texts: Safely connecting a preamp powered by a benchtop DC power supply to a power amp

texts:
I pulled the preamp out of a broken guitar combo amp. The preamp has positive, negative, and ground leads for powering it at +/-25V. I would like to power the preamp with a dual channel benchtop power supply to see if it works. Is there any grounding or safety issue with plugging the DC-powered preamp into a power amp that is powered from an AC outlet?

With nothing connected to any power source, I verified that there is continuity from the preamp chassis all the way to the ground pin of the power amp's plug, so I think everything should be grounded safely. I also verified that the power supply's DC terminals are isolated. So everything seems correct, but I am still learning, so I wanted to double check before proceeding.


texts:
I have a question about current transformers being used to measure AC currents.

Say for example, we have a 50/5 amp current ratio, meaning that when there's 50 amps on the primary, there will be 5 amps on the secondary.

1. How is this secondary current affected by different secondary load resistances?

2. Is the CT manufacturer providing this current ratio based on a specific load resistance?

If I wanted to measure this 0 to 5 amp secondary current with a micro-controller or PLC, it would need to be converted to a voltage using a series shunt resistor and op amp (that's one way to it).

3. Would this shunt resistance affect the 1 to 5 amps from the secondary providing incorrect measurements?

Thanks


texts: Why does this low-cost battery powered device use ferrite beads on the power input?

texts:
I have just opened up a small, low-cost motion-activated (by PIR) LED light as I am planning on just using the casing for another project.

The PCB inside is clearly designed to be very cheap. It uses a BIS0001 PIR IC found in many other PIR products. There is heavy flux residue, the PCB is thin, and there are bodge capacitors straddling the IC. It's cheap.

For this reason, I am surprised that there are 4 ferrite beads on small wire jumpers, as shown in this image. The wires are the battery connections and the SPDT mode switch.

This is fairly common on mains powered equipment, switch-mode power supplies, networked equipment and anything involving high frequencies.

The device is battery powered with no option for mains power and is totally standalone.

The pyroelectic sensor and phototransistor are mounted on a separate PCB. These are connected by hookup wire that is twisted, potentially indicating there are other noise issues on the board.

But why are there 4 of them on this dirt-cheap PIR?


texts:
I am using a voltage divider to supply a voltage to a system (I don't know what sort of circuit I am supplying the signal to, except it's used to drive a very large motor. It needs a 0-5v signal). Other than this, there is another input to the system as well, a 72V switching signal.

I am using two 10K resistors at the moment (this is for testing purposes) for the voltage divider. The voltage divider has a supply of 5V, so the signal is 2.5V. The circuit is given below, and the red arrow indicates the signal.

The strange behavior occurs when the switching signal is turned on, at which point the voltage signal suddenly jumps to 5V.

In addition to that, there is no response to the input signal at all. The system is working, because it responds to the original signal from an accelerator pedal.

Any idea what could be causing this behavior?

Thank you.

EDIT: The original accelerator pedal is the one in this link: https://www.alibaba.com/product-detail/electric-vehicle-foot-pedal-with-potentiometer_60649371220.html?spm=a2700.7724857.main07.9.28a05756UO1eV2.


texts: What's a good way to mount an OLED display to a glass/acrylic window?

texts: I have a graphic OLED display I'm using for a project and need to mount it in a chassis.  I was planning on using some sort of clear window in an aluminum panel.  Perhaps acrylic or glass.  I'm wondering what is the best way to mount the display to the window on the inside of the chassis.  Adhesive?  Optically clear UV cured clue?  Nothing?  What's worked well in your experience?


texts:
I've been studying some vlsi lately and came across instances where the author mentioned that it is easier to use MOSFETs at the micron level than it is to use a resistor. Therefore at many instances(such as load inverters) MOSFETs are used in place of resistors.

MOSFETs are complicated silicon devices with various n and p regions whose operation is much more complex than resistors. Reducing their size to micrometers/nano would make the task of creating a MOSFET very complicated and the operation difficult to sustain given the small size of the various regions in a MOSFET. Consdering all this how is it easier to fabricate and use MOSFETs than resistors in IC chips ?


texts:
I wanted to model a transformer in LTspice. So I searched on internet how to do a transformer in LTspice. I found the following model with the coupled inductor:

But I didn't like this model. (I didn't say that it didn't work) but it is not helpful for understanding how a transformer works. It hides a lot of things. And without a huge knowledge (that I didn't have) of how a transformer works, I think it will lead to me to do errors.

So I decided to find an other model in LTspice. And I found the following from here: http://ltwiki.org/index.php?title=Transformers

Then I tried to understand how it works. I have written what I understand on the picture (at least what I think have understood). Nevertheless according to the model and what I understood there is some differences between the electrical model and the LTspice model. Here is the equivalent electrical model:

What I do not understand :

In the electrical model, the voltage across the magnetizing inductance is equal to Vp (primary voltage):
$$VLmag = Vp$$
where as in the LTspice model, the voltage across what it seems to be the magnetizing inductance is equal to Vp/Np (Np is the primary number of turn):
$$VLmag = \frac{Vp}{Np}$$
In the electrical model, the current through the magnetizing inductance is equal to (if I did not do a mistake):
$$ILmag = Ip - \frac{NsIs}{Np}$$ where Ip is the primary current, Is is the secondary current, Ilmag is the current through the magnetizing inductance.
In the Ltspice model, the current through the "magnetizing inductance" is equal to:
$$ILmag = NpIp - NsIs$$

The two formula makes sense to me as when Ilmag is equal to 0 (ideal transformer) we get the current relation of an ideal transformer.

Nevertheless what I do not like is that Lmag from the Ltspice model and from the electrical model seem to be not equal. So if I measure the magnetizing inductance of a transformer I will not be able to simulate it without knowing the relation between the two models.

Did I do mistakes? What do you think about this model?

Thank you very much and have a nice day :D

--------------------------------------------------------------EDIT---------------------------------------------------------------

Here is what I finally have :


texts: CMOS inverter with gate of PMOS transistor always grounded

texts:
If there is a CMOS inverter such that the gate of the PMOS transistor is always attached to the ground and the input voltage is only applied to the gate of NMOS, then how would the inverter behave, as in: Will it be similar to a NMOS inverter with a resistor connected between its source and Vdd supply?

I need to calculate the Vout for Vin =0 and Vin=2.5 volts and the switching voltage ( where Vin = Vout); thus I would like to find the equations characterizing the behaviour of the inverter.

So, for any Vin, the PMOS is always saturated and it can be replaced by an resistor of resistance same as ON resistance of the PMOS and the current flowing throught it would always be the saturated current. Please tell me if my approach is correct or if not, how should I tackle this problem?

To clarify, the devices are all short channel and channel length modulation is ignored.

Here is a schematic:


texts: Do two encoders connected to a microcontroller interfere with each other?

texts:
I connected two AMT 103 rotary encoders (mounted on two separate DC motors) to a dspic30f4011 and read the values using interrupts (instead of qei as the dspic only has one). However, the error in the values increase the farther and faster we go when running the motors simultaneously. One of the theories is that since the interrupts have different priorities one of them overrides the other and causes the error, note that when only one motor is run we don't have an error. Is this causing the error? If yes how can it be fixed? Will using one qei and one interrupt fix this? Here's the dspic code:

#include "p30f4011.h"
#include <delay.h>
#include <stdlib.h>
#include <math.h>

_FWDT(WDT_OFF)

#define InterruptFlag0_A    IFS0bits.INT0IF //Rising Edge on Signal A, Encoder 1
#define InterruptFlag1_A    IFS1bits.INT1IF //Rising Edge on Signal A, Encoder 2
#define Encoder0_B  PORTBbits.RB0 // Signal B of Encoder 1
#define Encoder1_B  PORTBbits.RB1 // Signal B of Encoder 2

//Variables for Calculations
long T1=0;
int counter=0;
int NR=0;
long T2=0;
int counterone=0;
int NRone=0;
long i;
//-------------------------

int main()
{
    ADCON1=0x0F;//digital
    TRISBbits.TRISB0=1;//RA inputs
    TRISBbits.TRISB1=1;//RA inputs

    //Interrupts init
    IFS1bits.INT1IF = 0;    /*Reset INT1 interrupt flag */
    IEC1bits.INT1IE = 1;    /*Enable INT1 Interrupt Service Routine */
    IFS0bits.INT0IF = 0;    /*Reset INT1 interrupt flag */
    IEC0bits.INT0IE = 1;    /*Enable INT1 Interrupt Service Routine */

    while(1) //NEGATIVE ROTATIONS ARE CW. POSITIVE ROTATIONS ARE CCW
    {

        T1= ((long)NR*10000)+(long)counter;
        T2= ((long)NRone*10000)+(long)counterone;

    }
    return 0;
}

void __attribute__((__interrupt__)) _INT0Interrupt(void);
void __attribute__((__interrupt__, auto_psv)) _INT0Interrupt(void)
{
    if(InterruptFlag0_A==1) {
        if(Encoder0_B==1) {
            counter=counter-1;
            InterruptFlag0_A=0;
        } else if (Encoder0_B==0) {
            counter=counter+1;
            InterruptFlag0_A=0;
        }
    }
    if(counter==10000) {
        counter=0;
        NR=NR+1;
    } else if(counter==-10000) {
        counter=0;
        NR=NR-1;
    }
}

void __attribute__((__interrupt__)) _INT1Interrupt(void);
void __attribute__((__interrupt__, auto_psv)) _INT1Interrupt(void)
{
    if(InterruptFlag1_A==1) {
        if(Encoder1_B==1) {
            counterone=counterone+1;
            InterruptFlag1_A=0;
        } else if (Encoder1_B==0) {
            counterone=counterone-1;
            InterruptFlag1_A=0;
        }
    }
    if(counterone==10000) {
        counterone=0;
        NRone=NRone+1;
    } else if(counterone==-10000) {
        counterone=0;
        NRone=NRone-1;
    }
}

Thanks


texts: How to call void function in response to receiving serial data (Arduino)

texts:
I'm new to Arduino, and I'm trying to decipher this code. There are various void functions that I am trying to call in response to receiving serial data (the Monitor outputs "Please enter valid function to call"), but I suppose I don't really know how.

typedef void (* Caller)();
Caller FuncCall[] = {a, b, c};
String func_list[] = {"a","b","c"}; //correspond to functions in FuncCall, order matters.

"a", "b", and "c" are 3 separate functions that are written out later in the code.

Am I missing something here? I can elaborate if needed.


texts: How can I disable the jtag in atmega 32 using serial programmer?

texts: How can I disable the JTAG in the ATmega32 using a serial programmer?


texts: Reducing the order of transfer function while maintaining same response

texts:
Scenario:

I have been going through Ogata Modern Control Engineering book and working through several exercises to improve my understanding of basic control principles. I came across the following example which I am struggling to solve.

I am stuck with reducing order of my transfer function while maintaining the same (or very similar) response.

I am modelling a system which includes a mechanical and an electrical part. The overall transfer function for my system is 5th order.

The time constant for the electrical part is very small when compared to the mechanical time constants and due to this we can replace the electrical system with a gain and get an equivalent 4th order system.

As an example, my system is similar to this (taken from Ogata's control book):

This is my transfer function, and it includes both the mechanical and electrical parts of my system:

I want to reduce the 5th order system, to a 4th order system, while maintaining the same response.

What I have tried:

In order to know whether I have reduced the system correctly, I designed the block diagram for my model on Simulink.

This is the response to a chirp signal:

My idea was to use the above response, to see whether I have reduced the transfer function correctly.

Next, I proceeded to find the poles, zeros and gain of my system. To do so, I used this piece of code available on MathWorks, with the 5th order TF above:

b = [0.0001 10];
a = [0.005 5.00010060 0.661600001 61.01102010 2.1101 10];
fvtool(b,a,'polezero')
[b,a] = eqtflength(b,a);
[z,p,k] = tf2zp(b,a)

The output was as follows, which is exactly what I had expected:

and the equivalent PZ-map:

The above results show the pole associated with the electrical circuit, which is far to the left. This can be removed, thus reducing the order of the transfer function from 5th order to 4th order.

Next, I proceeded by using zp2tf to eliminate the pole on the far left as follows, however the output does not seem to make sense.

z = [-100000]';
p = [
  -0.04 + 0.0347i  % *100
  -0.04 - 0.0347i
  -0.02 + 0.0041i
  -0.02 - 0.0041i
];
k = 0.0200;
[b,a] = zp2tf(z,p,k);
[bnew,anew] = zp2tf(z,p,k);
bnew/200
anew/200

ans =

         0         0         0         0    0.0001   10.0000

ans =

    0.0050    0.0500    0.0001    0.0001    0.0000    0.0000

I was expecting the above to result in a 4th order system, but clearly I am doing something wrong with my approach.

I am stuck with replacing the electrical part of the block diagram with a simple gain block, while maintaining the same (or very similar) output response.

How can I get the equivalent block diagram model for the fourth order system?

Any pointers, tips and/or advice on what I should do would be appreciated.


texts:
Does anyone have experience with the Maestro A2200 GPS module? I bought this module primarily on price, it's only 15 euro, but the datasheet indicates that sudden removal of power can result in bricking the device.

This seems rather hostile to me - there are many times where a battery could become disconnected and I don't wish the result to be this disastrous. Has anyone used this module and destroyed it like this? Is it fixable afterwards?

I do have a voltage supervisor handy but the datasheet says "the shutdown is complete after maximum 1s". 1 Second! I don't think I can have a capacitor supply current for that length of time!

I'll admit the device will be driven by a Raspberry Pi or similar which has the same requirements for shutdown, but at least I can redo the SD card on a Pi.


texts:
Newbie question:
I've an Android TV stick (Rikomagic MK802 III) and I'm having wifi signal problems. I've opened the device, and this is what I've found:

Both the wire and the shield are connected to the antenna, is this normal?
The connection to the board is identical, wire and shield.

Here is another photo so you can see the entire antenna:


texts: What is feedthrough in vlsi standard standard cell library gates?

texts: I come across with the term feedthrough in standard library cells, but i did not understand its function.


texts:
Wire the AND gate so that its (former) X input is driven by the counter’s Q1 output, and its (former) Y input is driven by the counter’s Q0 output. The output is still F. To ensure that you can see the values of the gate inputs in the simulator trace, connect counter’s Q1 output to your new output X, and its Q0 output to your new output Y.
I'm just confused on how to wire this up if the AND gate only has two inputs, and the counter has 4 outputs.
I also have to do this with an OR gate included with the AND gate, the one with an inverter (NOT gate), AND gate, and OR gate.
Any help would be appreciated as I'm super confused with this.


texts: Phase splitters/inverters using valves with directly-heated cathodes

texts:
I'm building an audio amplifier using Raytheon 6418 valves and I'm struggling with the phase splitter.

The 6418 has a directly-heated cathode and I'm wondering what limitations this might introduce. Ideally I would use a cathodyne design but, from what I understand, this might not be possible because there is no seperate cathode and thus no cathode resistor (Rk).

For the same reason, I assume that long-tailed pairs cannot be used either. One solution I have come across is using a paraphase inverter (schematic), however I would ideally avoid this as it might introduce high levels of distortion.

Am I correct in thinking that I cannot use a cathodyne/long-tailed pair?
Is there a way of adjusting them to work with a directly-heated cathode?
If not, then are there any other alternative designs that might be more suitable than a paraphase inverter?


texts:
I am aware the arduino requires at least 250mA and to power several components 1 amp would be better. source [http://playground.arduino.cc/Learning/WhatAdapter]

This is a motor the driver I am using and upon scrolling down it said 2 amps is the driver IO and driver supply should be anything from 5v to 46v.

I am powering my robot using a 9v source along with 2 resistors, one 4.7 ohms and the other 10 ohms.

The resistors and power supply are in the center. My question is will this setup work without heating and/or blowing up (Im just a bit paranoid).


texts: How do I connect two solar panels in series?

texts:
I've got two solar panels which each provide 9V. I need them to provide 18V, and according to different sources (such as this forum thread) that should simply be a matter of connecting them in series.

So I did. I connected the negative on panel A with positive on panel B, and positive on panel A with negative on panel B. As far as I understand, this is how you connect solar panels in series.

However, I came across a surprising observation. Each of the panels produce about 10V - 11V each on a good sunny day. I've checked (and double checked) readings on my multimeter. However, when I connect them in series the voltage drops to 4V - 5V. I get this reading on both solar panels by connecting my multimeter to the connectors on any two of the solar panels. As you've probably figured out, I don't understand why this happens.

Now, the panels have 4 soldering connectors each (see below picture). The first two are positive and negative (which according to my multimeter outputs nothing) and the two second ones have some chinese letters next to them which I've got no idea what means. However, these connectors (the ones with chinese symbols next to them) are the ones giving 10V - 11V. These are also the ones I've used to create a connection from panel A to panel B.

Since I could not figure this thing out, I called a friend. I was advised to put Schottky diodes in between them in case the panels somehow was discharging through each other. So I did. However, still only 4V - 5V when i put them in series.

Right now, I'm at loss what to do. How do I connect these panels in series to get 18V from them?

To summarize:

Each panel outputs 10V - 11V
Connecting my multimeter to the bottom and top right hand (or left hand) connectors indicates resistance, so these can't be the same connectors as that should give zero resistance as far as I've been told.
The connected solar panels give 4V - 5V regardless of whether I've got the Schottky diodes in the middle or not.

What am I doing wrong?


texts:
I have an arduino with a multiplexer for i2c expansion (I have multiple same boards exceeding its adress range) where every pin leads to separate sensor box. My question is: is it possible to put multiple same devices (with different adresses) on one pin of the multiplexer?

Lets say "*" is the multiplexer, "A-Z" are different various sensors and boards and the a1-a3 are for example 3 same AD/DA converters in parallel on the same multiplexer pin but each with unique adress.

           L1    L2

           /|---|B|
          | |---|C|
          | |--->a1,a2,a3
Arduino---|*|
          | |
           \|---|Z|

Would this configuration work?

Thanks in advance!


texts: Filling the unused space with ground plane in mixed signal pcb

texts:
I'm designing a 4-layer pcb which consists of a GSM module, GPS module, a microcontroller (SAM4S) and a proper dc to dc buck converter.

The traces of the antennas are extremely short, fewer than 5mm long.

And the highest speed of signals is the SPI which I chose for external nor flash and/or a micro sdcard communication.

There are also few analog signals for monitoring very low frequencies (100 Hz in worst case).

I was thinking if it's a good idea to fill every unused space with ground plane stitching with vias (as if it's manufactured in cnc). I will not let any dead copper though.

Will this cause any problem in signal integrity?


texts: Single-point ground vs multi-point ground - large DC system

texts:
So we're working on a DC system with little space for cabling and a size which requires at most 1.5m cable length. We're running power on 48V DC (hence, frequency = 0) with a max of about 5Amps per device connected.
There are 4 devices connected along the 1.5M.
We desire a multi-point ground system such that we could run just a single power line rather than a power line for each device which belongs to a single-point grounding system.
After doing some reading in 'Noise reduction techniques in electronic systems' by Henry W. Ott, we can conclude that it's best for us to still run a single-point ground system but this trade-off does require us to run more cables.
Is this trade-off worth the space needed in a interference-sensitive system? We do run seperate data-communications between the devices as well.
What could be good arguments for both or makes one topology significantly more wise to implement? I'm very curious about the technical aspects as well, makes me learn a lot!
I drew a picture to show the single-point system vs the multi-point system.

Edit: I added an image that shows not only power, but also (digital) communication lines. As you might notice, this has shielding which is connected to (common) ground at one single point such that noise will not find a gnd path over data.

I drew only 3 devices, but in fact, there are four with all the same power requirements.


texts: How do they produce batteries with the same voltage but different current?

texts:
If we take a 12V  battery, according to its work place that it works in different current consume.

How do they make batteries with the same voltage but different current flow, and why?


texts: MSP430 serial communication failing in cold weather

texts:
I have a product using the MSP430 microprocessor, which has been selling for a couple years now.  One of the MSP430's jobs is to communicate over async serial to a low-power radio.

With the onset of this winter, there has been an unacceptable failure rate (several percent) in cold temperature.  Investigation has found that the serial communication with the radio is failing. The baudrate generator for the serial port is fed by SMCLK, which is divided from the MSP430's digitally-controlled oscillator (DCO).

Why is serial communication failing at low temperatures?

(Note: I have already solved the problem and will be posting the answer soon.  Hint: it was a software bug.)


texts: What is the purpose of oil in a transformer?

texts: I'm trying to understand how transformers work. I understand the primary/secondary stepping down/up voltage or current, but why do they use oil (in oil tank) with transformers?


texts:
I need to derive an expression for Zin = Vin/Iin, which is the equivalent impedance looking into the input. I'm not sure how to approach this. I know that no current flows into the op amps and it doesn't look like this circuit can be separated.

Thanks

simulate this circuit – Schematic created using CircuitLab


texts: Why is that when we analyze diode clamper circuit, we always start thinking with the first negative cycle (they say the point where the capacitor charges up)? Whats wrong with starting with the positive half cycle first? Thanks.


texts: Long term car storage requires 2 batteries

texts:
I store my second car for 4 to 6 weeks at a time.  There is no access to electricity, so a battery tender is not practical.

The vehicle electronics slowly discharge the battery so it goes dead in a few weeks.  Is there any way to hook a second battery in series so I can go longer before draining the batteries completely?

I’m guessing some sort of diode to isolate, but what size?

Is it even necessary to isolate or should I just go direct to the terminals?  I’m using AGM batteries. This set up would be temporary and only used during storage.  Thank you for suggestions.

Addendum: Agreed, parallel is what I meant. Problem is that with a sophisticated sports car, disconnecting the battery creates many troubles that require resets and on some systems, hours or many miles for the cars computer to readjust to. Also, the trunk, where the battery is Located is operated by power. The emergency release requires the rear seat removal. How convenient! Maybe the best solution is to visit more often...

Agreed, parallel is what I meant. Problem is that with a sophisticated sports car, disconnecting the battery creates many troubles that require resets and on some systems, hours or many miles for the cars computer to readjust to.  Also, the trunk, where the battery is
Located is operated by power.  The emergency release requires the rear seat removal.  How convenient! Maybe the best solution is to visit more often...


texts: Where I can find an USB dongle to connect two devices with external power?

texts:
Can you please tell me where I can find an USB dongle which follows this diagram:

I have a tablet and a BobjGear USB to RJ45 Ethernet Adapter, but the battery will discharge while using the tablet connected to the network cable.

I want something as described in the diagram where A is the tablet, B is the Ethernet Adapter and C is the regular USB charger !

Does such a thing exists ?

What will happen to the tablet when I will try to provide the input power while it's supposed to be outputting power ? Is it even possible to connect the power in parallel - as the Tablet A is supposed to power the Adapter B ( A -> B )
Connecting the charger will force the current to flow in the opposite direction ( C -> A & C -> B ) ?


texts: Max allowed inductive load (pump) for a given relay

texts:
I am using Omron G5RL-1A-E-HR relay in my project with these specs:

I am using the high inrush type with max allowable current of 16 amps. I have used with water heaters up to 2 kW and air conditioners rated approx 2000 VA. Good thing about air conditioners is that they have a stabilizer which also delays the turn on of air conditioner. As such, there is no risk of high inrush current. However I am not sure if I turn it off when the air conditioner is running. Anyways, I haven't seen a failure in almost an year.

What's the max hp pump that I can put on this relay for a reliable operation? This case is different from air conditioner because motor will pull current as soon as I turn the relay ON. Do I need to make any changes to the circuit to improve it's life?


texts: How can i make a circuit such that output voltage is reduced by golden ratio, using feedback

texts: I want output voltage to equal input voltage divided by phi. Is there a way to use feedback such that i get an exact result? I don't want use numerical convergence with resisters but rather use feedback so as to create the Fibonacci pattern in electronic design.


texts: Is there a way to convert BSDL format to synthesizable verilog?

texts: I have a BSDL file for a device for which I need to generate test patterns through an FPGA. I learnt that BSDL is a subset of VHDL but the file looks like it describes the hardware of the DUT. I know this file is interpreted by an ATE which I don't have access to for obvious reasons. Is there any tool that can generate synthesizable RTL that can I can put into the FPGA to generate the vectors described by the BSDL file?


texts: Motor bridge no longer responds to lower voltages

texts:
I'm making a circuit that I used for a previous project on a bread board to power two electromagnets. I'm using the same wiring and parts as the first time. It's a simple circuit using an Arduino to control a motor bridge.

Here's the problem: when I try to operate it from the arduino, nothing happens. When I run the logic pin (and Vref, etc) through the 12v power supply I would use for the electromagnets (instead of the arduino), everything works fine.

Using an voltmeter, the arduino looks fine with volts going up to (and a little over) 5v. The motor bridge is 4.5~20v. Instead of a magnet, I'm just using a voltmeter for testing. The ground is run through the power supply, not the Arduino

Here's the circuit: circuit http://www.e-alexander.net/slippers_img/circuit1.gif
and the schematics for the ta7291P http://www.electronicaestudio.com/docs/1437_2_4025.pdf

I have multiple ta7291P motor bridges and all have the same problem: all worked fine last year when I did the project, but now none of the work from the arduino, none of them work from a 5v constant current used instead of the arduino (second input pin is grounded in that case), all of them work with 12v used to power everything.

Are my chips just aged/abused or am I missing something?

Thanks in advance!


texts:
I'm looking for some information for the type of the connector this drone is using.

My nephew lost his charging cable for it and he can't reachage it anymore.

Can someone provide me with information if this connector has a specific name that I can look for or it's some proprietary connector that can't be found.

Below is a close up image on the connector in question and here is the link to the drone itself: https://uae.souq.com/ae-en/taiyo-water-drone-29717429/i/

Any info will be much appreciated.


texts: Anything wrong with this Mosfet H-bridge?

texts:
I am very knew to electronics and was planning to build my first robot. I search around google for H-bridge designs and drew the following schematic(OLD)

NEW

I know that testing a circuit on a simulation and in real life are to very different things, on the simulation the circuit works good.
The two inputs are coming from a RF module with a PT2262 decoder, that's why I chose two logic level n-channel mosfets(IRL520) at the low side.
The motors are both(same circuit twice) 12V and 2,19A of stall current each. Each optocoupler is a 4n35.
My power source is a 12V 5A lead acid battery.

The problem:
(When testing on a breadboard)When one input is high, the mosfets that are not being used get really hot and the motor turn very slow or not at all. I was thinking maybe the way that I wired it to my breadboard is off? This problem has been bugging me for a little while. I am hoping one of you experts are able to tell me what might be happening here?
I decided to build my own motor driver for educational purposes and cannot get any other components for now

*EDIT: I've uploaded a new schematic with the changes and switched the p-channel mosfets(my bad)

*EDIT 2: Motors are 12VDC brushed gearmotors.

EDIT 4: Sorry for the delay, here are some measurements that might aid in answering;


texts: Mathematically modelling RC circuit with a linear input

texts:
I have found a plenty of documents and books that model how the voltage across a capacitor behaves within a transient RC circuit, using the following equation:

$$V_C=V_{MAX}(1-e^{-t/RC})$$

Unfortunately, I have found no resource that discusses how to mathematically model an RC circuit, were one to provide a linearly increasing voltage source as an input.

Attempting to substitute VMAX in the equation above, for a linear equation, results in an equation that converges towards the linear equation, meaning current would cease after a time (I=(VS-VC)/R). This is obviously untrue, since we should be seeing current approach a constant value with time, as given by:

$$I_C=C\frac{dV}{dt}$$

I am fully aware how the voltage across a capacitor would behave with a linearly increasing voltage source, there are plenty of simulators that display that, and I can even think of a physical explanation for the results. What I wish to know is how one could mathematically model the voltage across a capacitor with a linearly increasing voltage source, in a similar way to the equation that models voltage across a capacitor in transients.


texts: Why does adding a gain to a Sallen-key second order HPF change the amplitude response?

texts:
As the title suggests, I have done all the necessary calculations to implement a gain into my second order stage of my 6th order high pass filter but for some odd reason, it would change the amplitude response of the circuit. I have recalculated the resistance that affect the filter by implementing K into their equations and I cross checked it with analog.com which proved that it was spot on so Im not really sure on why the response changes hence changing the cut-off frequency.
The difference in the cut-off frequency is huge, the original design is at 100Hz whilst the gain version reduces it to 180Hz.
The schematic without the gain:

The schematic with a gain:

And also if someone could explain why resistance of 150kOhms and above only work with the gain of the amplifier that would be appreciated!


texts:
As many of you probably know, a normal light emitting diode, while very handy as a cheap and ubiquitous indicator, can double as a power generator. The mechanism is the same that is exploited in photovoltaic cells, aka solar panels.

When an LED is exposed to light it produces a current flowing from anode to cathode. This current can be used to directly power a device, or to charge a capacitor so that a periodic load can use the stored charge all at once, when needed.

To give you a better idea of the values involved, the short circuit current ranges from tens of nanoamps up to a few microamps, while the open circuit voltage is somewhat less than the standard forward voltage of the LED.

I am currently in the process of choosing a range of LEDs to test them and see if they are suitable for my application, but I am kinda stuck, mainly because using a led to power something is convenient only money wise, while a photovoltaic cell or even a photodiode is a better choice under many other aspects. No manufacturer that I have seen list the photogeneration current in the datasheet, and this seems fair enough to me, but since I want to avoid testing thousand of LEDs I would like to buy a selected range of them, so I need to better understand the underlying mechanism that leads to photogeneration.

Let's just write down the diode equation:
$$
I_D = I_s(e^{\frac{V_D}{V_t} - 1})-I_G
$$

simulate this circuit – Schematic created using CircuitLab

Where \$I_s=J_s\cdot A\$ is technology dependent, and die area dependent. \$I_G\$ is the generation current, and is the parameter I am interested in maximizing.

Here are some things I have thought of:

LED color since the LED can absorb a lightbeam only if the energy it carries is greater than the gap, choosing LED with low energy (i.e. low frequency) gap is a must, to be able to absorb a wider portion of the spectrum. This lead me to choose red or infrared LEDs.

max current max forward current is proportional to die area, and power dissipation capabilities. Since photogenerated current is proportional to area, choosing an high current LED seem wise to me.

forward voltage this is somewhat related to the open circuit voltage and is not currently an issue for me, and I believe it has no relationship with photogenerated current.

reverse current I am not sure this has much to do with photogenerated current, but the bigger the reverse current, the bigger the area, which is a good thing.

breakdown voltage I do not think this has a relationship with photogeneration.

My question finally is:
Do you agree with my analysis, and do you think I am missing something?
or better
What are the parameters to look at when searching for a photovoltaic panel in the LED section of a supplier?


texts: interfacing multiple ADC: sharing master clock

texts:
My project involves interfacing two analog-digital converters to an STM32F411RE microcontroller.
The first ADC is an ADS1191, the second is an ADS1158.

Those two ADCs will have to convert signals simultaneously and their samples retreived by the MCU.

I've been used to work with a single ADC. The program is interrupted as the DRDY (data ready) pin goes low, and the samples are retrieved.

The questions are:

Do I need to make sure the two ADCs share the same master clock? If yes, I suppose I should use the internal clock of one of them, and feed it to the external clock pin of the second one.
ADS1191 has an internal clock of 2MHz and requires an external clock of 2MHz.
ADS1158 has an internal clock of 16MHz and requires an external clock of 0.1 to 16mHz. Is it safe to use ADS1191 internal clock and feed it to ADS1158? Will I have to sacrifice anything by feeding a master clock of lower frequency (2MHz vs 16MHz)?

Regards,

Laurent.

Clarifications

The "continuous read" mode which I'm used to use with a single ADC consists in connecting an interrupt signal to the DRDY (data ready) pin of the ADC. When data are being sampled, the DRDY pin switches high. Then, when the data are ready to be transferred, the pin switches low. The MCU detects the falling edge of DRDY and starts transferring the data byte-per-byte.

What I'm looking for is to have "correlated" samples, i.e. make sure that two respective samples from each ADC retrieved at the same time indeed correspond to the same time "bin", which might not happen if the respective master clocks show a drift.
From the valuable answers below, I conclude the following regarding the use of two (or more) ADCs.

Suggested solution
Make sure the two ADCs share the same master clock. In my application I'm able to redirect the internal master clock of the first ADC to an output pin. This clock signal would then be fed to as "external clock" on the second ADC. To reduce the frequency (which most of the time is related to the sampling rate), one can resort to a d-type flip-flop (to divide freq. by two).
The principle would therefore be the same as in a single ADC application: trigger interrupt on DRDY of one ADC (the one with shortest hold time). When this first transfer has finished, retrieve samples from the other ADC.


texts:
I have bad caps in my LCD monitor. While taking it apart, I disconnected the LCD backlight wires to get to the power supply. I blame bad product design and my own stupidity for not checking how the wires were connected. It looked something like this, except in my case one of the connectors is rotated 90 degrees. Since the connectors are the same, I'm now afraid of switching the two cables and killing the backlight or the electronics.
How can I find out where to put each plug?
Edit: Based on the advice by Rohat Kılıç, I popped the wires in and the monitor not only did not explode, but it now also works as expected. Another piece of consumer electronics saved from going into the junkyard, yay!


texts:
I set my pic microcontroller (16f688) to energize a relay after 3 secs and to energize two more relays another 2 secs after. Problem is, sometimes, after it executes this command, it deenergizes the relays and repeats the command again, and again. Sometimes as much as 7 times before it finally settles. Sometimes, it starts again after the first relay is energized.  Sometimes it works fine. It's kinda random, what could be the problem?
Please note that I used an analog pin to monitor input AC mains voltage. The monitoring circuit steps down mains to small DC voltage


texts: What is the difference between burden resistor and a normal one?

texts:
I just came across the word 'Burden Resistor'. Is it any different from a normal resistor?

If it is different, where can I possibly get one?  Sparkfun hasn't got one listed.  Any help is appreciated. I am trying to build a current sensing circuit.


texts:
Let's assume the following scenario:

uC (@3.3V VDD) drives an I/O pin HIGH 3.3V (just to be clear, it's not an open-drain pin, so the p-channel mosfet of the output pin is actually driving the pin to VDD level)
Pin is also rated as a 5V tolerant input (so it's not clamped to VDD).
The line that the pin is driving is also connected to a pin of another uC(@5V VDD) which may drive the line to 5V level also
Between the two pins of the different uC's we assume an ~2470R resistance

The questions are:

What happens if while the 3.3V uC drives the line HIGH (3.3V), the other uC also tries to drive the line HIGH (5V)? What can then be stated about the 5V tolerance of the 3.3VDD uC OUTPUT pin?

Is then a 680uA current ( (5 - 3.3) / 2470 ) sinked to the VDD of the 1st uC? What does actually happen inside the I/O pin circuitry of the 1st uC? Is this inter-connection safe?

I post this question in case someone with a better understanding of is cares to answer, as this case is not documented in the uC datasheet and I couldn't find any definitive reference on this after doing a fair bit of research.


texts:
I'm having some trouble working with the Shockley's Ideal Diode Equation. I'm trying to generate a model plot for a 1N4001 type semiconductor diode, but the resulting graph seems incorrect.

Is (Reverse Saturation Current) = 5 * 10^-6 A
Vt (Thermal Voltage) = 25 * 10^-3 V
n (Ideality Factor) = 1

Id = Is * (e^(Vd/(n*Vt) - 1)

Nearly everything I've read states that the "Turn On" voltage should be closer to 0.7V. I'm inclined to believe that I'm doing something wrong. Any ideas?


texts: OpAmp comparator circuit having unexpected behavior

texts:
I'm working with the following circuit. It integrates a constant current, and when the output reachs a threshold, another circuit activates the switch, discharging the capacitor. The switch is simplemented with a transmission gate, and it is on long enough for the capacitor to discarge through the transmission's gate resistance.

What I'm expecting, is that when the switch is on, the capacitor is discharged to 0V, thus taking the output to Vref1 (1,3V). This is what happens when I simulate with an ideal opamp

In red is the control signal, when it turns on, the capacitor voltage (cyan signal) goes to zero, making the output signal equal the voltage of the non inverting terminal, 1.3V.

However, when I replace the ideal opamp by another one designed by me (a simple two stage opamp), the signals behave unexpectedly, as shown in the following figures

The capacitor indeed discharges completley to zero, but the output signal does not change to 1.3V as expected. After the control signal goes to zero, all signals start to grow, until the ouput reachs almost Vdd (1.8V), as seen in the following figure

I suspect this is being caused by one of the parameters of the custom opamp not being ideal, but I don't know which one. I thought of the gain not being enough, but a simulation with another opamp with less gain resulted in an overshoot not so big, as it can be seen in this figure

With an opamp with less gain, the output is not settling at 1.3V as expected, but it settling at a much closer value than the opamp with higher gain. So, apparently, less gain gives a better result.

Any help is appreciated.

EDIT:

Here is the opamp implementation


texts:
Hi I’m building an Ebike and using a reclaimed relay board from an old electric moped. My question is the relay board has 3 small wires presumably for the switch, but this confuses me as I only need 2 for a switch. See picture:
Also why use 8 relays.
Extra info, 1500w hub motor, 2x12v 40ah batteries.
Any advise would be great.


texts: I read that Shockley diode belongs to family of power devices but what is difference between schottky diode and Shockley diode?


texts:
After a lot of theoretical studying of MOSFETs, I decided to try out at least the basics of it in practice.

Here is the first circuit I ever made using MOSFET:

simulate this circuit – Schematic created using CircuitLab

https://www.onsemi.com/pub/Collateral/BS170-D.PDF

I haven't used resistor in series with gate, because MOSFET is obviously voltage driven component (input gate current is negligible).

I chosen next parameters for the circuit:

Id(sat) = 10mA
Id(bias) = 5mA; where Vds = 5V
Vr1 = 5V
Rd = Vr1/Id(bias)

Then I didn't really knew which way to calculate Vgs (since the actual gate current can't be really calculated), so I tried next:

gm = Id/Vds, then Vgs = Id/gm = 5V,

After I made the circuit on breadboard, this are the values I got with measurement:

if Vgs = 1.8V or less, then Vds = Vcc
if Vgs = 2.4V, then Vds = Vcc/2 (I wasn't even close to this value...)
if Vgs = 3.8V or more, then Vds = 0

Where did I go wrong on this one?


texts:
I'm studying cert 3 in Electrotechnology as an electrical apprentice. My tafe lecturer is insisting that in an ac circuit, and increase in voltage will cause a decrease in current. I'm aware that it depends which voltage you talk about. Ie, supply or volt drop, but his words were that in dc circuits, voltage and current are directly proportional, but in ac circuits they are not. I don't agree with this, could anyone help me understand, maybe with some formulae or something, I'm a bit stuck..
Thanks


texts:
I am designing an embedded system and I am hoping to achieve maximum power efficiency as the system will be running off of 2x CR1620 batteries. In addition to power efficiency, I would like to keep the BOM as low as possible.

The system consists of 3 primary components
1x 5mm RGB LED
1x PIC16F18325 (5v Processor) or PIC16LF18325 (3.3v Processor)
1x MMA8452q Accelerometer (I2C and 3.3v and as advertised is NOT 5v tolerant)

The LED will consume the vast majority of the power as it will be on whenever the system is in use.

A primary design consideration, the LED's must be AS BRIGHT AS POSSIBLE regardless of consumption, it is the rest of the system that I need to optimize.

My questions are based on these scenarios:

Scenario 1
PIC16F18325 (5v version is able to be powered directly by the 2x CR1620 batteries)
3x BSS138 (N-Channel FET)
 1- to power the accelerometer (3.3v)
 2- SCL
 3- SDA

Scenario 2
PIC16F18325 (5v version is able to be powered directly by the 2x CR1620 batteries)
3x Resistor voltage dividers to power the accelerometer (3.3v), SCL and SDA
****Note, I'm not even sure if this works******

Scenario 3
Combination of Scenario 1 and 2, maybe use 1x BSS138 for power and 2x voltage dividers for SCL and SDA or 1x voltage divider for power and 2x BSS138 for SCL and SDA

Scenario 4
PIC16LF18325 (3.3v MCU)
using a LM3940 to regulate the voltage from 6v to 3.3v (at approx 55%-65% efficiency since its a linear regulator) and connecting everything directly.

So my questions are these:
Which of these scenarios will work? (I'm pretty sure 1 and 4 works, but not sure about 2 & 3)
Which of these scenarios is the most power efficient?
In scenario 4 will the LED have any difference in brightness being driven by 3.3v vs 5v? assuming I adjust the resistor value to drive the RGB LED at 20mA on each channel

Ideally scenario 4 would be the easiest and most reliable way to design the system, but I'm worried about all the loss of power from the linear regulator. Additionally I am worried the the brightness of the LED would suffer from 3.3v.

Any help and advice would be greatly appreciated =)
Thanks in advance


texts: Reducing a variable DC voltage by a set amount

texts: I have an analogue signal that's 0-4 V that I want to measure using a micro-controller that only measures up to 3.3 V. I want to reduce the analogue signal by 1 V. I've seen designs using voltage splitters, but the voltage reduction is a function of the input voltage. I need something that's a constant 1V.


texts: Why we gradually increase size of inverters in buffer design?

texts: When trying to drive a high capacitive load why do we gradually increase size of inverters in buffer design. Why not give the output of a circuit to one large inverter?


texts: Expand heatsink contact area with larger copper plate?

texts:
I'm looking at DIY projects where a COB LED is cooled by an all-in-one CPU liquid cooler, however the contact area in a CPU heatsink will only fit one high-power LED. I'm considering how I could use several, perhaps less powerful LEDs with a single heatsink.

Is it feasible to mount LEDs on a larger copper plate, which is then tightly fixed to the heatsink (screws + paste, or thermal adhesive)?
What can be expected from and what should be considered for this solution?

UPDATE - already got a great answer with general principles, but here are the specific numbers for my current project:

4 COB LEDs of 25W, 19x19mm large. Will be at least 70mm apart because of lenses.
Cooler is a Liquid Freezer 120 with a surface diameter of 60mm and recommended max TDP of 250W.
Based on the answer below I'm considering a 6mm thick aluminum disc with a diameter of 144mm, for mounting the LEDs on and then attaching to the cooler.


texts:
I recently bought a Cyclone II FPGA here.  I have been able to program it with a USB Blaster cable and the Altera Quartus Software.  The problem is that when I disconnect power, I lose the program.  How do I program it so it will continue its operation after power is lost?

Note: this question is similar to this one, but the name of the question made it hard to search for, so I agree with "The Photon" that this one should be kept open.


texts: Flyback Isolation Transformer Alternative

texts:
I am using the mEZS84801A as a reference design as shown below. It uses the MP8007 PoE chip. I have modified and tested this PoE system successfully and my camera be powered and it can run at 1 Gigabit.

The T2 coil 750316206 Wurth Np:Ns:Na=22:10:6, Lp=47.4μH, Core=EE13 47.4uH, cannot be found anywhere. The flyback transformer seems very specific to the designs, and the topologies seem to vary depending on PoE chip. I am having a lot of trouble trying to find an alternative for the design. My system runs on 12V and consumes ~10W.

I have read that it is a step-up transformer with very large ratios but I am also wondering if there is a way to use the transformer to output 5V to the system instead of 12V since most of my circuitry runs of 5V. I currently have a step down converter but seems like a waste of space. Any help or suggestions would be very much appreciated! Thank you in advance!


texts: Making a 64 pin breakout board, looking for help with best practices and any glaring design errors. First design in a few years

texts:
Long time lurker first time poster. I am making a breakout for a MCU we want to prototype with and I was curious if there are design rules I should follow for these.

The datasheet for the MCU says "0.1 µF ceramic at each pin plus bulk capacitor 1 to 10 µF" for each power pin. But since I am tying all the power pins together can I get by with one or two bypass caps and a bulk cap?

I have attached images of my board layout and the datasheet section in particular.

Please ignore the silkscreen I am working on that last once placement of parts is done.

https://imgur.com/a/XkTFsxl


texts: Building 3 Stage amplifier, Couple Questions

texts:
General question, how can I improve it? or make it more efficient? mabye there is something im missing...

Questions:

How can I deliver more dc voltage to the load? how do I improve my swing, im getting around 5.5volt
How can I improve the voltage distortion when increasing voltage input?
My phase is shifted in the output? tried to increase C7 didnt help.
How to improve BW and CMRR?


texts: How to drive a transistor with an active low output from a switch?

texts:
I have a set (3) of switches (bell pushes) that are a considerable number of years old. They are connected up to a four core cable, one for each switch and one common. The common side of the switches however, are connected to the plate in which the switches themselves sit.

This is a problem as it means I can't simply supply the common with a voltage and use it to switch the rest of my circuit.

As I see it my options are:

Bring the voltage way down (switching regulator) and limit the current (resistor) and go ahead and drive the common and detect the small voltage at the other end.
Drive the switched lines and put common to ground, and then use an IC like the 74LS04 to invert the output.

I don't really like either (1) because even though its a tiny amount of power it just feels wrong driving any large, exposed metal surface high, (2 (and 1 really)) because the the inverter and all the other circuitry get to sit around consuming power waiting to detect a push which will be very very rare, whereas before the switches could disconnect the entire circuit from the power supply completely until it was needed.

Have I missed something? Is there another way to utilise by board?


texts:
I've got a project at my university that includes a peltier module for heating and cooling stuff. A big problem I'm encountering is that the peltier module sucks 5A at 12V, but the biggest power supply allowed is 12V 3A, so I've got to limit the current through the module. At first I thought of a big-ass 12ohm resistor but that is not really practical, and a 12W resistor is both hard to find and kindof expensive. So is a buck regulator the solution to this problem? I've come up with this design for the regulator:

The ATTiny45 is supposed to increase or decrease the pulse width going to the switching mosfet until the sensed current is around 1A, in this case until ADC_IN is about 1 volt.
If this principle would work, let's say there will be a resistor divider to sense the voltage for the output of the buck regulator to control the pulse width based on the delivered power instead of only the current (which seems to be a better idea now that I think of it), how do I calculate the best frequency to drive the switching transistor at? :)


texts:
I'm hoping you can help me identify this component.
I need to replace it but I don't know its name to find it and purchase it.

Is difficult to find it in my city.


texts:
I just finished with theory understanding of FET transistor principles, etc.

Right after that I tried to make simple circuit Common-Source with FET and MOSFET the problems occurred one by another.

I could begin with JFET (n-channel) for start:

Idss (when Vds = 15V) = 6mA
Vgss(off) (when Vds = 15V & Id = 10nA) = from -0.5V to -8V
Different admittances at Vgs = 0 and I don't know which to chose for calculating Id

All I wanted was to bias the FET, so that Vds = Vdd/2, so in the middle of the load line (for the start). Vdd would be 20V and Id would be 5mA > Vds would then be 10V, right?

I can't find appropriate Vgs and also don't know how to connect gate resistor (series or parallel) + I can't calculate its value since gate current cant be calculated and/or is not practically usable (neglected).

simulate this circuit – Schematic created using CircuitLab

Transistor's datasheet: www.mouser.com/ds/2/149/bf244a-292510.pdf


texts:
I was recently looking into Nixie tubes however the requirement of high voltages was a bit scary, especially given that these voltages were in the 150-200V range.

Instead of using a boost converter with a low voltage supply like the 5v rail on an Arduino, I decided (for the sake of simplicity) to simply do what most cheap LED torches do - Put 50 or so CR2032 batteries in a plastic tube with wires on each end. This way I can get a voltage of 150V or so easily without any boost circuitry. The problem, however is that I have absolutely no experience doing so, nor have I ever heard of someone doing this with more than 6 cells before.. Will the batteries do something bad?

Also, would I be able to power a Nixie like the IN-14 with a setup like this?


texts: SRAM isn't blank on powerup, is this normal?

texts:
I had finally finished my Z80 memory board, but I was disappointed to see that it wasn't working properly (simple NOP test with the address lines connected to some LEDs) as the counter quickly spiraled out of control instead of incrementing as it should.  However, I am not one to give up and after about thirty minutes of continuity testing to unveil no short circuits and all proper connections, I finally thought to check if the SRAM chip was powering on with all 0s stored.  I am well aware that SRAM (unless non-volatile, which my particular chip is not) will lose all of its contents upon losing power, but I had always assumed that it would be filled with 0's (ie "empty") when it regained power.  The SRAM I'm using seems to be randomly filled with 1's and 0's each time the power is reset.  It never remembers any data, but it isn't loading empty.  This isn't really a problem as I can simply write a small program in ROM to load all 0's into RAM on powerup, although I would still like to know if this is how the SRAM should be functioning or not.  Thanks!

Edit: I forgot to mention that after using the ROM to load 0's into SRAM the system worked fine, so this was indeed the issue.


texts: Finding variation in input impedance by varying a resistance using LTspice

texts:
I am trying to find the input impedance \$R_{in}\$ for the circuit given below using a 1 kHz sinusoidal source.
I want to plot the input impedance on the y-axis and the parameter \$R_{2}\$ on the x-axis.

However, when I run the simulation I get a set of graphs corresponding to different values of \$R_{2}\$ with time on the x-axis.
How can I get the graph for variation of input impedance with respect to \$R_{2}\$?


texts:
All of the LED cathodes have been connected together. I want to regulate them with an MCU but I think the fact that the cathodes are connected on the diodes makes it impossible for me to wire it up so I can get my opamp follower working.

Here is my almost completed circuit (notice the opamp inverting inputs arent connected and also i need circuits for the mcu outputs too) where i have three outputs from the microcontroller (naturally it must be grounded somewhere so one end of those outputs are connected together) and then the LED cathodes are also connected together. Is there any way for me to get this wired up without needing to have 3 separate microcontrollers if i'm using this particular led configuration?


texts: Is there any such logic gate that accepts inputs from both sides and also stores information within the gate itself?

texts:
I'm trying to design a logic circuit that will end up looking a binary tree (there will be a "root" logic gate at the top and a whole bunch of "leaf" logic gates at the bottom).

Input is fed as bits into the leaves and the outputs are passed upward towards the root.  But at any time (not necessarily at the root) the flow could change direction and they need to "follow" the path where they came from down to the leaf where they originated from.

I feel like the only way to create "breadcrumbs" is to create a storage bit at each gate indicating either right or left down the tree, leading to the leaf node.

Am I way off in my thinking here? Is it possible to have inputs go upward towards a root logic gate and then reverse the direction and go back to the leaf logic gate?


texts:
So I'm building a musical sequencer that uses a shift register to close relays and pass the discharge pins of three 555 timers through a manual switch and potentiometer (acting as a variable resistor) to vcc. Here's somewhat what it looks like, but with only a SPST relay, and no integration of the flip-flops that will add a single bit to the register when the device is turned on.

I want the shift register to trigger all three 555 "channels" at once, so I can play chords.The only problem is, I'd need one TPST relay for each step, that's 8 per 8-bit shift register, and they're fairly expensive.

I was just wondering if there was a cheaper alternative to TPST, or three SPST, relays.
Name ideas are also cool. Not sure what I want to call the thing. It's going to be modular and block-based, so I can daisy-chain more shift registers to the end to add more notes.


texts: Is it necessary to limit a battery's current output?

texts:
Is it necessary to limit a battery's current output, or will the load inherently draw no more than is needed?

I have a 4S LiPo I want to connect as directly-as-possible to a DC fan of the appropriate voltage.  Do I need to add resistors to limit the current flow, or will the internal resistance of the fan ensure I don't draw more than the required current?

The 4S can deliver nearly 120 amps in burst, so I want to avoid melting/destroying things.


texts: Finding transistor width for equal rise and fall times

texts:
I am trying to understand how the below CMOS transistor schematic has  approximate equal rise and fall times (resistance pull up equal to resistance pull down)

Below is the schematic:

I notice that there are two different paths in the pull up network:
    - width 4 in series with width 5 (resistance pull up = 2*(1/4 + 1/6) = 0.83
    - and 3 transistors of width 6 all in series. (resistance pull up = 2*(1/6 + 1/6 + 1/6) = 1

And for the pull down network:

two transistors in series, both width two: resistance pull down = 1/2 + 1/2 = 1.
Again, two transistors in series, both width two: resistance pull down = 1/2 + 1/2 = 1.
transistor of width 1: resistance pull down = 1

I then found the parallel combination of these:

Ie. for the pull up network, I simply calculated 0.83 in parallel with 1, to get: 0.45

And same for the pull-down network, I calculated 1 in parallel in 1 in parallel with 1 to get: 1/3 = 0.33

Is this correct?
I appreciate any help.


texts: Meaning of "Supply Voltage: 3~132V" on an electric drive system plate?

texts:
I have an electric drive system for a garage door that has the supply voltage mentioned above. What does the 3~132V mean?. The output torque is 190 NM and the output speed is 85 rpm. The input current rating is 13.3 A.
Here's the best photo I have of the plate:


texts: Why is the upper hole in a plug point bigger than the rest?

texts:
In a plug point you can see that the upper hole is bigger than the other holes in it.

Why is this hole bigger than the other two?


texts: Window comparator using LM339 - invert output

texts:
I'm using the LM339 for an application with different voltage ranges. I am using the window comparator circuit since I want to test a specific range (4 - 8V). The circuit shown below actually identifies this "window" but not as I am expecting. When the input value is in this window I want to light the led, instead the led is off. Is there a way I could invert this output to light it in the window and turn it off when it's out of range?

Sorry if it's too dumb, but I'm stuck with this.


texts: Am I designing this circuit correctly using Arduino?

texts:
I've never used Arduino before, so I'd be really grateful if any errors in the following circuit could be pointed out to me:

As far as I understand it, I have two super-bright LEDs connected in parallel each with their own resistor.  I've connected these to one of the digital pins which I think can give 5V each.  The resistors are 100 ohms for these LEDs (these green ones)?
In terms of the power setup, I have a 9V battery with the positive terminal connected to Vin power pin and the negative to the Gnd power pin which I think powers the board.  The wire after the resistors then goes to the Gnd pin on the other side of the board with the digital pins:

As a side note, if I am powering the board with a 9V battery, can I only set one pin to high (5V)?
Is this the most effective way to construct this circuit?


texts: Cannot make a couple of HT12E & HT12D work properly together

texts:
I have built the following setup, which pretty much comes from the specification documents of the HT12E & HT12D thelselves:

https://www.holtek.com/documents/10179/116711/2_12ev120.pdf

https://www.holtek.com/documents/10179/116711/2_12dv120.pdf

I am using Vdd=5V, Rosce=1M and Roscd=51K. There's also a LED with its anode connected to VT, its cathode to a 470 resistor and from there to ground. The A pins can be either connected to ground or left open, with the same configuration on both ICs. All AD pins on the HT12E left unconnected. VT normally has a voltage of 0V. Now, when connecting TE to ground, the LED lights and VT goes to almost 5V. If the A pins on both ICs do not match then VT stays low. If the AD pins are all connected to Vdd the LED also lights.

Up to here is the behaviour which I was expecting. However, my first concern is that in the previous setup, having left all the AD pins unconnected, the D pins remain with a voltage of around 0.3V. I was expecting all of those to go high, to something almost 5V.

My second problem is that as soon as I connect any of the AD pins to ground, the LED will not light, VT will stay low, and again all the AD pins will remain unchanged - so, even worse.

I have capacitors close to the power pins of both ICs and am using short wires - around 10 cms. I have also tried attaching the D pins to the input pins of an SN74HC125N (4 buffers), and connecting its outputs to LEDs, with no improvements with the results.

Any idea about what might I be doing wrong? Have I missunderstood the specifications somehow?

Thanks in advance.


texts: Voltage across a capacitor.(steady state)

texts:
At the circuit above I built a simulation that shows the voltages on both sides of the capacitor(in red and green).
However the voltage measurement shows that the voltage on the 3u capacitor is only 1[V]
I couldn't understand why is that (and not 6[V])?

Important fact - it is a steady state condition.

Thanks a lot.


texts: How can I measure the Thevenin equivalent impedance of the source side?

texts:
Let's take a look at the general picture of any signal generator with one output port shown just below.

I would like to experimentally measure the Thevenin equivalent series impedance of the signal generator (it is an output impedance in the Thevenin equivalent circuit of the generator). How can I measure it? I think I've heard that the network analyzer will work for this purpose, but I don't know how can I properly use it. Although I need to study this instrument, could you please tell me a general way of measuring this impedance? And can I measure it while the generator power is on (the generator is just on without giving power to the load). I would like to make up a list of the output impedance value by varying some parameters of the generator.


texts:
Details: I try to build the single TRIAC circuit for ON/OFF, Dimmer(600W AC Light), and AC fan Speed Control. I trying this the first time.
Problem: I using MOC3041 to control the TRIAC ON/OFF it seems to work fine but while I Tried Dimming I found using MOC3041 cant able dim the lamp due to Zero crossing in the MOC3041. Now I try to change MOC3041 to MOC3052, Please clarify to me what are the things I need to take care of before proceeding.
What will happen to my switching if I change MOC3041 to MOC3052?
Note: snubber Circuit value - Rs-50E/1W, Cs-0.01uF/400V
Thank You.


texts: How can I tell if a particular multimeter measures AC with RMS or Average

texts:
I require a multimeter measuring RMS but unfortunately know little on the subject and am unable to tell which method one uses from it's description.

Its states:

  MAX. Voltage between terminals & earth ground: 700V AC rms or 1000V DC
  Fuse Protection: µA and mA: F 750mA / 250V Ø5x20; A: F 10A/250V Ø6.35 x 31.8

I appreciate it says rms in the above, however would like to ask for confirmation and also if possible help understating the other values it specifies.

Full spec here

Thanks


texts: Why should a transistor circuit be grounded? The way I understand it is that ground is an infinite supply of electrons and so it is equivalent to the negative terminal of a battery. But in this page , there is both a negative terminal and the circuit is also grounded. If I've understood rightly, for a circuit to be complete, we need a positive terminal, some circuit elements & a negative terminal. If grounding is equivalent to a negative terminal, why do we need it in the circuit shown above? (By the way, all the circuits in the book I'm referring were not grounded until transistors started off. You could say that added to the confusion)


texts: Analyzing this bode plot for frequency break point

texts:
So given this problem:

circuit http://imagizer.imageshack.us/v2/640x480q90/902/1FzzwZ.png

The correct bode plot for it is:

bode plot http://imagizer.imageshack.us/v2/640x480q90/661/yILL19.png

What I don't understand is how the -3db was measured. I know that -3db can be found through 20log(1/sqrt(2)), but how is it measured right at frequency 10kHz?


texts: History, reason for and implications of the 2 modes of a modern microprocessor?

texts:
The modern microprocessors I've dealt with could have 2 modes: User and superuser (and sometimes this difference was just in the manual and not actually implemented like with the Nios II which states that it has 2 modes but only implements 1). Therefore I wonder if this is true in general about microprocessors i.e. it is not very advantageous to add more modes than 2 for instance a third mode that could be "supersuperuser" (which in practice could be that a "supersuperuser" could change the privileges of "superusers") if there could be need for 3 modes? And is it this mode difference of the CPU in modern systems that has caused the design difference between operating systems where some operating systems are called "microkernels" because of their way to load device driver programs in user mode instead of in superuser mode, which is the way of a monolithic os kernel? What is the history about the 2 CPU modes getting developed? It says in another SE comment:

I saw the names "user mode" and "supervisor mode" in ARM2 first (late 1980's),

So the early microprocessors like Intel 8080 and Zilog Z80 didn't have modes so any program that was run could run any instruction?

https://superuser.com/questions/634733/why-so-many-modes-are-in-cpu

Are these 2 modes usually implemented in hardware and if so, what does the implementation look like? What is it that changes when a microprocessor switches modes between user and superuser?


texts: Why are typically fatal currents non-lethal when they pass through your body for a short time?

texts:
I've been reading up on electrical safety, and the commonly cited controversial quote "it's not the volts that kills you, it's the amps". What I have gotten out of these sources is that it is in fact the amperes that stop one's heart, but the voltage determines this current, and the body is a non-ohmic resistor. (I have read this which mentions a lot about the volts and amps).

However, I am confused as to how much time a current must be passed through your body in order to be fatal. This video states that if you were to model the human body as a 100 picofarad capacitor with a 1500 ohm resistor in series, a high voltage static shock would pass a very high current through the body, but for an extremely short time (less than a microsecond). How long would a potentially dangerous (>5mA) AC/DC current have to be passed through the body in order to harmful? I understand that this is maybe too general a question, but is it possible to give a figure accurate to a few orders of magnitude?

Also, if it is in fact the amperes delivered over time that are detrimental, would a unit such as the Coulomb be more suitable for determining how fatal an electric shock might be?

EDIT: I am assuming that the electric shock is delivered hand to hand where it is most likely to pass through the heart and thus heart fibrillation is of most concern. If there are other significant causes of death from hand to hand shocks that I have overlooked, please tell me.


texts: op-amp voltage follower - input volt is not equal to output volt

texts:
This is a fundamental question but I may be stuck in somewhere.
I have a circuit as below, the red texts are the actually values by a multimeter.
As you can see, for op-amp1 output, the simulator is the same as input, which is -1V, but actually, I have -3.2V.  The table in the right-lower corner is the current calculation, looks at all the voltages I am seeing is true.

Any inputs will be appreciated! Thank you so much!

Note,
I've uploaded the physical circuit.
basically, we use this circuit to provide a pulse current at 10A with 30us pulse width.  The op-amp U1 is a current-to-voltage inverter, the U2 is the sense feedback. The BJT/FET is for high current capability.

However, not sure why, when the power supply and K57c/d is off.
I was seeing a noise(0-200mV at ~1k-10kHz) on U2 pin#3 (pos input). so I am checking this issue.

Thanks again!


texts: How do I drive 60 back-to-back LEDs (Christmas Lights)?

texts:
I would like to reuse some old LED strings. I hope to replace the (failed) original controller with an AVR chip, but I do not know how to construct the differential MOSFET driver stage.

The sketch below is not complete (as the string is in fact 5 blocks of 12 parallel LEDs) but my problem is finding a way to provide the alternating current necessary to light firstly the odd LEDs and then the even LEDs?

simulate this circuit – Schematic created using CircuitLab


texts: Low Duty Cycle (LDC) Mode Issues on RF Transceiver

texts:
I am experimenting with Low Duty Cycle Mode (periodical sleep and active state transitions to reduce average power consumption) on the SPSGRF-915 RF Transceiver, based on the SPIRIT1 RF Module, which its documentation can be found here. The SPSGRF-915 module is connected to an STM32F3 microcontroller via SPI.
I managed to produce two different outputs on two of the SPSGRF-915's GPIO pins. The first pin (GPIO1) is configured to output whether the SPIRIT1 is in SLEEP or STANDBY mode, while the second pin (GPIO2) is configured to output whether the SPIRIT1 is in READY mode.
In the first example (first picture below), I am using an RX Timeout (duration of time the transceiver will be active to look for signals) of 3ms, and a full LDC cycle (total duration of one cycle of sleep time and one cycle of active time) of 20m, which would result in 15% cycle, and therefore consuming only 15% of the total power consumption in full READY state if it were not communicating with other transceivers.
The picture below is the Logic Analyzer's recording of the LDC Mode which seems to be pretty consistent/accurate:

I tried experimenting with different timing parameters: Rx Timeout of 0.8ms and full LDC Cycle of 1.8ms, which are the parameters I would eventually need based on the transmitter's datarate of 90kbps and 32 byte preamble word (the Rx Timeout that I have calculated should be enough to detect the signal's RSSI based on Section 1.1.2 of this document here and an explanation of how everything should work from this link).
The picture below is the Logic Analyzer's observation of the LDC Mode with the timing parameters above:

The LDC Mode on the second picture seems to be less 'accurate', as in the timing of when it stays asleep or awake is not constant or similar most of the time, while the LDC Mode on the first picture looks more consistent with all the other cycles.
I also tried implementing the second LDC Mode with the transmitter and the setup fails to capture most of the signals, which I suspect is because the LDC Mode seems to be inconsistent. I also have to note that both Logic Analyzer captures were taken when the system is running off the USB power source, I noticed that if I use a battery source for the setup, the LDC Mode will be inconsistent regardless. So I assume that power source also has an effect on how the Transceiver's LDC Mode operates.
My question is: What might cause the second LDC mode to not be as consistent as the first one?
Any help would be greatly appreciated. Thanks!


texts:
How do real world algorithms for sensorless BLDC motors handle startup under load?
Right now I run phase 1 for a few milliseconds to get the rotor in a known position, the I run open loop for a constant number of commutations by picking with a constant, hand picked by empirical observation, and each phase is held for a constant period of time before switching to the next phase.
This really beats ass on the motor, sounds awful and only hands off to the sensorless algorithm about 60%of the time.

How are you supposed to get the motor started more consistently?


texts: Choosing a digital oscilloscope for a self learner

texts:
I'm about to start a course about electronic interfaces. My intention is to learn to debug hardware by doing measurements etc. with oscilloscopes and multimeters.

According to the course, the recommended device to buy (digital oscilloscope / multimeter) is the following:

National Instruments myDAQ

The main problem with the above is that it needs LabView to work (which is not for free). I want to buy a tool that I can use without paying exorbitant software licenses.

Looking on the internet, I have found this one:

PicoScope 2000 series.

I see that it is an oscilloscope, but I'm not sure if it will work as a digital multimeter.

Is the PicoScope a valid option to replace the NI myDAQ? If not, do you know anyone I can buy that doesn't need non-free software to run?


texts: Can I and how to install a bypass diode on a solar panel?

texts:
We have a Solec 70W 12V mono-crystal solar panel. The junction box has one positive and one negative lead to connect to other panels or charge controller. It does not appear to have a bypass diode built in to the panel.

Can I install a 10A diode to provide some protection against shading, etc.?
And, if so, do I put it from the negative terminal to the positive terminal of the junction box?


texts:
I just modelled a P-Channel MOSFET in Eagle and now would like to do duplicate the device to make slight changes to both the symbol and the device for a similar N-Channel MOSFET.

I've searched and googled but I can't seem to find a way to copy the entire device to do this.


texts: Can two 12v power supplies be connected together to increase the amperage power

texts: I have two 12v 30amp power supplies and I would like to know if I could connect them together to get an output of 12v 60 amps of power


texts:
So many academic papers quote the following fact:
"A line commutated converter in steady-state operation inherently consumes reactive power of about 60% of the DC power transferred."

I do not want to see this from "generating" or "consuming" vars' view. My real question is more like this: HVDC is causing current to phase shift from the voltage, what is causing the phase shift?

commutation process itself? or the reactive elements in filters, transformers and the transmission line?

I strongly believe that alpha angle in the commutation process is NOT the answer. I think, the fundamental of reactive power is the fact that I and V are out of phase. Alpha angle blocks the occurrence of current, it does not cause phase shift. blocking and phase shift are very different!

For example, imagine a simple circuit with an AC source and a resistor in series. if a diode is inserted between the AC power source and the resistor, current may be blocked for half a cycle, (strictly speaking, more than half a cycle. Since the diode will only start conducting @ 0.7-ish volt, we technically have a none zero alpha angle here as well), but the current is still in phase with the voltage, no phase shift, no Var.

I find this frustrating, as most of you just accept the conclusions "var is due to alpha angle" without truly thinking it thru. I highly suspect that, at normal load of an HVDC line, the transmission line is a huge inductance, and that's the reason for the reactive power consumption.


texts: Applying USB to UART and RS-485 to UART to the single MCU UART port

texts:
So basically I'd like to put two external interfaces into one device. One of them will be RS-485 (I'd use SN75176 for that) and the second one is USB (with FT232BM).

I will use ATmega48PA-AU CPU as the core. So I will have only one USART port at the CPU end.

One of important assumption is that only one interface will be used at one time.

What I intend to do is to use diode-diode decoupling for RxD line:

I expect that this schematic should work for low frequencies (9600 in my case). But I've never used FT232BM chip in particular, moreover I've never designed any device with USB interface. So some troubles I'm not aware of can surprise me. Is there any?

And is there any better cheap and simple solutions for decoupling interfaces for such case?


texts: Why does water damage low-voltage microelectronics so easily?

texts:
Everybody has had the time where water gets all over their electronics, and the whole thing gets ruined, like cell phones.

At that low of a voltage (3-5 volts), I don't understand why it is such a short-term harm (long term makes sense - corrosion, etc.)

If an LED was in parallel with water, maybe a bit more current would be drawn, but it doesn't seem to be enough at all to short out the system, and the LED would still shine.

So what is it that permanently damages some electronics and what is the cause?


texts: I'm unsure of what DNM means on this schematic

texts: I looked up DNM Capacitors; however, everyone I saw had a footprint that was to large to be in this circuit. I also thought that it could mean "Does not matter" but that seems kind of silly to put into a schematic. The IC is a CC2640 which is a wireless MCU. Thanks for any help that is offered!


texts:
I'm wondering about the case of PRSNT PCIe connections for the case where a board might be supporting bifurcation (I think most common case would be NVMe) - for example utilizing dual x8 PCIe hard-IP in a FPGA - and could not find a quick easy reference for such a case.
If a board was installed in a x16 slot, bifurcated for x8x8, how should the PRSNT2 pins be connected? Would it simply be the same as x16 (PRSNT# connected to farthest PRSNT2# pin)?
Are there any references to this anywhere? (aside from PCISIG)


texts:
I am new to reading measurements in datasheet. I am drawing PCB layout of IC LT1761 for my circuit. What I do not understand is what does REF refer to in the datasheet (attached figure)? As far as I understand pin width is 0.62 mm (max) and length is 1.22 mm. Am I correct? Also what is the length of the IC? Is that 2.9 x 1.4 mm?

Thanks you very much for your kind answer.


texts: Trio CS1352 oscilloscope trigger/blanking board photo needed

texts: It may be a very long shot. But is there any one with a Trio CS 1352 who could send me a photo of the trigger/blanking board both sides? My board has some weird jumpers that do not match the schematic and  I need to check and not sure if those are factory revision or previous owner fiddling around.


texts: 50Ω Impedance Matching with Signals Through Vias

texts:
I'm working on an IoT board and it is all laid out (LTE, GPS, BLE, WIFI - 30mm x 30mm -- VERY TIGHT).

As a design concession, I have to use vias to route some of the RF signals.  There's no other way to keep the board that small.

I've impedance matched and tuned several RF boards.  I'm using the same PCB material, so I am confident the 50Ω traces will be correct.  And I have a VNA to tune the matching network to the antenna.

However, what happens when the 50Ω traces hit a via?

Is there an known equation for impedance matching through vias?

Should I even worry about it if the traces are 50Ω?

I have a matching network from signal out on the IC to the antenna, so is it a moot point?  Just use whatever via you want, and correct the impedance at the matching network?


texts:
I'm trying to optimize the behavior of a DC series blocking capacitor at microwave frequencies (my signal range is from \$5.3-5.9\,\text{GHz}\$). By optimize I mean keeping \$S_{11}\$ as low as possible in the signal range. One of the strategies I've considered is using a taper to transition between the microstrip width (\$0.38\,\text{mm}\$) and the blocking cap width (0402 cap, so \$0.5\,\text{mm}\$). I've seen the Klopfenstein Taper mentioned, but also a simple linear taper as a rough approximation to the Klopfenstein taper (for instance in the Transmission Line Design Handbook by Wadell, section 5.5). I've also seen linear tapers in a professionally-designed \$18\,\text{GHz}\$ VNA. In any event I decided to simulate the performance of several iterations of a simple linear taper on a step width discontinuity (i.e. no blocking cap) in a microstrip using OpenEMS. The step discontinuity has a width of \$0.5\,\text{mm}\$ and length of \$1\,\text{mm}\$. I've placed a taper on each side of the discontinuity, where the taper angle varies from \$10^\circ\$ to \$90^\circ\$ (i.e. no taper) in \$10^\circ\$ increments. Here's a bird's eye view diagram for a \$10^\circ\$ taper, in case the explanation wasn't clear.

The blue/purple is the PCB substrate and everything else is conductive, planar trace. It's all the same material, ignore the fact that it's several different colors.

Surprisingly, all tapers were worse than the non-tapered version for all frequencies in the simulation range (\$\text{DC}-18\,\text{GHz}\$). The difference between all iterations was small. Here's a plot of \$S_{11}\$ for two different tapers and the non-tapered version. I've omitted the other tapers from the plot because they're all in the range bounded by the \$10^\circ\$ taper and the non-taper and just clutter the plot.

Is this expected behavior? I was surprised when I got this result. Does this mean I shouldn't use linear tapers? Are there certain circumstances where they are effective?

Bear in mind that while I believe the simulation code is correct, there's always the possibility I introduced a bug somewhere. So, if this result is different from what you've seen in HFSS or CST etc., then this result may be erroneous, which would be useful to know.


texts: Options for powering 5 V from 24 V AC relay switch

texts:
I have four switching relays with internal transformers that control pumps for my heat. From what I can tell they are powered by 120 V and it's stepped-down to 24 V that is sent to the thermostats which then make the connection when heat is needed.
Instead of buying "smart" thermostats I'm going to hook these into my existing system that currently controls my heat pumps. I think the best way to do this is to but a single controller near the boiler that then triggers each zone similar to the way the thermostats do now.
My main question is I need to power the controller so I can either run a separate power source (wall wart) to give it the 5 V or I can hook into the 24 V AC sources and convert that down. If I used relays to control the 24 V AC sources if I used a separate power source it would be isolated so that seems like a bonus but I'd have extra wires running around. If I want to control it from one of the control boxes would it matter which one I used, I'm assuming not since 24 V AC is 24 V AC (for this purpose)?
edit: Adding a sketch as requested. The parts below the line are what exist now and above is what I would like to add.


texts: Strange results for NMOS component in LTSpice

texts:
I am testing the I V curve of the mosfet in LTSpice

I get strange results when the standard 'NMOS' componant is reverse biased, (when the source is more positive than the drain) I get tera-amps flowing into the drain and mili-amps out of the source, no current into the gate.

Is this because the model for the MOSFET is incomplete and only works for the positive I V quadrant, or could there some kind of bug in the software?


texts: How does this current limiting circuit work?

texts:
A tutorial electronicsArea explains a transistor based current limiting circuit.

Problem is that I am not able to understand how T1 gets switched on in the fist place. To make T1 on it needs a voltage of 0.7 in its base. But to get that value, current has to flow through Resistor R(which makes the transistor T2 ON). Again for the current to flow through R, T1 has to be switched ON.

Does this circuit really work? Where am I making mistake in the assumption?


texts: Another 'What is this component?' question

texts:
I have looked through all the other 'what is this component' questions and have not found my component. I am looking for the component in the red box. It is from a rectifier circuit off a 1973 9.8 hp Mercury 110 Outboard. I ripped the silicon off the red plastic housing and this is what is underneath! I'm sure there is more than one person out there looking to source these parts.

Also I built the circuit in CircuitLab to see what it's like. The component in question is (F1).. you can see from the schematic it's a Bridge diode circuit. Right now the best guess on F1 is a fuse (I used to think it was a high wattage resistor - to drain transient current) If it's a Fuse, how is it being used successfully in this circuit? It doesn't seem to prevent any current from going to the output when blown.

simulate this circuit – Schematic created using CircuitLab

The circuit has two oscillating inputs like I believe the ignitor coils see when the EMF is passing through them. The switch to short them is while the coil is just left there - acting as a resistor of sorts. It is a magnento type ignition system where both the magnets and ignitor coils are positioned 180 degrees from each other, so that both magnets pass over the coils at the same time, creating a voltage in each coil to power the spark.

SW1 - is the high speed coil (~2K ohms)
SW2 - is the low speed coil (~4K ohms)

Can anybody tell me what the component in the red box is? It looks like straight carbon - like from a brushed motor but have not had any luck finding it through google or online part warehouses (digikey, mouser, etc..).

* I now believe this to be a Ceramic Cartridge fuse but need verification before assuming that is correct.

Thanks in advance!


texts: What steps would it take to hack an Xbox 360 controller to accept input from a computer program?

texts:
I understand the Xbox 360 encrypts it's signals from controller to console but I'm curious if there is a way to trigger the analogue and button signals on some under-the-hood 'surface' layer that receives inputs before the encryption takes place.

PS: I originally asked this in Game Development Exchange (https://gamedev.stackexchange.com/questions/28908/is-there-an-sdk-to-write-console-apps-to-simulate-an-xbox-360-controller) where it was suggested I try this Exchange over theirs and even Gaming.


texts:
simulate this circuit – Schematic created using CircuitLab
If IDSS= 10mA and Vp= -5V, when VDS=Vp, what is the value of ID and VGS?
Lets say I apply KVL on drain-source loop.
Then I get VDD-IDRD-VDS=0.
Substitute the value then I get ID=2.1x10-3.
After that, I apply

Solve the formula and get VGS=2.71V
Is the method I used correctly in solving this question?


texts: Driving an electromagnet for 10 seconds without overheating the coil

texts:
I have the following issue that I would like to discuss.
I have an electromagnetic lock based on an electromagnet rated at 24V/44 ohms and a PSU at 24V. Basically, you apply a voltage at the coil and the magnet pulls a metal part that opens the door.
I need to keep the magnet energized for 8-10 seconds. The problem is that during this process the coil of the magnet is getting warm and if we want to power it again in a few seconds it will not have time to cool and the temperature rise might prove fatal.
I thought of driving the coil with 24V for 100ms and then lower the output to 5V or even below this to keep the temperature low. This way the magnet will have sufficient energy at the beginning and then the low voltage will be able to keep the metal part of the lock in the open state without the temperature getting high.
I am using an LM317 adjustable linear regulator.
I am thinking of applying 20V at the beginning for 100ms and then changing the feedback network to output 3V for the rest of the duration.
My question is if this is logical or if there is another approach I should consider.


texts: ULN2003A to sink current when collector volatge less than base voltage

texts:
I am trying to drive a opto-isolator using ULN2003A. My question is that the ULN2003A datasheet here only states the maximum voltage that can be sinked, which is 50v.

In my application, the voltage to be sinked is less than 5 volt as I am driving opto-coupler which is pulled high at 3.3v with current limiting resistor. The opto-isolator is then connected to output pin of ULN2003A which needs to be grounded to complete the circuit.

Thus what is the minimum collector voltage with respect to base which can be sinked?

p.s. The datasheet mentions that the "com" can be left unconnected when driving resistance based loads.


texts: On which layers of 4 should the trace antenna be (433MHz)?

texts:
I have designed a simple PCB with the follow layers

Top Layer, high speed traces (rest ground copper)
Inner 1, Ground Copper area everywhere apart on the very left side where the trace antenna will be places and appart from the vias between bottom and top, however no traces on this layer
Inner 2, Power lines only (5V, 3.3V, 4V)
Bottom Layer, some low speed traces and some vias for the high speed traces go on bottom layer in order to facilitate their tracing. (rest ground copper)

The trace antennas I see are usually top and bottom layer but since the antenna is high speed, shall I only use the traces of it only on the top layer?
On the following picture you can see the antenna, Red is the Top and Blue the bottom layer. Can I leave
it like this or I should turn everything red?
Are there any comments/recommendations for the layering that I did(high speed top, low speed bottom and few vias for the high speeds on bottom aswel?


texts: Distribution of a 28.8MHz clock to 4 circuits

texts:
I am currently working on a project to time synchronize multiple RTL-SDR's. For capture frequency hopping GSM.

I have read that connecting the output of a single TCXO to multiple dongles only works up to 3 dongles due to increased inductance of the circuit. I need to have at least 4 to be time synchronized for my project.

How do I do that?

I am currently a student of Electronics 2nd year. I tried to figure it out online. Most of the circuits use fan out clock buffers, and I don't have much experience working with them.

So I am looking for a way to get 4 outputs from a single output of a clock to feed to my clock input of different dongles.


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Can we use zinc plated screws for PCB grounding?
Means the zinc coated screw head will be in contact with copper trace on PCB for grounding.
But this can cause galvanic corrosion between zinc and copper.
Can you all advise me on this topic?
Can this cause galvanic corrosion?


texts: Identifying and correctly using this component

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I have the two components, which are in the picture below.
I have a couple of questions. The first one is, how do I make sure that the IR LED detector is working? I tried searching for specs, but the searches for "IR sensor", "IR detector", "phototransistor", and "photodiode" kept throwing inconclusive information, at least for me (I don't have a lot experience in the field).
The second question is, how do I actually use the phototransistor (which I believe is what the one below is)? I tried making a circuit like so:
But I couldn't get the red LED to turn on, even when I made the emitter and detector touch each other.
I have jumped from site to site, but I can't seem to get it right. Could you help me?
Thanks.


texts: Can I replace LM358N with NE5532N dual op amp?

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In this circuit LM358N 1MHz 32V dual op amp is used (+12V and -12V). The question is, can I simply replace it with NE5532N 10MHz +-22V dual op amp for up to 8MHz DDS signal source?

Basically, this circuit has DDS output generated via R2R resistor network and adjusted via LM358N offset and amplitude regulating circuits. Offset can be regulated in range +5V..-5V while amplitude in range 0..10V.


texts: Phase angle between two sinsoidal currents

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I am having trouble solving an example in the book I came up with another solution, anyway the question asked to find the phase angle between two give currents- see attached image what I did I converted the I1 to cos by 90 it became 4cos(377t+145) and I drew both angles as attached image 2 . And I got that I2 leads I1 by 150.

The book's answer is different than mine is the book mistaken


texts: Theory: With an AC circuit adding capacitors will cause the current trend towards leading

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so if you add enough caps can you emulate what an inductor is doing, ie. Lead the current so far that it appears to be lagging?

I assume this doesn't work, why not?


texts: How to I calculate max current draw for this circuit?

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I’m trying to calculate the max current pulled from my 15V and -15V supplies. My OPAMPS also use the supplies for current.

All of my numbers seem really whack.

The part I am most confused about is the part with the transistors...
I have struggled with transistor circuits a lot and am hoping someone could help walk me through what I need to do.

IC Datasheet

Assumptions:

Caps are shorted because that is when we have max current
Both the speaker and mic do not draw current (?)

Questions:

What equations will I need for the PNP and NPN transistors? How do I implement them
Do I need to worry about the mic or speaker in this situation?
Should my voltages seriously be that large? I feel like they are too large but I cannot justify why since my gain is so large.

Photos:

Circuit

Work


texts: How to get an analog signal 0 to 12 V DC based on reference 0 to 5 V DC?

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I have an Arduino which is creating an analog voltage from 0 to 5 V (I used external DAC for it) and I need to use it for the regulation of "big" circuit with 12 V DC. So I am trying to get on the "big" circuit analog values from 0 to 12 V DC (the maximum current by 12 V is 55 mA).

Right now I am using MOSFET IRF520 for it, but it doesn't work as well as I expected. The MOSFET starts to open by voltage approximately 3 V and is fully opened by 4 V. So for the regulation of the big circuit, I am using just 1 V difference.

Right now I am considering maybe some JFET (e.g. J112?) could be a better choice for this type of job but I am not sure.

Can you please tell me, how would you solve this issue and what for a device would you use? Maybe can you propose some concrete FETs/transistors good for it?