texts: Close/open a physical button circuit via Arduino

texts:
I have an electronic dog door that is triggered by an ultra sonic collar on the dog:

Electronic Dog Doors are NOT All Created Equal

The end game is to be able to trigger this door using an arduino.

The door works great from an opening/closing standpoint and sealing out the outdoors.  The problem with this detection method is that the collar is bulky for a small dog, requires custom batteries, and is expensive to replace.  What I want to do is hack the door to also be triggered with an arduino and an RFID sensor.

There is a button on the door frame that will open the door.  Holding it down keeps the door open until you release it.  My idea to hack the door is to tap in to that physical button and simulate a push.  My arduino will be a separate circuit and could even have it's own spearate power source.  I'm not good with circuts but I'm really good with coding.  I can code an arduino to detect the rfid tag.  But I need to know what circuit I would use around this switch so that I can close and open the button from code.  I would then solder my connection to each side of the switch.

Possibly I'm not providing enough information.


texts:
I would like to digitally control an analog VDO water temperature gauge.

These are three terminal devices, with +12v power, ground, and sensor input. The sensor provides variable resistance using a thermistor. For example:

https://www.vdo-gauges.com/cockpit-250-deg-f-water-temperature-gauge-use-with-vdo-sender.html

I don't know specific values, but for the purpose of argument, imagine that the sender range is 200 to 0 ohms.

My initial direction is to simulate the sender by building a voltage controlled resistor using a TI LM13700 op amp fed by a DAC.

Are there better ways? I'm concerned that a PWM driven LDR isn't stable enough, though the simplicity is attractive.


texts: Separate GND-plane for microcontroller crystal resonator

texts:
1.  Background info

I'm designing a board for an STM32F767ZI microcontroller. This microcontroller has a primary oscillator for the SYSCLK (overall system clock) and a secondary oscillator for the RTCCLK (real-time clock).

I selected the following crystal for the primary oscillator:

NX3225GD-8MHZ-EXS00A-CG04874 [DigiKey: 644-1391-1-ND]

And the following crystal for the secondary oscillator:

NX3215SA-32.768KHZ-EXS00A-MU00525 [DigiKey: 644-1386-1-ND]

I selected the same crystals as those on the NUCLEO-F767ZI board from STMicroelectronics.

2.  Recommendations from STMicroelectronics

The chip manufacturer recommends to provide a separate local GND-plane underneath each crystal. This GND-plane must be tied to the nearest GND-pin on the chip. I got that from Application Note AN2867. The following figure is from that document:

You can see two crystals on the figure: X1 and X2. Each has its own local GND-plane, separated by a gap from the overall board GND-plane.

3.  How to apply?

I wonder how I can apply these recommendations on the STM32F767ZI chip:

Please note the two oscillators on the left side: RCC_OSC32 for the real-time clock and RCC_OSC for the general system clock. Also note the 9 GND pins (named VSS) on the chip.

Unfortunately, there is only one (!) GND pin on the left side of the chip. How can I properly apply the recommendations from STMicro? No matter what I try, I end up with one of the local GND-planes stretching out to reach a GND-pin far away ... probably not what the manufacturer had in mind.

EDIT

On the advice of @isdi, I looked for the gerber files of this NUCLEO-F767ZI board. With a gerber viewer, I discovered that the general GND-plane runs under the oscillators as if they were no different from any other component. They definitely don't have their own local GND-plane.

Why is STMicro not following their own advice?


texts: Where does all the power consumed by a CPU go?

texts: Where does all the power consumption of a CPU go? Does all the power drawn by the PC's CPU get transformed into heat? Or does it get transformed into part heat and part some other kind of energy?


texts: Setting a potentiometer to increase the lifespan of an LED

texts:
i have a electrical circuit with a 9v battery,LED(0.018Amps),ressistor(500 Ohm) and potentiometer. And im trying to work out the correct ressistance(for the"pot")for the LED to light up at optimium level for the longest life span.Is this formula/calculation correct ?

