texts: Power supply - purpose of the capacitor on the side of the transformer before full bridge rectifier

texts:
I was wondering if someone can explain the purpose of the capacitor C1141 from the attached picture. I know that C1142 is a filter cap: that much is obvious to me. However, I can't seem to grasp the purpose of C1141. I observed that it is obviously not polarized so it's dealing with AC because it is placed before the rectifier diodes. My guess is that it is not involved in filtering but rather some kind of RF blocking (maybe?). I am obviously missing a term for that because I couldn't find anything online or in literature.

A little context: It is the power supply of an old Tektronix type 453 oscilloscope.


texts: is it safe to have hot wire connected to ground (metal case, shield) via a capacitor?

texts: I have opened a psu, and I saw a small capacitor is connected between one of the ac inputs and to the ground/shield. We don't have ground in our ac outlet, so a hot 110v ac line could be connected to the metal case via a capacitor, and I don't know if it is safe for me to touch the metal case. Should I removed that capacitor?


texts: What is the End of Train Device RF Path?

texts: A railway end of train (EOT) device is applied to the last car in a train consist.  It communicates in the 450 MHz band with a head of train device in the lead locomotive.  Modern trains can reach upwards of 14,000 feet - almost 3 miles long.  The EOT is mounted on the knuckle of the last car (about 3 feet off of the ground) essentially behind a wall of steel. It has an integrated Omni antenna with 8W RF power.  How does the RF travel to and from the head of the train to the end of the train?


texts: LSE 32.768 kHz oscillator on STM32L433 won't start reliably.

texts:
I'm using a 32.768 kHz crystal FC - 12M on a board with STM32L433 in a LQFP48 package. There are two 10pF C0G load capacitors used.

The problem is that on one of the boards (I have two of this revision) the LSE oscillator won't start until I touch it with a scope probe (10x setting, 10M, 16pF). After that touch with the probe, it stabilizes in a second or two and seems to work correctly until I unplug the board.

I've tried with 4.7pF, 10pF, 12pF and 22pF load caps. (the other board that works has 12pF installed).

I've tried cleaning the board with iso alcohol, thinking flux residue might cause this.

I use short traces and ground underneath the oscillator.

Any ideas?


texts:
Whenever I'm working in labs, I have always disconnected the +V terminal first because I've always been taught powering a chip without a ground is dangerous and likely to blow the chip. I've also experienced that happening so I'm pretty sure it's true.

However, the other day I was messing around in my car and long story short the battery died. I was instructed to disconnect the ground first because if I was disconnecting the +V and accidentally shorted it to a piece of metal the circuit would still be complete and a whole bunch of amperes would flow and perhaps electrocute me.

Now it seems to me that even with the ground terminal disconnected, if I short the +V of a battery to say the chassis of a car with something like a screw driver, won't current still flow?

Are there other reasons for the reverse paradigm? Any other safety considerations I should be aware? Thoughts in general on this situation?


texts:
I have bought an LED mirror that is powered by a battery.
Unfortunately, it didn't work after charging the battery and I tried to see if the cables were joined correctly.
I was too dumb to take a picture before removing the "cable holders" and since I have no knowledge of anything electrical, I have no idea which cable to join.
I made a picture of the cables... can you please tell me which ones I have to join for it to work?

Thanks in advance
Edit:

Battery:
1x Red
1x Black
LED
1x Blue
1x Brown to On/Off Switch
Charger
1x Brown
1x Blue
On/Off Switch
1x Brown to LED
1x Brown


texts:
I need to simulate digital circuits which have custom gates.

For now I am not concerned about the specific CMOS technology, the transistor Length and Width, etc. I only need to glue NMOS and PMOS transistors together and build some primitive digital components, like inverters, AND and OR gates, etc. and simulate circuits built with those basic components. The reason that I can not use the standard library provided in simulator software such as LTSpice and MultiSim is that I need some special latches and gates (like Muller gate) which is not available in standard CMOS 4000 series so I have to build everything from scratch in transistor level.

Can I just randomly pick a technology like: 0.35u CMOS components

Does the technology really matter?

If not, then what CMOS library models do you suggest for general purpose simulation of digital circuits built with MOSFETs? Is the link to colorado.edu 0.35u CMOS models which I mentioned above good enough?


texts:
We are designing a ultra low noise USB 2.0 hub.

I am thinking to add a common mode choke to + and - of the USB connector, in addition to the D+ and D- choke to remove the common mode noise. I am aware that adding a CMC on the D lines will degrade the signal integrity but I am using a signal conditioner afterwards.

My question is: will the additional CMC (on + and -) help with common mode noise reduction and will it interfere with USB signaling ?


texts: Protect small DC motor from too much solar power

texts:
I'm setting up a hobby project where I have a DC motor running from a small solar panel.
I've tested connecting the panel directly too the motor and it works great.
The problem is that in bright light the panel could theoretically generate too much power.
I'm wondering if there is a simple way to clamp the power to some maximum value.
I know you can buy circuits that regulate solar power for charging batteries.
Is there anything similar that is appropriate to use on a motor?
I've read that adding a battery and a charging circuit could solve my problem but since I'm only using the motor during the day I'm curious what other options might exist.
I don't have an exact specification for the motor but it was originally running off 8 AA batteries in series so I think that's around 12V 50mA. The solar panel's maximum output is 15V 100mA. I know I won't get that in practice very often, but if possible I'd still like to have something in place.
The motor doesn't need to spin at a constant rate so if the voltage varies with the amount of sun that's ok as long as it's within a safe operating range.


texts:
Recently my microcontroller does not run any program, I am testing the code below:

#include <mega32.h>
#include <delay.h>
#define xtal 16000000
void main(void)
{
    DDRA=0xFF;
    DDRB=0xFF;
    DDRC=0xFF;
    DDRD=0xFF;

    while (1)
    {
        PORTA=0x00;
        PORTB=0x00;
        PORTC=0x00;
        PORTD=0x00;
        delay_ms(500);
        PORTA=0xFF;
        PORTB=0xFF;
        PORTC=0xFF;
        PORTD=0xFF;
        delay_ms(500);
    }
}

I have tested four different controller, both mega32a and mega16a. The code is compiled by CodeVisionAVR Evaluation and programmed by Atmel Studio 6.1(I have tried PROGISP too). The programmer is an original MK2 and ISP programming.

Fusebits:

low: 0xEF
High: 0xC9

Internal and external clock crystal tested. LED with 220 \$ \Omega \$ resistor connected to a pin.

Another test code:

When I program the code below:

#include <mega32.h>
#include <delay.h>
void main(void)
{
    DDRA=0xFF;
    DDRB=0xFF;
    while (1)
    {
        PORTA=0x00;
        PORTB=0x00;
        delay_ms(500);
        PORTA=0xFF;
        PORTB=0xFF;
        delay_ms(500);
    }
}

All LEDs are off, and when I program the code below:

#include <mega32.h>
#include <delay.h>
void main(void)
{
    DDRA=0xFF;
    DDRB=0xFF;
    while (1)
    {
        PORTA=0xFF;
        PORTB=0xFF;
        delay_ms(500);
        PORTA=0x00;
        PORTB=0x00;
        delay_ms(500);
    }
}

All LEDs are on. What's the problem?
Another test:

#include <mega32.h>
#include <delay.h>
#define xtal 16000000
void main(void)
{
    DDRA=0xFF;
    DDRB=0x01;
    while (1)
    {
       PORTA=0x00;
       PORTB=0x02;
       delay_ms(500);
       PORTA=0xFF;
       PORTB=0x00;
       delay_ms(500);
    }
}

Second pin of port B is on low light and PORTB=0x00; after delay_ms(500); No matter if it is:0x00; or 0xFF;


texts: NPN transistor: collector current flowing to emitter without connecting base?

texts:
I have a circuit where a LED has its cathode connected to the collector of my C8050 (or SS8050) NPN transistor, with the emitter grounded.
Even though the base is left floating, the current is still flowing freely to the emitter.
Applying any current/voltage to the base doesn't change anything.

Here's the circuit:

Is this how it's supposed to work? Why?
What can I do to use this transistor as a switch correctly?

(EDIT: I tried the same circuit setup with two different C8050 transistors, with the same result)


texts: Simple circuit analysis with node potential method

texts:
I can't find the correct solution for this exercise and I can't figure out why.

simulate this circuit – Schematic created using CircuitLab

The question is: What is the current \$I_3\$ ? (answer: -2A).

I want to answer to this question using the node potential method.
I chose the left -> right and top -> down direction for the current in every component. There are 2 nodes A and B so I can write \$(N-1) = 2-1 = 1\$ equation for the KCL. I chose the equation of B which is also the node set to potential 0 (ground).

\$-I_1 +I_4 +I_3 = 0\$

Note that \$I_1\$ is negative because the current in the voltage source is equal to the current in \$R_1\$ but with opposite direction (respectively top-down and left-right). Then I replace the currents in the equation above with the potentials:

\$-{ {B + E_1 - A} \over R_1 } + {{A - B} \over R_4 } + {{A - E_2 - B} \over R_3}\$

By removing B (=0) and by replacing the resistor and voltage values I obtain:

\$ A/5 + A/5 + A/15 = -90/5 + 100/15 \Rightarrow A = -170/7\$

Unfortunately replacing the variables with the values in \${{A - E_2 - B} \over R_3}\$ doesn't give the correct answer. Why is that ? Where is the error ?


texts: 6-Pin Battery Connector to 2 Wire Terminal Connection

texts:
I have a 16V 6-Pin battery. I am trying to get it so that I am going from a 6-pin connection to a 2 wire connection. I have been unable to find any adapter online so I went ahead and cut off the connector and soldered wires to the power and ground. When I hook up the connections to my multimeter it reads 0V. What I suspect to be the case is that there is an enable pin that is deactivated that is preventing voltage from flowing. Am I on the right track?

Any input or advice in tackling this problem would be welcome. Thanks in advance for your time.


texts: Troubleshooting periodic noise in raw data collected from ADC

texts:
We are working on an ADC that has maximum sampling rate of 2.5MSps at clock frequency of 40MHz and Vref of 2.5V. The architecture is SAR and it carries out the calibration internally.
Currently we are running at clock frequency of 32MHz and sampling rate of 1.25MSps.
We are reconstructing the analog waveform using MATLAB from the raw data collected and are observing a periodic noise. We are unable to comprehend the cause of this noise.

