texts: Match impedance and net dimensions of RF power amplifier

texts:
this could sound a repeated answer but to me it seems to be not so trivial. Or at least, it is so due to my ignorance.

I need to use an RF6886 power amplifier to interface it with a 50 ohm antenna. Are present the schematics of my frequency range (400-450MHz) and it is stated that it works pretty good with these 50 ohm.

With the PCB stackup used, 4 layers PCB, the RF traces are surrounded by GND planes on the LAyer 1 and the Layer 2 is a complete GND plane. Other signals/GND are on remaining planes. With this structure, the 50 ohm is achieved by a net of width around 0.65 mm (or less, now it is not importante the exact value).
Here comes the problem: the reference schematic (in here, page 10) reports the component used, but I feel unconfidend on the physical parameters of the nets before the antenna connector, therefore everything that connects the components of the matching network. Moreover, the output uses all of 6 pins of one side. But unifying them in a large net, means having a much lower impedance (just as every other combination of this output).
I could simply use the reference layout, but I didn't find it yet.

How can I extrapolate the allowed net characteristics (Width), while the only thing known is the maximum VSWR? The length should not be a problem (I suppose), being more more less than the wavelength.
Not to mention the input: it is a sort of CLC T-network, but I'm totally unaware of the input impedance of the chip, so there is the same issue. I'm entering to it with a net of 50 ohms, but it is the only assumption that seems valid. I'm sure I am missing something.

A possible answer, for the OUTPUT only: In page 9 of that datasheet talks about load impedances of the reference schematic: assuming that it is the load saw just at the output pins, so before the matching network, I can extrapolate a net dimensions. But how about all the intermedium connections of the output network? (so...as just mentioned before)

I hope to be clear. Thanks and sorry if it is too silly.


texts: I am trying to do a dimmer and below is my schematic. Before doing an actual PCB, I did a proto on a veroboard and the circuit works perfectly. Now when I did a PCB and got it back from the manufacturer, I have noticed that MOC and BTA is heating up too much quickly. The only difference between my proto board and the finished PCB is that, on my proto board I have used the through hole resistors where as in the finished PCB they are SMD. R14, R15 and R7 is 1 watt SMD. In the PCB, I had footprint of SMD versions of 4N35 and MOC, but as the vendor did not have the SMD versions, they soldered the through hole versions on the ptoto PCBs. Also I used 4 1N4007 to create the bridge rectifier on the veroboard, where as on the PCB, I have used a rectifier IC. Everything else are just same. But in the proto PCB, the MOC and BTA is heating up even with a 60W bulb :( Any clue?


texts:
Say we have a RLC circuit, connected to a source. Say, regarding to the positive side of the source, we have in order, an inductor L, followed by a resistance R and a capacitor C in parallel. So we have L in serial with R || C. My question is ...

How could I calculate the resonance factor, Q?

I have solved parts of the problem... but I'm stuck at calculating Q (i think Q is also called the "quality" factor)

Basically...

I have the resonance frequency when the impedance Z is only of resistive (real) nature :

$$
L\omega - \frac{R^2C\omega}{1 + (RC\omega)^2} = 0
$$

$$
\omega_{r} = \frac{1}{\sqrt{LC}}\sqrt{1 - \frac{L}{R^2C}}
$$

After obtaining $\omega_{r}$, what do I do?

I'm supposed to use formulas like
$$Q = \frac{Q_{L}}{P}$$

or

$$Q = \frac{Q_{C}}{P}$$

Where P is the active power dissiped by resistances, and $Q_{L}$ or $Q_{C}$ is the reactive power... either of the inductor (L) or the capacitor (C). I'm a bit lost. I know this shouldn't be complicated. I'm just confused.

Also, could you explain me why either one of these equations can be used? Why can we use both $Q_{L}$ and $Q_{C}$ divided by P?

Thanks


texts: How is this synchronous AC gear motor being reversed?

texts:
I just disassembled the shifter assembly in a washing machine.  It uses a synchronous 120VAC gear motor.  The motor says "CW/CCW Z.P."  It has two leads for the AC power and no other inputs.

I discovered that the direction sometimes reverses if I allow the motor to stop, then quickly cycle the input power, then re-apply the power.  However, this is not reliable, as sometimes it reverses and sometimes it doesn't.

How is this motor being reversed by the washing machine control board?  There must be a reliable method, otherwise the shifter arm assembly would be damaged.


texts:
After getting some ideas (thanks to users Russell McMahon, akellyirl, The Photon...) and some extra research and redesign, I would like to hear opinions about how to approach my LED flash project. Thanks.

I want to use 240 High CRI LEDs to build a LED flash ligh for camera shooting.
There will be 6 camera shots delayed 500ms among them. So the LEDs will be turned on 6 times each 500ms for a duration of just 3ms. The same sensor triggers the camera shot and the LEDs.

These LEDs come in strips of 1m (versions 12V and 24V available), each of them carring 60 LEDs. So 4 strips are needed.

Within 1 strip (24V version), the 60 LEDs are distributed in 10 parallel groups (according to specs "60 LED pcs / meter, cuttable every six (24V) LEDs"). Each of these groups takes 24V and has 6 LED units in series along with some resistors in order to have the 120mA flowing through each 6-LED group (specs doesn´t explicitly say so but I think it´s the way).

I´m planning to connect the four 60-LEDs strips in parallel so I´ll have 40 groups of [6LED + resistor in series] connected in parallel.
I want to power up the strips with a Constant Current PSU adjusted at (120 mA * 10groups) * 4stripes = 4.8 A

(I know I may have trouble if one series group fail so I could get higher current flowing through the rest, but I´ll probably make use of this solution)

Here comes the problem, since the LEDs have to light just 3ms at full power in the precise moment, I´m wondering if the PSU will be able to deliver the power right in the instant needed or if I will have issues related to the Transient Response of the PSU. Does anybody know about this?

In case the power couldn´t be delivered within the time contraints that I need, I was thinking about using capacitors. How the scheme would be in this case?

Any ideas are welcome

Thanks


texts: Philishave (Norelco) HS550 reverse-engineering

texts:
My first question here. Image is schematic for Philishave (Norelco in US) HS550 shaver - 110V-230VAC.

I am puzzled how this works.
I think that on the early part of the positive half cycle the supply is routed to OUT+ via D2, and Q1 is switched on via C1 (with base voltage limited by D3), and when the voltage exceeds a limit (probably somewhat over 120V) Q2 will turn Q1 off (with Q2 base drive via R12/D4/D5/D6/R10).
R1 is probably to limit inrush, and runs pretty warm.
But I cannot fathom the purpose of R3.
Or R2.
Nor the parallel R7 and R8 pair (and why not use a single 0R47 or similar?).
Nor D7 and R11.
Nor R5 (which looks like 1/4W?).
D1 is integral to Q1.
D6 is unknown, but tests as a diode. This has two colour bands, brown and grey, on a black background. It does not test as either a 1.8V or 18V zener (took it up to 29V with series 1k), but may be defective.
The shaver is faulty, with the motor speed changing (speeding up for a few seconds, then slowing until almost stopped, repeating). But Q1 (BU724AS) measures with a hFE of about 45 when specs for this is > 1000, so...
(Q2 - BC547 - seems to be fine.)
Any thoughts?


texts: STM32F030F4P6 - Application Not Starting

texts:
I have been developing code to control an LCD using STM32F030F4P6 mcu. So far everything was working fine.

However I just added some new code with timer, and now when I uploaded the updated code, the system just stopped working. The only changes I made to the system were in code.

It seems as if my application is not executing as a test to light up an led right after entry to main is also not working. The mcu seems to be working since I am able to upload code to it.

#include "stm32f0xx_rcc.h"
#include "utilfunctions.h"
#include "spi.h"
#include "sdcard.h"
#include "nokiac100.h"
#include "pwmdac.h"

void setupPeriphClocks(void);
void setupPins(void);
uint8_t checkClocks(void);

int main(void)
{
  setupPeriphClocks();
  setupPins();

  TEST_LED_ON;

This should turn on the led but nothing is happening.

Any idea what could be wrong here? i suspect it could be something related to a hard fault but have no idea how to check it.

Any help figuring this would be great!

UPDATE

So I found the culprit as the TIM1 ISR that I have written in my code. Commenting out the ISR makes my application compile and execute just fine. However including the ISR compiles fine, but the application does not run.

The ISR is

void TIM1_BRK_UP_TRG_COM_IRQHandler(void)
{
  if(TIM_GetITStatus(TIM1, TIM_IT_CC3)==SET)
  {
    if(PWMDAC_CURRENT_AUDIO_SAMPLE_NUMBER<=PWMDAC_AUDIO_DATA_SIZE)
        {
            PWMDAC_CURRENT_AUDIO_SAMPLE_NUMBER++;
            if((PWMDAC_CURRENT_AUDIO_SAMPLE_NUMBER%512)==0)
            {
                //get next audio block
                PWMDAC_CURRENT_AUDIO_BLOCK_NUMBER++;
                //make sure sd card not being accessed by video system
                //before trying to read from it
                if(SDCARD_READ_ONGOING==0)
                {
                    SDCARD_Read_Block(PWMDAC_CURRENT_AUDIO_BLOCK_NUMBER*512, (uint8_t *)PWMDAC_AUDIO_BLOCK);
                }
                else
                {
                    PWMDAC_CURRENT_AUDIO_BLOCK_NUMBER--;
                    PWMDAC_CURRENT_AUDIO_SAMPLE_NUMBER--;
                }
            }
            TIMER_Timer1_SetDuty(PWMDAC_AUDIO_BLOCK[PWMDAC_CURRENT_AUDIO_SAMPLE_NUMBER%512]);
        }
        else
        {
            //end of audio samples. loop
            printf("looping audio\n");
            PWMDAC_CURRENT_AUDIO_BLOCK_NUMBER=PWMDAC_AUDIO_DATA_SD_STARTING_SECTOR;
            PWMDAC_CURRENT_AUDIO_SAMPLE_NUMBER=1;
            if(SDCARD_READ_ONGOING==0)
            {
                SDCARD_Read_Block(PWMDAC_CURRENT_AUDIO_BLOCK_NUMBER*512, (uint8_t *)PWMDAC_AUDIO_BLOCK);
                TIMER_Timer1_SetDuty(PWMDAC_AUDIO_BLOCK[PWMDAC_CURRENT_AUDIO_SAMPLE_NUMBER%512]);
            }
        }
    TIM_ClearITPendingBit(TIM1, TIM_IT_CC3);
  }
}


texts: Shunt resistor specifications do not contain thermal resistance data. How come?

texts:
I'm looking at the specifications of an ohmite shunt resistor: http://www.ohmite.com/catalog/pdf/10_series.pdf

It is a 0.005 ohm resistor, rated at 2,3,5 and 7 Watts (4 different parts in the same datasheet) at 25C ambient. But there is no information about thermal resistance.

If my current over this resistor is going to be, say 30A, then power dissipated on this resistance is going to be 4.5W. Does this mean that if I pick a 5W or 7W resistor, I will be OK in free air (no cooling requirements)? What if my ambient is not 25C? Since there is no thermal data in the datasheet, how can I go about calculating cooling requirements for an ambient temperature of 50C? Are shunt resistors never cooled?


texts:
I have a PCB board from my washing machine which has an faulty inductor (marked as L4) on it. This inductor is in all probability used to limit the current on the Vdd of a series of ICs.

Now its a 0805 SMD package without any coding and any documentation on the PCB is not available.

I was wondering if anyone could advice me with what kind of inductance value I should replace the faulty inductor with? The available values for these case dimensions range from 560nH to 330uH.

Any help would be greatly appriciated!


texts: How to measure capacitance without LC meter?

texts:
I would like to use capacitors salvaged from old electronics, but I currently don't have an LC meter.

What would be some really simple circuits, that would convert capacitance to something I can measure (voltage, current, frequency)?


texts: What are possible methods of interfacing with a button on a PCB?

texts:
I have bought an electrical appliance which has buttons sticking out of it. I want to interface with these buttons from a microcontroller, but the buttons are baked on a flex PCB in the underlying circuitry. I can not get to their pins, partly because I'll void warranty, and therefore I decided that a mechanical solution would be best. I would've much preferred an optoisolator wired to the signal lines, but it showed that it can't be done.

I measured the force needed to press the button and calculated that it would be around 4 Newton. (Placed object on scale, zeroed and measured weight while pressing button)

Because the electrical appliance is quite small (approx. 60x60x60mm) and my power supply is limited to 5V 2A I started looking at linear solenoids within this range and found that they are unable to deliver the required force. I then thought of using a stepper motor with gearbox, but this feels a bit overkill.

What are some recommendations to interface with either the physical button or its underlying circuitry, keeping in mind the constraints?


texts:
I got a good deal on a 3-phase generator, but everything I have is single phase. There's a sticker on it that says 230v 60hz.

The output is a 4-wire plug. I did some testing with my multimeter and it seemed I had the following:

Green wire: Ground
Red, Black, and White wires: Somewhere around 110v I believe (hard to read on the analog multimeter I had handy).

I'm used to having 110 house wiring have a hot wire, a neutral, and a ground, so I'm a little confused on what I'd have to do here. Would I wire one of the 110 wires to hot, the green to ground, and a common wire between all of my outlets as the neutral?

Second question is what to do if I wanted 220v? Two of the hot wires, green to ground, and common wire between all outlets?

And finally, I've read that it's best to distribute load across all the phases. So would that mean if I wanted 3 110v outlets, I'd want to wire one up to each of the hot wires?


texts: How to avoid damaging relay used for controlling motors?

texts:
I've got a circuit with two DPDT relays controlling a motor - the diagram below is borrowed from a related but different question.  RLY1 turns everything on and off, RLY2 switches the direction of the motor.

I've found that after a brief amount of use the relays are damaged.  Both relays have the same problem - on one set of contacts common/NO/NC are all connected, even when the relay coil is unpowered.  (The other set of contacts is as expected - ie. common/NC are connected, NO is connected to neither of the other two - so only "half" of each relay is currently damaged).

Questions: what is likely to have caused NO/NC terminals to be connected, and how should I have avoided that problem?

Gory Details (possibly not needed):

motor runs on 30V
PSU that came with the motor is rated 30V/2A
relays are rated for 2A/30VDC (model Meishuo MCB-S-205-C-M)
relay is controlled from an ATMega MCU
relays both have an IN4001 protection diode across the relay coil - not shown in diagram
I did manage to "fix" one relay by tapping it on the table.  Unknown if that will stay fixed or if permanent damage is done.  The other relay doesn't respond to this treatment.


texts: How can I "filter out" a small offset current from a current source?

texts: I have a current source that produces a 1 kHz 1 mA sinusoidal current.  Unfortunately it also outputs a small DC offset current (microamps).  The current source does have a small trim pot to zero out the offset, but it is never perfect, and I need to hook this current source up to another circuit that can't sink any net current.  Therefor I'd like to "filter out" the small offset current.  My first attempt was to put a fairly large capacitor (1 microF) in series to block the offset.  This would work if it were a voltage source, but since it is a current source, the small trickle of current eventually charges up the capacitor until it hits its voltage rails since there is no way for the current to escape.  Can you suggest a way to zero out the current source reliably other than just twiddling the trim pot?  Thanks!


texts: Positive/Negative interference in a carrier signal

texts: So my problem is that a 800MHz carrier signal arrives at a receiver via two paths that differ in length by a distance of ∆d. I am unsure how I would determine the smallest values for when negative and positive interference occur, along with phase difference at 100m. The only value given is the MHz so I dont know how I would calculate any of these things other than getting the wavelength. I am basically stuck.


texts: Using higher I2C voltage then MCU supply (but still in limits)

texts:
I am working on a project where there is 1x MCU and 2x I2C devices

device needs 2.8 V using I2C1
device needs 3.3 V using I2C2 (I have a need of seperating bus apart)

If I understand correctly, a I2C port is only like a switch? So could I supply my MCU (possible 1.8 - 5.5 V) with 2.8 V and connecting device 1 to I2C1 (2.8 V bus) and device 2 to I2C2 (3.3 bus - which is higher then MCU supply 2.8 but still under 5.5 V)? I would like to exclude the use of level shifter.

Will appreciate any help or thought about this, thank you :)


texts:
It's said the microcontroller AT89C51RC2 has 256 B RAM for data, 32 kB Flash for program, 1 kB XRAM and 2 kB BOOT ROM.

The RAM adrressing area is 00h to 0FFh, which takes all 256 B. SFR has adresses from 80h to 0FFh, which means 127 B. Now where, physically, this memory is?


texts: How do you make / connect an Analogue gauge with Arduino?


texts: How do airplane in-seat power detection circuits work?

texts: Airplane in-seat AC line-voltage power outlets have limited available current/power. I remember reading that laptops or laptop power adapters can somehow detect this and inform the laptop that it needs to limit power consumption. If this is true, they must have detection circuits of some kind. How do these work?


texts: Modifying Transistor Properties in Proteus

texts:
I'm trying to simulate a Common Emitter circuit using Proteus. The NPN transistor which I fetched from 'DEVICE' Library has a value of VBE = 0.77V
What I want is to adjust this property to 0.6V. When I right click on the component and select 'Display Model Help' there are some initial parameters like in the figure below. My question is that, is there a way to adjust these parameters arbitrarily?


texts: Using an NMOS as a switch for a 10V DC source in a 555 timer circuit

texts:
I used NI multisim and created a circuit with a 555 timer that will allow a diode to flash at a frequency of about 4HZ. This is the circuit:

As you can see in the above image, the oscilloscope graph is a square wave constantly changing from high to low which means the light is flashing on and off. Nothing wrong with this.
After that, I tried to make a simple modification to the circuit by adding in an NMOS as a switch for the 10V DC source. In the image below, I am pretty sure that I set up the NMOS correctly. I'm feeding the gate of the NMOS a voltage of 0V. You'd expect the output of the oscilloscope to be a flat horizontal line at y=0 which means that no current/voltage is reaching the diode. However, this does not happen. I see the same square wave from before.

I hope the images are clear enough. I am unsure what I have done wrong. Any help would be greatly appreciated. Thank you!


texts: Timing differences with a 27 MHz data clock

texts: I'm considering using a chip which outputs 8-bit data on a 27 MHz clock. The data will go from the chip to a FPGA, a distance of a few cm max. Do I need to be concerned about timing differences between traces on a PCB, and if so, how can I mitigate these? I've often seen motherboards with traces in small coil shapes, presumably to act as little delay lines.


texts:
I am going to make a conveyor like this

There will be a optic sensor which detects a box.

There will be motor (3 phase, 380 V, 1 A, 0.37 kW, 1400 rpm) with gear reduction (coefficient of reduction is 36). Power from this motor is enough for me.

The question is about the control and power systems.

My suggestion:

1) power line (3 phase) go to Schneider GV2ME08 (circuit breaker)

2) then go to Schneider lc1d09 (contactor)

3) then go to the motor.

Ic1d09 will be controlled with 24 AC. So I need transformer (220/24 AC)

I need a relay for commutating the 24 V.

This relay will be controlled with 5 V from Siemens Logo 24 RC. When the optic sensor sends a signal to the controller then this controller turns on the relay.

It is how do I see this picture.

My question: Is it correct? If it is correct does I can do it better? Will my conveyor do twitch? Do I need to use a frequency regulator for smooth start?

I will be glad for any opinion.


texts:
I have looked through the web and couldn't find a model of a capacitor at the moment of breakdown.

After a circuit that I built failed, I took a few capacitors to test and found out that some of them breakdown before they reach the rated breakdown voltage. I
also found out that the current is bigger than I expected.

From data sheet : 10nF capacitor @ 100V rating

Some of them broke at 96ish V and some after 100 V (not exactly at 100 V).
The current rating was high as kA which I can't understand. Is the ESR and ESL module are still relevant at the breakdown?


texts:
I'm new to this forum and glad to be here!
I'm building a 1 watt led circuit (planning to...) most of the circuits I found online, make a lot of heat and I wish I could find a better one to get bright and power friendly flashlight for my "power bank".

Recently, I've built a 555 based LED driver which is super efficient and bright enough for smd leds it is actually blinking at high frequency so you won't see by naked eye, it is so beautiful. Anyway the problem is that it cannot drive 1 watt leds so I'm wondering if I could do something about it, I bought lm317 for 5.1 to 3.3 volt conversion but I’m pretty sure lm317 is not the best idea (cause of voltage conversion and wasted power by heat)
Can I mix ne555 and lm317 or even a transistor? So again it blink at high frequency
I mean using pin 3 of 555ic as trigger for the transistor or lm317 to bright the 1 watt led
Vcc=5.1volt @2amps


texts: Semi-flexible cable for control panel terminal blocks

texts: What is the proper name for the semi-flexible cable connecting the terminal blocks? I have seen people making a 90 deg angle to these wires and it    stays that way. I went out to the market but most cables are soft.


texts: Gyroscope and compass. When its better to use one instead of another?

texts: Why people prefer gyroscope instead of compass? Does gyroscope replace compass? I would like to see the pros and cons of each.


texts:
Is it possible to DIY your own capacitative touchpad on a PCB? The last page of this mentions it:

http://www.ebv.com/fileadmin/products/Products/Fujitsu/FMA1127/FMA1127_PCB_Layout_Ap_Note_FINAL_021809.pdf

"The sensor channels are grouped as rows and columns.
Row and column cells are arranged in an interleaving
pattern. The size of the cells should be designed so that
when a finger touch is detected, a few cells are covered by
the finger. Proper overlapping of cells is important to obtain
good finger resolution."

So it seems like you have to have two layers, one having metal vertically and the other horizontally. I'd like to do this as cheaply as possible so I'd like to try to implement this on a standard 2-layer piece of FR-4, probably 0.8mm thick (half the standard thickness).

Or, the matrix keypad method mentioned above seems like it'd work, if the "keys" were placed together to have little gap. My overall goal is to have smooth input instead of discrete keys.


texts: simple network analysis doesn't give correct result

texts:
Well I tried to calculate the circuit below, because of little experience the calculation became terribly messy and I didn't solve it. I need to calculate the power given by the 3A current source.

simulate this circuit – Schematic created using CircuitLab

First I summed the voltage & current sources. To a single voltage of 5V at the top and in the middle a source of 1.75A. Then I used superposition to calculate the voltage at the top (resulting in -2.5V)

simulate this circuit

I thought I could then simply say "this 1.75A source pushes current from 0V down to -2.5V so the power is \$P = -2.5V \cdot 3A = -7.5W \$
Simulation shows this is wrong, how would I calculate this problem? With nodal analysis?


texts:
I have written a program to estimate the stack usage in the following manner
I have defined a global pointer variable to unsigned char. I have defined a local variable in the main program and have taken the address of this variable which will be my starting stack location. In every subroutine I go I will define my known variable and take the address of this variable. The difference between
the first stack location and the new stack location will be my size from which I can calculate the maximum stack size.

unsigned char *startingstacklocation;
unsigned char *endingstacklocation;
unsigned int maxstacksize;

int main()
{
unsinged char mydefinedlocalvariable;
startingstacklocation = &mydefinedlocalvariable;
subroutine1();
}

void subroutine1(void)
{
unsigned char existingvariables[20];
unsigned char mydefinedlocalvariable;

endingstacklocation = &mydefinedlocalvariable;
stacksize = endingstacklocation  - startingstacklocation;
if(stacksize > maxstacksize)
{
 maxstacksize = stacksize;
}
}

My question is it the proper way of doing?


texts:
I found 220V AC to 12V DC - 30A power supply schematic:

My question is, where Ib1 current goes (where base pin is connected)?

Edit:

Here is one more schematic with same strange base pin connection:

Edit:

Is it same as:

?


texts: Xilinx Programming FPGA from SPI Flash without JTAG

texts:
I'm trying to be able to configure my FPGA by loading the configuration into the flash memory. I am able to write to the SPI flash through an ethernet interface, so I think it would be possible to write the bitstream to the flash over ethernet, and that way I could program the FPGA over the network without using a JTAG cable. Is this possible? How should I generate the bitstream in Vivado? What address in the flash should I use?

I am using a Kintex-7 FPGA and and a Spansion S25FL256S SPI flash chip.

Thanks!!


texts: Why is there no variation caused by this swept parameter?

texts:
I quite like Qucs now that I more or less have the hang of it. Unfortunately, I can't figure out how to get a parametric sweep working.

I'm running an AC simulation on this circuit:

For now I'm not asking on how to improve or fix this circuit; solely on how to fix parametric sweep simulation.

The output of the simulation is shown in this table:

The gain is not being affected by the inductor sweep when it most certainly should be. How do I fix the sweep?


texts: Can Inkscape be used for layout editing for photolithography?

texts:
Inkscape is capable of exporting DXF files, a format that is accepted by photolithography masks manufacturers.

Before I start working on layouts with Inkscape I would like to know if the exported DXF would actually contains all the information (layers, etc.) that is expected from a proper layout file such as GDS.


texts: How should I go about reverse-engineering this printhead?

texts: I'm interested in using the Epson FA04010 printhead in a project. I'm pretty sure it uses piezo-based inkjet tech, and I can see in the product images it has 21 pins. I can't find any specs at all for this printhead, which makes sense from the part of Epson. But is there any way to reverse-engineer it to figure out how to drive it?


texts: At what edge of the clock, SDA signal is sampled in I2C for data? At rising edge / falling edge / after rising edge?

texts:
I found this from wikipedia page.
It says, data is sampled after SCL line rises.


texts: How to derive transfer function for DC feedback coupled transistors?

texts:
I am not sure where to start deriving the transfer function of this circuit.
If I do a control diagram then I need to know the initial values to convert the system into the Laplace domain, so I guess that is really key to where I am stuck.
How would I derive the initial values t(0) for this system?  It seems like every transistor affects the other, so how do I know where it settles to?

simulate this circuit – Schematic created using CircuitLab


texts: How does one determine the millivolt reading across a Wheatstone bridge?

texts:
When determining the millivolt reading I'm confused on the order in which you subtract V(2-4) and V(1-3).
Would it be: V(1-3) - V(2-4) or
             V(2-4) - V(1-3)

I've seen it done both ways, so how would you know?


texts: Determining sample rate / bandwidth for a gyroscope with no ODR setting

texts:
My understanding is that a sensor's bandwidth should be half it's ODR (the rate at which you sample data). I am working with the BNO055 sensor and trying to get angular velocity from it, which will be used for a gesture/air mouse.
The gyroscope lists the following characteristics:
 Ranges switchable from ±125°/s to ±2000°/s

 Low-pass filter bandwidths 523Hz - 12Hz

It doesn't mention ODR anywhere in the datasheet. Is the output data rate the rate at which I'm sampling it in my loop? Should I be aiming to set the bandwidth to be half of that?
Also, the range specified would be on a per sample basis? So if your microprocessor allows it you should be aiming to sample frequently at a lower range?
Thank you very much for your help.


texts: MAXIM31855T thermocouple chip, is there a through hole equivalent that works on the spi bus, having problems with SMD routing

texts:
I need to produce a circuit board to measure 16 temperatures from different thermocouples of  types J and T, Maxim has the perfect chip, the MAX31855(T,J), the only problem is that it is surface mount and my CNC PCB router which is a Chinese 3020 hack does not like the tight tolerances required for SMD.

I was wondering if there is an equivalent through hole chip that operates on the SPI bus? I want to use an Arduino DUE and a multiplexer chip (CD74HC4067E1) to read the individual temperature chips via the chip select pins and the SPI bus.
Does anyone have any thoughts on this?


texts:
I am building some electronic circuits with some arduino in it to animate LED-strip.

The device is powered by 3 USB cables, because as I am using 270 RGB LEDs I can have 5A running trough the cables, so I splited it in three circuits. They are all powered from a powerbank and USB cables.

I already made a first version witch works correctly but I ended up with 4 117S switchs to turn in on.

I already found a way to lower it to 3 switchs but I do not know how to only go to only one since they are on different circuits. Because it is annoying to have to turn on 3 switch each time because the device is made to have all on them tu be turned on to work properly.

Here is how the circuit looks actually:

Is there some 2 state switch that can have multiple outputs? Like 3 inputs and 3 outputs? Each circuit carries around 1.5A. Should I use AND gates?

I'm still new a beginner in all this, I have a programming background and doing some electronic as a hobby.


texts: Building a regulated power supply AC-to-DC

texts: What components do I need to build a regulated power supply with an input voltage of 220V AC and outputs of 3V, 6V, 9V, 12V? Assuming max. current of 1A in each outputs.


texts: Can the output of a TCXO drive a LPC1114 uC?

texts:
Is it possible to drive the on-chip oscillator of LPC1114FN28 using the clock output of a FOX924B TCXO? The Datasheet of the uC indicates that a 100 pF cap needs to be put between the oscillator and the XTALIN pin with an additional cap connected to grnd to keep the voltage limited to 1.8V. Considering that output load as per the FOX924B datasheet is limited to 25pF, the 100 pF cap recommended by NXP seems too much for the TCXO. Am I right?

Also, why can't I simply use a resistor based voltage divider to bring the TCXO output to 1.8V?


texts:
I am not pretending to use this, but as a general curiosity, when the AT32UC3C2512C datasheet says in page 1259, Table 40-20, parameter Iout, that the internal 3.3V regulator has a 35mA DC output current, does it mean I can actually use it as a power source, as long as I don't use more then 35mA out of it?

EDIT:

As requested:


texts:
I am trying to wrap my mind around a design for a long light sensor bar. This is actually a laser sensor that needs to sense a moving laser beam continuously over a certain distance. I would need this sensor to be modular so I could make the sensor bar longer or shorter depending on the application. Think 2" x 6" pcb size that could have 30 connected together.

My thought is to design pcb that has a lot of phototransistors on it (thinking ALS-PT19) and tying the open collector outputs together. So as the laser hits the sensor at least one of the photo transistors is on and outputting a high signal. Then I would have connectors where I could plug a 2nd pcb (exactly the same) board in that would tie even more phototransistor outputs together. In the end there could be hundreds of the phototransistors tied together.

Basically, I don't care how many of the phototransistors are on. If even one phototransistor is on I want a high signal.

So does that make sense at all? Is there an issue with this design? Or would that work?


texts:
I'm using a MCU ADC, PIC18F26K22, to sample and calculate a RMS value of a sine wave that is rectified by the full precision rectifying circuit in the schematic below. This ADC has 10 bits and I'm sampling at 50 kHz. The signal is 2 kHz and at the ADC input has 700mVp. This voltage was measured with a digital oscilloscope.

I already did the compensation for Gain and Offset errors, using DC voltages and a very good quality multi-meter, but when I'm sampling this sine wave I'm having a very poor accuracy in the results, for instance, in 700mVp Sin Wave the ADC is sampling peak values of ~620mV. I'm using the internal voltage reference of 2.048V, which guarantees a low error.

So, I'm really clueless about what could be done to solve this, I already increased the acquisition time, with the cost of reducing the sampling frequency, but still the voltage peak values do not change.

What is the cause of the incorrect peak voltage? How can I fix this problem?


texts: Selecting rectifiers for a welding machine

texts:
I have a welding machine that has a rated output of 230 amps with the AC output. The DC output is 140 amps. I was a bit puzzled as to why this was, but from what I can tell they use a lower voltage tap on the output of the transformer. Since the output is rated at 140 amps, they likely selected an automotive rectifier from an alternator to keep production costs down.

I intend to fit a full bridge rectifier to allow me to use the full 230 amp output with DC welding current. The AC frequency is 60 Hz from the mains. So switching time is not likely to be an issue. Although the welder is rated at 230 amps, the peak output current can be much higher. Closer to 300 amps. The voltage listed on the front of the unit is 38 VAC with no load.

An additional design constraint is that the output has an inductor in series with it. This is done so that smoother current is delivered to the workpiece. It can cause a large voltage spike when welding stops.

Another constraint is that I want to add a high frequency high voltage current source in parallel with the welding leads. I intend to use a bypass capacitor to try and prevent the rectifiers from seeing this, but they could still see some of the voltage.

How should I go about selecting rectifiers for this unit? How much safety margin should I select in the rectifier's peak current rating? Is it generally cheaper to find an integrated unit (4 diodes in a package) or should I buy four independent diodes.

simulate this circuit – Schematic created using CircuitLab

V1 is mains current
D1-D4 are the diodes I need to add
L1 is a current limiting inductor on the primary side
L2 is a current smoothing inductor on the output
V2 is a HF high voltage power supply. This is known as "arc-start"
R1 represents the welding leads and workpiece. The actual impedance is whatever the sum of the leads, clamps, and arc happens to be.


texts: Can anyone identify this thermometer probe?

texts:
I've tried to use this probe to detect temperature from an arduino microcontroller.

Unfortunately, I can't seem to get a decent reading out of this. I need to know appropriate coefficients for steinharts equation if they are applicable to this type of probe.  My attempts at finding these coefficients have failed with various measurements of resistance and temperature. It seems as though this isn't a NTC thermistor. Can anyone offer some guidance to  interpret an analog reading from this probe?


texts:
I have some troubles with reading this
datasheet.

For example the plot

I know normal log and double log scales but the plots in this datasheet have only 4 divisions. Is it then 1,2,4,6,8,10?


texts: M48Z02 (16Kbit ZEROPOWER SRAM) is TTL compatible?

texts:
I've some problem using together TLL and CMOS integrated. I'm developing a project and only now I discovered that the two standards can create troubles together.

So I decided to use only TTL chips. Luckily I can also use HCT integrated, that are bot compatible with TTL and CMOS.

I'm not sure about compatibility only about one chip... the M48Z02 (datasheet). It is a 5V, 16 Kbit ZEROPOWER SRAM. In the datasheet it is also written:

  Pin and function compatible with JEDEC standard 2 K x 8 SRAMs

Does it mean something about the compatibility with TTL technology?

If not, where can I find information about the compatibility between M48Z02 and TTL technology?

Any help you can provide will be really appreciated.


texts: What to look for in the datasheet when choosing a MOSFET?

texts:
I thought that choosing the right MOSFET for my LED strip would be easy until I discovered how many different models there are.

Basically I want a MOSFET that allows me to control with PWM a 12V 6A (MAX) led strip, but every time I see the Vgs I get confused because of numbers like +-20V..
(I'm controlling it with an ATtiny13A or ATtiny85 - 5V pin output)

I done a lot of searching a came across a lot of different models: IRFZ44N, TIP120, STB36NF06L and a bunch more.. but I not sure if they will do the job

What MOSFET should I use and how do I read in the datasheet why this is a good choice?

I am new to hobby electronics.


texts: SMPS transformer orientation with respect to PCB: what's best for EMC?

texts:
I have the option of either using a vertical or horizontal bobbin for a flyback SMPS transformer, and I can't conclusively decide which would be best for minimal radiated interference to be picked up by nearby signal circuitry - of all the EMC/layout related material I've looked at, I have found nothing that mentions specifically this issue directly.

To be totally clear, I'm using 'vertical' to mean perpendicular to the plane of the PCB, and 'horizontal' to mean parallel. Here's a quick diagram - this is not meant to be to scale, just to illustrate the concept:

The diagram shows the two transformer options mentioned above, and some signal circuitry which could  be anywhere on the same PCB, not directly connected to the transformer.

So far, here are my assumptions - of course please correct anything that may not be quite right:

The return currents from the signal circuitry should ideally flow in a plane directly underneath, therefore the signal circuitry should not contain a loop along the PCB plane with a vertical magnetic axis. However, instead, as there is a distance between the signal and ground plane, the signal traces and their return paths would create small loops which circulate down through the PCB and back up, producing a horizontal magnetic axis - see drawing below for an example. Hence, the transformer should have a vertical magnetic axis (Option A) for minimum pickup by PCB traces arranged in such a way.

If for some reason a signal cannot be routed so that the return flows directly below, this would create a loop which has a vertical magnetic axis - see diagram below for an example when this happens. Although this will  be avoided, for minimum interference in such an arrangement the transformer should have a horizontal magnetic axis (Option B)

In general, out of the cases in the 2 points above,  the case in point (1) will be the most common and the one in point (2) will be avoided. Based on this, so far I think the vertical transformer (Option A) is best here.

I'm not too confident that I have considered everything that's important, so I'm asking for any suggestons from anyone with more experience for any other relevant factors, anything I've overlooked or otherwise verification whether or not I'm on the right line.

Thanks in advance!

Edit: some further information about the specific project following responses below - I will be using EE cores with a centre gap, and will most likely use a flux band aroud the windings to attenuate radiation, though I don't want to make the question too specialised to this project so it would be nice to establish some kind of general approach for dealing with this situation, as I think it's quite broadly applicable.


texts: What bluetooth chip should be purchased to solder onto the Nook motherboard?

texts:
From what I researched the e-reader's motherboard contains three unused serial ports that can be connected from gps modules to bluetooth chips.

U2713 PIN OUT CLOSEUP

  The article that gives instructions states that its hardware does not
  include a logic level to RS-232 voltage level
  translator("transceiver") so one must be added for RS-232
  communications.

  The board was apparently designed to use a connector similar to
  Digikey part number A99963TR-ND.

I don't know if a bluetooth chip has anything to do with the aforementioned sentence. Because this tutorial is meant for a gps module.

Based on this pin out and the board's design; if possible, what kind of bluetooth would I use preferably without wires to minimize hassle in soldering?

This is the site that gives the instructions.


texts: Level shifting 8 output IO Expander from 0V-5V to -2.3V to +2.3V

texts:
I have a circuit problem that I'm trying to find a solution for.

I have an 8 output IO expander which outputs 0V-5V. It is running analog switches which have a Vdd and Vss of +-2.3V.

Using the 5V right now is causing a dc offset and noise on the output of the analog switch.

I know I could just use an op amp to translate the voltage level, but that would require a lot of hardware for all 8 outputs.

I can't seem to find a level shifting IC that will accept a 5V signal and output a differential analog signal.

I've also thought about running it off of an 8 channel DAC. But that would be a costly solution.

Update for clarity:
I am looking for a single IC that can accomplish the level shifting for all 8 signals instead of having to use a group of discrete components for each signal.
OR, I am looking for an 8 ouput IO expander that has seperate supplies for communication with the microcontroller and IO outputs.


texts: How is the Correct Surface Load of a Heating Element Determined and Verified?

texts:
A heating element should be operated below its maximum surface load (power per surface area.) For a given element, one might be tempted to say the surface load is the power given by Ohm's law divided by surface area.  However, my gut tells me that's wrong.  It's more probably the power density from the Stefan-Boltzmann law.  1.) Is that correct?

Clearly, the temperature of an element radiating into "empty space" will be less than the temperature of an element very near other black-body radiators (which have been heated by the element) - or even it's own structure (which may not be a straight wire.)  In these cases, I suspect the surrounding black body matter will effectively "back heat" the element.  Thus, the shape of the element and the arrangement of bodies in proximity will affect the surface load.

Obviously, this is non-trivial to calculate, but when using the radiative heat transfer equation for heat transfer between a resistive heating element at temperature, T1, and other black-body radiators at temperature, T2, (with appropriate constants, k1,k2.)  ...

Power/Area1 = k1*(T1)^4-k2*(T2)^4  ...

I believe the temperature of the two bodies must be such that the radiative heat transfer balances the power of the resistive load, i.e.:

(V1)^2/(R1*Area1)  = k1*(T1)^4-k2*(T2)^4

2) Is that sound, and is the term, k1*(T1)^4, the surface load of the element? (It may be much higher than the resistive power divided by the surface area!)

3) How is the surface load for a given element (in a given geometry and operational state, i.e. temperature,) measured in practice?

4) Manufacturers specify maximum surface loads for elements of different shapes and for different applications, yet the elements are made of the same material.  Why does the recommendation vary depending upon shape and application?


texts:
I was analyzing a circuit and when simulating it in PSpice I came across this:

Is there a way of calculating without simulation (i.e. just looking at the circuit and doing the algebra) that \$V_{BE}=-0.2V\$?

Thanks for your time!

EDIT: I measured this value in a real circuit and I got the same value, give or take a few mV, so the simulation was pretty accurate.


texts: Is it possible to terminate FFC/FPC by hand?

texts: Given (for example) a 15cm long ribbon of 12 conductors at 0.5mm pitch, could I cut it in half and scrape the cut ends with a razor blade or something to produce two shorter but usable ribbons? What's the best/correct way to do this? References to guides/tools for this task/etc are welcome


texts: Advice for building a dual rail, +- 10V, regulated, DC power supply, 25mA

texts:
I am looking for some directive to build a dual rail, +-10V, regulated DC power supply to supply 25mA to two resistive loads. I am very new with this; I am an engineering student and this is my first design project. I have been told by the instructor that Google is fair game so I may as well take full advantage and directly ask a few people who actually know this stuff.

If anyone could provide some guidance on where to start for the project that would be appreciated. The transformer we are using has a centre tap for the ground.


texts: Can this circuit validate AT89Cx051 micro if best valued components are used?

texts:
This is a circuit I made in an attempt to validate that the 20-pin microcontroller is an AT89Cx051. and the correct LED will turn on based on how much ram the chip has.

While the first step is successful, the second step causes a reset. I don't know if I should blame the chip itself or if there is something I can do to improve my circuit, especially with the clock. I only need to advance the clock by one. Now I did add a 47nF capacitor across the clock button to try to avoid debouncing.

Here's How the circuit runs

The NORM button (top left) is pressed so RST = 5V. This works.
The first byte of data is verified through the 1st decoder (IC1E) so 1E_DETECT is zero. This works.
I hold clock button down to make the clock a low to high transistion. Sad truth is contents of P1 do not change until I let go of the button (making XTAL high to low transistion which is contrary to what the datasheet indicates).
Upon releasing the button, the circuit resets because the MSB at port 1 is a logic high.

Based on all datasheets I read for AT89C2051, AT89C4051, and AT89C1051, They (Atmel) indicate the data at 1st address (which is always detected correctly by my circuit) is 1Eh. Then they indicate the 2nd byte is 11h, 21h, or 41h depending on how much ram the chip has. Nowhere in their documents does it state that the MSB of P1 is set when reading signature bytes.

So what's the best course of action I should take here?

Complain to the people I bought the IC's from that their chips don't work?
Add/change/remove capacitors and/or resistors?
Something else?

And in case anyone  wondered, All diodes are 1N4148, and resistors for LED's are 1K, and power is 5 VDC regulated. and the diodes arranged in groups of three are 3-input nor gates and I used diodes because it would have been impossible to create a single-sided PCB if I used the actual logic gate chips themselves.


texts: Heat output from a 200W electric radiator?

texts:
Im looking at installing an electric towel radiator. The heating element is 200W.

Dose that mean that it would both :

use 200W of electricity
provide 200W of heat output to the room ?


texts:
I am working with an ATmega128 and need to reset the microcontroller after some 10 seconds has passed and the user has not interacted with microcontroller. As an example when the user has not pressed any key from a keypad for 10 seconds the controller should get reset.

A watchdog timer is available in the ATmega128 but I am able to get a maximum of 2 seconds delay before it resets. But I require 10 seconds.

Maybe I can do it using timers but I don't know how to proceed?


texts: Do the formulas for capacitive and inductive impedance always hold?

texts:
The current through a capacitor is given by \$i_c=C\cdot \frac{dv_c}{dt} \$.
Let's say the voltage across the capacitor is a cosine wave. \$v_c=\cos(\omega t) \$.
Due to the complex exponential function we can write this as \$v_c=\Re(e^{j\omega t}) \$.
Let's calculate the current
$$i_c=C \cdot \frac{d}{dt}\Re(e^{j\omega t}) $$
$$i_c=C \cdot j\omega \Re(e^{j\omega t}) $$
$$i_c=j\omega C\cdot v_c $$
The impedance is defined as \$Z_c=\frac{v_c}{i_c} \$.
Which finally makes us arrive at
$$Z_c=\bigg(\frac{i_c}{v_c}\bigg)^{-1}=\frac{v_c}{i_c}=\frac{1}{j\omega C} $$
A similar thing can be done for an inductor.
My question is, do these formulas always hold? In the derivation I assumed that the voltage was a sinusoid (well, a phase shifted sinusoid) but this is not always the case.
What if the voltage across the capacitor is a sawtooth function or maybe a triangle wave? Then the derivation above wouldn't work at all.


texts:
I have been trying to fix up my turntable but I can't get the potentiometers at fault replaced because the knobs are glued on.

I found online that the conventional solution for cleaning potentiometers is using contact cleaner.  I stopped by home depot and picked up a little bottle of "CRC 2-26" electrical grade lubricant.

It worked like a charm for cleaning the potentiometers.  Looking at the label it seems that it can also be used for pretty much any electronic device.

How does this work?  It smells like WD-40, but I'm guessing that it does not have all the junk in it that WD-40 has.


texts: Wiring an SPDT thermostat to simultaneously control heating and cooling devices

texts:
I've set up an old fridge with a custom thermostat to finely control the cooling levels of the contents but would like to provide heating to the unit if the temperature drops below the thermostat's defined temp.

The thermostat has 2 modes, heating & cooling, as described in the wiring diagram below.  I've got it running the fridge over the "2-C" configuration but would like to hook up a heating device as well.  Can I use the one thermostat to control a heating and cooling device simultaneously?  Can I just split the active line to each device or is there some other technique I need to use?


texts:
Please check my understanding of the components in the following guitar pedal audio circuit and elaborate/ fill in missing knowledge where necessary.

Left of the op-amp inputs

R1 & C1 presents an input impedance to the output of the previous circuit
C1 sends high frequency in the input signal
to ground
C2 blocks DC from entering/ leaving via the input
R2 loads the C1, C2, R2 filter network to ensure a high impedance - thus the input signal reaches the non-inverting input of the op-amp and doesn't disappear down C2-C1 to ground

Above the op-amp

R4 and R5 provide a DC-offset for the single supply circuit.
C4 filters ripple & noise from the 9V source and works in conjunction with D1 to 'quickly' pass the AC element of back EMF to ground
C3 further filters the noise and suppresses ripple, cleaning the bias DC voltage
D1 clamps transient current when the DC voltage source is switched on/off (like a flyback diode). The reverse-bias-voltage of the component would have to exceed 9V to prevent the components p-n junction from breaking down (shorting)
R3 presents a high impedance at the junction of the non-inverting op-amp input to prevent the audio signal from input source being filtered by C3

Below the op-amp

R7 // C6 in conjunction with C5, R6 and the potentiometer set the gain.
C6 rolls off 'high' frequencies, reducing their amplification
C5 Blocks DC from reaching ground, thus preventing op-amp saturation from amplifying the DC
The potentiometer enables variable gain, R6 prevents the gain trying to reach infinity when the potentiometer impedance tends toward zero

Shouldn't C5 and R6 be reversed to prevent the DC building up at the inverting terminal of the op-amp? Does this influence build-up of charge & thus saturation?

Right of the op-amp output

C7 Blocks DC from leaving the circuit via the output
R8 presents a higher impedance than C7 and works in conjunction with the potentiometer to provide an output impedance and set the output 'volume' and control the current of the circuit when unloaded?  These three components also create a high-pass filter on the output side
D2, D3 and D4 asymmetrically 'hard-clip' the signal for a rough distortion sound
C8 draws high frequencies to ground to avoid being 'hard-clipped' by the diodes D2, D3 and D4

Thanks in advance

Power stabalisation  - issues will occur due to C3, C4 and C5 when powering on the circuit. A number of seconds will elapse before the circuit is ready to use at nominal DC bias and gain.


texts: Simple and cheap overload protection for multiple secondary taps of a transformer

texts:
I have got an old transformer with multiple secondary taps with the ratings shown in the following figure:

I plan to put the transformer in a suitable case and connect the secondary taps to binding posts. This apparatus would be used for conducting some experimentation with AC currents, so it would be susceptible to some degree of abuse. Therefore I'd like to protect the transformer from short circuits and gross overloads.

Of course on the primary side I'll put a switch and a fuse, to avoid catastrophic failures. However I'd like to have a more lenient form of protection on the secondary side: replacing a fuse any time a secondary tap is shorted (or overloaded) would be a real hassle in a lab context.

What kind of simple and cheap protection measures can I adopt in this case? I thought of putting a suitable rated polyswitch (i.e. resettable fuse) like these in series with each secondary tap, but I never used them and I cannot say what kind of problems they could present and what parameters to consider in the design.

Is my idea a sensible one (for example, do polyswitches reset themselves reasonably quickly after an overload event -- I'd like to be able to recover in a couple of minutes, at most)? Are there alternatives which are comparably cheap and simple to implement?

To sum up my requirements:

individual protection of secondary taps: if a tap is overloaded, once the cause is removed the other taps should keep on working, even if the overloaded tap is "recovering" from the fault for some time.
simple and cheap to implement (not much more complex or expensive than adding a fuse in series with each tap).
the overloaded tap should have a recovery time that is reasonably short (a couple of minutes max).
the overloaded tap should recover automatically (preferably) or the recovery system should be hassle free (say, press a button).


texts: Need help understanding simple diode clamp & voltage divide combination

texts: I am trying to understand Art of Electronics 2nd Edition page 50. The bit that I don't understand is that the impedance looking into the divider has to be small compared with with R (see first picture). Can any one explain this? I know how to get the Thevenin equivalent shown in the second picture, and I understand why voltage dividers' output can drop when a load is attached (especially for relatively low resistance load).


texts: Why is it safer to place a switch on the positive side of a voltage source?

texts:
According to the research I've done, it is safer to place a switch on the positive side of a voltage source:

http://www.allaboutcircuits.com/textbook/direct-current/chpt-3/safe-practices/

This only makes sense to me visualizing the circuit using conventional current (counter clockwise). When visualizing it in electron flow (clockwise), the opposite seems true. I think this stems from my use of the "water analogy."

Why does a switch go on the positive side of a voltage source?


texts: Where to select the voltage from, from a voltage divider?

texts:
I want to utilize 2.5V, from a 5V source.
This is a diagram:

My question is, where do I draw the 2.5 volts from?
Is it from the wire I painted pink, or from the wire I painted green?
Or it doesn't matter since the voltage in the sides of a resistor is the same?
I have to make sure.


texts: How can I get the value of current from this NGSPICE Code?

texts:
I tried this code for a simple simulation with ngspice-30:

vcc 3 0 dc=10
vin 4 0 0.8
vdummy 1 2
R1 4 5 50k
r3 3 1 1k
Q1 2 5 0 mybjt
.model mybjt npn(IS=1E-16 VJE=0.7 CJE=2.6734e-11 CJC= 1.4040e-11 BF=200)
.control
op
dc vcc 0 10 1 vin 0.7 0.8 0.02
run
plot i(vdummy)
.endc
.end

But I always get a blank graph out of it. What could go wrong with my code?


texts:
I'm having an issue currently with using an N Channel MOSFET. I would like to control a 12 volt LED using an Arduino Uno. The Uno puts out 5 volts. The issue I am having is that the 12 volt LED stays on but dims if there is no signal being sent from the Arduino. If there is no signal the 12 volt LED should turn off complete. The Uno is programmed with a simple blink program to test the LED. I connected the Gate to a pin on the Uno with a resister in between. The drain is connected to the 12 volt LED from the 12 volts being supplied from the bread board. Source is connected to a ground. There is another pin connected to the blue LED with the same code. So I knew when the 12 volt LED was supposed to blink.

I am using FQP30N06L MOSFET from spark fun. 12v LED. 12 volt wall adapter.


texts: Trapezoidal vs sinusoidal BLDC motor, back EMF speed caclulation

texts:
First of all do these motors differ electrically and if yes, how?
Can you measure BLDC generator speed using back-emf independent of its waveform type?


texts: Should I use an LP2953 to power an ATTiny85 with a 12v battery?

texts:
Like a lot of people I'm building a little transmitter unit with one of those cheap 433mhz transmitters and an ATTiny85, and I am having a problem with the power supply. Actually it is only the power supply, everything else works nicely. But my battery is dead my morning, where 'dead' means under 4v and the circuit no longer works.

I initially tried with three AA batteries to power both RF and ATTiny. That worked but the range was not as good as I need. I got about 30m using 17cm whip antennae on both transmitter and receiver. That doesn't reach my letter box :)

Moving the voltage on the transmitter up to 12v did wonders for the range, but the ATTiny doesn't like more than 5.5v so I put a 7805 and some caps in there (the caps improved the range too) and ran the transmitter directly from the battery and the ATTiny from the 5v battery. That worked really well. But that sucks the battery, which is my current problem.

The battery I'm using is a 23A, about an inch long, alkaline 12v. It keeps the device quite small.

What I am looking at next is using an LP2953 pretty much like this (from the data sheet):

I would delete the 'out of regulation' but keep the 'low batt' signal if I can, I had that working on the earlier 4.5v AA version of this. I think it means I need to change the voltage divider on the left. What I've read is that the LP2953 ought to be smarter about sucking battery, though I also notice in the data sheet they recommend hooking the designated pins to a copper base on the PCB, so if it is dissipating heat that means it is still sucking my battery isn't it?

This guy used a CR2032 but that only gives 3v, not enough range for my application.
This guy has a slightly similar question which has an answer (from me!) but not to this question.

Given this is my third try at powering this thing any advice is appreciated. The receiver end has another ATTiny85 hooked up to a Beaglebone and that all works nicely.


texts: Can an infrared thermometer (IR gun) be used to measure the ambient room temperature?

texts:
I know the principle of an IR thermometer, but have one question regarding that are as below.

As an IR thermometer senses the radiated IR waves from external bodies coming in their field of view and gives surface temperature reading, can we point in air or random far space and measure the temperature of the surroundings/room?
Will the reading, whatever comes, be near room temperature, or will it just be a garbage value?

One example of an IR thermal sensor: https://www.sparkfun.com/products/9570


texts: What is the difference between dual single-ended op amp and fully differential opamp?

texts:
Are they same things? Don't they both output bipolar/mirrored outputs?
Im confused with the terminology here.

What is the difference between dual single-ended op amp and a fully differential opamp?


texts: Modulation ideas for old and long analog bus cabling

texts:
Need some feedback on techniques to make an old analog bus work with bidirectional data(half duplex is fine) at speeds upto 256kbps

The cable itself is a shielded twisted pair with a nominal impedance of about 50 Ohms. It's wired to various points in large buildings in anyway the installer felt was optimal (this includes daisy chaining, branching off into a star at a daisy-chained node etc). I believe it was used to pass audio and/or very low bit rate security data up to 500meters in length

Some of things I considered include:
1. A variant of 10Base2 at a lower data rate. The manchester encoding and csma/c(d/a) shouldn't be too hard to implement but the uncontrolled bus cabling worries me. At 256kbps(kHz) and some controlled slew rate the reflections and signal integrity shouldn't be too bad?
2. Restricting bandwidth to 40kHz or even 20kHz and increase bits/symbol by using QAM. This is not my preference because of the complexity of implementation unless if I can find a single chip SoC. Maybe there are bits and pieces of the old school v92 soft modem libraries I can re-purpose
3. Adapt Power line Communication techniques like G3-PLC

There is not much I can do to change the cabling as it's an existing installation. There won't be anything else on it, if it helps with reflections I can terminate it at each and every node. These cables are by and large interference free because of the shielding and differential signaling

Any thoughts/stories that you can share are most welcome. Thank you.

EDIT: The solution is not specific to one site, the wiring is different in each site and there about two dozen sites all up.

EDIT: There can be between 12 to 15 nodes on each bus


texts:
I'm building a simple ring counter with two jk flip-flop. I'm using 74HC76 integrated that contains two jk.

This is the integrated pinout:

This is my schematic (very basic):

simulate this circuit – Schematic created using CircuitLab

To build a working circuit it's necessary that you connect pin 5 to Vcc (5V) and pin 13 to GND. But...

The problem is that in the circuit that I'm observing on my desk the ring counter only works when pin 5 (Vcc) is unwired. It means that if I wire pin 5 to Vcc I got always 10 output. Is that possible?
If no what's the matter of my circuit?

I've tried all:

I've substituted the integrated -> same problem
I've checked another time pin connection -> same problem
I've changed wires -> same problem

EDIT: I initialize the first jk with 1 using a button and preset and clear pin.


texts: Emulator vs. simulator in the context of EE

texts:
What is difference between a simulator and emulator?
I have tried to google but I see there responses on SO that are much close to CS.
How can I understand the difference between a simulator and emulator in the context of EE? Does  it means that an emulator is hardware just like a DSP kit or micro controller or FPGA kit and simulator is software like MATLAB or PSpice?


texts: If a wire of 5ohms resistance connected in circular and at any two points if we connect a multimeter it will reads 1.25ohms,like that one of my sir told me that,is that true?if yes why it will show like that?


texts: Op-amp based audio amplifier not working

texts:
I have a problem with audio amplifier I am trying to build. Given my ignorance, I cannot figure out how to fix the issue. There is absolutely no sound on the output. This is what I have assembled:

EDIT1

Kaz, Venny,

Perhaps I misunderstood something you said, but trying my best I modified the circuit into this form:

And sadly it is not working yet. I would like to apologize for my utter nescience of the topic.


texts:
I have a single AA battery, I used duck-tape to attach wires to - and +. I tried to attach wires directly to the legs of the LED (without resistor) to see if it burns out, just for playing around. But I didn't see any light. I changed plus minus on legs, still nothing.

I have few questions:

Is this because voltage of 1 AA battery is not enough? (I doubt
this).
Is this because by attaching two thin wires with duck-tape,
there is less current passing through? (I doubt this too).
Is LED dead? I tested few and none worked (how do I test LED, if it is alive
or not? with multimeter? Is led like bulb, if current passes through
it means it is fine?)

So, I know... this is the dumbest question ever asked. I have little experience with electronics, mostly from childhood, when I was taking toys apart instead of enjoying them :)

But I want to learn how to do things myself, I'm a software guy, and as great minds once said.. if you want to make great software you have to make hardware too :D:D But probably this is the future, I hope in a year I will get hold of things... plus this site is awesome.


texts: PIC32MX270F256 Project Build Error: pic32m-gcc.exe: error: build/default/production/main.o: No such file or directory

texts:
I am trying to build a simple project for PIC32MX270F256. The code is just this:
#include <xc.h>
#include "PIC32MX270_STD.h"
#include "Delay.h"

#define LED LATBbits.LATB14

/*******************************************************************************
* Function Name: void initMain (void)
*
* Specification: initializes main
*
*******************************************************************************/
void initMain(void)
{
    uc_init();              // initialize microcontroller
    TRISBbits.TRISB14 = 0;  // set PINB1 as output
}

/*******************************************************************************
* Function Name: void main (void)
*
* Specification: main function
*
*******************************************************************************/
void main(void) {

    initMain();         // initializes main function

    while(1)
    {
     LED = !LED;       // toggle LED
     delay_ms(1000);   // delay 1 second
    }
}

I am using MPLABX v5.30 and XC32 v2.41.
But I am unable to build the project. I get the following errors:
pic32m-gcc.exe: error: build/default/production/PIC32MX270_STD.o: No such file or directory
pic32m-gcc.exe: error: build/default/production/main.o: No such file or directory
pic32m-gcc.exe: error: build/default/production/Delay.o: No such file or directory
make[2]: *** [dist/default/production/01_Blink.X.production.hex] Error 255
make[1]: *** [.build-conf] Error 2
make: *** [.build-impl] Error 2

BUILD FAILED (exit value 2, total time: 1s)

Please see the following screenshot for further clarification:

Your help is much appreciated.


texts: Datasheet Notation for Filter Parameters

texts:
I've been reading through the LTC1264-High Speed Quad Universal Filter Building Block datasheet but I'm having some trouble deciphering the meaning of some of the variables used in the equations for the different modes of operation. For example, in the image below I have highlighted the variables fi, f0, and fn in the equations that govern the Mode 1b topology. Unfortunately, Linear Technology does not include a "Definition of Terms" anywhere in the datasheet (seems kind of silly).

Can anyone tell me what these three variables are? My assumption is that f0 is the center frequency of the filter but I don't have a clue about the other two values. To make things more confusing, later in the datasheet in the "Guide to Bandpass Design" on page 11 these equations are shown:

These equations are for the same circuit in the 1b mode. What then is fcenter and why does it not appear int the equations in the previous image?


texts: Can I use a capacitive divider to run an AC/DC converter from a higher voltage than its rating?

texts:
Suppose I have an AC/DC converter rated to run from 120-240VAC, and I want to run it off 480 VAC. I think I should be able to put two capacitors in series as a voltage divider, and run the converter off the lower voltage.

simulate this circuit – Schematic created using CircuitLab

One problem I see is that the load of the power supply will cause the voltage on the supply terminals to drop. The bigger C1 is (and presumably C2 to maintain the divider ratio), the less this effect will be. The other issue is that the capacitors may need to be X-class for UL purposes. For an example 10W converter, I'm getting numbers in the 1-5 uF range, which is easily obtainable.

Am I missing anything? Is this a terrible idea for reasons I'm not seeing?


texts: help with auto shutoff circuit with negative voltages

texts: I have a circuit that has constant current but the load drops in resistance over time. I need to be able to shut off the circuit once a voltage level drop is reached. The voltage starts at -95vdc and reaches -10vdc when I would like the circuit to shut off. Any ideas would be great appreciated.


texts: AT-CIPSEND Number of Characters SIM Tech GSM modules

texts:
I am succeeding in sending an update string via a SIM800L to ThingSpeak but the channel is not updating the channel.  I know the string is correct since it is provided by the site that I am posting to.

I have read on this site that the string length needs to be defined to be 4 more than the character count.  Does this always work?

Where would one find instructions regarding correct use the AT-CIPSEND command with SIM Tech devices?

I using an Arduino Pro Mini and interfacing with the modem using a Software Serial connection.


texts: Running an old battery in parallel with a new one

texts:
I have a 100w solar panel on top of my van and with a cheapo AGM 200ah battery. After 3 years of misuse and abuse the battery is pretty worthless.

If I buy a new battery, would it be beneficial to keep the old and run it in parallel?

If so, do the batteries need to have the same amp ratings? (or is there anything else I should consider...)

(moved from http://sustainability.stackexchange.com)


texts: PCB manufacturing - Why etch resist such as Tin is removed after the etchant has removed the unwanted copper

texts:
Alright so I'm learning the PCB manufacturing process.
I have seen many professional PCB manufactures use "Tin" to be used as an "etch resist" which protects the copper traces which makes the circuit. Then the "etchant" will only remove the unwanted copper but will not have any affect on the copper traces since it is "tinned". This will give a better etched product since the etchant will not remove any of the copper traces of the circuit. Seems like a great idea, can easily be done at home. I haven't seen anyone on the "DIY" internet that follows this process.
What I don't understand is that the PCB manufacturers remove the tin after the etching process.
Isn't it better to just keep the plated tin rather than removing it?
I know a solder mask will be applied to protect the PCB circuit traces after the removal of tin.
Does it make any difference to just keep the tin traces and put a solder mask on top and not remove the tin?
Does the etchant changes the chemical properties of the tin, is this why the PCB manufactures remove it?
I know many people Tin their PCB so that it protects the copper traces and then add a solder mask on top.
Here is a reference video, scroll to video time 19:22:
youtube.com/watch?v=sIV0icM_Ujo
Edit, answer to the question:
I just spoke with a PCB manufacturer technical team from "sfcircuits.com", I was told the reason why PCB manufacturers remove "Tin" from copper traces is so that "Tin Whiskers" will be avoided. So basically after applying "Tin" to your PCB traces and over time will grow "Tin Whiskers" and can potentially cause a short between traces...


texts: Is there a pitch limit to applying solder paste through a PCB stencil by hand?

texts:
I've ordered two stencils from two different companies, two different materials. Both times I've been completely unable to effectively apply solder paste to the pads of a QFP-64. I end up with a mess of solder all along one side, instead of a discrete amount of paste on each pad. Applying more pressure to the stencil or to the squeegee does not seem to help. I suspect I'm simply doing something wrong, perhaps missing some vital piece of equipment everyone assumes I have for stencil work, or I'm pushing stencils past their reasonable limits.

Can someone explain to me how I can, by hand, repeatedly and consistently, apply solder paste to a QFP-64 footprint through a stencil, without bridges? Or if that's not possible, what's the next best thing?


texts: Why is it so important that an amplifier is unconditionally stable?

texts:
When studying microwave/milimeter wave amplifier design, one often finds discussions about stability. Stability means that the amplifier will not generate signals by itself (except for noise). As we often find in microwave amplifiers that there is always some form of feedback path that can lead to oscillations (in addition to input and output reflections), considering their effects is an important part of the design.

The definitions of the two types of stability are generally something along the lines of the following:

Unconditional stability: The amplifier will be stable (= not oscillate) for any load and source connected, provided it does not have a reflection coefficient greater than one in magnitude (\$|\Gamma_{L}|<1\$ and \$|\Gamma_{S}| <1 \$).
Conditional stability: The amplifier is stable for certain, but not all load and source connections. This means that an amplifier that is stable when connected to a matched output might oscillate when mismatch occurs due to an open output. Sometimes also called "Potentially unstable".

We have mathematical techniques to determine stability, based on concepts such as the Rollett Stability Factor. From this we can determine if an amplifier is unconditionally stable. When designing amplifiers we put this unconditional stability as a requirement: We will only consider our design done once the amplifier is unconditionally stable. If it is not, we might use design techniques (such as adding gate resistance or such) to ensure that our amplifier is unconditionally stable.

Now to come to my question: Why? When one is designing an amplifier, I often know that impedance I am going to connect to. When building an amplifier for a radio system, I probably know what the impedance into my antenna is. If it's for distribution over cable networks, it will likely be 75 Ohm. When it's part of an ASIC, I will likely know exactly what the load impedance and source impedance are since I or my teammates will be designing the preceding and next stage, or the circuit board it is placed on! So then why would I sacrifice gain (as this is a result of many stabilizing techniques used), in order to ensure it is stable for all loads, when it will only be used with a single load impedance? Why not just ensure it is stable for that load impedance (well, the range of impedance we can expect due to production errors and such).


texts:
I would like to build a multi processor motherboard using ARM processors (e.g. the ARM Cortex A8 or A9 or others as well), for low-power computing.
Is this possible ? I mean interconnecting the processors ... or the maximum I can do is putting e.g. 5 processors, RAM modules, EEPROM, etc (separated for each processor) and let one processor only coardinate the timing between them ?

I would do this only for the fun now, but I cant exlude the possibility of running this on an actual machine (server maybe). I want to install GNU/Linux over it (maybe Debian GNU/Linux).
Right now I'm a student in electronics and electrical engineering in bachelor 3rd year ... would like to do this in the summer holidays since we have a printed circuit board lab in our school which we can use almost for free.


texts: Which pair of an Ethernet cable does a router transmit on?

texts:
I've seen numerous articles about straight-through and crossover cables and why they are needed. With conventional straight-through cabling, one device transmits on pair 2 (pins 3 and 6) while the other transmits on pair 3 (pins 1 and 2).

But here's the thing they never clarify:

Which device, the computer or the switch, transmits on pair 2 and receives on pair 3? (And vice versa.)


texts:
Is there any reason one might want to measure both the primary and secondary coils on an LVDT? I assume the primary coil excitation voltage would be constant, but I see circuits around that measure both for some reason.

Thanks in advanced


texts: how to detect power failure and make micro-controller save data in EEPROM

texts:
I am using Arduino nano for a project in which I have on a counter which is continuously increasing. And I want to retain count after a power failure. Data is changing more frequently so storing it continuously into EEPROM is not an option as EEPROM has erase/write cycle limitation. Additionally, data is of 4-byte maximum.

please, can anyone suggest an IC or circuit design which can detect a power failure and interrupt Arduino so that it can save data into EEPROM.

I guess I will have to use a capacitor to power Arduino after the power goes down so that Arduino will be able to save data into EEPROM.


texts: How to read RPM from 3-wire fan - PIC18F4550

texts:
I am working a PIC µC project. I am using 12VDC PC fan (Coolermaster) for my application. A part of the project is to return the RPM from the third wire of the fan to an LCD.

First of all, How can I read the signal? Is it a sort of pulses every rotation?
Also, Do I need to use an ADC pin or just a Digital one would suffice?
I found lots of diagrams telling to connect a pull up resistor to +5V. Why?

A sample code of how this works will be helpful.

Thanks.


texts:
I'm new here, I have some fairly basic doubt.
I am creating a PWM signal in MatLab by comparing a sine wave (50Hz) and a triangular wave (2kHz) .... So what is the PWM frequency will output?

After getting the PWM signal filters I want to get a sinusoid, using an LC filter, but do not know what the frequency of cut should I use?

Thanks for help


texts: Shaping ground plane on a 4 layer USB Midi controller PCB

texts:
I have asked about this before but I have to admit that I didn't read enough before asking and therefore was'nt able to ask the question properly. I hope I am now.

I'm designing a 4 layer board with 46 analog inputs (rotary and slide potentiometers) and 45 digital inputs (momentary push buttons). The board is controlled by a teensy 3.6. I'm using 8-channel multiplexers (M74HC4851, datasheet) since the teensy doesn't have enough inputs. The multiplexers are decoupled by a 0.1uF cap each close to their vcc pin.

I'm wondering how I should shape the ground layer. I know that the most common advise in this forum is to not shape it at all and arrange the components in a smart way instead but since my layout ist mostly determined by the hardware user interface this is not really an option in my case.

Option a)

My first idea was to separate the analog area from the digital area completely by a weirdly shaped moat and connect the analog area to teensy's agnd pin, but I learned that it's not a good idea to let signal lines cross that moat and every single analog component is connected to the multiplexers which are probably the noisiest components on my pcb.

Option b)

My second idea was to use several moats to force the digital return currents to not cross the analog area but then I wondered if this wouldn't create several ground loops on my board. In this case (and the following cases) I wouldn't use the agnd pin of the teensy at all.

Option c)

I could leave only one opening in the moat, put the multiplexers close to it and guide all signal lines through this opening (on their own layers of course) but this would make routing rather complicated and lead to rather long signal lines (the board is 35 by 23 centimeters or 13.3 by 9 inches)

Option d)

My last idea was to use one solid plane and move the multiplexers to a remote area on the board. This would have similar downsides as option c) and wouldn't control the return currents of the push buttons at all.

What's my best option? What would you do? (If moving the input components was not an option)

I'm sorry for my probably very noobish approach and thankful for your answers in advance!


texts: How do I build a USB joystick/button encoder board without using an Arduino or Teensy

texts:
I am making a macro keys button box and need something to convert the buttons into keyboard inputs on a PC, such as a shortcut key in a game.

Previously I have used an Arduino Pro Micro, although in order to make it more professional, I am wanting to make a custom PCB with terminals for the buttons to easily connect to. I then want to make a computer app that easily allows me to change the buttons. I am considering using a Atmega32U4 chip to control everything and then simply have terminals for buttons which go to ground and a pin on the chip.

Is this a good way to do this and how would I actually program it?
Would it be as simple as uploading the Arduino firmware and then uploading my own sketch to it, or is it more complicated than this?

I basically want to make a USB Joystick Encoder which I can program the buttons with my own app. Although, rather then purchasing a USB Joystick Encoder, I want to make the PCB and solder on the parts myself.


texts: How can i transfer 12 V, 50 Hz, 1 A wirelessly?

texts:
I want to transfer electical power wirelessly from a transmitter to a receiver coil.

Input energy is provided by a single phase step-down transformer - 230V/12V AC, 50 Hz, 1,000 mA.

Using the 12 V AC output I want to transfer as much of the available power wirelessly from transmitter coil to the receiver coil over a distance of 5mm.
How can that be done ?
What calculations should i solve so as to achieve this ?

I want to transmit across 5 millimeters.
The radii of the transmitter and receiver coils I am currently using are are 5cm and 2cm respectively

After transmitting it to the receiver coil, I wish to rectify and filter it and then regulate it to 5V DC use it to charge a battery.

I want 5V DC at the end of the circuit, but how can I accomplish that ?

What calculations and equipment specifications do I have to use so that I can figure this out?


texts: How to keep rarely-used Li-Ion batteries functional?

texts:
I have many gadgets around the house that I don't use often, recently I notice that a battery failed on an Mp3 player not used for a year. The battery now has a life of 1 minute from the original 5-7 hours.

What would be the maximum amount of time to leave a Li-Ion uncharched that would not make the batteries unusable.

What other considerations should I take if I use rarely a device to be able to still use the battery, should I leave it fully charged, etc ?


texts: How to find a DB9-type connector color code?

texts:
I'm looking to splice wires from a DB-sub (9 pin) connector out to a breadboard but I'm getting different pictures for color-coding which makes me confused. What's more confusing is the connect I have only has 4 wires form the cable despite having 9 pins. The colors (red, black, brown, and orange) include some colors not listed in the color code I found below. I must be looking at the wrong color code but I don't know where to find the right one? Thanks

.


texts: Modified BoB smith termination for PoE-- Will it work?

texts:
I am using DP83620SQ/NOPB PHY for our 10/100Mbps Copper Media Ethernet Interface. We had connected through the Magnetics part 749013011A which is not PoE supported. But we need to use this for powering external devices without following the Standard PoE process (simply appending power with the data signals).

For PoE interface, the legacy (general) bob smith termination would not suit. Hence the 10nF capacitor is added along with the 75Ω termination resistor. To increase the power handling capacity through the bob smith termination during surge condition, we are purposely added one more 10nF+75Ω  termination resistor combination along with the existing each 10nF+75Ω  termination combination.

Will this scheme affect the cable characteristic impedance matching scheme?


texts: How to properly store components efficiently and effectively

texts:
Possible Duplicate:
  What's the best way to store and categorise resistors/capacitors/ICs/etc?

I have MANY resistors and many other components as well and currently I am using a very cramped type of organization to store them for easy access and to be easy to find which is impossible for trying to locate certain values. If you could show me your setup it would help me very much. (If you could give me a system for storing other components as well you would make my day :) Such as how the periodic table of elements was created organization wise.


texts: Please troubleshoot this full-wave rectifier circuit using op-amps

texts:
I am designing a full-wave rectifier using op-amps, which need to rectify a signal between 0 and 10 V, to a voltage between 5 and 10 V.

The circuit works properly when the input voltage is between 0 and 5 V. That is:

Input -> Output
5 V -> 5 V
4 V -> 6 V
3 V -> 7 V
2 V -> 8 V
1 V -> 9 V
0 V -> 10 V

But when the input is between 5 V and 10 V, it works properly for the first few volts but then the voltage drops off, as if there is a voltage drop somewhere:

Input -> Output
6 V -> 6 V
7 V -> 7 V
8 V -> 8 V
9 V -> 7.8 V
10 V -> 6.86 V

Can anybody tell me how I can solve it, or what the issue is?

The desired result would be:
Input -> Output
6 V -> 6 V
7 V -> 7 V
8 V -> 8 V
9 V -> 9 V
10 V -> 10 V

By the way, I know it's not in the the schematic, but the LM324 is being powered from a single rail supply of 12 V.


texts: How can I duplicate Apple's tiny USB power adapter?

texts:
I'm designing a project that controls 110VAC (plug in, socket out), and also has a microprocessor inside.  I'd really like this project to not need a wall wart to get it's 5V, so I want to include a small DC power supply inside.

Apple's USB power adapter looks like a great small design that I can fit inside my case.  I'm guessing this is a switching power supply but I can't find any teardowns or schematics anywhere.

Does anyone know how this thing works?  I know I could make my own 110V->5VDC supply from a bridge rectifier and some caps, but I'd like to also be super safe.  What's in the Apple brick?


texts:
I'm trying to confirm a fault on an electronic unit of which no documentation is available, I can't even tell which MCU it is so it's largely guesswork so far. It's an automotive control unit and let me describe the circuit as I understand it.

I have a simple switched ground input from the car which runs a control unit. It can be assumed the input pin on the MCU has a pull up. During the normal operation of car, the switch is normally open until the switch is pressed. Now the vehicle fault doesn't recognize when the switch is opened anymore, therefore I can assume the MCU input is connected to ground or thereabouts. (Short circuit?)

The unit has since been removed, and is not powered. When the resistance is checked between the ground rail and input pin - it measures 25 ohms resistance, which would be a low input.

My question is this: Does the 25 ohm resistance indicate anything? Is it typical for a rested state input pin?

Or can I conclude that it has shorted internally providing there is no physical short circuit on the PCB?


texts:
Regarding the post from: https://www.bambusekd.cz/dev/raspberry-control-5V-relay
Hi I create raspberry pi project for fun and I followed this post for controlling my relay. What formula is used to deduced the values for the resistors?


texts:
This question actually has a few parts.

Basically I have 4 12V 0.45 A computer fans,which I want to use in a DIY cooling pad project I'm currently working on. I know that as per the standard USB 2.0 spec, all I'll get out of my laptop is 5V and 0.5 A. I've read about DC step-up converters, would they be suitable for getting the required 12V the fans need for full speed? Can the fans run at all with the limited output current they'll get? Is there any way at all I can run these on full speed off a USB port?

I also wanted to have a physical control of some kind for the fan speed, can I use a simple potentiometer for this?


texts: Is it safe to drive a 5V servo using a logic level shift board?

texts: I would like to turn off and on a servo while it is not used. The LV would be 3.3V and the HV would be connected directly to s lithium battery. Could it work if I replace R4 with a servo? What problem I might face?


texts: How many logic gates are realistically feasible?

texts:
I'm actually more of a software developer and don't really know much about electrical engineering. But I do have a basic understanding of Boolean diagrams. So I had an idea for a Boolean circuit, the only gates I need are AND and OR gates. But to make my circuit useful, it needs about 2.5 million of those gates. How realistic is that something like this works? Can estimate how big or expensive such a circuit would have to be.

Like I said, I don't know much about electrical engineering. But as far as I know, AND and OR gates made up of only a few transistors. When I google for size of transistors, it tells me that they are about 5 nanometers in size. That has given me hope that somehow that my idea is still realizable...


texts:
I'm wondering how exactly voltages are transfer between wires. I mean, once I've a voltage lets say 5v and I pulls from it a "wire" (not resistor) then at the end of the "dangling" wire itself the voltage is 5V and I know why! but I ask how exactly 5v transfer to the wire to be the voltage at the end of the wire 5v?! is it taking time while transfer from voltage source to the end of the wire?!

for example lets say I have voltage source(5v) and I pulls from it a dangling wire, so at the dangling wire the voltage is 5v, is it take time from the voltage source 5v to be transferred to the dangling wire to be 5v?! I mean once we connected dangling wire to the source of 5v, is it taking time from the the time that I connected "dangling wire" to voltage source(5v) to be 5v at the wire?

thanks in advance.


texts: How is inductive wireless charging of a moving vehicle on a public road possible in efficient way?

texts:
Looks like one of the major problems of wireless energy transfer is efficiency. For example, Magne Charge high power charging system seems to have about 86% efficiency which means that quite a lot of energy is lost when passing several kilowatts of power.

Yet seems like Bombardier PRIMOVE technology is efficient enough for powering and in-road charging a moving bus or even a moving tramcar in a wireless manner - a ton of wires is installed under the road or the driveway and those wires are controlled by some clever service electronics to be energized when a vehicle is passing over them and act like a primary coil of a wireless energy transfer system. The vehicle is equipped with the secondary coil.

Each time I inquire about wireless energy transfer seems like the distance between the coils is one of the critical factor. In the above scenario there will be some clearance under the vehicle and also the wires will be installed into the road and so will be covered with asphalt or concrete, so the distance can't be less that say 0,2 meters. Also the vehicle is moving which means that its secondary coil won't be perfectly aligned with the wiring in the road.

How is efficient energy transfer possible is such setup?


texts: Little circuit to turn off start&stop of my car

texts:
I bought a new car with s&s and, every time I turn the car on, s&s automatically turns on. There is a button to turn it off manually, but I want it automatically off. I was thinking about adding in parallel to this button a 555 timer or a transistor timer (transistor+capacitor) to "simulate" a human pushing the button. I don't know on how many volts run this circuit, but I know that requires 500 ms to "understand" that i want to change s&s state (I can turn it off and on with this button). Can you help me to do this? Sorry for my bad english, I hope it's all understandable :c

I added this scheme, hoping that it's all clear
Summing up, every time I turn on the car, also start&stop turn on automatically, but I can turn off/on by pressing a button for 0.5 s. So I want to do this last task automatically. How can I do it?


texts:
I'm trying to design a guitar pedal effect, a looper to be precise. My idea is to use the PIC24FJ128GC010 which has a 16 bit ADC, in order to have a good audio quality. Since my idea is to convert, register and then save  the sound in an external SRAM module, I'm trying to find a SRAM module which can fit my project. I've made some calculus but I'm not sure that they are correct:
Since the bandwidth of the guitar frequencies goes approximately from 80Hz to 15KHz, the sampling frequency should be around 30KHz (Nyquist-Shannon theorem),
so if I have a 16 bit ADC for example for a minute of sampling I will have:
30'000 Hz *60 s = 1'800'000 samples/min * 16 bit = 28'800'000 bit/min = 3.6MB/min
Am I right?  Am I missing something? I accept every suggestion, also about the choice of the SRAM. Thank you.


texts:
I want to measure the distance between two moving objects which are face-to-face most of the time.
The distance between them is around 5-10 meters.
I couldn't find reliable sensors for this distance.

My approach is to put equal sensors in each of the objects and trigger synchronized measurements in opposite directions.
I'd expect that both sensors measure half of the distance this way.
I'm using the MB1000 from MaxBotix: http://www.maxbotix.com/Ultrasonic_Sensors/MB1000.htm
I'm connecting the trigger pin from both ends, and my initial experiments seem to be working.

Is this method/technique standard?
Are there special electrical requirements that both ends must meet?
Would it work if the ends cannot share wires (Vcc, GND) and the triggers are synchronized via a wireless method?
Are there other alternatives to measure moving face-to-face objects (techniques, sensors, etc.).


texts: BJT output impedance seen from emitter vs collector

texts:
In a BJT there are two accesses for output, namely emitter and collector. And both accesses behave with output impedances that will be completely different.

What I read from texts if I'm not wrong: the impedance seen on the emitter side will be very low(the resistivity seen on the emitter will be very low); but the resistivity of the collector is very high.

What is meant by this? Can this be explained in an easy fashion?


texts: What is XBee and how is it different from Zigbee?

texts:
It's easy to get an introductory explanation of Zigbee.

Zigbee on Wikipedia
Home networking with Zigbee
Zigbee alliance

But technical information on XBee seems harder to find. It's unclear to me what its similarities and differences to Zigbee are.


texts: Allan std deviation: why do we need to read the values at specific sample times?

texts:
I'm trying to deduce the white noise and rate random walk for an IMU. Some sources recommend deducing those values by fitting a line to the corresponding part of the log-log plot, and then reading the values from those lines at respectively \$t\$ and \$3t\$ where \$t\$ corresponds to about \$1s\$. For example, this is what they recommend here.

My question is about how this values are usually determined, and why it makes sense to read them as described. For example, take this figure that is taken from the aforementioned source:

I think that I vaguely understand how Allan Variance relates to the Power Spectral Density. If I'm not mistaken, the part of the plot that has approximately a slope of \$0.5\$ is where the data behaves like a process in which random walk noise is dominant, and the blue line is fitted (more or less) to that part. But then, why would we read its value at \$t=3s\$, where the signal behaves as a process that is tainted by white noise?


texts:
Choose a frequency \$f_0\$.We have to project a circuit such as:

all the \$f \ge 10f_0\$ can pass without attenuation
all the \$f \le \frac{1}{10} f_0\$ pass with an attenuation of a factor of 10.

The solution is giving by

simulate this circuit – Schematic created using CircuitLab

but I can't understand why. Could you help me?