                        V=IxR
                        V=Ix(R1+R2)        R2 is the potentiometer
                        R2=(IxR1)/V
                        R2=(0.018x500)/9
                        R2= 1 Ohm


texts: How I can to reduce 9V battery to 7.4V - it is for R/C model

texts:
What size of resistor I can use to reduce the 9V rechargeable battery to 7.4V output for R/C model please?
I would like to use rechargeable 9V batteries instead of 7.4V as it´s handy to go a grab one normal (non-rechargeable) 9V battery from shop near by when my own batteries goes flat out.
Most likely it will be wired resistor used between 9V battery adapter and input to the small motherboard on the R/C helicopter.


texts: How do I manipulate a large number of moving platforms?

texts:
I might not be in the best place to ask this and feel free to tell me to move my question to another Stack Exchange.

I am trying to build a device that will allow me to control at least a couple hundred raising platforms. The goal of this is to create a real time editor for board games (more precisely Dungeons and Dragons). Ideally all the platforms would move simultaneously and the platforms would be transparent to allow us to place L.E.D.'s inside them to color the platform (this way we can make wood brown, water blue etc).

On our current setup, we would use acrylic prism 1 inch x 1 inch x 6 inch (width, length, height) and we wanted to use a CNC motor to move around on a X/Y axis and change the platforms elevations. Obviously, this is NOT simultaneous raising at all and had (on paper) quite a long update time (calculated approximately 1 sec per platform).  CNC is the only solution we found that had a reasonable cost/quality (a CNC motor per platform also raised the power consumption very high).After a few weeks of looking around, planning and throwing stupid ideas away, we found  this.

Clearly, WAY better then our idea but I have no idea how he did this. They have 900 and they all work simultaneously; his platforms are much smaller too which could be nice to have but 1 inch ^2 is fine for our use. We also don't want the real time interactive thing. Loading from computer and staying static until we change it is good (though water movement would be really nice). So my question is.

What would you guys recommend to raise simultaneously a thousand small platforms?

Also this document that the devs made. Doing a bit more research I found that the device they used to move the platforms cost approx $30, I imagine some of this price is due to the fact that there is sensors in it that we don't want or need, I don't think I need to say this, but I don't have $27000 :(

Key difference between their implementation and our goal:

No real-time interaction with the table. Controlled by and arduino and or a computer is fine.
Size of the platforms will be closer to 1 inch^2
All sides of the platform should be light up, but I believe this is mostly a question of choosing the right material


texts:
As shown highlighted in attached photo,In case of 6713 dsp,during each clock cycle, up to eight instructions can be carried out in parallel
Does this happen in case of every processor that multiple instructions can be carried out in parallel in one clock cycle? What about general purpose processor like 8086?How many instructions can be carried out in parallel in one clock cycle?


texts: Determine with Arduino if 220V AC power is on or off

texts: What would be ways to determine with example with Arduino, is current 220V AC socket on or off state? Any other than using relay (noisy) or current sensing sensor (too big)?


texts: Power two connected circuits with one battery

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I want to use a 9v 1200mAh battery to simultaneously provide current to a 9-12v motor and microcontroller. The microcontroller would ideally switch the motor circuit, which would derive power from the battery. The reason I want to do this rather than use two separate power sources or power the motor through the microcontroller is that the microcontroller only has an output of 6v, making the motor either useless or underpowered. The constraints do not allow for multiple power sources.

Is there a way to feasibly do what I'm hoping? I don't have much of a background in electronics or EE, not entirely sure where to begin with this.


texts:
When we take the Laplace transform of a function, why is the frequency (s) complex? I can not understand the significance of complex frequency.

Please help or give some references.


texts: What is the power dissipated by a resistor

texts:
I was doing a homework question, which is states as follows:

  2 resistors, \$R_1 \$ and \$R_2 \$ are connected in series with a potential difference V across them. The power dissipated by the resistor \$ R_1 \$ is..?

I was basically thinking that it was just \$ \dfrac{V^2}{R_1} \$, but it is wrong. I have no clue why, but I'm guessing it is because I don't understand what is meant by 'power dissipated' by a resistor is. I know that power dissipated by an electric circuit is just \$P=VI \$, but in the case of a single component (in series), how do you calculate this?

p.s. - The answer is either of the following 4:

\$ \dfrac{V^2R_1}{(R_1+R_2)^2} \$

\$ V^2R_1 \times (R_1 + R_2)^2\$

\$ \dfrac{V^2R_2\space^2}{(R_1(R_1 +R_2)^2)}\$

\$ V^2R_2 \space ^2 \times (R_1(R_1 + R_2)^2) \$


texts: SOIC-8-EP instead of SOIC-8 is that okey?

texts:
I have a FDS4559 which is a SOIC-8 package.
However I wonder if i could use a SOIC-8-EP instead and put some thermal compound between the PCB and the component for some extra cooling and use the PCB as a heatsink.

I don't think there will be any consequences if the pin number 9 is connected to the ground plane for extra cooling.

However I ask this question to verify that I've nothing to worry about?

Best regards


texts:
I posted a more in-depth outline of what I'm doing here, but basically I'm building this circuit (for n=3):

The circuit displays an output based on the combination of three three-input DIP switches. One LED is displayed at a time so rapidly that it looks like they're all lit simultaneously.

I've designed the transistor digit drivers to light up each display for a logic 0 and do nothing for logic 1. I have to build a multiplexer out of 7403 open-collector NAND gates. The way I understand it, the digit driver communicates to the multiplexer which three bits to activate on the bus; so there needs to be some logic implemented. I imagine that I have to construct a truth table or K-map and determine the logic based on that. But how do I determine the logic?

Based on the counter rate, the digit drivers turn the displays on and off, so do I want logic that will make the output of each digit 1 when the digit driver is 0, and the output 0 when the digit driver is 1?

I believe the multiplexer should be something like this (I didn't see a symbol for open-collector NAND gates, but imagine they are with a pull-up resistor on each output):

simulate this circuit – Schematic created using CircuitLab

So I would have one of these for digits 0, 1, and 2; three in total.

Edit: Still trying to figure this out. I think I understand how to do it with an actual multiplexer IC; For each digit, all of the corresponding bits act as inputs and the output is determined by the control/enable input. Then I could implement some logic between the digit drivers and the MUX. However, here I think the goal is to form a control tied to the NAND gate inputs for each digit and use logic to have it perform the function of a multiplexer.


texts: Is it wrong to write HIGH to a pin used as an open collector?

texts:
I'm a software engineer playing with PICs and have an old PS/2 mouse that I am using (successfully), which has CLK and DATA connections as open collectors.

So I have configured the internal pullups on the relevant PIC pins and am setting TRIS to 1 to let the lines go high and setting TRIS to 0 and writing 0 to the relevant PORT bit to force it low.

However, I've seen several similar PIC-to-PS/2 mouse implementations that, when writing to the mouse, set TRIS to 0 and write 1 to the PORT bit instead of setting TRIS to 1.

As I understand it, either of these will result in the line going high (is that correct?), but I'm not clear if one is somehow "better/safer" than the other.

Should I just follow the examples of the (presumably) more experienced implementations and write 1's to the PORT when the PIC is in control of the bus, or should I always make the line high by tri-stating to high impedance and letting the pullup do it?

I hope that makes sense and I haven't mixed any terminology - any general advice about best practices for open collector connections would be welcome.


texts: Requirement of 100Mbps/1Gbps bandwidth on automotive applications

texts: I do not understand the requirement for 1Gbps bandwidth for automotive applications. I know that ADAS, infotainment systems require high bandwidth due to audio and video, but do they really require such a high bandwidth? Is that much bandwidth necessary for these applications. If so, what are the possible applications that can push the bandwidth requirements to such high levels?


texts: I am beginner in electronics. What i came to know until now is that mostly we have to find the current in a circuit in our text books. I wonder what useful work we do after finding the current, dc current, current as a function of time, transient current , ac current. What do we do after findings these currents. I know this question would be offensive to many of you here but as i am a beginner so kindly forgive me in advance.


texts: Flyback Transformer Saturation in Secondary

texts:
I am trying to select a flyback transformer for a prototype I'm designing. