega328P that generates an 8-bit digital waveform on pins D0-D7. Those lines go through an R2R resistor network to generate an analog signal in the rough range of 0-4V. Then I use the negative power rail and an op amp to center the signal on the 0V virtual ground.

So it works, but the waveform is noisy as hell. I kind of expected this, but not this bad. It's not breadboard noise because it's soldered on a real prototype board. There is relatively little noise across the positive and negative rails, so I think the noise is mostly in the virtual ground. (I know that "ground" doesn't normally have noise, but this is a virtual ground and the "noise" is relative to a theoretical 0V point centered between the +4.5V and -4.5V rails.)

I measured the noise between the virtual ground and the +4.5V rail and used the FFT function of my oscilloscope to see if there were any dominant frequencies. I am not so good at reading this but nothing stands out.

I tried capacitors of different values across the virtual ground and +4.5V rail. A 10pF capacitor did nothing. But a 10uF capacitor reduced the noise dramatically!

The stairstepping is due to the 8-bit resolution of the waveform and my not having a capacitor to smooth it out. I know the frequency of the stairstepping and the frequency of the waveform, and knowing the resistance of the R2R network (10k) I was able to calculate that a 1nF capacitor would filter out the stairstepping, and it does.

But what I don't understand is, how do I calculate the value of the capacitor necessary to eliminate the virtual ground noise? I think I need a low-pass filter that just allows my waveform through. That's an RC filter, but what's R? Do I use the resistance of my load and use that to calculate C?


texts: How to create an airline headphone adapter?

texts:
So, I have a predicament: I am a 6'5" guy with massive ears. Like it's not funny how big my ears are. When I go on an airplane, the headphones they give me are terrible and hurt my ears when I wear them.

So last year, I thought I would get my own pair of headphones and take them on the plane. Lo and behold however, it was a 2-hole jack, and I had no adapter on me.

So I am going traveling again in a couple of days (14-hour flight), and I would really like to be able to use my comfortable headphones without having to purchase an adapter (my Best Buy didn't have them, and it would take until after I leave to get them if I was to order them from Amazon).

I am pretty handy with electronics as well (as I do computer engineering for a living), and so I wanted to make my own adapter. But it seems like there is no documentation for how to do it! I have solder, a couple of 3.5mm male plugs with their cords, and a couple of 3.5mm female plugs with their cords. Is it possible to make an adapter out of this?


texts: Can one circuit only compute one boolean function?

texts: Can one circuit (with fixed position of gates and wires) only compute one boolean function?


texts:
Part 1: the system and how it's connected

I'm working on a system that would monitor the water level of a water well in remote areas . Here's what the system is designed ( drawn briefly ) ,

On the left side are the microcontrller , External I2C Analog to digital   converter ( isolated with ADUM1250 ) & the Water level sensor ( 4- 20 mA) which has a very long cable . The right side has the solar panel which then enters through a linear regulator based circuit (MIC29752) lead acid battery charger that is controlled by a mosfet that is switched on/off by the microcontroller which is monitoring the battery level so as not to overcharge the battery, the output of the 12V battery enters the Isolated 5V regulator which then at this stage the output is now 5V .

Part 2: my findings for far

Here's my guess,

I've been reading alot that we may have a problem when working near water pumps and generators, this may or may  not affect the system ( analog readings flicker , electrical instability) which would destroy the circuit thus deciding to use those isolator ICs.
Found claims that coating the enclosure box with an EMI/RFI nickel based  spray will shield the system from the stray Electromagnetic interferences outside the box .

Part 3: My questions

Am i going in the right direction for protecting my system from External EMI from say nearby pumps and generators ?
All of the isolation Solutions used in circuit , do i really need them for my applicaiton or is it just plain overkill ? .
EMI/EFI Coating , it is useful in my case ?


texts: Is there a difference between connecting the input of a logic gate to the anode or cathode of LED

texts:
I am still learning about basic circuit analysis and I was wondering if there is a difference between the two circuits in real life. Technically the polarity at the anode of the LED will be higher than the cathode to allow current to flow, so i'm which is the more "correct" way to connect the logic inputs.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm receiving this RF signal from a temperature only weather station transmitter. But i can't figure out what encoding is being used.

I can't seem to decode the binary. In order to rule out noise or interference, this signals are directly from the micro-controller before entering the RF module.

Thanks in advance for your help.


texts: Command Line GPIO Access - Pin Types (Orange Pi)

texts:
I am trying to set GPIO pins to high and low state on an Orange Pi using the following command:

echo 0 > /sys/class/gpio_sw/PA1/data
echo 1 > /sys/class/gpio_sw/PA1/data

This turns the pin on and off.

The /sys/class/gpio_sw/ folder has locations labeled

PA0, PA1, PA10, PA13, PA14, PA2, PA21, PA3, PA6, PA7, PA8, PA9
PC4, PC7
PD14
PG6, PG7, PG8, PG9

Do the prefixes (PA, PC, PD, PG) have any meaning?

Are these all references to GPIO pins?


texts:
I am making a 12 volt regulator for a solar panel to power an audio amplifier. I already have a switching regulator for most application but it is very noisy for amplifier even with a lot of filtering.
The amplifier draws over 3 amps on full load.

I want to build a regulator using 7812 with series pass transistor for higher current as shown in the datasheet, page 20.

http://www.mouser.com/ds/2/149/LM7812-461970.pdf

I made the same circuit as shown in the datasheet and used the 2SD1047 as Q1

https://www.st.com/resource/en/datasheet/2sd1047.pdf

simulate this circuit – Schematic created using CircuitLab

But as I connected it to my bench power supply set to 18V I was not able to get a regulated output. It just showed ~2V less then the input voltage.

At 18V no load I got 16V output, 0.5A load 15V and 3A load 12V.
I tried different values of R1 calculated by the formula shown in the data sheet.

Is the output voltage affected by the the value of R1?
Please Help.

While calculating R1 I assumed the value for Ireg to be 0.1A, Beta of transistor to be ~95, and IQ1 to be 3A, when that didn't work I tried a bunch of different values of resistors with the same results.

The LM7812 works great when no series pass transistor is attached.
And the transistor is good too.

I already have a switching regulator and I also have a higher current linear regulator so don't suggest them please. I want this circuit to work, and I also want to understand this circuit further so if you could point me to other learning material concerning this circuit then that would be great. The only thing I had to work with was the datasheet. Thanks

PS: SOLVED!! My mistake, I connected a NPN BJT instead of PNP.


texts: Is it possible to shift the signal phase in the digital domain without the use of a microcontroller, only with the help of logic gates? I would like to have control and, for example, use a potentiometer to continuously variable phase shift of one clock signal in relation to the other - both of the same frequency. The phase shift range between 0-170 degrees. Thank you.


texts:
Two parts to my question.

I see multiple suggestions to use the fiberglas bags for storage of Lipo batteries. How do these help prevent fires?
With the oxidizer a component of the Lipo battery, would storage in an all-metal ammo can be a good idea.

Seeking safety...


texts: My transistor used in a transistor amplifier does not get turned off with PWM based input

texts:
I am working on a project; driving a DC MOTOR using an NMOS MOSFET amplifier and Arduino PWM signal.

My problem is my transistor amplfiler is always on when I vary the PWM input value from 0 to 255. Also, the motor runs faster in smaller PWM value and runs faster in larger PWM value. But, my intention is to run the motor faster in larger PWM value..

The below is my current circuit diagram. My transistor is "RFP30N06LE" NMOS MOSFET, my motor is Buehler 4-wire Precision DC motor That can run from 6V to 24V.

Could someone educate me on why my transistor is not getting turned off, and the motor runs faster with smaller PWM value to the amplifier please ?!


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I'm designing a bandpass filter and have been doing some reading on it. I found a transfer function describing the circuit (which apparently all formulas describing this circuit are derived from):

$$\frac{V_{\text{o}}}{V_{\text{i}}} = -\frac{Kj2\pi f}{\left(1+\frac{jf}{f_1}\right)\left(1+\frac{jf}{f_2}\right)}$$

simulate this circuit – Schematic created using CircuitLab

Circuit Diagram of Inverting Bandpass Filter

Where do they get \$C_1\$, \$C_2\$, \$R_1\$, \$R_2\$ from?


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I'm replacing a Dell laptop power supply with an old Mac Mini supply I have laying around. The broken Dell psu outputs 19.5V and 4.6A and the Mac psu supplies 18.5V and 4.6A. I hoping that's close enough and will suffice.

My issue is splicing the Dell cord onto the Mac cord coming out of the Mac psu. The Mac cord simply has a red wire and a black wire, as seen here:

The Dell cord has the outer layer of black rubber, then a layer of wire mesh, surrounding a layer of white rubber, then another layer of wire mesh, then another layer of white rubber, and lastly a thin wire in the middle. Here's a picture. The two wire mesh layers are twisted up.

My question is which is negative and which is positive? Here's a picture of the Dell connector:

Thanks


texts: Does anyone know through direct experience if LTSPICE or other major circuit emulators actually report component failures in some way. If I were to plug in say over voltage values to known components in even simple circuits. Or does it just freeze up.


texts: Can someone please explain this Bluetooth Antenna Test Result, I am new to RF?

texts: This is the test of a Bluetooth (BLE 5.0) passive antenna test result. I am new to RF and do not know how to properly interpret this result.


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I have a 10 kV 23 mA ignition transformer.

Apparently the way to make a jacob's ladder is to just connect the electrodes to the secondary, plug the primary into the wall, and call it good.

But of course, as a transformer this thing has no current limiting, and I have no way to calculate the effective resistance of the arc. (I'm guessing a theoretically perfect transformer has no current limiting, but a real life one probably might limit current in some manner I am not familiar with, magnetic saturation, etc, but I'm guessing also this is not the "correct" way to limit current when designing a circuit)

What's the best way to limit current here? I can use a power strip that will trip at 1800 W, but this thing will draw 230 W at the max of the spec.

Do I just fuse it at, say, 0.5 A on the primary side and use a slo blow to avoid blowing the fuse on the inrush?

Or do I use a single resistor on one half of the secondary side to limit the current?

Or use a variac on the primary side along with a killawatt meter to measure the current draw as I turn up the voltage?

What's the correct approach here?

Yes, I have worked with HV before and I understand this thing will kill me easily, I have built plenty of woodburners with scrap MOT, etc and I know how to handle HV.


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We have mutiple same-sized, same-tech RFID Tags (Mifare Classic), in the Field we have discoverd that some tags are less readable than others. For example, the distance is smaller or it takes more read operations to sucessfully read the tag.
The current test station only checks if the tag is readable and then marks as "good". Since there are different readers in the field (tolerance) the test method is not ideal.
I would prefer a test method that gives a value, rather than a binary result (good/bad). For example, the tag should say "10%, or 45%" of a known good reference.
The test method should be as easy as possible to operate by the tester. For example the tester should place the tag in the reader and press start.
Any ideas how to achieve this?


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I am working on an RF design which includes multiple frequency synthesisers and sensitive receive stages. However I need to terminate an unused RF port on the synthesiser, what is the best way to do this?

I understand that you would normally use an RF 50 Ohm terminator, but there is no such connector as I am working at IC level, how do these terminators work?

Many thanks!


texts:
I have been doing a project involving partial reconfiguration of a FPGA for some time now. I am having trouble understanding what is meant by terms like 'partial bit file', 'bitstream' etc. How can a .bit file be partial? Also, I know Xilinx provides PlanAhead tool for reconfiguration, but does it require some sort of license to get it working?
I know that for reconfiguration, I would have to separate my fabric into two parts-static and dynamic. While static part is what is usually done, is there a specific way to code my dynamic logic in HDL?
Any help would be appreciated! Thanks!


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My question is regarding the protection needed at the DAC pin generating the video signal.
I am doing the generation on a STM32F4Discovery. The STM32F40x has a DAC built in and it can drive the signal without an op-amp. The IC has a buffered output according to the user manual. Can I simply wire the DAC and GND pins to the video cable? I read there is a risk of ESD on old CRT TVs, but I'm using a LCD one. Do I need a protection circuit? It's just for testing, not for production.


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I'm in the process of exporting a PCB design from Altium. At present I'm saving the output as a .cam file. I've sent this file to a fabricator that uses CAM350 v11 and they are getting an error along the lines of "database unrecognized".

Does anyone have experience exporting Gerbers from Altium for import with CAM350?

Should I be using .cam files for output or should I be using individual files per layer?

Is there another way to export Gerbers from Altium that I'm overlooking?