The noise is approximately equal in amplitude ~80mV. We have also observed noise on power supply of the FPGA that is collecting the raw data but the frequency of the noise was very low.
We need your help in troubleshooting this noise. Even if you could give us any pointers to look at, that would be greatly appreciated. Please let us know if you need further information regarding the setup of the system.
EDIT: Schematic is attached below. Analog input is given to the "Input circuit". C42 is shown DNP but we have connected a capacitor of 1uF 16V. We are using Analog Discovery 2 as our signal source.
Regards.


texts: Quartus II - State Machine Viewer does't show all arrows/conditions?

texts:
As can be seen in the red circle, only arrows with condition a are shown, there is no !a condition at all. To replicate this problem, use the SystemVerilog code below (01 sequence detector, taken from Digital Design and Computer Architecture, page 212). In Quartus, after Analysis & Synthesis, go to Tools -> Netlist Viewers -> RTL Viewer, then double click on the state machine to view the diagram.
module patternMoore(input  logic clk, reset, a,
                    output logic y);

    typedef enum logic [1:0] {S0, S1, S2} statetype;
    statetype state, nextstate;

    always_ff @(posedge clk, posedge reset)
        if (reset) state <= S0;
        else       state <= nextstate;

    always_comb
        case (state)
            S0: if (a) nextstate = S0;
                else   nextstate = S1;
            S1: if (a) nextstate = S2;
                else   nextstate = S1;
            S2: if (a) nextstate = S0;
                else   nextstate = S1;
            default:   nextstate = S0;
        endcase

    assign y = (state == S2);

endmodule

As a side note, if I change
S2: if (a) nextstate = S0;
    else   nextstate = S1;

to
S2: if (a) nextstate = S1;
    else   nextstate = S0;

I will be able to get arrows implying !a condition in the state machine viewer.

What's on going on? Thanks in advance!


texts: li-ion pack charging with buck boost xl6009

texts:
I'd like some feedback on implementing a CC CV 3s li-ion (laptop) battery pack charger using a 12V supply and a XL6009 switched regulator.

I want to use a current sensing module to sends it's analog output to the feedback pin on the xl6009 thus implementing a Constant Current.

Usually the feedback pin is connected to a node on a voltage divider which adjusts output to make sure the voltage at the node stays at 1.25V but I would break this connection with a zener diode. When voltage at the output gets to around 12.6V the diode allows a reverse current overriding the current sensor and producing voltage regulation.

Here's the generic XL6009 schematic:

And then here's the hacked version:


texts:
I have recently found that we need a security system in our home but am unwilling to pay a company $80/month to monitor and let them run wire all over the house. So I got to thinking that why can I not make my own simple mesh network and run it all off a head unit? (Possibly an old WRT54G router even)

My problem is finding an actual RF product for my needs. Battery life is #1 with size being a close #2 as these will be on windows and doors and can not be bulky.

I saw Synapse's SM200 which is a great size and has a fantastically easy python scripting language to work with but it seems that nobody stocks these things.

I looked down a scale of integration and see that the Synapse modules are based on a ATMEGA128RFA1 These chips bare however are quite pricey and I would still need a PCB and chip antenna.

Another Chip is Microchips rfPIC12F675F. These are much more affordable but are nearly impossible to find a stock of and even worse their is no official C compiler for this core (Not 100% sure, was just the word on some forums)

Ideally I would love to use the Synapse module as I doubt I could make my own board for cheaper but does anybody know where I can get these from? IF that's not going to work then are their any other RF solutions that meet my criteria? Possibly a separate RF IC that I can tie my favorite micro to?

Thanks for helping me out!


texts: How to mount a toroidal transformer in a waterproof plastic case

texts:
I have a toroidal transformer with mains input and 24V output, which I want to mount in an IP65 ABS plastic case. The transformer comes with two rubber and one metal disc for mounting, along with a metal bolt to connect them.

As this project is intended for outdoor use, I do not want to compromise the seal of the case by drilling a bolt hole into it. Is there a recommended solution to secure the transformer in such cases?

On a related note, where should I connect my earth lead? Given that there is no metal case, the only place I can see is the metal disc/bolt for mounting the transformer.

Edit: Here is a schematic of the general arrangement


texts: Whats the simplest heating surface for a DIY project

texts:
I'm trying to make a very small (3x3 cm or less) cup or surface that will heat to around 200C. The surface needs to be dry and I only care about heating the surface and not any particular volume of air around it. Ideally this would be on fairly low voltage (nothing more than a 9V hopefully, or even possibly on a USB connection) so it could be semi-portable.

I don't have a lot experience with heating elements, so I'm not sure of the best way to do this. Is this even a feasible project? If so, are there any out of the box things I can buy that will do this?  Or will I have to resort to something like fixing some nichrome or heating pads to ceramic and doing a lot of testing?

Additionally, are there any recommended ways of controlling the temperature of the surface? I was thinking of making some kind of PID control with a temperature sensor, but I'm sure there's a simpler and safer way.

Thanks for your help!


texts: What kind of components are black blobs on a PCB?

texts:
In low-cost mass-produced items I often run into black blobs of what looks like resin applied directly on top of something on the PCB. What are these things exactly? I suspect this is some kind of custom IC that is layed out directly on the PCB to save on the plastic  housing/connector pins. Is this correct? If so, what is this technique called?

This is a photograph of the inside of a cheap digital multimeter. The black blob is the only non-basic piece of circuitry present, along with an op-amp (top) and a single bipolar junction transistor.


texts:
I'm trying to make airsoft chronograph/chronometer (a device that measures airsoft bullet speed). The idea is to measure time in which bullet is traveling from point A to point B, and then I can calculate bullet speed.
Bullet is shot into plastic pipe with diameter of 32mm. I've tried to put on one side IR LED and on the other side phototransistor (BPW 40), both at the start and end of the tube. Something like this:

Blue circles are phototransistors, red circles are IR LEDs and white circles are airsoft bullets.
When bullet passes through area where bullet 2  is drawn (just in between IR LED and phototransistor), everyting works perfectly. But when the bullet passes where bullets 1 and 3 are drawn, it isn't detected. That is expected, but unwanted behavior.
So my question is: how can I detect bullets regardlessly of it's position ? I've thought about putting IR LEDs and phototransistors around the pipe (not only in one place), like this:

but this solution isn't cheapest: 5 IR LEDs + 5 BPW 40 = cca $12 times 2 (because I need it on both sides of the pipe) = $24. Is there any cheaper solution ? Is BPW 40 good choice for phototransistor ? I don't know which IR LEDs I'm using (and salesman in the store also doesn't know - he told me these are generic ones for remote controllers, like TV or DVD controller).
Diameter of the pipe is 32mm and it will be long about 14cm (sensors will be 10cm apart).
Diameter of airsoft bullet is 6mm.
EDIT:
I'll go for my second idea. I just have one more question:
is it better to arrange IR emitters and photo transistors this way:

or this way:

Thanks !!


texts:
I built a stick welder using two microwave transformers and a DC bridge rectifier. To control the heat, I created a triac current regulator attached to the AC input of the transformers. I have used this specific circuit for a long time with these transformers however I got an overheat blow out of my BTA41-600B triac last time (the triac physically caught fire). I ordered 4 new ones, and  they seem to be instantly failing with the load terminals stuck open. If I allow full current to pass through the triac, it doesnt break, however when I try to regulate the current, it instantly stops regulation and stays shorted. Is there something wrong with my design? And if so, why are these the only triacs being affected?

simulate this circuit – Schematic created using CircuitLab


texts: How to calculate THD using only the first harmonic?

texts: How can I calculate THD using only the first harmonic? How can I implement in C code DFT voltage formula in order to calculate THD?


texts:
I have what I think is a centre tap transformer with 0V and 230V inputs and 0V, 20V, 0V, 20V outputs.

Is connecting the two middle outputs to each other safe and will there then be a difference of 20V AC between the inner and each two outer outputs and also a difference of 40V between the 2 outer outputs?


texts: How can I power a circuit while charging its Li-ion battery pack?

texts: I'm creating a portable device that can be powered by a battery pack, or plugged in and used while charging the battery. At 4:18 in this video (shown below), it shows that the circuit can be powered by the battery charger while it is charging the battery pack through the BMS. I feel like the current draw from the device would interfere with the charger's CC/CV modes and battery state monitoring, causing incorrect battery charging, or insufficient power for the device. Am I missing something, or is the video wrong?


texts:
I constructed a circuit that calculates the absolute value of a signed 4-bit number in two's complement

Then the second question of the exercise was to show the correctness of my circuit using the definitions of two's complement representation [.] and the binary representation (.)! With a possibility to use the lemma rule
$$2^n = 1 + \sum_{i=0}^{n-1} 2^i$$
and the definition ¬x = (1 − x).
How am I supposed to verify this circuit using these 2 rules ?


texts: Analog Telephone Frequency Response Curve

texts:
Old analog telephone circuits using carbon microphones seem to be said to have a frequency response of, from various low frequencies which differing reports put at between 275 Hz and 400 Hz, up to various high frequencies, reportedly between 3 and 3.4 kHz, with possibly a peak a around 1 kHz, depending on the manufacturing decade of the carbon mic, and otherwise not that flat.

Does anyone have a reference for some actual audio frequency response curves, including the shape of the peak(s) if any, and the steepness of the high and low frequency roll-offs, for these old analog (POTS) telephone circuits?


texts:
I'm working on a project for automotive environment in which I need to read signals from the power mirrors switch in a microcontroller. The power mirrors switch controls the mirror's moving directions by connecting VCC (12v) and GND to some wire while leaving the others opened. As I need the microcontroller to know which mirror is moving and what is the direction, it needs a circuit to convert the signals from the power mirrors switch (12V, GND or high impedance) to two logic level signals (5V), for example, one to indicate VCC, another to indicate GND and if both are off it means high impedance. In other words, the circuit needs to be able to detect high impedance or tri state. I have stupidly thought of the following circuit using optocouplers:

It seemed fine, because if the input was high, the output of O1 would be gnd, activating the VCC sinal in the microcontoller (pull-up resistors turned on in the microncontroller inputs); if the input was low, O2's output would be on and it would activate the GND input in the microcontroller; and if the input was opened, none of the optocouplers would be activated and the microcontroller would know the signal is high impedance. It seemed fine until I found out in practice it was a silly idea: what happens is both optocouplers stay on when the input is opened or high, because current flows from O2 12V to O1 GND, keeping both LEDs turned on.

I wonder if someone knows a circuit that can do this job, with the smallest possible number of components, considering I don't have much space for implemanting it.

Thanks in advance for any help!

UPDATE

As said by @brhans in the comments, this circuit works for detecting tri state, just not the way I thought at first. When the input is opened, both optocouplers activate; when the input is VCC, O2 turns off while O1 keeps activated; and when the input is GND the opposite happens, O2 keeps activated while O1 turns off. So all I had to do was adapt my microcontroller logic for this situation.

Thanks @brhans for the hint and also thanks to all who sent other circuits suggestions!


texts: Temperature-Dependent Electrical resistance Si and SiC

texts: In a power electronics device, it seems that silicon carbide (SiC) has a higher variation of electrical on-state resistance with temperature in comparison to silicon (Si). Does anybody know the reason? I googled it, but I did find nothing in this case.


texts: I'm an electrical engineering student in college and am very confused about some things in electronics. I have a pretty good idea of how basic electronics components work but im have trouble with knowing how to choose a component for a particular application. For instance if I am to use a diode, capacitor, or transistor how do I choose which one to use? Is it a mathematical thing like ohms law using specifications and reference sheets to calculate the one you need or is it something more complex?


texts: How to drop 28VDC for Voltage regulation between 14VDC and 16VDC

texts:
I want to convert 28VDC to run a LED map light that turns on at 14VDC and reaches its safe brightness at 16V (30mA). I used a 1k ohm potentiometer and a 1kohm resistor and dropped the voltage to where the potentiometer shows the max voltage of 16V.

Now the issue is, that the potentiometer rotates to about half the distance (0V to 14V) and then powers up the LED from 14V to 16V safely.

How do I modify the circuit such that I get the potentiometer to power the LED from range 14V to 16V and not have a dead zone as it is in the current setup?

EDIT: Thank you for the answers. I was able to run the LED safely using the circuit shown. But when I replace the 1k potentiometer with RHS1K0E, the circuit does not function in the same manner. The potentiometer stays off for half of its range, and then the voltage shoots up steeply and blows up the LED strip.
Look at the pictures for details of the circuit that works.
I do not have the detailed specs of the potentiometer in this circuit, but I have to replace it with the RHS1K0E for fitment purposes, that's all.


texts: Do high-temperature rated coin cells exist?

texts:
I'm currently working on a project that will implement a coin cell as its primary power source. My PCB will likely be exposed to high temperatures ranging from 100C upwards. Now I realize that I will likely need a proper enclosure along with other cooling capabilities, however, I would still like to select the highest temperature rated coin cell possible.

So I'm curious if anyone is aware of coin cells that possess high temperature ratings. Also, what would determine whether or not a coin cell possesses high temperature rating? Would it primarily be based upon battery type (alkaline, lithium, etc.), or would it depend primarily on how the battery was manufactured?

Thanks!


texts: How LC oscillators work with a continous DC power supply

texts:
I am having serious trouble understanding oscillators. I read a lot of articles and books
but no one explained it simply and intuitively.

From what I know, LC circuits oscillate for a small amount of time if the battery is disconnected from them, so how could they oscillate with a continuous power supply as I find it in oscillators like Hartley oscillator, where the battery is connected directly to the LC part ,

I find it very unintuitive and hard to understand. I wish it could be explained, using a flow of water analogy or something like that, how could a continuous DC at the input become a continuous AC at the output.


texts: Switching input BNC signal to two output BNC signals using BJTs?

texts:
simulate this circuit – Schematic created using CircuitLab

Hi everyone, I recently completed the construction of a spectrometer that studies electron transfer events in inorganic molecules. I am trying to further improve my design however, mainly one major flaw.

I'd like to control where the output of my photomultiplier (PMT) tube is going using a set of BJT transistors as we currently have to manually plug the BNC into the appropriate device. Given the complexity of the setup, it's not feasible to expect workers in the future to be able to do this.

I am somewhat unsure as to how BNC/coax cables operate and would like to ensure that my circuit will work before I invest the effort into building the switch box.

The TTL logic to each gate is to come from an NI USB 6008 IO box.


texts:
We are attempting to electronically determine which of 10 cards, numbered 1-10, is currently in front of a stack.  Initially card 1 is in front.  Eventually card 1 will be flipped around to the back of the stack, and card 2 will then be in the front.  Then card 2 will be flipped around to the back of the stack and card 3 will be in front.  This process repeats for all cards labeled 1-10.

These cards will be viewed by people so we are looking for a solution which won't require a device positioned in front of the cards (such as a barcode scanner).  These cards will also be outdoors making any type of IR sensor not possible.

Does anyone have any ideas on how we can detect which card is in front?

See an example image:

(source)


texts: Troubleshooting a round fluorescent bulb with 4 pins in a square formation?

texts:
I purchased a new magnifying desk lamp.  It uses a round fluorescent bulb.  I plugged it in, turned it on, and it doesn't light up.  No buzzing, no lighting, nothing.  So, how do I go about testing it to determine if the bulb is bad, or if the fixture is bad?

I don't want to go buy another bulb.  I just want to test the existing bulb and fixture.

The connectors on the bulb are in a square formation.  Is there a way to test it with an ohm meter?  I've scoured the internet for an answer to this and seems like a bunch of folks just guessing at answers.  Does anybody here actually know the right answer here?  Please don't respond if you're guessing, just if you really know.

Can I test output voltage on the socket/fixture to see if it's working properly?  What should the voltage be across the 4 receptors?  How to I test them?

Thanks


texts: I've been looking for a comparator IC for a circuit I'm trying to build and I'm a little confused with what I've found. I've looked at some parts labeled as comparators but it looks like the parts are just Op-Amps with different ratings. I'm aware that comaprators can be built using Op-Amps, however, I assumed that any extra design that was needed, such as preventing hysterisis in the circuit, would be built into the IC. From what I've seen from the data sheets, however, it looks like they're just plain old op amps. So my question is, are comparator ICs just Op-Amps, or do they have the extra circuitry I'm thinking of? In other words, will I be able to just plug in the two voltages I want to compare or will I have to add some parts around the IC first? It might seem like a silly question but I'm new to PCB design and I wanted to make absolutely sure before I purchased my part. For reference, I've looked at TLV1702-Q1 and LMV7275-Q1 among other parts on TI's website, both of which came up when I searched for comparators.


texts:
I'm driving 6 serial-5 branch LED strips with PWM driver. Each branch has 90R resistance. OSRAM GW JCLPS2.EM 6500K LEDs are used in the strips.

simulate this circuit – Schematic created using CircuitLab
My input voltage is 28VDC and on this voltage level, the duty cycle of my pwm driver is 30%. My switching frequency is  about 800Hz.

simulate this circuit
My principal schematic is shown below.

When I measured one LED's forward voltage(Vf) on one strip with osciloscope, I saw the signal shown below.

---Why I saw about 960mV Vf at off time of PWM?
So, my output of the PWM driver signal at full load (50 pcs. LED strips) is:

I saw that there was 8.25V when the off time of PWM signal.
Finally, I connected a 4 ohm full resistive load (rheostat) to the end of my PWM driver output.
The signal was become as follows.

Why the signal I measured is different at LED strips load and resistive load?
Thanks for your answers in advance.


texts: 3.3v ESP8266 MCU controlling 220v 20A suggestion?

texts:
I´m building an esp8266 + ds18b20 (3.3v) thermostat for my daughter´s room.
Basically I need to switch an electric heater rated at 2500W, 220v AC.

Should I use a TRIAC? SSR are expensive, but if that is the best option, I´ll go ahead with it. Should I use a "heat sink"? How do I size it?

How could this be accomplished without using a "noisy" coild-based relay?  Any schematics, ideas, etc. to point me in the right direction would be very useful. (The clicking noise on big relays can maybe be an issue while my daughter is sleeping).

Many questions, sorry!
Appreciate your help..

Cheers!


texts: Optimizing Resistor Values for Comparator Reference

texts:
Curious if there is a general rule for optimizing total resistance values in a voltage divider reference in a comparator circuit. Guessing it ultimately comes down to whether maximizing accuracy or minimizing power is a bigger concern.
For instance, the LMV331 (http://www.digikey.com/product-detail/en/stmicroelectronics/LMV331ICT/497-10355-2-ND/2217242) gives a max input bias current of 400 nA:

Assume VDD = 5 V, my process would be to take Ibias*100 = 40 uA. 5 V / 40 uA = 125 kΩ (total resistance). Then set up R1 + R2 as needed to get the desired voltage reference. This would give ~1% accuracy at a power consumption of 5 * 5 / 125k = 0.2 mW.
So, if we wanted to compare against a 1V reference, the resulting circuit would look like:

simulate this circuit – Schematic created using CircuitLab
Is this a good overall approach?
Edit: changed reference to 1V per Tony's correction.


texts: Analogue current and voltage regulation and rectification thereafter

texts:
I am a research scholar working on mechanical metallurgy as a part of my engineering study.
For my project (a new kind of electroplating,) I need voltage ranging from minimum 0V to maximum 170V DC. We need a minimum of 130V to trigger the reaction and 150V to effectively carry out the reaction.
I am currently achieving the voltage regulation using a 3 phase auto transformer-bridge rectifier-capacitor setup. To avoid short circuits, I have installed a 32A MCB on the primary and 15A fuse on the filtered DC side.
As my solution heats up, the resistance drops, and current draw increases preventing me from achieving the desired result. Is there a way to regulate or set or limit current to a certain value. For example, 15A DC or 32A DC. while still maintaining the same voltage.
My lab has wiring to handle 45A per phase continuous load, I have access to a 3-phase auto-transformer with 36A/phase capacity corresponding rectifier-filter setup. I do not want to add variable resistor or incandescent lamp in series as it would waste power and reduce the voltage.
Please suggest a suitable way to limit the current and meet my requirements.


texts: Can I use a DC SSR that is switched by a PID controller to control the speed of a 12 V DC fan?

texts:
This is my first post here. Let me start by saying that I do not have an engineering background. I tinker with electronics in my spare time (Arduino, solid state low-power guitar amps, etc.), but I do not have a classical engineering education. Please forgive (and feel free to correct) any incorrect terminology that I use.

I would like to use a PID controller (CD101) that will switch a DC SSR that controls the speed of a 12 V low-power DC fan. The desired application is controlling the amount of air that enters into a BBQ smoker grill. I want the PID to hold the temperature inside the grill at a constant level.

I've done a lot of google-research, and I haven't found a lot of people who have taken this approach with motor control. I'm all for learning lessons the hard way, but I wanted to see if anyone in this forum thinks this is a simple approach, or if there are glaring issues with this idea.


texts: Time Warp - Controling an analog clock from another room

texts:
My goal is to be able to spin an analog clocks hands forwards and backwards through a controller box that I build and wire to an analog clock.

To accomplish this I imaging that I need a small hobby motor that will work in forwards or reverse mounted to the adjustment wheel of the analog clock.

I suppose that I then wire the motor with about 75 ft of electrical wire that will run into the plenum ceiling , through a wall, and into my controller box.

Id like to control it with a potentiometer knob.

I would also like an off switch on my controller box.

I would like my controller box to plug into a regular wall outlet for power (v/s batteries)

The challenges Im having are that Im not an electrical engineer! I know I need to match the power of the Potentiometer and the motor, and I don't know what I need to wire the power into my box either...


texts: How could I design circuit to make filter?

texts:
In most books, it just has an image and said "this is bandpass filter" and that's all. Sometimes they explain why this is bandpass filter with graph or something.

However, what I really want to know is how to think those kind of design with value of
components like \$C = 220\text{nF}\$, \$R = 100\text{k}\Omega\$, etc. How to set those specific values to each component?

Below is an example of my thinking how to design bandpass filter. Is it correct?


texts: Motor in a parallel circuit slowing down, how can I speed it up?

texts:
I have a simple circuit, with 5x 3v/20ma LED's in parallel (each with a 330 resister in front of them) and a dc motor (rated 6v to 24v) also in parallel, all running off a 9v battery.

The problem is the motor is slowing down thanks to the LED's. I would have thought that with having everything being in parallel the motor would not be slowing down, but it is.

What is happening here? Why is it slowing down? Is it to do with the voltage, or the current (amps)?

Can I speed the motor up using a transistor, or is there something else I can use to speed it up?

Thank you!


texts: How to measure propagation velocity through a trace on a pcb?

texts: With a pcb in hand, how to measure the propagation velocity of a path from point A to point B, with accuracy in the picoseconds range?


texts:
After installing a grid tie inverter (GTI,) the power factor dropped from 1 to .85 over the last week.  My loads are a combination of inductive and resistive.

I have an option of setting my GTI to feed .8 lag or .8 lead.

Which one should I use?

The default setting is unity.

I understand why the drop but what can I do about it?

My utility mandates a PF of .9 at least


texts: I got 2 inputs, both form 0-5V how can i see if they diverge form one another by more than 10 percent?. And if so my output must be a 0V. How can i do such thing?


texts: How to implement constant current LED driver for WS2811?

texts:
I want to use WS2811 to drive high current LEDs. As it is mentioned in the datasheet this chip provides 3 channels with 18.5mA constant current sinks. Maybe what I need is a simple PNP BJT with constant amplification factor of 18 (18.5*18=333mA for 1W LED) like the circuit below

simulate this circuit – Schematic created using CircuitLab

But I know there is no such BJT with fixed beta. Is there any simple circuit that can do just that?
(I'm just a hobbyist, excuse me for any mistakes)


texts: Why my circuit only draws max. of 2.8V across the electromagnet? (Circuit picture included)

texts: I created a circuit using Arduino Uno and the goal is to use pulse width modulation (PWM) so the voltage across the electromagnet decreases from maximum value to zero, and then the cycle repeats. The PWM already worked, but the maximum voltage the magnet draws is only around 2.8V. I used an external 12V DC power supply. How should I modify the circuit so I can reach voltage across the magnet close to the power supply's value, 12V? Thank you in advance for your help.


texts: required wattage of chip resistors in audio opamp circuit?

texts:
I have the following DAC output stage in a design I'm working on, which takes the differential outputs of a DAC to create an unbalanced audio signal, 5.7Vpp.

For the R and C I would like to use 0402 chip capacitors and resistors. How do I figure out the required watts for the resistors and if the standard 1/16 watt  power rating will be adequate?

The differential inputs to the stage are 2.8Vpp signals centered around 5V.

I'm not an everyday user of opamps, but have used TINA-TI by texas instruments to simulate the stage to make sure it works (i.e. that it has the current gain and frequency response).

The circuit is powered by +14/-14V rails and I did put an amp meter in the simulation software on the rails, which gave me 4mA both for each of the rails, but that doesn't tell me everything?

I also have a second (similar) version of the below circuit in which I want to use the opa1622 headphone amplifier opamp to drive headphones, and there this question will be even more important since that opamp is capable of outputting a lot more power than the ne5532.


texts:
I think I understand more or less how an ordinary semiconductor diode works: Crystal doped differently in different regions, carrier depletion where they meet, bla bla bla.

However, actual diodes that one builds circuits with do not end with bits of n-doped and p-doped silicon. They're little ceramic/plastic packages with metal leads coming out of the ends. Somehow the current needs to pass between those metal leads and the semiconductor inside.

And there's a problem. If I understand things correctly, a metal ought to be the ultimate n-carrier material -- every atom in the lattice contributes at least one electron to a conduction band. When we stick a metal lead onto the p-doped end of the semiconductor, we ought to get another pn-junction, one that goes in the wrong direction for forward current to flow.

How come the entire component can conduct in the forward direction anyway?

Is it just a matter of making the area of the silicon-metal interface so big that the total reverse leakage current of the p/metal junction is greater than the forward current we want the entire diode to carry? (I'm imagining large volumes of finely interdigitated metal and silicon for multi-ampere rectifiers). Or is there something else going on?


texts: Preventing Interference when using RF transmitters and receivers

texts: I want to use a "listen-before-talk" approach to transmit data from sensors connected to a transmitter and receiver pair to a MCU connected to a transmitter and receiver, which means that the sensor will only transmit data once it has been asked to do so by the MCU, but the problem I'm having is that my receivers will have no way of knowing if the information it's receiving is from one of my transmitters or from some other 433 transmitter in the area.The receiver I want to use has a product description here which seems to suggest there may be a method of pairing up my transmitters and receivers but how? If I transmit transmitter ID information e.g if the transmitter is transmitting 4 bits, I make the first two bits always "11" so the receiver knows that the information is from one of the transmitters it should listen to would I then be able to filter data I don't want on the AVR?


texts: Design approach for a servo and LDO for rest of the circuitry

texts:
I have 3 D cell alkaline batteries in series. They are rated at 20Ah.
https://uk.rs-online.com/web/p/d-batteries/9145058/
The circuit spend most of its time in deep sleep only consuming 8 uA of current. Whilst active, it has the following current demands:

Between 40mA to 60mA for RF module.
Roughly 50mA for the MCU and other sensors.
Between 300mA to possibly upto 1A for servo, which only drives the load from 0-180 for 10 times during 24h.

In case you guys wondering why use such heavy duty batteries, the aim of the product is to last 3 -5 years on batteries.
In my design what I have done so far is, I have used a 250mA LDO to power the MCU and other circuit whilst I supplied the servo power directly from the battery, whilst servo PWM control is coming from the MCU.
https://uk.rs-online.com/web/p/low-dropout-voltage-regulators/6694897/
My servo circuit is shown. I have 100uF to account for peak current surges. My servo is SG90 https://www.rapidonline.com/rvfm-tower-pro-sg90-mini-servo-37-1330.
Now my circuit works fine for most of the time, but sometimes servo fails to operate the load. I have a couple of choices here.

I could increase the capacitor from 100uF to possibly 1F cap.
Use a boost for the voltage supply for the servo because I am mindful the 3 x 1.5V alkaline batteries in series are 4.5V. Boosting the servo voltage to 6V might be good way forward.


texts: Output of Brushless ESC for controlling Brushless Motor

texts:
Suppose, I have 40A ESC and Brushless Motor with max current capacity of 30A. I am using Receiver for controlling Motor speed and Arduino as controller. Receiver sends 1ms to 2ms pulse every 20ms. Same way Arduino sends 1ms to 2ms pulse every 20ms where at 1ms pulse ESC will not spin motor(Stops) and at 2ms pulse ESC will spin motor at top speed.

But as mentioned ESC is of 40A and motor is of 30A then at 2ms pulse ESC might sending pulse to Motor of the range of 40A (I doubt) then it should damage motor? Or, is ESC smart enough to figure out max current capacity of Motor(30A and calibrate itself accordingly and sends pulse signal of 30A capacity at 2ms pulse)?

If not then how to decide the width of pulse sent from Arduino to ESC for max current capacity of Motor?

Thanks in Advance.


texts:
I used power transistor to drive high power LED (used in streetlights)

I added resistor between the Transistor Collector and the LED to verify which part of the transistor causing too much heat, and found out that it is really on the collector part.

Originally, the LED is powered up by 42 DC Volts so I wanted to keep that source level.

I added Photoresistor to turn ON/OFF the LED

The problem is that the transistor heat much.

I also wanted to keep the luminous/power dissipated by the LED as much as possible.

UPDATE: I don't know the specs of the LED but I know the original power source of it: 24V - 40V; 0.45A - 0.8A; Maximum 42V


texts: What happens to a normal transformer when the frequency is increased and the sine wave is changed to rectangle?

texts: What happens if I grab a 220 sine wave 60 Hz transformer with an output of 12v if i feed it with a 220v square wave? And what happens if I increase the frequency? Like 100 Hz? And if I grab the secondary and set it to 220v I know that it will burn out the transformer, but if I put a resistor high enough to limit the current in the secondary it will burn out too? Or will I get high voltage in the primary?


texts: What is the simplest instruction set that has a C++/C compiler to write an emulator for?

texts:
I'm looking into writing a little software emulator that emulates/runs instructions.

The easiest would be to invent my own instruction set, but I thought it would be more fun if I write an emulator for an instruction set that already has a C++/C compiler.

What is the easiest instruction set/architecture that has a (hopefully stable) C++ and/or C compiler?

By easiest, I mean the least number of instructions.


texts: Design of Single input DC - Mutliple ouput DC circuit

texts:
I am trying to build a circuit to drive different loads with different ratings. The block diagram below outlines what I am intending to do. Briefly,

Block A: a circuit splitting power into +/-15V DC to supply op-amps.
Block B: a circuit the supplies 1A DC to a 3ohms load.
Block C: a circuit supplying 9V DC to a micro-controller

For the input supply, I am thinking about an adapter: 120VAC in, 48VDC, 1.5A out. Current rating could be different, e.g. 2A.

Any hints on what might be the best implementation of each block, is greatly appreciated. I do not think a voltage divider is a good one for blocks B and C.


texts: Safely Charging a 5V Power Bank with a 6V Solar Panel

texts:
I am essentially trying to mimick the Voltaic power banks that are designed to be used with 6V solar panels, but cannot seem to find decent spec sheets on most other brands of power banks like this one from amazon. I would love to use Voltaic's, however they are too large for my use case.

What are industry standards for max DC input into the power bank? Is 6V safe? Or should I design a quick drop-out circuit to regulate to 5V input into a normal power bank?


texts: Nesting entities in VHDL (Altera Quartus)

texts:
I want to ask a question. I'm trying to simulate a cpu. I did my schema and basically there are two logical parts of the CPU.

The first part is composed of a FIFO buffer, Cache memory for instructions and a PC register.

I created architecture and entities for each of the 3 named elements.

Can I make one entity that contains all of these 3 entities and their architectures? I'm stubmbled on how to do that, and I would appreciate any help you can provide ;)

EDIT:
I found this tutorial
http://vhdlguru.blogspot.com/2010/03/entity-instantiation-easy-way-of-port.html

It's rather useful, but I'm interested, if I have entities ab, ac, ad and one top entity in which I want to instate those entities.

If I want to map ports of entity ab to ad entity ports, how should the code look like:

HA1 : entity work.ad port map(
    out2 => InstCacheIn1,
    out2 => InstCacheIn2,
    sum => s1,
    carry => c1
);

How to explicitly tell that out1, out2 are ports of entity ab, and I want to map them to ports InstCacheIn1 and InstCacheIn2 of entity ad?


texts: second order low pass filter simulation and configuration

texts:
Can someone explain what the sets of resistors and capacitors do?
im a student in my second year in EE
we were asked to simulate this circuit for various sinusoidal frequency inputs and record the amplitudes and i have done it and as i increase the frequency the amplitude of the output voltage wave decreases yet i still dont understand why theres a third opamp if the measurment is taken from the output of the second and what does each set of resistors and capacitors do individually i know that a capacitor and resistor in parallel will have a Zeq=R/1+rsc in laplace domain but how does this affect the cutoff frequency in this circuit


texts: Capacitors burning through in PSU (AC-DC) of 3W LED

texts:
Basically my problem is probably simple, but I could not find anything searching google and here - maybe I was looking for the wrong things, but here is the problem:

I work in a Hostel and we bought five 3W LEDs with each having their own PSU. (see Photo 1) After installing them just three weeks ago, one of the LEDs stopped working and we didn't think much of it and my boss replaced it incl. the PSU (because they come hooked up to each other and he didn't know that they are easily disconnected). Then the next another one stopped working today, not even 4 days later so I decided to take a closer look at it. Took it all out, connected a new LED to the old PSU and it didn't work. Must be the PSU, opened that up and it was all burnt and black on the inside, quite obviously at the capacitor. So now I am wondering what can cause this? Kinda important to know as there are 5 of those in a wooden wall in a wooden building and the last thing I would like to do is burn in this place :)

The input of the PSU is (supposedly) rated at 100V - 265V (Photo 2)

Thanks in advance!

Misha

Photo 1:

Photo 2:


texts: Will charging 2 capacitors seperatly still result in a lower value?

texts: I have 2 150F 2.7V SuperCaps. I know if I put them in series, and charge them, I will get a result of only 75 farads. I am wondering if I charge them each separately to full capacity before putting them in series, I will get 150 farads at 5.4 volts out of it.


texts: Will the B constant for 10k ohm NTC thermistors be the same from all vendors?

texts:
I recently purchased a 10k ohm NTC thermistor from a local electronics store for which I couldn't  find a datasheet. By going through the post How to measure temperature using a NTC thermistor I understand how to calculate the resistance. My questions are:

Can I use B constant for my 10k ohm NTC thermistor as 4050 or is there any other way  to calculate the B constant?
Will the B constant vary between different vendors?


texts:
Can someone explain which address will be used for ADV7511 for I2C if it is stated that it is either 0x72 or 0x7a in adv 7511programming guide [page 16]?

If I am right, we send 8 bits per transfer, so if R\W bit is LSB, we need to shift that address left for 1 bit for 7 bit address to fit to that byte? So it should be 0xE4 or 0xF4?


texts:
I have a Logitech Steering wheel which I would like to interface to an Arduino whilst using it on a Playstation. My aim in the have the inputs from the gas and brake pedals light up a bar graph to give me a visual reference.

I figured the easiest way to do this would be to take two leads from the potentiometer in the steering wheel and plug one into analog input and the other into ground. When I measure the voltage from the leads using a multi meter I get 0.40v without the brake pressed and 2.70v with it pressed.

When I plug into the Arduino I get 4.4v regardless of the position of the brake.

Any ideas where I am going wrong?

I have two wires coming out of the steering wheel (from the potentiometer) which I then put the positive end in an analog input and the other into ground on the Arduino.


texts: DC-DC converter inductor current DC component

texts: How does the dc-dc converter (e.g. basic buck topology) ensure that for different load currents (considering CCM mode only), the DC component of the current through the inductor is auto-increased/decreased (auto-adjusted), while the "triangle" $$\int u dt$$ part remains unchanged for fixed output voltage?


texts: How do digital watches use so little power (and how do I do that?)

texts:
The title of the question is pretty self-explanatory.

I did a quick back-of-the-envelope calculation for my own digital calculator watch (the Casio CA-53W for those who are interested). The battery is supposed to last around 5 years on the 90 mAh coin cell inside. This means that the watch must be using $$0.090\ \mathrm{Ah}\  /\  (5\ \mathrm{years} * 365\mathrm{\frac{days}{year}} * 24\mathrm{\frac{hours}{day}}) = 2.055\times10^{-6} $$ or just over 2 µA!!!

Now, I know that with enough tweaking, the ubiquitous ATMega328p can use as little as 1 µA, and there are specialized microcontrollers out there that use even less, say in the tens of nanoamps...

...but what about the display? My watch shows the time on a 7-segment lcd, and the display is never off. Where on Earth can I find a display that only uses something on the order of 1 or 2 µA??

(Incidentally, I'm just trying to make own simple Reverse Polish calculator watch, kind of like the µwatch project at calcwatch.com, but with a focus on long battery life.)

Would I need to buy an fpga, fuse my own logic circuit onto it, and somehow hack the display out of an old watch to get these kinds of results? Is there an easier way?


texts:
Sorry if the question seems stupid, im not much into electornics just trying to get into it...
I'm trying to figure out the purpose of current mirror, I read everywhere that it copies reference current to another node but why we're doing it? why can't we just use that current source without connecting them to N-channel transistors? also why 2 transistors are used?


texts: Is input current of a gate driver auto-regulated?

texts:
I have tried googling, but almost everything I can find on gate drivers discusses only the maximum current parameters.

I'm looking at a gate driver for a university project. The gate driver uses 3.3V logic, and on the datasheet lists the maximum 'Input Logic Current High" at 1uA.

I was planning on using a Raspberry Pi 3b, but the gpio pins can only be programmed to output 2mA-16mA. As it stands, is the Pi not compatible at all with this gate driver?

Part Number: MD1213 High-Speed Dual Mosfet Driver
Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/20005713B.pdf


texts:
On a 3-wire load cell that has a black , red, and white wire.........
I would think if I ohmed out the resistance between the red and white or red and black or any combination there of, that I would see some kind of change in resistance when putting as much as 200 lbs load on the load cell.No change in resistance at all, so how does the load cell develop a voltage drop,even in the milli-volt range if there is no change in resistance as weight is put on the cell?


texts:
I'm implementing a calculator in a microcontroller which is controlled over the serial port. For example, I'd send 1234*5678= and it would reply with 7006652\r\n. I've written the code for this using the C18 compiler.

When I send 123456*789123=, I get the reply 2932688576, which is incorrect. The correct answer would have been 97421969088, but that overflows an unsigned long.

I do not want to increase the overflow limit, but would like to have a way to check if there has been an overflow. In ASM, that would be possible by checking the relevant bit in the STATUS register, however, with C, this bit would be cleared before I could read it, wouldn't it?

The best would be a general solution to see if an overflow has occured.


texts:
I've been working with the ATmega328 microcontroller for some time, with great success, but recently my projects have gone beyond the edge of its capabilities. I thought of switching to ATmega2560 but held that thought and went further.

I've acquired a Raspberry PI board, and it's great but I really don't need a full computer here.

What I need is a development board with plenty of I/O, ADC, and PWM pins, support for multiple UART modules, I2C, SPI and CAN communication, fast enough to mess with video, network, and a community support on the web.

Feel free to give any opinions, my area is home automation aka domotics.


texts:
I just graduated last year with an Electrical Engineering degree. Currently pursuing a Masters's Degree, so I am fairly new to design.

We have several HiPot Testers we use on the manufacturing line. Currently, production workers manually record Pass/Fail. This method is not efficient; however, I have not seen a HiPot that records the Pass/Fail that is reasonably priced.

I was thinking there must be a way to automate this process, so we could view trends in the future. I thought I would ask here for advice.

Is it possible to design a "system" that would record the Voltage and Current applied during the test, then maybe a button that a production worker would press if it was a pass or fail? I would not want to tamper with the calibrated equipment. I have reached out to the manufacturer of the HiPot tester, but I have not heard back.

Maybe someone has run into this issue before and has a method I should look into.

Thanks!


texts: Input circuit to handle both single ended and differential motor encoders

texts:
I'm working on a motor controller design that I would like to be as flexible as possible without driving up my BOM cost and board area more than necessary. To that end, I would like to use a single input circuit and connector to handle both single-ended and differential encoders. I'm operating under the assumption from my own experience that most encoders run on a 5V supply (is this a bad assumption?).

I've come up with a couple of options so far but I'm not sure which is better or if I'm missing something else entirely.

Use a single-ended logic buffer such as a 74LVC07A. When a differential encoder is used, only connect the positive lines. My concern here is that I'm not sure of what the voltage of a single line is relative to ground. Does a 5V differential encoder typically output 0V and 5V, or is it more like +/-2.5V?
Use a RS-422/485 differential line receiver. When a single-ended encoder is used, ground the negative input. I'm not sure how complex the grounding configuration would need to be here. Is there a pulldown resistor configuration that won't interfere with a differential encoder? If not, I would probably need to use a FET to selectively pull the line low.


texts:
I have a set of 4 rovers crawling on the ground, each of them equipped with a standard GPS positioning system. The rovers start together from a known position. Each rover is locating itself via GPS.

I command the rovers to move 1 meter straight, with a control loop on the GPS positioning. GPS absolute accuracy is larger than 1 meter but how do they behave relative to each other?

Atmospheric conditions can influence the absolute accuracy but the 4 rovers are very close to each other (let's say in a range of 10 or 20 meters). Shouldn't all the GPSs on board be influenced in the same way?

If that is true, the relative positioning should be kept and after crawling for 1 meter forward, the relative position of each rover should be the same. Is that correct?


texts: Connect microphone with pre-amp to STM32 ADC

texts:
I need to record audio with STM32. I've got electret microphone and pre-amp based on MAX9812.

This is a schematic from datasheet:

How I can connect this pre-amp to the ADC? If I just connect it as-is I will get only positive half of wave, so I need some shift +Vcc/2. How can I do this? Maybe I can just remove output capacicator? Also, STM32 has differential ADC. Maybe I can use it here?


texts: How to run a 8-12V AC old-school doorbell with a 12V DC source?

texts:
I found a fat AC doorbell lying in my garage taking dust, and I want to use it as an additional acoustic signal for my DIY home alarm. As per printed specs on its downside it accepts 8-12V AC, and sure enough inside there's the very simple solenoid magnet pulling a small plunger against the outside metal cup.

I know I could just use a simple AC transformer, bypassing the internal full bridge rectifier to get a low-voltage AC output, but my requirement is avoiding the AC mains completely, and only using the 12V line which already powers all my burglar alarm hardware.

I was surprised there isn't, from the usual low-cost suppliers, a simple dc-ac inverter that won't raise the output to 220V, they are all 12V DC - 220V AC inverters with at least 100W output, that are bulky, overloaded and especially expensive for what I need.

I thought I could use a 50Hz oscillator based on a NE555 chip (2$ shipped or something like that), but they can withstand a max of 200mA output current and I'm not sure it's enough for my doorbell. I could have the oscillator control a relay to give power to the doorbell, but I'm not sure it would output a nice "electric bell" effect, and that's also too convoluted for me.

Can you suggest an extremely simple, extremely cheap way to feed something that resembles "8-12V AC" to the doorbell by using 12V DC as source?


texts: Strange powering of the TL710 comparator

texts: I have an old schematics of 80th fancy synthesizer VCO. It uses the TL710 comparator, that according to the datasheet has -7V Negative Supply Voltage. I cant find the  emitter-base breakdown voltage of EN5179. For me, it looks like it is used as a Zener diode. The EN5179 is almost impossible to find. So the question is: may I use 7.1 or 6.8 Zener for negative supply of the comparator? Or there is a trick that I don't see?


texts: Where is the benefit in SQI parallel interface over SPI? Parallel vs. serial

texts:
Microchip is offering a number of serial SRAM chips with a communication protocol called SQI which is similar to SPI but with 4 parallel bits written at each CLK toggle.

If you can spend the extra 3 pins this makes sense. You can achieve a throughput of 4 times the rate of SPI.

However there is a catch - SPI is supported by all modern MCUs as a hardware module so it runs automatically and very quickly and CLK rates of several MHz are not a problem.

SQI is not supported by hardware so you have to bit bang the protocol. If my MCU, for example, runs on an 8MHz system clock and it is executing most instructions in a single cycle (AVR) I can expect SQI CLK rate of under 1MHz. This is based upon software SPI implementation which is also sub 1MHz and has slightly less code in it.

So let's say I can transfer 4 bits at a time, using SQI, with 800 KHz CLK (real world numbers), that is 3.2 Mbits per second.
However I can run SPI at 5MHz and get 5Mbits of data with less code and without having to wait with my application code while data is being sent or received over the communication lines.

So what is the point here? What am I missing?


texts: Problem with Wien's Bridge basic working and simulation in multisim

texts:
I am very new to the concept of Wien's bridge and am trying to make a basic circuit of it  but didnt get the expected output (noise only).Tried to simulate on Multisim but got the same output.I have gone through many documents on the web but they are either too technical or incomplete.

Here is my circuit:

I believe since both my attempts gave me the same output I must be doing some mistake. Also I have problems understanding the concept of gain, why it should be slightly greater than 3 and the requirement of initial noise for the circuit to work.

Can someone please help me out.Any help is greatly appreciated.Thanks

EDIT:

SOLUTION

I made a couple of changes in the circuit and it was working well enough.

First of all, I changed the OPAMP from "AJ741JN" to "741". Second I added an extra R5 (22k) resistance to the circuit and changed the connection from pin 2 (see new figure).

After making these changes the circuit starts to produce a signal of 50 Hz frequency but the wave form is a distorted sine wave. Adding a couple of "1N4007G" diodes as shown eliminates this problem as well (dont know how).


texts: specs for LED driver to power 18 x XML T6

texts: I'm building a flashlight comprised of 18 x XML-T6 LEDs. The battery bank can be configured as 2 or 4 x 26650 batteries 7.4 or 14.8 volts input. What kind of driver could power these 18 x T6 in terms of output voltage and amps? I tried two drivers HX-1175b which is DC3V-18V 7A LED Driver for CREE SST-90 and 1-Mode 3V-18V Flashlight Driver Circuit Board Cree XM-L T6 XM-L2 U2 U3 and nether appear to work. BUT when I connect 12V DC straight, the leds flicker.


texts: Powering a low voltage device from a two wire light circuit

texts:
I am about to embark on a home automation project, but I'm having trouble finding Wifi based IoT devices which can be powered from a standard two wire light circuit.

The idea is to replace light switches in each room with smart switches, powered from the light circuit, which also do things like monitor temperature, movement or anything else I can hook up to an Arduino. I could power the low voltage side with batteries, but I don't want the hassle of having to keep replacing them.

Most devices on the market designed to go behind a light switch, such as remotely operated light switches/dimmers expect a three wire lighting circuit (live, neutral and load) at the switch. In the U.K. our circuits are almost exclusively two-wire, i.e. only the live and load wire come two the switch, while only the neutral and load wire goes to the light fitting.

I obviously don't want to have to re-wire my house to make all of the light switches three-wire, but I have only been able to find one device which says it can do what I want without re-wiring (and it doesn't do Wifi).

What I want to know is how this circuit works, so I can work out if I can build something similar myself (given the usual caveats regarding circuits which run on mains voltage). Alternatively, if this circuit has a name, knowing it should help me find a power supply which does what I want.


texts:
I've got a power supply delivering +/-28V, referenced to a common ground.

In addition, I have a device (an isolated DC-DC converter, RS3-4815D) which accepts 36-72V input voltage across its V+ and V- pins.

Noob Question: Obviously I'm seeing the opportunity for 56V (28V and 28V from the power supply) to power my device. How can this be wired? This is a followup to the answer to this question.


texts: LED brightness control using PWM according to temperature of RTD/PTC/NTC thermistor

texts:
I am working on this project. Everything is going okay; I am generating PWM using a 74HC14 IC and I have used a potentiometer to vary the brightness of LEDs until now. The actual problem arises when it comes to generate PWM and vary the brightness according to temperature of any temperature sensors I have mentioned above. Any insight would be appreciated. A circuit diagram of the same is welcome. And where do we find the application of the same??

My current circuit is: -


texts: Designing castellations/half holes using EAGLE

texts:
I wish to use some castellated pads or 'half holes' for board to board connections but I'm having a hard time finding a reference detailing how to specify these in my CAD package of choice (EAGLE).
My approach has been the following:

Create a custom package
Place a large rectangular pad on the top layer.
Place another similarly sized pad at the same x,y on the bottom layer
Place a via whose drill lies inside the pads
In the library's device editor, append both pads and the via to the same pin
In the board layout, run the board outline through the center of the vias on the dimension layer

The result looks similar to this:
result http://files.zzattack.org/img/upload/tmp878E.png

Now for my question(s):

What are reasonable pad width/length, via diameter and drill diameter for castellated pads aligning with SOIC (0.05" spacing) package pads?
Should the pads run all the way down the end of the via, to the center of the via, or does it not matter?
Can I get rid of the 'dimension' DRC error?
Is there perhaps a 'proven' library package that I could have used/modified instead?


texts:
Is there difference between Timer vs Counter in ATmega328P?
Or is it the same thing?


texts:
I have the ADS1113 ADC connected to the Arduino using the I2C protocol. I'm just trying to read the analog data from the ADC. I have 5 volts connected to the AIN0 and AIN1 inputs. When I check the Wire.endTransmission() value I keep getting a zero back, meaning the data was successfully transmitted. Yet, when requesting 4 bytes I keep getting this, even if I change the voltage at the AIN0 and AIN1 inputs.

I pretty new to using I2C and learning how to setup particular ICs from reading the data sheet:  http://www.ti.com/lit/ds/sbas444c/sbas444c.pdf
The QuickStart Guide is on page 33 (Sorry I tried posting a pic of what it says, but I don't have high enough reputation to post more than two links...).

So I guess my question is, how do I obtain the second and third byte values? Or am I completely off and not even supposed to be reading the data from the conversion register?

#include <Wire.h>

void setup()
{
  Serial.begin(9600);
  Wire.begin();

}

void loop()
{
  int sensorValue = analogRead(A0);             //compare to ADC data
  float voltage = sensorValue * (5.0 / 1023.0);
  Serial.println(voltage);
  Serial.println();

  Wire.beginTransmission(B1001000);         //Address of ADC
  Wire.write(1);
  int ack = Wire.endTransmission();
  Serial.print("I2C = ");
  Serial.print(ack);
  Serial.println();
  delay(15);

  Wire.requestFrom(B1001000,4,1); //Requesting 4 bytes
  while(Wire.available()){
    float RAW = Wire.read();
    float RAW_voltage = (RAW*4.096/32768.0);
    Serial.print("Raw ADC value = ");
    Serial.print(RAW);
    Serial.print("\tVoltage = ");
    Serial.print(RAW_voltage);
    Serial.println();
  }
  delay(1000);

}


texts: How does a LM386 audio amplifier become to a radio receiver?

texts: Recently I made an audio amplifier by following this video(https://www.youtube.com/watch?v=4ObzEft2R_g). The interesting thing is that when I plug the battery in, suddenly I received a very clear radio signal and the audio input acts like a antenna. Can anybody tell me what is going on here?


texts:
I have a problem with this logic circuit I have designed:

The intended behaviour is: when the clock comes high, the counter's state is latched and decoded

What happens is: when the clock is high, the old state of the counter (if it has been incremented last cycle for example) is very briefly present on the line decoder's input before the latches switch to the 'new' data and the decoder's output then becomes correct

This means the 'fetch' mode is enabled again for a few ns before the decoder switches to 'load'. This causes the counter to be incremented again amongst other problems!

I have tried adding a string of NOT gates on the line decoder's enable, but it does not seem to help. Also, I tried using a capacitor+resistor to add a delay but this only helps when the created delay is a few micro seconds - far too long.

In summary I need to make sure the data is valid on the decoder's input before it is enabled - to prevent false triggering of its outputs.

NOTE: The increment input is decided by other circuitry that is triggered by the decoder - it is in phase with but is not necessarily the same as the clock

tl;dr line decoder is enabled too soon, chains of gates to delay signal don't help


texts: 3.3V regulator does nothing for first ~12 seconds after power-on, then outputs 5 volts

texts:
In my circuit I'm using a TPS78633DCQ low-dropout regulator to regulate my 5 volts power input down to 3.3 volts. However, when powering up the circuit board for the first time today and measuring the voltages, I was getting 5 volts on the 3.3 volt rail.
There was no smoke or anything — I was watching quite carefully for this during the first power-on — and none of the chips on the board were getting hot when I felt around with my fingers; I was also very careful to check for shorts not just to ground but from each rail to every other rail before turning it on, and there weren't any.
On probing it with my oscilloscope and examining it while turning it on, it looks like the regulator isn't actually turning on at all until 10-12 seconds after first applying power, and when it does it jumps all the way to 5 volts:

(yellow is 5 volt rail, pink is 3.3 volt rail)
Note that this is on an assembled printed circuit board, so I don't believe it's possible this could be a grounding problem; the ground and thermal pins both have vias directly to the internal ground plane as close by as I could manage.

This is the power supply section of my schematic:

U17 is the 3.3 volt regulator that appears to be behaving incorrectly; initially I suspected it may have been assembled with an incorrect chip, but the chip on the board at the very least has the correct markings:

Here's my full schematic, pcb layers, and EDA project, for reference:
Full Schematic (pdf)
PCB Layers (pdf)
EasyEDA Project
Note that other 1.8 and 1.1 volt rails did come up to their correct voltages after that, so those regulators are at least functional (were able to regulate down the 5 volts rather than the 3.3 they ought to have been getting).
However having 5 volts on the 3.3 volt rail did exceed the voltage rating on the TS3USB221 muxes (datasheet says 4.6V absolute max for VCC) and TUSB4041 hub chips (datasheet says 3.8V absolute max for VDD33), so it most likely has damaged this board. Hopefully I can fix the problem with the regulator on the other boards before powering those ones up.
What is going on here? Did I not connect the voltage regulator (enable pin?) correctly, or something? Were my boards assembled with a wrong/counterfeit chip despite the markings? I have never seen a behavior like this before, and I have essentially no idea what to actually do about it.
For the moment, I can remove the regulator from my other boards and feed their 3.3 volt rails with a bench supply (in order to test the other features of these boards), but I don't even have any concept about how I would redesign the circuit to make this not happen.


texts: How can I design a circuit that will generate a sinc function?

texts: sinc function is given by sinx/x. How can i design a circuit to generate such type of signals what concepts should be used?


texts:
I have a on-off switch that'll use for a kill switch for my car using the gas pump. The switch says 6A/125V 3A/250V 22 AWG.
For my purpose it needs to handle 12V 20 Amps max.


texts: Reducing current consumption for a PIC16 in Sleep mode

texts:
This might appear as one of those tens of questions that ask about power consumption on a PIC microcontroller. But after I have failed to reduce the current consumption to an acceptable level despite of the fact that I tried most of the suggested guidelines in those question here, I have decided to ask a separate question anyway.

Microcontroller: PIC16LF15345
May not relevant but Development environment is MPLAB X v5.20, XC-8 Compiler v2.00. (Free versions)
Operating at: 3.0 V and at 25 Degree Celsius. There is no regulator on board. It shall operate on a CR2032 battery.
Unused pins are NC on board, no pull-down/up provided.

The design requires the following:

System operates on internal HF oscillator, 1 MHz.
3 GPIOs (Digital Inputs, Switches, pulled up through an external 470k resistor). System spends the most time in SLEEP mode with occasional wake-up through these switches.
Analog voltage measurement through internal ADC, interval FVR (Fixed Voltage Reference of 1.024V).
Interface a I2C-like protocol by bit-banging implementation. Data and Clock lines are pulled high via 4.7k resistor.
Two LEDs (Digital outputs), made Low to turn ON, made high to turn OFF.
A Timer is required for some application-specific behavior when system is active.
A UART for configuration. Desired: System should wake-up when a command is sent from UART, process it and then sleep again. Shall take place very rarely, possibly once in an year.

Schematic:

Note: For this troubleshooting, we have removed the I2C-like slave chip from the board, so it is not consuming any current. Along with that the following have been removed for testing: Both LEDs, R1, R2, R6, R7, R8, R9, R10, R11, C7, C8, C9.
I understand that with these removed, there is no way to wake-up the system from sleep mode.
For now, Watchdog and BOR are disabled.

My understanding:
Before going into sleep mode (by SLEEP instruction), the code should implement the following:

Since LEDs are removed, the pin is made Low.
Unused pins should be configured as Output and made Low. PGC and PGD pins should be considered unused and hence be configured just the same way.
Timer module halted, disabled. Timer interrupts disabled.
ADC module disabled, FVR disabled. ADC interrupts disabled.
Disable Global interrupts.
Clear the IDLEN bit in CPUDOZE register.

I have connected a multimeter in series with the supply. I know its not the correct way of measuring the current, and I have asked someone to connect a resistor in series with supply and measure the drop across it. I implemented the code with above understanding/considerations, the current consumption when system is in sleep mode is 10 uA.
The datasheet claims the sleep mode current to be 50 nA @ 1.8V (Page 1).

What have I already looked into:

Datasheet
PIC tips and tricks for Low Power by Microchip
Deep sleep mode consumption of PIC
Reducing current consumption in deep sleep mode

Questions:

Is the process that takes place before SLEEP mode is entered correct?
What else can we do in Hardware and/or Firmware to reduce the current consumption?


texts: Why did my motor drivers burst into flames when I disconnected them?

texts:
I have set up an old mobility scooter to be remote controlled with some cobbled together boards from the usual sources. Everything was working well for weeks until one day when I was trying to bind a new receiver. I accidentally unplugged the supply to the 5v step down board while the 24v scooter battery bank was still connected to the motor drivers. About 5 seconds later, the octal buffer chips on both drivers released their magic smoke and caught fire. Below is a simplified schematic of my setup:

The JST connector on the left is what I disconnected accidentally. The flame icons are the octal buffers that exploded. I am using two of the very common IBT_2 driver boards. I believe this is their schematic:

What I'm after is understanding why this occurred? Do the 74hc244d buffers enter a strange when when unpowered? Was there some low resistance path back through the logic lines that caused this?


texts:
I am trying to get a simple blinking LED program working on my FPGA and I am having problems. Instead of blinking the LED stays on the entire time. I tried writing my on but then I just copied an example program so I'm sure the program is fine.

Thi sis the board I am using: http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,400,836&Prod=ATLYS
From what I've read you are supposed to use DCMs for all clock needs but in my example I have just attached my clock to the global clock which is supposed to be 100MHz.

Any help for my poor noobie self would be appreciated! Below is my code and my ucf which can be verified with the ucf listed at the above link.

By the way, do any of you know offhand how to import a DCM in ISE? I can figure out how to use it I just can't find an import reference.

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.std_logic_unsigned.all;
use IEEE.numeric_std.all;

entity counter is
port( clk: in std_logic;
    rst: in std_logic;
    led: out std_logic;
    led2: out std_logic;
    sw0: in std_logic);
end counter;

architecture Behavioral of counter is

constant CLK_FREQ : integer := 1000000;
constant BLINK_FREQ : integer := 1;
constant CNT_MAX : integer := CLK_FREQ/BLINK_FREQ/2 - 1;

signal cnt : unsigned(24 downto 0);
signal blink : std_logic := '1';

begin

process(clk)
begin

    if (clk='1' and clk'event) then
        if cnt = CNT_MAX then
            cnt <= (others => '0');
            blink <= not blink;
        else
            cnt <= cnt + 1;
        end if;
    end if;

end process;

process(sw0)
begin

    if sw0 = '1' then
        led2 <= '1';
    else led2 <= '0';
    end if;

end process;

led <= blink;

end Behavioral;

ucf file

# Bank = 1, Pin name = IO_L42P_GCLK7_M1UDM, Type = GCLK, Sch name = GCLK
NET "clk" LOC = L15;

# Bank = 1, Pin name = IO_L52N_M1DQ15,     Sch name = LD0
NET "led" LOC = U18;

# PlanAhead Generated physical constraints

NET "led2" LOC = M14;
NET "rst" LOC = F5;
NET "sw0" LOC = A10;


texts: Trying to flash STM32f030f4 (ARM, Cortex M0) - what is proper wiring?

texts:
I've got STM32F030F4 chips from shop, made a small breadboard adapter for it and tried to connect to its built-in bootloader via USART1.

I've failed and I'm somewhat bewildered about wiring. My current schematic is the following:

pin 16 (VDD) to +3.3
pin 15 (GND) to GND
pin 1 (BOOT0) to +3.3
pin 4 (RESET) to GND, temporarily
pin 8 (USART1_TX) to RX of the FTDI-cable
pin 9 (USART1_RX) to TX of the FTDI-cable

The cable I use constantly with NXP chips, so I think it is using. It also provides +3.3 volts and has LEDS to indicate TX/RX activity.

I've tried this tool http://sourceforge.net/projects/bootstm32/ after plugging the cable and temporarily applying RESET to GND.

Magically, it could not connect, though I see the TX activity LED blink...

I've rechecked datasheet and I am somewhat bewildered. There are also pins 17 and 18 for USART1 TX and RX. I've tried them also but to no avail.

Another concern is that I think this chip do not have BOOT1 pin (many manuals write about driving it low). So I assume it is not needed?

I also thought I can test with multimeter either one of pins is in strong HIGH state, which should be TX - but none is. Though probably TX is turned to output only after auto baud rate detection is completed?

What else can be wrong? I think I need not quartz for simplest schematic, yes? Thanks in advance for your hints!

UPD Solved! It appeared that VDDA should also be connected, otherwise chip is in reset state. Please see my own answer below for more details.


texts: can we use 8051 pin as Input and output at a time?

texts: is it possible to use 8051 microcontroller as input as well as output at a time? if i use particular pin as input and then how to make it as output as well.tell me please i born just now in microcontroller


texts: How to DSP filter a signal that has a variable time base?

texts:
I am measuring frequency on a microcontroller by measuring the time between pulses on an input.

DSP filter theory requires the time base of an input signal to be regular, e.g. IIR and FIR filters. But the time base of this is by its nature irregular (if I have a 1kHz signal, I get 1k data points a second, if I am running at 20Hz, I get 20 data points per second). I have considered several non linear methods where depending on the frequency, the filtering technique changes, but I'm not in love with this idea. Is there a family of filter algorithms to solve this kind of problem? If so, what are they called?


texts: Topology for a DC-DC step up converter for a single AA battery with 50V 10mA output

texts: I need to design a very compact step up DC-DC converter for the single AA battery (input voltage 0.7-1-5V) with an output of 50V 10mA. The load should drain in a typical case about 2mA, but in certain cases, the load could drain even up to 10mA. The goal is to achieve the most efficiency possible. What topology do you suggest to use for it? Maybe you have some design ideas.


texts: Setting up Raspberry Pi detection of multiple FSRs

texts:
I am trying to start a home project with a raspberry pi. I want to link a number of these force-sensitive resistors up

The issue is i really want to assign some form of id so i can tell which has been triggered. Can you get sensors with this ability or is there someway i can add a chip or something :$

I literally have no idea and am just messing about at home - so hopefully someone can lend some helpful advice!


texts: Can I use a 3.3v tolerant microcontroller to drive IR leds that require 5v with a darlington array?

texts:
I have a microcontroller that is not 5v tolerant and I need to drive IR leds just like in the attached circuit.

What I thought of doing is using the 5v line from my raspberry pi as the load voltage across the leds and grounding the ULN2003 back to my raspberry pi instead of the other 3.3v tolerant microcontroller.

But I'm wondering if:

If it even matters if I ground the uln2003 to the raspberry pi or the other 3.3v microcontroller? I obviously know that you should not apply a voltage greater than 3.3v to a 3.3v tolerant microcontroller, however, doesn't the voltage drop to 0 at this point, so in theory it should be safe?
like I said before, "I obviously know that you should not apply a voltage greater than 3.3v to a 3.3v tolerant microcontroller." but can you apply a larger voltage to a component thats in a circuit with that microcontroller?

To note: I cannot use the raspberry pi to drive the leds instead of the microcontroller.


texts: I have a device with two voltage sources and therefore I need atleast a diode on the lowest source to secure it. The lowest source is a 5V USB, and it is protected with a schottky diode with a 0.5V drop. I will also use a polyfuse to protect the USB, but I am starting to worry that the voltage drops over the fuse and diode is too much, as the USB voltage needs to be over 4V after the fuse and diode do be accpected by my buck regulator. Is the polyfuse really necessary? I have read that the USB voltage can vary between +-5% of the 5V. This is of course worst case scenario.


texts: How to efficiently heat a lithium-ion battery so that it can be charged in sub-zero environment?

texts:
A common knowledge and practice on lithium-ion batteries is that they significantly loose the capacity and cannot be charged when their temperature drops below 0 deg of Celsius due to increased degradation (lithium plating).
I'd like to charge the 1.2Ah lithium-ion battery from a solar panel but in winter season (sometines minus 25 deg C) some pre-heating would be required.

The lithium-ion batteries heat up when loaded and I wonder if this phenomena can be smartly used. Is this a common practice? Are there any ICs or known circuits that would control this process?
What other options do I have except for using a lead-acid battery?


texts:
So assuming it's a simple oscillator like so :

How can I start this oscillating with an initial value then make sure this value doesn't affect the operation of the circuit?


texts: What would cause a square wave to become rounded?

texts:
I have a square wave going through a thousand feet of cable.  The cable has \$120 \,\Omega\$ characteristic impedance.  I measured the capacitance and inductance of the cable and they are pretty close to the spec sheet.

According to PSpice, the signal I should be getting out the other end of this cable is attenuated but still very much a square wave, only with very minor distortion.  What I'm actually seeing is more like a sine wave, it's really rounded and spread out.  And it takes a long time for the signal to completely return to zero.

If the cable matches what the spec sheet says, how can it be distorting the signal so much?  The cable is twisted shielded pair and I have a \$120 \,\Omega\$ termination.  The signal is differential square wave \$\pm 0.8 \,\rm{V}\$ with pulse width of about \$1.4\,\mu \rm{s}\$.  Also the cable is currently wrapped on a reel, could that be making a difference?  The shield is grounded.

The signal is coming from a MAX942.

EDIT:  Thanks for the very detailed responses.  I have some more investigating to do.

I'm having trouble commenting on individual answers for some reason, so I am replying in the edit.  I have 1000 ft of cable but the goal was 4000 ft and I have been playing with both.  4000 ft of cable is 5.8E-8 Farads.  With 120 ohms, the corner frequency is 22 KHZ!  Great reply thank you.

I was using the tline lossy in pspice.


texts: Which has better efficiency: step-up or step-down switching voltage regulator?

texts:
I have a Lithium battery pack circuit that converts 4.2V  (two 4.2V cells in parallel) to 5V.
Another option is to use a step-down converter from 8.4V (two 4.2V cells in series) to 5V.
Considering both cited circuits are well implemented, which choice would be more efficient in terms of power dissipation?

I am looking for some general rule as "step-down is always preferable than step-up" or "the absolute voltage difference matters" etc.


texts: Is it possible to call Timer ISR when we want it to execute.?

texts:
I am using PIC32 and I am doing a timer example. I am using the example of Timer1 provided in microchip documents. My understanding with the timers is when our main program start, timer also start with given timing. So its ISR start functioning with the given timing. Is it possible to start the ISR when we want. For example, if a button is pressed then timer ISR should be called.

#include <plib.h>
#pragma config FNOSC = FRCPLL, FPLLMUL = MUL_20
#pragma config FPLLODIV = DIV_1, FPBDIV = DIV_8
#pragma config POSCMOD = OFF, FWDTEN = OFF

#define FOSC 80000000
#define PB_DIV 8
#define PRESCALE 256
#define TICKS_PER_SEC 4
#define T1_TICK_RATE (FOSC/PB_DIV/PRESCALE/TICKS_PER_SEC)
int main(void)
{

  OpenTimer1(T1_ON | T1_SOURCE_INT | T1_PS_1_256, T1_TICK_RATE);
  ConfigIntTimer1(T1_INT_ON | T1_INT_PRIOR_3);
  INTEnableSystemMultiVectoredInt();
  while(1)
  {
    //... do something useful here ...
  };
 }
 void __ISR(_TIMER_1_VECTOR, ipl3) Timer1Handler(void)
{
  mT1ClearIntFlag();
}

How to call __ISR(_TIMER_1_VECTOR, ipl3) Timer1Handler(void) when we want in our program.


texts: How many MOSFETs can a linear controller handle?

texts:
I designed a circuit for a high current linear regulator (20A peak, 16.4V (max) input regulated to 13.8V) using a Micrel MIC5158 together with a BUK9575-55A. The 20 A peaks are short, since the use is for a radio with non-continuous transmission.

I used the reference design, only with the addition of a Zener to protect the MOSFET gate (10 V max in my case).

It is not clear to me how to calculate from the datasheets whether it's possible to use multiple MOSFETs and how many of them can be safely connected to the IC. In the datasheet I also cannot find any information about the choice of the MOSFET(s), the text refers to the MOSFET always using the singular. Is a single MOSFET with big capacitance the same as multiple ones with a smaller one? what is the acceptable capacitance? and so on.

For better heat dissipation or for higher currents I may want to increase their number to two or three of the same model and batch.


texts:
Background:

I've a problem where I need to measure the inrush current of some parallel DC/DC converters in a system where the input voltage may vary between 360-600Vdc on start up. The inrush current is roughly estimated to peak around 500A for a short duration before settling for a max current on around 15A.

I've previously tried with a mechanical relay however that particular relay, bounces on and off before making a solid contact making me unable to make an reliable measurement. Therefore I need a solid state switch solution.

The measurement is done by a current probe , P6303 from tektronix.

Idea

Despite my non previous experience of thyristors my idea is to solve this with the use of a thyristor. I think that I in this way will get a faster and less noisy switch than the mechanical relay.

At the moment I've a MCD56-12io8B thyristor laying around,which I think I can use as followed:

or

I have also thought of skipping the SW in the circuit and just turn on the Voltage of Vc, directly from the bench supply and hope it doesn't exceed the Vgc max.

I know that in this configuration I will only be able to turn on the thyristor however this is not a problem. I will just turn off the supply (vin) for that.

I guess the low-side solution would be easiest and safest.
However I'm a bit unsure what will be the maximum allowable gate voltage for the thyristor. I can't find Vgc max or any equivalent in the datasheet to what "vgs max" is called for mosfets, which I'm familiar with, but I guess if i'm below 4V it will be chill. If you look at the pic below from the datasheet fig 5

Right now I would set the gate voltage to slightly above the gate trigger voltage, and the current through the gate to a value above 100mA.

May this be a good solution to my problem or should I just buy a shit expensive ready made solid state solution..


texts: What are the IEC standards/certifications to look for in a DSO while making measurements pertaining analog parameters like CMRR, SNR, THD etc

texts:
I am in the process of measuring CMRR for our mixed signal system that deals with bio-signal acquisition. I am using DSOX2014A keysight entry-level oscilloscope to make measurement to derive CMRR, SNR and THD. My test-plan is almost ready for it but I am stuck only here, that how can we know whether a test-equipment qualifies to make measurements of such peculiarity. CMRR and SNR are the parameters which are highly considered while pursuing standards and certifications like IEC, CE etc for a Device under test.
I definitely know, what signal I am measuring, what is its range and accordingly the bandwidth of scope required, the least count of different measurements that the scope can offer. Also I am sure about oscilloscope's accuracy. I am asking in terms of certifications that, what IEC certification, certifies a test equipment to make measurements of these type in a laboratory set-up. After a long research conducted on this, I am unable to come to any conclusion. I found IEC 61000-4-16:2015, but that is for the DUT to qualify during mass production, nothing of the sort of test equipment standard.
Thanks in advance.


texts: Connecting a keyboard PCB to wires without soldering

texts:
I have a PCB from inside a Dell keyboard that I took apart.  I would like to be able to affix wires to the edge card connector, without needing to solder anything.
I don't want to solder anything, because when I need to take it apart (which I will), that would make it much more challenging.
I was thinking something that the PCB could simply be slid into, that could also have the wires connected to.  Any ideas are welcome, thanks in advance!
I also have a pretty tight budget, so nothing too expensive, I was thinking I would build whatever it would be, but not necessarily.
The PCB, for reference:


texts:
I need to build a system to control lights using line-level audio signal.

My idea is to acquire the signal from my mixer using a microcontroller (or FPGA), apply some filters and finally drive 5 leds totem (columns, whatever is a cylinder with leds sticked on it...) few meters away from the control unit using arduino (or a general lowcost micro) and power mosfets.
I'd like to control each totem individually and cascade them (fewer cables around).

Since I only need to send a light-on/off command on the bus I don't need a fully fledged I2C communication: just a basic one, the standard 100KHz would be way more than enough. But I need to use a wire of several meters (let's say 10 or 20).

Would a standard I2C work?
Should I use DMX or I2C?

I know DMX is the standard in this applications, but I'd like I2C the most for the following reasons:

Since this is for University (not targeted at market) I think is more "educational"
I could update the project using fpga and then I could use an I2C enabled ADC and don't have to write the code for DMX.

What do you think? Any suggestion is highly appreciated and I hope I didn't miss something obvious.

Thanks in advance, Andrea


texts: What's the difference between a CPU core and a CPU/GPU thread?

texts: I've heard the term core and thread being used synonymously a lot of times. In Minecraft, if you press F3 to show coordinates, it tells you how many threads you have in your CPU but uses the term "core" for them.  I know some things about threads and cores, but they are almost indistinguishable. Both can run programs and have memory, but there are typically more threads and the threads can also appear in GPUs. Is there any difference in architecture between cores and threads?