texts: Old power supply regulation board will not trim to spec

texts:
I have an old voltage controlled synthesizer that relies on accurate power supply voltages (+/-) for everything to run in tune and so it can interface to other similar instruments.  Yesterday I opened it up and replaced the 35 year old power supply rectifiers and caps as maintenance.  At that time realized that the board was set at 9.64v.  Even when maxed out, the board would only reach 9.97v.  I feel that the board should regulate at the proper 10.000v spec with the trimmers around their mid point. My best guess is precision resistors (R39,34,44) drifted over the years?

The pic of the board shows the top left trimmer (R21) at factory position (9.64v) and when fully CCW, only got me to 9.97v

Link to full size schematic


texts: How to connect multiple sensors to single PLC input?

texts: Hello. I have a scenario where I have multiple PNP "error signal" from several sensors (let's assume 3 for now). If the sensor output is HIGH, then there is error. If the sensor output is LOW, then there is no error. The design is that if any of the sensor detect error then the PLC input will be HIGH. My question is, suppose if all three sensors detect error, it means all three will send voltage to the same port in PLC. Will it cause over current and damage the PLC input? Is the current in PLC port = current sensor 1 + current sensor 2 + current sensor 3?


texts: Broadcom component library for Eagle circuit design software?

texts: I can not find any broadcom components in Eagle, can some be download to be imported?


texts:
This is PWM controller I bought for speed control of DC motor:

http://www.ebay.com/itm/6-30V-DC-Motor-speed-Controller-Reversible-PWM-Control-Forward-Reverse-Switch-/162002954574?hash=item25b820e94e:g:RAMAAOSw6EhUQgOp

DC motor rotation direction is controlled using switch: when switch is in position I motor rotates in one direction and when it is in position II motor rotates in opposite direction.
Since I need to have limiters also, I removed this switch and shorted controller on this way:

Instead of only motor, I put on output of controller DPDT switch, limiters and motor. It looks like this:

Here is schematic:

Now I can change direction of rotation using DPDT, I have also limiters and of course I can control speed.
My question is, is it possible to remotely control direction of rotation instead of manual control using DPDT?


texts: Making a blender built for 120V work on 220V

texts:
I have a Vita Prep 3 (Vitamix) which is built for 120V and I want to use it in Europe with 220V.

I'd like to avoid a converter because of its size.

There is a motor built for 220V available:

Would I need to exchange any other parts than the plug and the motor?


texts:
I am designing a small switch mode power supply using the TPS63060DSCT, based on the data sheet I will require a 1.5uH inductor. I have be told that the Q-factor must be considered in the inductor (and capacitor) selection. Is it the case where the higher the Q-factor the better? and what would be the minimum q-factor for this design?
*assuming the chosen indicator also meets Current requirements.


texts:
I need to identify a connector on this image. It is the one labeled as 'Input Cable'. Image is from https://www.alphaomega-eng.com/neurofortis.html.

This is how the corresponding cable looks like (black connector). Unfortunately this is the only image available (to me) since I do not have the cable at my disposal to take any images myself:


texts:
Sometimes it seems my bluetooth speaker is particularly sensitive to the distance from my smartphone, sometimes it seems completely indifferent. The variable seems to the battery charge.

My question is: Is my bluetooth range impacted by the remaining battery on my smartphone as a scale or ratio?


texts: Controlled Impedance Trace-reference plane Placement

texts:
I am new to high-speed PCB  design. I was studying controlled impedance traces from the internet with the help of various documents.
Everywhere it says controlled impedance traces need a reference plane directly below it. I know that the reference plane is used to return the current path(Please correct me if I am wrong).
My question is why controlled impedance traces need a reference plane immediately below them.
What will happen if we put a signal layer below the layer which contains a controlled impedance trace.


texts: What determines Charge Controller PV input limits?

texts:
What determines how much PV wattage a charge controller can accept?

For instance - I am looking at a 50 amp charge controller with a max input voltage of 150v.

In the specs it lists max PV input as 750W for 12v and 1500W for 24V. This would put the input around 60A.

In this particular PV array I'm working on, I have 1000W - 68v at 15a coming off the roof. According to the CC input limits (150V,~60A) it should be able to accommodate that much PV. But the specs list a much lower PV input limit.

What am I missing? How can I properly size a charge controller?


texts: Rx data rate on CAN bus faster than polling rate

texts:
I'm working on a safety-critical SIL 4 system and so interrupts have to be kept to a bare minimum (hence using only timer interrupts). CAN is used in polling mode.

Suppose data arrives at a CAN node and is not read from the buffer before another node sends its data, will the data be over written or corrupted or will the first node's data persist and the second node's data be lost?

Is it Ok to use more than one interrupt in a safety-critical SIL 4 system because the only way to service data in time without loss of data will be using the Rx interrupt for CAN or each node must be given a time slot to communicate on the bus (not good approach since CAN is multimaster communication protocol approach)?

Note: I'm using an LPC1778 microcontroller.


texts: How to prevent noise when connecting "speaker out" of SIM800L to audio mixer?

texts:
Aim

I'm trying to build a device to be used for call center agents. They could make calls via this device, which could be connected to a PC to be able to record this conversation.

Solution

Build this device with GSM, Arduino and audio mixer, to mix both the voice of the client and the agent, then send it by audio jack to a PC.

Question

I'd like to ask how I could remove noise produced when I connect the SIM800L to the audio mixer? When I connect the audio mixer input to SPKP with common ground for both circuit and Arduino, I get a lot of noise. But when I connect my headphone to SPKP & SPKN, I get pure sound with no noise.

I tried to use a passive low-pass filter to prevent any noise due to GSM freq (850 MHz, 1900 MHz) and allow audio voice frequency.

Any suggestion please?

Notice

I can't connect SPKP to the input of the audio mixer and connect SPKN to the audio mixer ground, since it produces GSM error. So I have to connect only SPKP to the input of the audio mixer.

I found this circuit configuration on the datasheet of the SIM800L. If I applied it to my GSM and connected it to the audio mixer, will it solve the issue?


texts: Energy consumption of mathematical operations

texts:
Are there any general estimates of the (relative) power consumption of mathematical operations in electronic circuits? Surely, this is chip-dependent, but for example, exp(x) and log(x) seem to be universally much more computationally heavy than power (x^2, sqrt(x)) and addition/subtraction because the former is approximated via iteration/expansion.
The context of this question is that I was having a discussion with a colleague about whether to update a computation to include the term exp(x) rather than just x and it will run approximately once per second when the chip is non-sleeping. This is part of a larger battery-powered electronic unit that has two piezo actuators, sensors, and several other components. The argument came up that the extra energy consumption of computing exp(x) each second would significantly reduce battery lifetime.
The precision needed is only around four significant digits. Unfortunately, I don't know what chip used in this particular instance, but it's relatively low-level. It runs on a battery for 10+ years and can do linear interpolation and multiplication. But since I can't find a single number on the cost of computing e.g. exp(5.24) for any chip out there, it's hard to assess the problem of whether it will substantially drain the battery.


texts: What is the simplest circuit to measure RELATIVE RF signal strength with multimeter?

texts:
I need to use a multimeter to align two low powered dipole antennas which are in the same room. Naturally, I cant hook up the antenna directly to the multimeter. Which is the simplest circuit to get relative measurements of RF signal strength with multimeter?

I found this one online, but I'm not sure if it will get the job done. Would I connect one pole of the dipole to "RF" and the other to "GND"? And how would I interpret the output on the multimeter?


texts:
I've been working for some time trying to figure out how it might be possible to translate a schematic into something like a node graph, where each node is a component.

I've taken some liberties in creating it due to my limited understanding, but it seems to be working now for basic resistor circuits, for example:

# define the components
V1 = Battery(5)
R1 = Resistor(100)
R2 = Resistor(200)
R3 = Resistor(300)

# connect the components and graph
c = Circuit()
c.connect(V1, R1).connect([R2,R3]).ground_all()
c.graph()

Now I have a directed graph that solves for the currents at the edges (Everycircuit on the left):

This only handles the most basic cases (nothing time-related, multiple input/output, etc.). A couple questions about this:

Other than showing current, what additional things would a normal 'current-solver' show or do?
What seem to be the main ambiguities from the representation of the circuit on the right?


texts: What is the difference between zero leading and zero lagging?

texts:
The armature reaction of an alternator will be completely magnetising when load power factor is

A unity
B zero lagging
C zero leading
D 0.8 lagging

Though the answer is zero leading.

As per my understanding if angle =90 then only magnetizing  will be maximum. So by this load power factor cos90 =0
But I am confused about the lagging and leading power factor in this ?
How will I decide if its leading of lagging power factor ?


texts: How do these new-fangled phone chargers achieve step-down?

texts:
There appear to be two kinds of power supply adapters in market.

The first/older kinds were such that they were reasonably heavy and had a small transformer inside the adapter itself. The newer ones in market (those that come with a mobile phone for instance) are surprisingly lightweight; I find myself wondering whether there is even a transformer inside.

How do these new-fangled adapters achieve step-down?


texts: Single supply inverting op amp: output not as expected

texts:
I'm using a single supply op amp. Specifically the LM2904NG. I am trying to invert 0.67 V to -0.67 V. My output is in fact positive. I simulated the first single supply op amp I could find (LT1006) in LTspice in order to see if I could figure it out. I started with just trying to invert 3.3 V before adding in more circuitry but it does not work. It outputs 136 mV in fact.

My expectation is that the output will be
where Rf=R4 and Rin=R1.  This is not the case.  Am I missing something basic about single supply op amps?  Can these not provide a voltage below their negative rail? I suppose this seems reasonable.


texts: Do I need to use a MOSFET to drive 60 WS281Bs?

texts: I’m building a custom keyboard and have 60 WS2812Bs as part of the backlighting system. I’m worried about the signal integrity as I’m using an STM32 and the max current on that pin is 25mA. Do I need to add a MOSFET to boost the signal or is connecting a 330 ohm resistor enough?


texts: Why does only the tip of the electrode melt when arc welding?

texts:
I saw on youtube some people performing arc welding with "consumable electrodes". At a first glance, I saw that the current flows through all the electrode and the workpiece and my question comes from this fact.

I think that the workpiece doesn't melt because it is usually a lot bigger than the electrode, therefore, it can dissipate the heat a lot faster.
The electrode is thinner though, and I don't understand why the whole electrode doesn't melt if the current that flows through it is high enough to melt the tip of the electrode.

I thought about it and my guess is that it has something to do with the contact resistance at the tip of the electrode being different from that of the electrode's material. The reason is that the power, which is somehow proportional to the heat generated, should be $$P=I^2R$$
But I don't think that the difference between the two resistors is high enough to explain this phenomenon, so I was wondering what part I'm missing!


texts:
I have code like this in IAR Embedded Workbench. At least Led0 should blink?

#include <io430.h>
#include<signal.h>

void main(void)
{
  WDTCTL = WDTHOLD + WDTPW;
  P1DIR = BIT6 + BIT4 + BIT3 + BIT7 + BIT0;
  P1OUT |= BIT6 + BIT4 + BIT3 + BIT7+ BIT0;
}


texts: I need help Building A Solid state Electro magnetic Mixer

texts:
I'm just getting into electronics, and I would like to build an electromagnetic mixer. See here. Most of the tutorials I have found have magnets stuck to a motor spinning under a non magnetic material causing a piece of ferrous material attracted to the magnet to spin in a glass or plastic container.

I'm thinking of one with NO moving parts to wear out: instead of a motor spinning, have a series of electromagnets in a circular pattern. I'm thinking 8 equally spaced from each other (octagon with them at the corners). It would work by energizing two of the electromagnets at a time across from each other in the circle with opposite poles, one North the other South. Then quickly turn off those two and energize the next two opposing electromagnets in the series in a clockwise direction.This turning on and off would cause the ferrous material to spin. By controlling how fast the magnets swap you would control the spin.

Now the Help I need:

Is this feasible?
How do I control the turning on and off, using simple components.
I would like to use a 10k ohm potentiometer to control the rate of spin (magnet swap). Mainly because I have one laying around.
Since each magnet will be energized in ether direction at some point in the sequence, how do I swap it.
Would I require a cooling system?

(Key Point of Design: NO moving Parts)

Thanks in advance for any help given.
I'm a student mechanical engineer, whose got a love of electronics and control systems I really want to get seriously into electronics.


texts: Threshold ramp frequency voltage converter

texts:
My issue is understanding how the socalled "threshold ramp frequency voltage converter" (translation from Italian) works. In what follows the block diagram

and in the next picture a time plot of \$V_s\$, \$V_C\$ and \$V_O\$ respectively

As far as I understand, the "an" subscript of \$-V_{an}\$ means the signal is analogic. \$-V_{an}\$ enters into a integrator circuit, the output of which is going to be compared with \$V_S\$, the shape of which is reported in the first of the plots above.
When the integrated signal coming into the positive input overtakes \$V_S\$ than the comparator switches, The monostable device detects the transaction and provides an impulse on \$V_O\$ of constant time.
In the meanwhile, S switches, discharges the condensator, things go back to the initial state and the system is ready for the next loop.
I fill like I understood almost all of the circuit, but honestly I don't understand how such mechanism should provide a tension to frequency conversion. Is there anybody who could provide me a further explanation and/or web page in order to make me fully understand this device, please?


texts:
I have some questions regarding BJT amplifiers, for common emitter

1) How does the test equipment influence the frequency response of the amplifier ?

2) Why is the output voltage measured using a 10:1 probe ?

Test equipment:

Dual trace oscilloscope

Function generator

BNC “T” piece

BNC/BNC cables 1 m

BNC/BNC cable 30 cm

BNC/Crocodile cable

10:1 probe

Custom-built 40 dB attenuator


texts:
So i am going through this excellent book Patterns for Time-Triggered Embedded Systems and have a question regarding calculating values for hardware timers precisely. See "Hardware Delay" pattern in the above book.

My understanding is that, a "clock source" (aka "System Clock") generates a steady series of ticks (say f1 khz) which is then fed through a "Prescaler" unit which divides it (by a factor n which can be 1) giving another frequency (say f2=f1/n khz) which is then fed to the processor. Thus the "Processor Clock" has a frequency f2 and time period t2=1/f2 ms. To calculate a precise time interval (eg. 100ms timer) we just calculate the number of ticks in 100ms like 100/t2 = f3 "processor clock ticks". So we need to setup the appropriate timer registers to values corresponding to f3 to generate a 100ms tick.

However it does not seem to be so straight-forward (at least for the 8051) because of the number of ticks required for a "processor instruction cycle". A processor goes through its instruction cycle i.e. "Fetch->Decode->Execute->Interrupt" (interrupts are checked at the end of the current instruction) which takes a series of ticks. Ideally the entire instruction cycle should take just 1 tick (eg. a pipelined processor) and so i can use the above calculation to setup timers. However, apparently in the original 8051, the System clock ran at 12 mhz and each instruction cycle took 12 ticks. Since interrupts are checked only at the end of the instruction cycle, we now need a further division by 12 to get the correct "timer" clock tick, which is "processor clock"/12 i.e. f2/12.

Is my above understanding correct? If true, how can i calculate precise timings when instructions can have different cycle ticks (eg. mixed 32 and 16-bit instructions). Also do timers have to be incremented via a processor instruction cycle or is there a way in HW to increment a timer register strictly in sync with the output of the "Prescaler" unit?


texts: inductor DC resistance too low for el driver IC: can I still make this circuit work?

texts:
I bought an EL lamp driver IC from Microchip, the HV830, but I was not able to find the exact inductor indicated in the test circuit shown below, the Murata LQH4N221K04.  I found another 220uH inductor from the same manufacturer, the Murata 11R224C, but it has a lower DC resistance, 2.4 ohms, vs. the recommended 5.4 ohm value.  I tried following the values for the test circuit with my replacement inductor, but it is drawing too much current, about 395mA or so.  The spec sheet for the inductor says the inductor saturates at 240mA.  My output voltage is -6V->2V, a far cry from the -100V->100V typical of this circuit.

I also have a few other minor differences in the circuit: I'm using a short piece of EL wire (1 foot or so) for the load instead of a 3 square inch EL lamp, and a larger bypass capacitor (1 uF instead of .1 uF) since I'm not sure what my power supply impedance is.

First, I tried increasing the switching frequency of the mosfet, from 55 KHz up to 885 KHz, but this did not reduce the current enough to fix the issue.

Then I tried putting a 5 ohm power resistor before the inductor, but I believe this causes 2 issues:

1) the voltage drop across the power resistor is too large, so now the inductor does not get enough voltage to charge the capacitor with inductive flyback.  If I step up the voltage enough to compensate for the voltage drop, the inductor saturates due to the higher current (not to mention the other components aren't rated for that much current).

2) I think the inductor will charge at a different rate with the power resistor thrown in the mix.  I believe I might be able to compensate for this, as this IC allows me to change the switching frequency of the internal MOSFET with a different Rsw-osc value.  Unfortunately, I cannot adjust the duty cycle which I believe is set at 88% on.

So, my question is: is it possible to make this circuit work with my current inductor?  I was also able to find a 220uH inductor online with a 7.1 ohm DC resistance, but I haven't tried it yet.  Thanks in advance.

EDIT: Here is a technical note for a similar EL driver IC from the same manufacturer:


texts: General guidelines in making a choice between Combinational or Sequential approach?

texts: I have to design a functional unit, which can  be done either using Sequential Circuits or combinational.  I have to make a choice. Development time is not an issue, but resource usage and space are-should be minimum. I understand that there may not be a law stating which choice will be economical but are there  any general guidelines in making such choices keeping in mind the constraints (resource usage i.e amount of silicon, and space)


texts: Altium 3D View not showing properly and Via placement problem

texts:
Can some please tell me how to fix this?
I select all 3D views but every time I get transparent board.

and when I try to place a via for routing it moves outside of the board.

need help.....


texts: Footprint design for vibration resistance

texts:
I have a product that will be subjected to reliability testing (random vibration and thermal shock) and I need to design a footprint for an SMT power inductor that will give the best mechanical strength to resist damage during vibration testing. I've looked through the IPC 7351 standard but I cant find anything that talks about how different pad size (resulting in different fillet shape) will affect the mechanical strength of the solder joint. The part I am working with is Murata LQH3NPN1R0MMEL. It has a mass of approximately 0.05 grams.

Does anyone have a method for calculating a land pattern for optimal mechanical strength?


texts: What are the risks of powering fan AC motor with Triac dimmer?

texts:
I'm going to replace current resistor potentiometer with arduino-controlled triac scheme, probably this module.

I'm going to load it with 6 motors , 300W each.

How bad the EMI gonna be (would I be able to plug audio amlplifier
to the same line)?
Would it substantially influence reactive power
    section of my electricity bill? I am located in industrial building in the country that has charges for reactive power.


texts: How estimate Current Consumption In minutes reference

texts:
Hello I hope somebody can give a short answer.
I am confused about how estimate the current consumption of a Electronic Component/device. For example a led 20ma @ 3V or an arduino mini @ 50ma.
If I use 3 led the current draw is 60ma so in a battery of 2850mAh the leds can be power on 47.5 hours, right?.
I am confused when I want to estimate how much hours can be running the 3 leds if they are power on only each 15 minutes for two minutes, then turn off... And so on. I mean, for example, turn on at 15.15 and turn off 15.17, then turn on 15.30 and turn off 15.32 etc... I think in 1 hour the leds power on 4 times for total 8 minutes so the current consumption is 60mAh*(8/60) ???
In a 2850mAh battery the real life of my leds can be 2850mAh/(60mA*(8/60) = 322.5 hours ???

I am totally wrong?

Thanks you very much


texts: Loading effect of two stages of RC filter

texts:
The mathematics result does not match with simulator results.
The transfer function of a first order passive low pass filter is:
$$\frac{V_{out}}{V_{in}} = \frac{1}{(sCR + 1)}$$
If I have two stages and I need to calculate the phase shift of the output. All the resistors in the circuit are 1000 ohm. All capacitors are 100 nF. operating frequency is 1000 Hz (sine wave).
I think the new transfer function would be:
$$\frac{V_{out}}{V_{in}} = \frac{1}{(sCR + 1)^2}$$
Now I substitute the values of the circuit in the transfer function where,
$$s = j \times 2\pi f$$
The result was the phase shift = - 64 deg.
When I simulated the circuit on Protues, The phase shift was about - 72 deg.
This website says the result is -72 deg.
Why mathematical result is different from the result of simulator and the calculator of website? Am I missing something?
I used the arg function of my calculator to get the phase shift form the complex transfer function.


texts: STM32 NaN value for floating point operations on global variables

texts:
I am trying to implement a simple Odometry computation loop. Which is being run in a while loop. Following is the code:

double dx=0,dy=0,dw=0;
double v,w;

void computeOdom(){

    uint32_t ticknow=ticksms;  //global timer variable (gives current ticks in milliseconds)

    v=0.0;
    w=0.0;

    double dt = (ticknow - tickprev)/1000.0; //time elapsed since last odom update
    double res = (double)ENCODER_RESOLUTION; //Encoder Resolution ticks per revolution
    double leftvel = (double) ((((Left.position)/res) * 2 * M_PI))/dt; // Angular velocity of left wheel (rad/s)

    Left.position=0;
    double rightvel=(((double)Right.position)/ENCODER_RESOLUTION)* 2 * M_PI/dt; //Angular velocity of right wheel (rad/s)

    Right.position=0;

    double r_L= 0.260/2;
    double r_R= 0.260/2;

    v += (r_L/2.0) * leftvel; //Linear velocity of the robot
    v += (r_R/2.0) * rightvel;
    w += (r_R/0.610) * rightvel; //Angular velocity of the robot
    w -= (r_L/0.610) * leftvel;
    double tempx=0.0,tempy=0.0,tempz=0.0;

    if(!(w==0.0f)){
        dx += (double)(dt * v * arm_cos_f32(dw + dt*(w/2.0))); //The line where dx becomes NaN
        dy += (double)(dt * v * arm_sin_f32(dw + dt*(w/2.0))); //The line where dy becomes NaN
        dw += (dt * w);
    }
    else{
        dx += (double)(dt * v * arm_cos_f32(dw));
        dy += (double)(dt * v * arm_sin_f32(dw));
    }

    tickprev = ticknow;

    printf("prev_x: %f\n\r",dx);
}

I have debugged the code with GDB. I have checked for any exceptions that are being raised but everything looks fine. And if I change the code to this:

dx = (double)(dt * v * arm_cos_f32(dw + dt*(w/2.0)));
dy = (double)(dt * v * arm_sin_f32(dw + dt*(w/2.0)));

The NaN goes away. I have tried using temporary local variables. I have checked the cos and sin functions by executing them on local variables and they work as intended. No issues there. Only when I want to increment the global variables, the issue arises. dx, dy and dw are persistent global variables which keep track of the position.

This is the version of arm-gcc I am using.

  arm-none-eabi-gcc 5.4.1 20160609 (release) [ARM/embedded-5-branch
  revision 237715]

I am using STM32F429 discovery board with Arm-gcc toolchain and FPU has been enabled. Disabling the FPU has no effect whatsoever.

Any pointers or suggestions?


texts: Designing a matching network with biasing inductor

texts:
I'm designing a 345MHz transmitter using the MAX 7044 ISM transmitter with an electrically small antenna and need to test the matching network. I will connect the VNA in place of the transmitter using a short piece of coax. I also have made calibration standards out of the same coax and length.

How do I set up the circuit to measure the impedance as seen from the transmitter that includes the biasing inductor which is connected to the supply? I assume that because the DC supply and ground both appear as grounds to small signals, I should short the battery terminals (battery removed!) so that currents can flow through the biasing inductor out to the battery and onto ground. Doing this would have the added benefit of taking into account the inductance and resistance of the power supply traces.

Is this the right way to handle this?


texts:
I am making a project, basically consisting of 4 bulbs and 4 switches.
I want to make it such a way that when either of the 1 switch is pressed 1 bulb should glow. The bulb which glows should be the one pressed first. Once pressed, the other switches should be unable to operate.


texts: Multiple micro solar power wireless transmitters / receivers operating in close proximity? SRDs

texts:
Hi I have a few questions about a Tx / Rx idea.
Description
Approximately 10 transmitters and 10 receivers are expected to work in close proximity of each other. However Rx1 only receives information from Tx1, Rx2 only receives information from Tx2 and so on. The information being transferred is a recurring 12 bit binary data (hard-coded).

Technical specifications:
Very small size transmitter - 1 inch x 1 inch
Very small size receiver - 1 inch x 1 inch
Very short range ~ 1m radius

I am curious about a few design issues:
1.  Is it possible to have both each Tx and Rx to be solar powered by a 1 x 1 inch solar cell?
2.  Do I have to use a different band for each Tx? Eg 315 MHz/Tx1, 316 MHz/Tx2 ….etc? Is there any work around for all Tx’s to transmit on a single band?
Also can anyone suggest where I can get the components to build what I just describe?
 Looking forward to your responses.


texts:
I'm trying to control a 2.4GHz remote for LED panels. Inside there is a keyboard decoder chip and an RF chip, the markings don't return any immediate results.
I've decoded the data with a logic analyzer but I'm having a hard time replicating the results with an Arduino, i.e. talking directly to the RF chip.

I'm not sure if the chip is a slave or a master, since it seems to generate its own clock (SCK).

I can detect 5 pins that are actively used:

D0 seems to be a "command set" signal. Seems to be an input.
D2 looks like an SCK at 1MHz, but sometimes it has long pulses. Seems to be driven by the RF
D4 seems to contain the data that the RF needs as input, clocked on D2
D5 seems to return a "1" when a byte has been sent on D4, when clocked on D2
D7 slave/chip select?

When driving the D0 line with an Arduino, using around the same timing as the keyboard chip, I can see the LED on the remote flashing in rhythm and all the other lines wake up with a digital signal on them.

I've tried bit-banging D0 + D2 + D4 + D7, then just D0 + D4, but I have the feeling there's some need for interactivity.

The chips are really small and close together, I cannot really isolate them (such as adding resistors for determining direction.

Is this some kind of an SPI protocol? Does this look like something commercial or for which there's an Arduino (slave?) library? Are any of my assumptions wrong?

Edit: added a PCB photo


texts: Light Sensitive One Pulse Activated Switch

texts:
Hello I planned a light sensitive one pulse activated switch to know when water tank is completely filled and to turn the water pump off using a relay until I reset the circuit using its N/C Switch.

NOTE: There is an external circuit to detect if water starts to overflow through overflow pipe and turns a Red LED on to make this light sensor circuit detect it.

Light sensitive part is working fine, but the problem is when I supply power to the circuit, Relay 2(RL 2) I mentioned in this circuit diagram keeps turning on and off continuously and I hear its extremely fast continuous switching sound like a damaged speaker. Relay 2(RL 2) will die if it turns on and off in such speed. (The purpose of RL 2 here is giving continuous current to the RL 1 to act as a one pulse activated switch.) I want to keep Relay 1(RL 1) turned on even light turns off and only to be turned off when I reset the circuit.

Here is the circuit diagram.

What changes can I do for this circuit to keep the Relay 1 (which activates by a light falling on LDR) on until I reset circuit using N/C Push Switch?

Thanks in Advance.


texts: I'm trying to set up a electrical polling field that produces 2000 V/mm inside a kiln

texts:
I'm attempting to produce my own piezoelectric ceramic materials.

I wish to manufacture half dollar size x 1/4" thick ceramics which are kiln fired at just under 1020 degrees Fahrenheit while exposed to a 2000 V/mm linear uniform electric field. Applications of this sort are carried out in the semiconductor industry - I'm trying to do something similar with home manufactured or assembled equipment.

I am looking for information and/or advice on how to achieve this. I am seeking details of appropriate wire sizes and spacings and of circuit diagrams and components suited to achieving the above described result. Information on suppliers of any specialist parts would also be welcome.

I would like to be able to place a half dozen or more discs in the oven at a time, so to achieve a uniform electric field it would ideally would need to cover the entire inside of the oven.

My understanding is that semiconductor industry solutions utilise a parallel plate capacitor and with the thin ceramics used, they seem to need close proximity of the parallel plates. I understand that it is preferable to have the probes make contact with the ceramic material.

Any information on how I can implement such a system on an amateur/ DIY basis would be welcome.

=================================

Previously:

This is for half dollar size x 1/4" thick ceramics.  I need wire sizes and components and schematics or suppliers for the outlined specs. I would like to
be able to place a half dozen or more discs in the oven at a time so the
electrical field ideally would be the entire inside of the oven.  The temperature
in the oven will be just under 1020 degrees farenheit.  This is typically done
in the semiconductor industry with a parallel plate capacitor and with thin
ceramics yielding close proximity of the parallel plates.  It is advised to
have the probes make contact with the ceramic material.  Thanks


texts: Why is the feedback of op-amp oscillators connected to inverting input instead of positive input

texts:
I'm new to the subject of oscillators and learned that sustained sinusoidal oscillations are made possible by positive or regenerative feedback. Is that right? If that's true then I can't quite grasp why, especially in op-amp LC or RC oscillators, is the feedback network terminated to the inverting input while the non-inverting input is usually grounded. Doesn't it make it negative feedback? My circuit analysis ability is not yet fully developed so please bear with me.

Also, I would highly appreciate if someone patiently traces out the operation of this particular colpitts oscillator for me in relation to this question.

One more thing: does the LC network act as the feedback or it's just a tank circuit while Rf entirely serves as the feedback? I know. silly questions.

Thanks everyone.


texts: What is this multiplexer doing in this design?

texts:
The design is from a Xilinx FPGA doc. I think these are preprogrammed look up tables because there is no select bit input, but on the bottom it says they are:

  Multiplexer[s] Controlled by Configuration Program

I'm not sure how to interpret that. The design sort of looks like an edge detector.

What is this and what is it doing?

Is it configurable to have the same functionality of these two circuits?


texts: How do you input the voltage signal to an oscilloscope?

texts:
I was watching this tutorial on "analyzing actual Ethernet encoding"
https://www.youtube.com/watch?v=i8CmibhvZ0c&ab_channel=BenEater

Orange pair is transmitting data to the oscilloscope and the green pair is receiving data to the right. This oscilloscope measures the voltage across the two wires of the orange pair and plots that voltage over time on the graph.

Using Manchester coding, he's decoded 16 bits. The first byte is 75 (K), the second is 65 (A).
My question is, how did he input "K" and "A" in the first place, which then shows up on the oscilloscope? Is it as simple as typing "K" and "A" on the keyboard? I want to know this so that I can replicate this experiment by myself should I wish to.
Thanks!


texts: System Generator: How to generate a .bit file?

texts:
I am using System Generator and I would like to generate a .bit file in order to load into my FPGA. Does anyone know how to generate a .bit file with SG?
Thank you.


texts: Design a PCB with an elevated surface in the middle (KiCad)

texts:
I have designed a PCB where a device is glued and there will be wires bonded from the device to transmission lines on the PCB.

I would like to have the bond pads on the PCB and device on an elevated surface with respect to the rest of the PCB (image attached). I wasn’t able to find a way to render something similar to what I drew in the image. Is this something I can do in KiCad? (as it stands, the PCB is perfectly flat (right bottom image) but I would like to introduce an elevated surface, similar to what I have drawn on the right top.)

Thank you!


texts: 4mA-20mA loop behaviour when out of range

texts:
I have a temperature sensor that records temperatures from 10ºC to 30ºC, but in my project they only want temperatures to be read in the range of 15-25 with 4ma when 15 and 20ma when 25.My problem is what is supposed to be the behaviour of a 4-20 loop when the sensor records <15 and > 25.Should it freeze on the minimum and maximum value or should it take 0 as value?
thanks


texts: Spectrum Analyzer: Resolution Bandwidth vs Acquisition Time

texts: Why a smaller resolution bandwidth (RBW) in a swept tuned spectrum analyzer RBW requires longer acquisition time?


texts:
I want to connect FT232R chip to android phone.
I have downloaded FTDI terminal for android from https://play.google.com/store/apps/details?id=com.ftdi.j2xx.hyperterm
FTDI program has to startautomaticly when I connect FT232R chip to phone.
Sometimes it works fine, but sometimes android does not detects chip.
sometimes chip is detected only 1 of 10 times.
What could be the reasons?


texts: Trying to identify part driving in magnetic levitator. Maybe a 2.5 V switching regulator?

texts:
Its from a toy magnetic levitator purchased on alibaba. I wanted to understand and modify it but the key component has the markings sanded off. I'm pretty sure I got the pins figured out and know how it works but I would love to find the actual part.

See the images below. The chip is a SOIC8 I believe and it provides an ~450 kHz PWM signal to drive the control coils at ~1 A. The PWM seems to be ~(50% + 100*(2.5-Feedback)) with the 100 number being a really rough estimate.

Anyone got any ideas? I would be really grateful.


texts: Parallel and series cut crystal difference

texts:
Section 2.2.2 of pic18f4550 datasheet says:

In HS, HSPLL, XT and XTPLL Oscillator modes, a crystal or ceramic
resonator is connected to the OSC1 and OSC2 pins to establish
oscillation. Figure 2-2 shows the pin connections.  The oscillator
design requires the use of a parallel cut crystal.
Note: Use of a
series cut crystal may give a frequency out of the crystal
manufacturer’s specifications.

How do I know the type of a crystal? Which type is more widespread?
I'm planning to buy a crystal from here http://belchip.by/section/?selected_section=02156&filter_var=&page=1&limit=120&query=&sorting=price
How do I select the right one, there is no any data about them. Maybe it's possible to tell the type by their look?
Also why, when and how does the type matter?


texts: What is the diode current when used in clipping/clamping

texts:
The rule of thumb is that when a diode is fully on, it looks like a short circuit (ideally).  So (to make this easy), say I have 100 V source and a diode which breaks down at 10V.  If my power supply/source impedance is 1 Ohm, will the current through my diode be:

I = (Vsupply - Vdiode)/Rsupply = (100 - 10)/1 = 90/1 = 90 Amps, or
I = Vsupply/Rsupply = 100/1 = 100 Amps?


texts: VHDL - Output an array to another module - or perhaps a better way to implement?

texts:
I have two modules in VHDL, they look something like this:

simulate this circuit – Schematic created using CircuitLab

In module U1 I have an input of 8 switches, and each switch is supposed to send a set of packets (vectors of 64 bits) from module U1 to module U2. Module U2 outputs every one of those packets in turn, with a 1MHz clock, to some external device.

For convenience, lets call each set of packets a command.

I have already implemented such a thing (without arrays), but it's messy and it creates a very long code. To avoid that, I thought about using arrays and functions/procedures, where each function/procedure (can a function's output be an array? I'm leaning towards using a procedure here) stores a command (theoretically this could be 18 packets) in an array, and that array is later sent to U2.

The reason I want to use a function/procedure is because every command could be done multiple times with each flip of a switch (for example, rising switch 2 could send command number 1, command number 2, command number 3, command number 1) and of course this will make the code much smaller and efficient.

Edit: Module U2 takes each packet (64 bits) and with a state machine separates it to packets of 8 bits each and outputs them to the external device in turn, using a clock. So obviously, I need to have one signal take each packet of 64 bits one at a time, that's why I've thought about using arrays.

My questions are:

Is that possible? Can an array be an output of one module and the input of another?
In your opinion, is there a better way to implement this? (that's the main question here)


texts: powering a fan with ATX PSU 5v standby when off, with 12v when on

texts: Using an ATX PSU, how would I design a circuit to power a load (dc fan) with 5v standby when PSU is off, and with 12v when PSU is on. I want to control (on/off or pwm, it should not matter?) the fan from a 3.3v mcu (powered with standby 5v) using a single pin. I guess it will require at least 2 P-mosfets, resistors on gates side and flyback diode across fan, but can't find how to do it cleverly without extra "logic" on both gates sides.


texts: I have been searching online on how to calculate power of a generator based on the rpm, but I cannot find anything. Is there a equation that relates rpm and power generated by a induction generator? Also, is there an equation that gives minimum force needed to turn the generate based on the strength of the magnets?


texts: Is it possible to turn an audio signal ON/OFF using a solid state relay?

texts:
I'm thinking about controlling an audio signal (turning it ON/OFF) using a solid state relay switch? Is that even possible?
If not, is there a different or easier way to do this?

I'm a noob in the field, so would greatly appreciate a simplified answer (i don't mind over simplification).


texts: Best way to get a low DC voltage from a high DC voltage for a power supply?

texts:
I have a 200V DC power input and I need to, with no external voltages, generate a 12V-24V voltage to run the control electronics off, at about 50mA.

I've considered zener diodes and potential dividers but they waste too much power; the resistor at the top must dissipate 9.4W to provide 0.6W, which is a ridiculous waste and difficult to handle. I've tried to look at how switch mode wall warts do it, but they seem to have some kind of fancy mechanism of powering themselves from the output, which I don't really understand. (Neither do I understand how they initially get a voltage.)


texts: Issue with wiring eMylo remote control switch

texts:
My eMylo switch has five electric sockets (which can be wired.)
The wiring diagram shows that the input positive (anode - the red wire from the 12 DC power) must be wired to the most right socket of the switch, the input negative (cathode - the black wire from the 12 DC power) must be wired to the second-right socket of the switch.
The wiring diagram shows, that the output positive is just the input positive (split before it enters the most right socket of the eMylo switch,) and the output negative is the third-right socket of the switch. The diagram also shows that there is a red wire inside the eMylo switch, which connects the second-right socket (the one connected to the input negative) with the fourth-right socket of the switch (I have no clue for what reason.)
When I wire the switch to the input positive (anode) and negative (cathode), the switch's light goes on. When I press the transmitter's button, another light goes on (indicating, that the switch is receiving the signal from the transmitter). HOWEVER, the voltage between the input positive and the third-right socket stays 0 (while it should become 12V at this point) - the switch does not do its job.
Am I doing something wrong? Can someone, please, guide me?

node)


texts:
I am about to use this TPA0211 chip to amplify my audio signal. Supply voltage will 5V and load resistor is 4Ω. According to figure 6 page 6, Output power will be around 2W. However, I need 1.5W as output power.

I see two solutions:

Low supply voltage thanks to diode
Increase speaker's internal resistor

Here is my questions: How is it possible to increase Rl (still in figure 6 page 6)?  Will a simple serial resistor work (Radd in the next figure)?


texts:
I have a exploded aluminum electrolytic SMD capacitor on a 12v somfy wireless blind motor controller (r28) with the markings

125
220
6Z

I'm trying to figure out what the markings mean so I can replace it. Is it 22v 125uf? Or 220v 125uf? Or 125v 22uf or 125v 220uf? Or something else? Which configuration would make the most sense with this?


texts: KiCad : How can I create a footprint with thermal vias?

texts:
I have a SMD chip that gets pretty warm when operating and I want to try and design a footprint that allows more ventilation and extra copper to keep it in range.

Does anyone know of a tutorial that covers how to make footprints (MOD files) with vias through it?

Have Googled it, but could not find a lot about this topic.

I know that it's possible to manually change the MOD file with a text editor, maybe that's an option.


texts: How to know if my voltage regulator is still working or not

texts:
I have a voltage regulator TPS788 from TI. The output voltage is 3.3v, and the output current is 150mA. I connected a LED to it, and I found that the LED is blinking really fast. Does that mean the Regulator is not working properly, or the LED it self is not standing this amount of current ?
Note: I am using another regulator TPS789 (1.8V,100mA), and The LED is working fine.


texts: Does a motor's stall current change with applied voltage?

texts:
In other words, if the load is great enough, will a 110V, 18A rated motor being run at 5V stall at the same current as if it were run at 110V? I'm asking because I'm currently working with a treadmill, which at its lowest speed (I read ~6V across the motor free-running) has enough torque to move a large amount of weight. I measured the motor's resistance to be 0.9 Ohm, so at its lowest speed free-running the current draw is around I=V/R = 6.7A? Or is that the stall current?

Would powering the motor on its own with a 5V supply be the same as the onboard controller providing 5V to the motor through PWM 120V?

I guess I'm just surprised a motor can provide so much torque with such little voltage. So what determines a motor's current?


texts: 7-segment display BCD decoder with normal hex values

texts:
I'm trying to find a 7-segment display BCD decoder IC with normal HEX display.

Most of the decoders that I managed to find have an output like this:

These hex values just look awful. I previously did this decoder on FPGA, and the output looked like this:

A b C d E F

Does anyone know some BCD decoder IC with "normal" HEX display?


texts: What is the difference between a 1st and 2nd Order Digital Filter

texts:
I was just curious as to the differences between the two order filters?

How I created these discrete filters for references

Designed in Continuous first then converted into Discrete
Using Tustin's method as I just want to convert the plant from continuous to discrete
Fc = 20kHZ
Used Prep warping nyquist frequency = 20kHZ (Sampling at Ts = 0.000025/40kHz)

Filter 1: 2nd Order Butterworth filter Analog

Filter 1A: 2nd Order Butterworth Filter Discrete

Filter 2: 1st Order RC Filter Discrete

As you can see in Filter 1A I was shocked to see that "Brick-wall" response and was curious to see what if I used a lower order filter.

In Filter 2 you can see a similar result. The only difference I can tell is that magnitude (dB). The 1st Order filter has a flatter pass band then the 2nd Order Butterworth Filter.

Is there any advantage in using a higher order filter when it comes to discrete? Why in discrete the "Brick-Wall" response is much more apparent now when its only a 2nd Order.

Let me know if I even approached this correctly has I haven't dont discrete in a long time, so I wouldn't be surprise if something went wrong.

Bonus question, why when I try to do a step response for both filters I get this:

Another question that came to mind: Could we use the Sampling time to essentially change the Cut off frequency then?

EDIT: Looks like my Sampling times are wrong no idea what I am doing anymore. How do you know which Sampling Time is suitable for you? Or is that the trade off sacrifice how close it looks to the continuous for sampling times

Code:

%% -- Low Pass Filter (LPF) -- %%
R1 = 15000;
R2 = 9100;
C1 = 0.001*10^-6;
C2 = 470*10^-12;

LPF_A = ((1)/(C2*R1*s + C2*R2*s + C1*C2*R1*R2*s^2 + 1));
opt = c2dOptions('Method','tustin','PrewarpFrequency',125663.706);
LPF_D = c2d(LPF_A,0.000025,opt);


texts: Simulation error and output voltage drop of DC voltage doubler circuit in Multisim

texts:
I have simulated the circuit provided in this link:http://www.circuitdiagram.org/dc-voltage-doubler-multiplier-circuit.html. But, when I simulate the circuit, the output voltage is dropped and I get a simulation error after 0.56s saying A simulation error has occurred. Would you like to run the Convergence Assistant to attempt to resolve this problem automatically?. I ran the convergence assistant to fix this issue and it worked saying successfully resolved convergence issue, and then again if I simulate, it gives the same simulation error and drop at the output.

Details : when I give an input voltage Vin=5V, the output should be doubled to 10V, but there is a drop in the voltage giving an output voltage of 8.916V as shown in the figure below:

//Multisim Convergence Assistant Summary Report

   Convergence Assistant Summary Report

   Outcome:

           The simulation error was corrected successfully.

   Changes Made:

           Multisim Convergence Assistant Log

     Step 1: Verifying Error Scenario
       ...completed.

     Step 2: Setting parameter Integration Method (METHOD) to Gear
     Simulating...
     ...completed. Simulation error fixed.

     Step 3: Attempting rollback of Integration Method (METHOD) to Trapezoidal
     Simulating...
     ...Rollback successful.

      Convergence Assistant completed successfully.

I am not able to figure out the reason behind this output voltage drop and the simulation error. Any help and guidance regarding this would be appreciated. Thanks.


texts:
The task is to design a bcd to gray code converter. The 5-bit bcd input is represented as A,B,C,D,E while the 4-bit gray code output as D3, D2, D1 & D0.

Could someone help me confirm my truth table?


texts:
I have designed a PIC18F877A micro controller project to read temperature from an LM35 using ADC, display it on an LCD and transmit it to a serial port.

When the program starts,  sometimes it shows a startup message - sometimes it doesn't display anything. Also, the serial port connection is not working. Can anyone help - am I missing something? Are there any ground connections missing?

My code:

#include <16F877A.h>
#device adc=10
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
#use rs232 (baud=9600,rcv=PIN_C7, xmit=PIN_C6)
#include <lcd.c>
float value;
float temp;
float temp2;
float temp3;
float temp4;
float temp5[14];
float count[14];
int c;
void main(void)
{
//setup_adc_ports( ALL_ANALOG );//Initialize and Configure ADC
//setup_adc(ADC_CLOCK_INTERNAL );
while(1)
{
lcd_init();
lcd_gotoxy (1,1);
delay_ms(1000);
printf(lcd_putc,"   WELCOME TO\n Micro Tech Sol.");
delay_ms(3000);
lcd_gotoxy (1,1);
printf(lcd_putc,"  Fuel Monitoring \n     PROJECT   ");
delay_ms(3000);
}

}


texts: Can someone extend this brief description of the superheterodine radio kit?

texts:
The Tecsun 2P3 radio kit comes with a sheet of paper with the following schema and description, but it doesn't explain too much about all the components. For a novice is  a bit hard to know the sense of all of the pieces, especially those not named. Taking the manual description as starting poing, I would be helpful if someone can extend it for learning purpose.

Specifications:
Frequency range: 530kHz~1620kHz
DC supply: Power requirements: DC 3V, two R6 AA batteries
Sensitivity: <1mV/m
Maximum Output: 120mW
Quiescent Current: 7mA

 - Mixing circuit: Mixing circuit is broken down into three sections,
    input tuned circuit, local oscillator and mixer. Magnetic antenna
    inducts radio signal, feeds into a tunning circuit comprised of
    variable capacitator VC4 and L1, where the signal frequency
    indentical to the tunning circuit resonance frequency is selected
    and inducted on L2, this process is called "tunning". L2 feeds the
    tuned radio signal into the base of mixer Q1 (S9018). Q1 has two
    functions.

 - A. Local Oscillator: Q1 working with VC3, C2 and T1, generate an
   equiamplitude sine wave at a frequency 455Khz higher than the tuned
   radio signal.

 - B. Mixer: Q1 mixes L2 inducted radio signal with local generated
   oscillator signal, a 455Khz intermediate signal (IF signal = Local
   Oscillator signal - tuned radio signal = 455Khz) is selected to pass
   the IF transformer T2, in fact, plural frequencies are generated but
   T2 is tuned at 455Khz so only 455Khz IF are passed and all other
   frequencies are filtered. The 455Khz IF is the fed to the IF
   amplifier stage.

 - IF Amplifier: In order to obtain enough gain, 2P3 has two IF
   amplifiers, comprised of Q2, Q3 and peripheral components. 455Khz IF
   signal passes T2, amplified by Q2, passes 455Khz ceramic filter CF1
   and feeds into Q3 for second stage IF amplification. Amplified IF
   signal passes T3 then feeds into detector stage.

 - Detector. When radio signal trasnformed into 455Khz IF signal, only
   carrier wave frequency changes, audio signal riding on carrier
   remains unchanged, but this IF signal is not audible by human ears,
   it must pass a detector to separate audio signal from its carrier,
   this detector is carried out by diode D1 (1N60) and peripheral
   components.

 - Automatic Gain Control: After passing detector D1, IF is filtered by
   C7, R11, part of it feeds through C6, R9, C4 to be stepdown and
   filtered, providing a negative bias to Q2. When radio signal is
   stronger, higher IF output causing Q2 to reduce amplification, it
   works reversely when signal is weaker, hence stronger and weaker
   stations will have relatively similar volume.

 - Audio amplifier: Part of detector output feeds to Audio amplifier IC1
   (CD7368) through C8, to be amplified and fed into speaker.


texts: How Efficient is a Thermoelectric Generator?

texts: There has been a lot of talk about power sources and their efficiency. I'm just wondering about how effective a thermoelectric generator's efficiency compares to mechanical turbines, solar panels, etc.


texts: Linear regulator that regulates even with negative current?

texts:
I require a voltage source which holds a large capacitor at a stable voltage. The following secenarios must be supported:

Something is feeding current into the capacitor. The voltage source needs to sink current to keep the voltage constant
Something is draining current from the capacitor. The voltage source needs to provide current to keep the voltage constant

I only need a moderate amount of current (a supported range of +10mA to -10mA should suffice). The voltage is very low, in the range of 1.5V.

Solutions which I've considered:

LDO

simulate this circuit – Schematic created using CircuitLab

Upsides:

Very low quiescent current
Stable voltage

Downsides:

LDO outputs can't sink current, therefore this doesn't work

LDO with constant load

simulate this circuit

Upsides:

Very stable voltage
Works

Downsides:

10mA of quiescent current. This is prohibitive since the circuit is battery-operated
Unpleasant surprises when the load current goes even slightly below -10mA

Zener diode voltage divider

simulate this circuit

Upsides:

Low complexity, cheap
Works

Downsides:

Very unstable (+/- 100mV over the current range with the shown 700 Ohm resistor)
High quiescent current (10mA with the shown 700 Ohm resistor)

This solution is inferior to the "LDO with constant load" variant: You can adjust the resistor, but then you either get even more quiescent current, or you get even more instability.

OpAmp in voltage follower configuration

simulate this circuit

Upsides:

Easily adjustable (could be controlled by uC etc.)
Low quiescent current
Very stable voltage

Downsides:

OpAmp outputs are not stable when connected to capacitive loads; therefore this doesn't work.

Any alternate ideas?


texts:
This might be a dumb question but:

If you have a Li-ion with a built-in protection circuit, and you discharge it until it cuts out (3V?), can you still recharge it? Is the protection circuit to protect the battery to improve it's life, or just to protect it from leaking/exploding?


texts:
I've been trying to build a dual power supply with an output of +/- 12V 3A, I have based on the circuit of a basic power supply using LM317 and LM337, but these components are limited to only 1-1.5A output, I have been making some changes with some transistors to increase the output current, however when I simulated the circuit in proteus, the maximum output voltage was only +-7V.
Could someone help me to know the cause of the voltage limitation?

This is the circuit in which I based, I just took the part of the dual power supply and ignored the part of +5V

This is the circuit which I made with some transistors

I have also found in the datasheet of the LM317 an example of a circuit made for high currents, however do not specify the range of currents that handles.


texts: What battery has more capacity: Lithium Polymer or Lithium-ion battery?

texts:
In my project I need a battery with a cylinder of 10mm diameter and 35mm high. I thought only Lithium Polymer technology can create battery for this size. Now I discovery Lithium-ion can have the same size!

Both are very equal in voltage and capacity. But, the capacity is critical and if I can win 10 mAh for the same size, I will choice this technology.

So, is it easy to say what technology is better? Or it depend from manufacture? Or even: The differences are so small that it doesn't matter what I choice?


texts: Driving high currents with parallel mosfets as the switch

texts:
I am trying to make my own battery spot welder from a car battery, car starter solenoid, and an Arduino to drive them. I came up with my concept and schematic and built the thing. The problem is that one of the two parallel MOSFETs burns when turned on. The coil features a very low resistance of 0.3 Ohms, I added a flyback diode across it but it doesn't help. The current flowing is quite high and for a short amount of time. I am thinking that the MOSFETs are switched for a too short amount of time and they don't have time to heat up and equalize their resistances to spread the load effectively so always one takes it all. Are my MOSFETs (IRFZ44N) too weak for the job? Should I put a resistor in series with the coil and use it that way if it works? Any help would be very appreciated, thank you!

Schematic: https://easyeda.com/pavelstoyanovdev/spot-welder


texts:
I have a Transformer with the following writing on top of it :

  TFM-00053
  CLASS B 130°C
  Z150H E154515
  LEI-4   8B25

it has three thick wires on one end : Blue Brown Red ; the resistance reading is almost Zero between any pair of them

the other end has 4 thinner wires Blue Yellow Brown and Red the resistance reading is ( in ohms ) :

Blue <-> Yellow : 1.2
Yellow <-> Brown : 12.6
Brown <-> Red : 1.9
Red <-> Blue : 13.4
Blue <-> Brown : 12.4
Yellow <-> Red : 13.9

Note :

the Digital miltimeter reads 0.8 ohms when in short circuit
the Transformer has been used before

I'm using this to replace a transformer of car battery charger which should take 220V AC in and output a 12 or 24 V AC

Q: which is the primary and how is the correct wiring of this transformer ?


texts: Relay or optocoupler to switch thermostat wires

texts:
I'm doing a project to replace my thermostat with a DIY one.

I'm trying to figure out how to switch the heating/cooling/fan/humidity wires. I'm inclined to go with an optocoupler like the 4N35. It can switch 24VAC with ease, but has a low threshold for amps (150mA).

Most older thermostats that I know, give the familiar clicking sound when heat is called, implying that they use a mechanical relay. But when looking to more modern thermostats, like the Nest or Ecobee, there is no clicking, either using an SSR or an OC.

The problem is that I can't find anywhere any "specs" of what a thermostat should be able to switch. As the wiring is only 24-28 gauge wire it should never use more than 225mA - 580mA.

Is my assumption correct? Should I opt for using relays or would a simple optocoupler do?


texts: Why are batteries measured in electrical charge unit (ampere-hour) and not in energy unit?

texts:
I've searched for an answer for this question for a long time. Specifically I've found this thread which is closely related to my own question: Why are batteries measured in ampere-hours but electricity usage measured in kilowatt-hours?

Here is my question: I would expect that the electrical energy that a battery produces would be constant, but according to tyblu's answer to the thread above, the charge is the one that's approximately constants. It seems odd to me, because it seems to violate the law of conversation of energy, because if a battery's charge is constant, but its voltage output decreases over time, then the electrical energy must decrease too, because E=V*Q.

What am I missing?


texts:
I am searching for a method/device for aligning chips with pins/pads underneath, like QFN, LGA, BGA and others. I've been searching the Internet, but I could find anything except expensive (several k€) chip alignment machines.

Is there a method/device for aligning chips, different from the expensive chip alignment machines?


texts: Circuit Gives DC Current instead of Sine signal (LTspice XVII)

texts:
I'm a mathematics and physics student.  I am trying to simulate the circuit from the paper "Design and implementation of a lightweight high-voltage power converter for electro-aerodynamic propulsion". However,  this is my first time using LTspice and I'm struggling with it.
What I don't understand is why the signal in the voltage in the primary of the transformer isn't sinusoidal as expected but rather a DC signal of 100V. Consequently the signal isn't being multiplied by the transformer and the output voltage is 0.
Picture of the circuit from LTspice:

Node n004 is the node linked to the primary of the transformer:

Edit: The link to the article was not working so I replaced it with another one.


texts: How can I find a replacement for a transistor?

texts:
I have a circuit that uses BC106 and 2N3634, which can't find in store (where I live).
Is there any website which could help me find an equivalent transistor?

For instance I want to replace BC106 and 2N3634 with others that act the same. Any suggestions would be appreciated.


texts: Determine if feedback is negative or positive?

texts:
Is there a way to know from how a circuit is designed that is has negative feedback or positive feedback. Here are some examples:

Example 1:

Example 2:


texts: Art Of Electronics - 2nd Edition - Absolute Value of a Complex Number - Math

texts:
In this section, I am struggling with the line

Abs(V) * Abs(I) = V0^2 / [blah blah]

I am not seeing how the math simplifies to that term.  After looking up the absolute value of a complex number, and seeing that it is basically Pythagoras theorem on the real and imaginary axis.  I just don't see the simplification for the line above power faster =

Can someone help?  I assume it is correct?

Thanks


texts: Classic essays on electrical and general engineering

texts:
I tutor English language and literature. I sometimes find that tutees are really keen on engineering, tech and so on, and find analysing the more traditional texts intimidating (I mean Shakespeare and so on).

I know there are classic essays on computing, and it occurred to me that the same might be true of electrical engineering and engineering in general. Classic books would be equally valid.

Can anyone suggest such a thing? Many thanks.


texts: Oscilloscope voltage readings factor of 10 too high. Is this due to the impedance?

texts:
For a university physics experiment, I built a circuit to test voltage (and conductance) steps across a nanowire break junction. The break junction was in a circuit with an I-V converter, and the I-V output was fed to an oscilloscope. The voltage steps measured matched the theory, however they were all a factor of 10 too large. Is this due to the impedance of the oscilloscope? I can't retrieve the exact model now but it was Tektronix and the standard oscilloscope used across the university, so I assume it is 1MOhm. Is there anything else involving the impedance (or any other factor) that could be causing the factor of 10?

I double checked the I-V contributions of all components in the circuit, such as the feedback resistor in the converter, and couldn't find anything so can only conclude it is the oscilloscope. But electronics is not my forte so I am not sure how an oscilloscope could cause x10 to the voltage.


texts: Hot Glue/Epoxy-like substance on DC-DC regulator

texts:
I have a board (an evaluation module for a USB-to-HDMI chip from Microchip) that has a feature I haven't seen before. On top of the 3 DC-DC regulators, there is a clear substance that appears to completely cover these 3 regulators (the IC's and related passives). The clear substance seems to be something between hot glue and clear epoxy - it's harder than hot glue, but softer than epoxy. I've attached a picture of the board below - the three regulators are along the bottom of the board, in between the 2-pin header and the 7-pin header. It's hard to see the clear substance in the photo (because it's clear..), but you can kind of see the reflection.

I understand that DC-DC regulators are typically an electrically noisy section of the board, and given the rest of the board has a lot of high-speed signals, I'm wondering if this offers some sort of EMI attenuation. My only other hypothesis is that it is intended to silence the high-pitched ringing you sometimes hear from these regulators. I would love to hear if anyone knows for sure what this is for, though!


texts:
I found this application in AD's OP77 datasheet:

Apparently they (ab)use a 2N930 transistor's B-C's junction as a low-leakage diode. Is there any reason why you would choose a transistor over a real low-leakage diode for this?


texts: Can I calculate the horsepower by only AC current flow in windings in AC motor?

texts:
I saw this AC motor parameter calculator online: http://www.engineeringtoolbox.com/electrical-motor-calculator-d_832.html

It says for 100 Horse power, in 90% efficiency, 0.9 Power Factor and 220 V AC supply, 300A current is needed. But when I calculate like:

220V AC  * 300 A AC * 0.707 (sine root mean sq) * 0.9 (PF) / 745.7 W (1 Horse power) = 56.3 HP

Where do I confuse about the calculation?

Also, for a special purpose, I need to calculate the horsepower based on current flow in windings. In these windings below:

Because I only know my inductance(L) value, radius(R), turns(N) and RMS current which is going to flow through these winding coils. I know these below;

L = 60 mH

R = 5 cm

d(wire diameter) = 0.4 mm

N = 210

And RMS current for each phase (current flow on armature windings) is 12 A (peak to peak)

how can I calculate the horse power by only these parameters? Can I be sure that this parameters are whether enough or not enough to drive a car? Thanks.


texts: What is the best way to detect the position / displacement of a linear motor ( solenoid type ) for feedback ?  I was thinking of using a hall effect sensor or an Infrared sensor .


texts: Cascaded RC Bandpass filter loading problem?

texts:
So I calculated the Highpass stage output impedance to be 22kohm and the input impedance of the Lowpass stage is 430kohm when f=5khz, still in the output I am getting half of my supply voltage despite the input impedance of the second stage being much larger than the output impedance of the 1st stage, I even tried putting a buffer op-amp in between the two stages and that didn't change anything. other than the two impedance of the cascaded stages, what am I forgetting to consider ?

*Note that the bandpass is between 5khz and 5.5khz and on the oscilloscope it's 5v/div.


texts: Assembly language, accessing bytes of memory

texts:
I have some memory address 0x00000100 that I want to read from. The lower 4 bits read from this address indicates the states of 4 buttons - So bit 0 shows the state of button 0, bit 1 shows the state of button 1, etc. My question is- How can I find determine the state of button 0 and button 1 in assembly language? I want to know when button 0 and button 1 are high.

I am using a MiteFPGA processor, and Xilinx Vivado, on a basys 3 board. I am using the MiteASM assembler.


texts:
I am looking at designing a low-power project that will have an ATMega328 running at a low speed for lower power consumption.

The current plan is to have the UART hooked up to a RF Link Receiver for communication at 1200baud.

What I'm wondering, though, is what the minimum speed is that I can run an ATMega328 at and still have a 1200baud UART running. Is 1MHz fast enough?


texts: Bonding yourself via GND pin of an USB-port?

texts:
A simple EPA (ESD Protected Area) consists of 3 things:

wrist strap
antistatic mat
common point ground

When doing field service (installing/replacing hardware parts) the ESD sensitive part goes straight into a static shielding bag and the replacement part comes out of a static shielding bag and goes straight into the PC. You only need a wrist strap to bond yourself to the PC.

On a desktop PC you can connect to the conductive case. Laptops on the other hand often have a non-conductive plastic housing.

Bonding to the ground pin of an USB port is an alternative option. This means: reaching equipotential with the motherboard's ground-plane via the USB port.

Can the USB port and/or motherboard handle the current spike? ESD damage?
What about user safety?
Should there be a resistor between PC and wrist strap?


texts:
I have the following circuit wired up on a protoboard.

The datasheet for the BSS138 MOSFET is here. I'm puzzled regarding what I'm seeing happen with this circuit - when I apply 3.3V at the gate resistor, the MOSFET turns on fully and I see 3mV at the output. This, of course, is expected.

However, if I remove 3.3V from the gate resistor, the pull-down resistor turns the gate off. I expected to see approximately 3.3V at the output, yet I only see 2.7V. If I replace the 3.3V on R1 with 5V, the output shows 4V. In other words, a volt is being dropped on R1 when the MOSFET is off. Is this expected? Somehow, I expected the MOSFET to have an immensely high resistance when off and hence expected approximately 5V being dropped on it when it's off.

Are my expectations not in line for this MOSFET?

Test 1: Passed.

Test 2: Drain to Source Vf = 0.515V, Source to Drain = 0.09V, Gate to Source = 0.07V.

This was quite bizarre. Please note, I have done test done multiple times. I always get a consist result. I have not seen a Open-Loop anywhere. This leads me to believe I indeed destroyed this MOSFET while handling it. A colleague told me that he destroyed another MOSFET from the same reel yesterday. This leads me to Test 4.

Test 4: Incomplete. I'm a bit more wary in handling these MOSFETs now. I didn't realize that the smaller the device, the more likely it is to damage it. I have handled MOSFETs before, but they were much bigger in size: TO-220. I did bring my anti-static wrist strap from home to work, but the room I work in does not have an Earth terminal(see note!!. But I'm working on getting this fixed ASAP. I don't think I'm gonna even bother doing anything till I'm properly grounded. I'm also ordering a anti-static mat. The environment here is fairly dry. But there are obviously no carpets anywhere in the building, let alone the room, this leads me to think it's either my clothing or my work desk.

I have made sure that the circuit is OK. I have gotten it checked by another person as well, this makes me think I'm OK here.

Note: These are just some of the things you have to put up with in a 3rd world country! Fortunately, at least the building has an earth connection. So getting it my room shouldn't be too difficult.


texts:
I know there are multiple questions about this topic, but I didn't found an exact answer to my question.

My situation: I'm having a 2 layer PCB. On the PCB there are multiple SMD components and traces both of them on the top and on the bottom side. All signals and power traces (+5V and +3V3) are already routed. Now my idea was to create a ground plane: one on the top and one on the bottom layer.

My questions:

Is it a good idea to have a ground plane on both layers?
Should the ground planes be connected with vias or is it enough that they are connected through the GND pads of my USB and Ethernet connector?

If anyone needs additional information, please write a comment and I will try to provide this information.

Edit: I want to add some future details about the PCB. The PCB has a size of about 60x60mm. The main components on the board are a microcontroller from Microchip (PIC32MZ) and a ethernet PHY from Texas Instruments (DP83848). Furthermore the board contains a USB-B and ethernet port. The 5V from the USB port is used as the power supply of the device.


texts: Adapter for drum module showing incorrect values?

texts:
I have bought this electronic drumkit by Roland about a year ago. It was second hand. It came with a 230v ac to 9 v dc 1000ma adapter. On the drum module, a few types of compatible adapters are written. It's official. The adapter I have is one of them and it's also made by Roland.
Now the problem. I wanted to take a look at how many amps the drum module takes from the maximum of 1A of the adapter by screwing the module open and using my multimeter on the power dc input. Weirdly, it shows that it's using about 4.3 amps, which is way more than the adapter should be able to handle. Then, I unplugged the module and left the adapter plugged into my outlet and checked the output voltage. It shows 13.4, not 9. This really surprised me. I checked my multimeter by checking other power supplies for their voltages, and they show about the same as they are claiming to output.

Does anyone know what this could be?


texts: How does the UART communication detect the true idle in this case?

texts:
When explaining UART communication it is told that the receiver will start sampling the data one start bit after the first falling edge. The falling edge occurs when TX goes from idle state to zero as shown follows:

So normally above the receiver listens the TX line and when it detects idle voltage goes to zero the sampling starts one bit after.

What is not clear to me is that imagine the following scenario where the receiver is turned on and started to listen the TX line at the point I marked in red below(on the leftmost):

In this case will the receiver think(interpret) bit1 and bit2 as idle and the first byte will be received wrong?


texts: 2N2222 Transistor and DC Motor on Ardunio but operates at 2.85V. How?

texts:
This is a typical set-up diagram for a low side transistor. The 2.85V is actually positive volts. However, typically this is designed for volts greater than 5 volts if the output of the micro-controller is about that from the base.

It would be nice to operate this directly with the usage of the 5V power given from the Ardunio board, but it has to be willing to draw 160mA and be at 2.85V.

This configuration won't spin the motor if I am using the 2.85V power supply, neither if the volts from the power supply is 5V. However, if the power supply is coming from the Ardunio board, 5V or 3.3V, the motor will spin. Now, when it is connected to the external power supply, things get strange for me. If I connect the motor, the voltage drops instantly to zero and the motor won't spin.

The 3.3V by the Ardunio board don't produce enough current. However, if I used the external power supply, the full 160mA is easily drawn from it, spinning the motor with a good amount of torque.

I also tried the PWM analogWrite command, but that will spin the motor, but the current will be much lower than as if I had the same voltage directly from the external power supply.

My goal is:
1. Use the power supply directly from the Ardunio board to operate 2.85V and 160mA;
2. If 1 is not possible, such that I use a 2N2222 transistor to draw the 2.85V and 160mA from an external power supply;
3. The voltage and current can only be for this specific element in the circuit, as other parts of the circuit rely on the 5V provided by the Ardunio board.


texts: What kind of connector is this, where can I get one, and how do I attach it?

texts:
I have to replace a fan in an older (circa 2010) NAS storage device, and I found a replacement but the wires don't terminate in a connector (see first image below):

The old connector looks like this:

What kind of connector is this, where can I get one (for as cheaply as possible), and how do I connect the unterminated wires to it? The old fan looks like it has the wires crimped in there somehow.

Alternatively, is it realistic to try to use the connector from the old fan? How do I remove it without damaging it?


texts: Can N-Channel MOSFETs safely discharge capacitors?

texts:
Can 3 ganged 120 A rated N-Channel MOSFETs discharge a charged cap dumping 300 A?

Will the FETs just explode or can they repeatedly discharge the cap?

What specific ratings and characteristics are important to determine if a FET is up to the task?

Granted the FET's Vds voltage would slightly exceed the cap voltage rating.


texts: Replacement for obselete Infineon TLE52062GAUMA1 device?

texts:
I have an existing system that I wish to replace one of these Infineon TLE52062GAUMA1 motor drivers in. It's a H-bridge 40V/5A driver in a TO263 package. (https://ie.farnell.com/infineon/tle52062gauma1/motor-driver-h-bridge-to-263-7/dp/2480504)
It turns out that the device is obsolete and unavailable from Mouser, Digikey, RS etc. I might be able to get it from other suppliers like TME (I'm in Europe), but I have never dealt with them before and anyhow the part is only available until they run out, which is not helpful for the future. Ideally I'd like a pin-compatible and functional replacement that is readily available. I'd be grateful for any information on this. Infineon don't seem to have a replacement, but maybe there is another manufacturer with something close enough.


texts: 2N2222 transistor datasheet saturation current

texts: I am designing a 2N2222 transistor common emitter voltage-divider amplifier. Using 9V for the power supply and trying to make the loadline to determine Q.  How do I determine the sauration point current for the load line?


texts: How do I simplify this sum of products expression into an easier sop form

texts:
'=Compliment

D=P'VST + PV'S'T + PV'ST'+ PV'ST + PVS'T' + PVS'T + PVST' + PVST
I'm having trouble simplifying this.


texts: What are the meanings of IC's suffixes? For a example, CD4511BE? What is the meaning of BE? What are the other suffixes?


texts: Op-amp Power Dissipation Calculation for a pulse output

texts:
I am trying to calculate the power dissipation of the op-amp for a circuit as below. I am wondering if I did it correctly. Can anyone provide any tutorial on this?

So this opamp will output approximately 11V rectangular wave for a duty cycle of 22%. One opamp will source and the other will sink, and vice versa. The quiescent current of the opamp is 10mA. The output current I get is 500mA peak by measuring with current probe. The two op-amp are single chip package.
Here is the simulated output waveform of both op-amp

The power consumption of the opamp I calculated as :
$$
P_{consumption} = V_{cc}*I_q = 12 \times 10mA = 0.12W
$$
Then I calculate the power dissipation of the output :
$$
P_{dissipated} = (V_{cc} - V_{peak})\times I_o \times D = (12-11) \times 0.5 \times 0.22 = 0.11W
$$
Finally, I combined both power to get the total power dissipated
$$
P_{total} = 0.23W
$$
I felt that my calculation is incorrect. Using the result of my calculation, the junction temperature is about 40C at 25C ambient but the case temperature is 45C when I measured the case with a RTD.
$$R_{\theta JA} = 65C/W$$
$$T_j = 25 + 65\times 0.23 = 40C$$
Could anyone look at this and teach me what is the right way to calculate the power dissipation of the opamp? Besides that, how do I calculate the power of the lower op-amp when it is sinking?


texts: How is called such a knob / potentiometer?

texts:
On a Roland TR09 (rear view) (Roland's 2016 recreation of their famous TR909):

we can see a stereo volume potentiometer, that is smaller than usual.

Question: Is this

a normal potentiometer + a "striated" black cap (if so, what is the proper name? I guess striated cap is not the right name, I haven't found anything with this name)

or

some small potentiometer with black rubber-looking shaft, all-in-one?

Note: it's not a sourcing question, but I'd like to know what kind of component it is, and the proper name of it (this will allow me to search then).


texts: emmc - mcu supports 4.2/4.3 but device is 5.1

texts:
I am using a Kinetis mcu (K64) from Freescale now NXP and interface with a SD card.

I am looking to replace the SD card with a emmc (8 GB) from Sandisk (WD - Western Digital).

Can't get an answer from NXP and WD won't reply to email or post on this subject so I'm hoping someone here may have an insight.

The mcu (K64) supports mcc specification 4.2/4.3.  The Sandisk device supports 5.1.

Question #1 - Can hardware that supports 4.2/4.3 be used to read and write sectors from a 5.1 emmc device?

Question #2 - If so, are there any unique commands for "trim" and "Bad Sector Management" which are supported on the 5.1 device that will not be able to be executed using 4.2/4.3 hardware (K64)?

The K64's SDHC supports 1, 4, and 8 bit interfaces.  I currently use 4 bit for SD card - would use 8 bit with emmc.

The K64 is a 120 mhz ARM M4 mcu.

Thanks


texts: Basic OS definitions and implementations

texts:
The Rowley Crossworks package (includes compiler, IDE, debugging interface, etc.) also includes something called the Crossworks Tasking Library (CTL). From their website:

  CrossWorks Tasking Library, known as CTL. CTL is a royalty-free tasking library that provides a multi-priority, pre-emptive, task switching and synchronisation facility. Additionally, the library can also provide timer and interrupt handling support.

I mostly understand the description of the tasking portion from my investigations into task schedulers (with the exception of synchronization... what's that mean?). However, timer and interrupt handling support has me completely thrown for a loop. Isn't that stuff built in the gcc environment (which crossworks uses btw)? Does that mean they use some kind of wrapper for the gcc syntax:

ISR(PORTB_INT0_vect)
{
    int_pin_handler();
}

If so, what advantage does it give to put that in a kernel versus just manually writing to the appropriate ports etc. as one would do in truly bare-metal programming? Finally, is it common for small OSes (I'm thinking FreeRTOS, VxWorks not linux kernels) to do this kind of thing?

Thanks


texts: How does feedback make a system stable even in the presence of an inherently unstable element in that?

texts:
Consider the transfer function of a block being $$\frac{1}{s-0.5}$$ which is unstable in open loop. If we go for a feedback, magically it becomes stable even with the presence of the inherently unstable block. My thoughts on these are

When an element is unstable , it doesn't mean it is unstable for all inputs. For certain inputs the block can still produce stable outputs.
During feedback, the input given to the the block gets modified such that output doesn't blow up.

My questions are

Are the above observations correct?
The impulse response of the block is $$ e^{0.5t}u(t) $$ What the block does is, take the area under the signal at present instant and blow it up for subsequent instants. If so, a positive valued input should blowup the output exponentially. Then why is the output not blown up (exponentially) in following case, shown in figure?

The signal shown as input is the actual error signal when we use the block in a closed loop format with unit step input.


texts: STM32F4 - Reading general purpose timer count

texts:
I'm using the STM32F4 HAL library on an emulated [in QEMU] STM32F4 Discovery board, and trying to configure TIM2 (general purpose timer) and read its' count register (without an interrupt). Currently I'm always getting 0 when attempting to read the timer counter with

uint32_t count = __HAL_TIM_GetCounter(&hTim2);

I don't want to move on to using an interrupt just yet, until I get this step working. Taking it step by step.

Here's how I configured the timer so far:

__initialize_hardware.c

__TIM2_CLK_ENABLE(); // Enable the TIM2 clock
// ...
Timer_Init();

timer.h

TIM_HandleTypeDef hTim2;

timer.c

#include "timer.h"

void Timer_Init(void) {
    hTim2.Instance = TIM2;
    hTim2.Init.Prescaler = 40000;
    hTim2.Init.CounterMode = TIM_COUNTERMODE_UP;
    hTim2.Init.Period = 500;
    hTim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
    HAL_TIM_Base_Init(&hTim2);

    HAL_TIM_Base_Start(&hTim2); // Trying to start the base counter
}

void HAL_TIM_Base_MspInit(TIM_HandleTypeDef* htim_base) {
    if (htim_base->Instance == TIM2) {
        __TIM2_CLK_ENABLE();
    }
}

void HAL_TIM_Base_MspDeInit(TIM_HandleTypeDef* htim_base) {
    if (htim_base->Instance == TIM2) {
        __TIM2_CLK_DISABLE();
    }
}

then in main.c

int main(int argc, char* argv[]) {
    while (1) {
        uint32_t count = __HAL_TIM_GetCounter(&hTim2);
        trace_printf("%lu\n", count);
    }
}

I'm always getting 0 in count above, not sure why? Can anyone please offer some advice?


texts: KiCAD: Potential error in designing schematic symbol

texts:
I received a part of a schematic. It is this one:

When i received my parts, i saw that the pinout was reversed. 1-8 was on the left side, while 9-16 was on the right side.
At that time, i didn't know that you could declare your pins however you like, and i thought you should comply to the physical package pinout.
So i did my best to try to translate the schematic i received, to the real physical part - reversing the pinouts, while keeping the circuit the same.
This is my attempt to this.

The people with much experience at this.... Do you think it's good?
I did my best, checked it many times and i think it is the exact same.
I am asking because my pcb does not work, but i do not why. It probably isn't this, because not even the RESET button works (it's an arduino shield).
But i am doing my best to figure out what's wrong, and i am checking everything out.
Those with an experienced eye, could you please take a look and see if the two schematics are the same? I would very much appreciate it.
Thank you very much and have a great year!


texts:
I've put together a power usage estimate for the FPGA board I'm developing and these are the numbers:

Voltage     Expected Current     Possible Supply?        Notable Peripherals
1.2V        1.578 A              2A     3A               ETH PHY
1.8V        0.754 A              1A     1.5A             DDR2 SDRAM
2.5V        1.124 A              1.5A   2A               ETH PHY
3.3V        0.903 A              1A     1.5A   2A        DVI

Do you think these numbers are reasonable in your experience?

I know that FPGA power usage varies a lot with the firmware application, so I used the Xilinx Spartan 6 excel spreadsheet for that and the datasheets for everything else, however the Xilinx 601 dev board on which I'm basing my design has 8A (!) ratings for all major rails (1.2,1.8,2.5,3.3), which seems quite excessive to me (and is making me quite concerned that my calculations are incorrect). Does the current usage by an FPGA really get this high?

The only extra thing it's using that I'm not is the SERDES + SFP connector which probably does use a bit of current (I can't imagine more than an amp?)

Also, I guess it's prudent to give myself a bit of PSU headroom. I'm not 100% sure on my figures so I'm going almost double in some places, still a lot less than 8A!

Also, chip recommendations? Is there anying I should be looking for in a regulator chip specifically for FPGA usage (low noise, etc?)


texts: Should via-stitched polygons connect to adjacent analog grounds?

texts:
I am putting together an analog PCB. I am reading an audio signal and using large gain to clip it (effectively a crude digital signal 0-5V) using a differential amplifier. It is a 2-layer PCB with the bottom layer being my ground plane. The datasheet for the op amp recommends surrounding the input stage resistors with a grounded polygon for shielding. The main trace digital output trace has to run back nearby the input stage unfortunately given design constraints.
My question is: should this shielding polygon (via-stitched) extend to connect to local analog ground pins? Or should my stitched polygon simply "float" and then only use vias to connect nearby ground pins directly to the bottom layer ground plane?
Not shown: bottom layer is solid ground plane. SGNL is the large-amplitude signal. I do not have a power plane, simply routed power traces. My concern is that connecting local ground pins to the polygon will allow a careless ground loop somewhere.
Perhaps the below image will clarify:

or


texts: DIY water tank gauge using analogue ammeter

texts:
Our (old) boat has a fresh water tank whose level was reported by a now broken gauge. For cosmetic reasons I need to replace the broken gauge with a similar form factor (I do not wish to cut the panel about). So I cannot just buy any new tank gauge.

The old gauge is from the Anders Acclaim AM25 series and had been adapted (messily) to act as an Ommeter with a "Euro type" tank sender. I can obtain a physically compatible replacement ammeter (1 milliamp max) and I can change the tank sender to the "US type" (240 ohms empty, 33.5 ohms full).

But I cannot work out what circuit to build such that the gauge will read zero amps when the tank is empty and 1milliamp when the tank is full.

Boat's electrics are a nominal 12v (more like 12.5 when exhausted and 14.4 when charging).

Edit: the replacement ammeter is described as having a coil resistance of 200ohms here http://www.topqualitytools.co.uk/meter-78x60-0-1ma-am25a2/

Edit: Further hunting has produced an alternative compatible gauge, a voltmeter, the AM25F2 (0-75mV DC). Might this be utilised in a solution?


texts: What would happen if two voltage sources (one a DC battery and a dependent voltage source Vx) are in series?

texts: If my battery is 18V and the dependent voltage source is Vx (Vx is the voltage across a resistor somewhere in the circuit), and if these two are in series, can I combine them into a new dependent voltage source 18+Vx?


texts:
I'm making a 12V power distribution box, and it's my first time I work with high currents. This is for a boat, and the idea is to run low-power up to the switch panel and having the high-power cables as short as possible.

Simplified schematic:

Input on X1-1, F1 is a 25A fast acting fuse, K1 is a relay switch and finally output X2-1. Ideally the X1-1 should be replaced with a copper bar soldered to the PCB to distribute power to the 10 similar on/off circuits I'm having. 250A is too much for any PCB I suppose... :)

The trace with calculator says I need a 25.5mm trace width. But the trace from the X1-1 to F1 is less than 10mm, and it will be a ugly blob of copper 10mm long and 25.5mm wide.

Hope someone can help me do the math here.

Ok, my math from here assumes a 2oz (\$70\mu m\$) board, single-sided and using through-hole components and still standing air as ambient:

$$R=\frac{\rho \times l}{w \times h} = \frac{1.7 \times 10^{-8}\times 10mm}{12.7mm \times 70\mu m}=191.23\mu\Omega$$
$$U_{trace}=RI=191.23\mu\Omega\times 25A=4.78mV$$
$$P_{trace}=IU=25A\times4.78mV=119.5mW$$
$$\Delta T=\frac{P}{Sa\times h}=\frac{119.5mW}{(1cm\times1.27cm)\times 0.001W/cm^2/^\circ C}=94.1^\circ C$$

It seems my \$10\times 12.7mm\$ blob is too small to dissipate the power adequately. If I use a \$35\mu m\$ copper board and double the area I get the \$\Delta T\$ down to about \$47^\circ C\$.

Are my calculations correct? If yes, will it also perform equally after I build it?


texts: What is the purpose of these passive high and low pass filters with this audio DAC which already has internal filtering?

texts:
The CS4334 is an Audio DAC. It already has internal on chip filtering and interpolation capabilities as clear from datasheet page 12 Figure 8. I assume that this means that no filter is require to remove the high frequency components that are typical of outputs on DACs. However, the recommended connection diagram on page 4 Figure 1 of the datasheet looks like this:

Questions

(1) Why are there networks of resistors and capacitors at the output?

(2) Why is load shown as resistive, should it not be inductive as speakers are represented? If a power amplifier is being used at the output that this makes sense. But then why is there in arrow pointed to right after the RL?

(3) Why is C variable? Certainly if we want to get a specific frequency response, we should have fixed values for RC in the high and low pass filters.


texts:
Recently, I've acquired an old SNES, specifically the SNSM-CPU-1CHIP-03 model, with no audio output.
I traced the issue to a dead S-Mix chip, essentially a buffer between the audio DAC and the line output.
While the DAC in question, an LM6379A, is technically capable of driving the line output on its own, I thought I'd try my hand at making a replacement buffer, using an LM358 op amp as a voltage follower and taking advantage of the passive components already in the board. The resulting circuit looks a bit like this, for each stereo channel:

Now, this does seem to work, at least for a little while - but eventually, after a minute or two, the output gradually lowers, before disappearing completely, or being drowned out by power supply noise. Placing my hand next to the amp did occasionally make the problem go away, making me suspect it's some sort of coupling issue, but I am not experienced enough with analog circuitry to pinpoint what exactly might be going wrong.
Is there anything I might be overlooking in this?


texts: I found a schematic where this component is used. Can anyone tell me what it is?


texts: Op amp output in unity-gain configuration goes to 0V for small inputs

texts:
I'm building a piece of automatic test equipment to be used in-house and have a need to measure relatively small currents (e.g. 3 µA).  So I'm planning on measuring the voltage across a 1% 1K resistor (3 mV) and multiplying it by 100 or so (in two 10x stages) and then feeding it into an 12-bit ADC with a 4.096 V reference (so one bit = 1 mV).

I picked what I thought was a suitable op amp for this task (ALD1722), and hooked it up in a non-inverting amplifier configuration (Rf = 9.09K, Rg = 1K) with a +5V supply, and discovered for input voltages in the tens of millivolts I got a value close to what I expected but as I decreased the input down to a few mV or so the output went to 0.

Puzzled, I hooked up the same op amp in a unity gain configuration, and discovered that the output was lagging the input by about 10 mV; i.e. an input of 50 mv results in an output of 40 mv, and any input below 10 mV results in no output.

I'm a mostly digital guy, so op amps have always been a little mysterious. (I never studied IC op amps in class, as the 741 wasn't even released until my senior year in college.)  I picked this op amp because the datasheet says it has a typical Input Offset Voltage of 25 µV, so I wasn't expecting this kind of error, but maybe I don't understand what offset voltage is.

Is there some sort of biasing circuit I can add to correct for this, so I can feed mV or smaller voltages into the op amp and get a 10x output?


texts: For a HASL Finish PCB, Can Gold Plating be done

texts:
We have a HASL finished PCB but the pads needed gold plating for wirebonding.

Can gold plating be done on top layer of PCB over this?

Will there be any reliability issues?


texts: Can reflection take place at the source in transmission lines?

texts:
I have read about the reflection of voltage and current, when passed through a transmission line through a load if the load is mismatched with the characteristic impedance.
According to my understanding, the reflection happens because the voltage drop across the load is VL and in order to drop the exact amount of voltage across the load, The exact amount of current, IL passes the load and the remaining current is reflected from the load.
and the currents can be given by,
load current IL = forward current(I+) - reflected current(I-)
Am I right?
And also if the above given explanation is right, if in order to drop a voltage of VL across the load, the current generated by the source is insufficient, will the reflection take  place at the source resulting in the reflected wave going to the load which gives rise to the current equation,
IL = forward current(I+) + reflected current(I-)?
And is this what happens when the reflection coefficient is negative?
Thanks in advance


texts: Buck Converter design, which is better? 48V->12V direct conversion or 48V->24V->12V conversion for 12V application

texts: I am designing a 1KW DC-DC buck converter with Vin(51V battery pack with Vnom = 48V) for driving four 250W motors. Is it advisable to step down the voltage directly from 48V to 12V or should I first step it down to 24V and then to 12V? This is the first time I am designing a converter for this much power. Could you also help me with some resources to go through before the design?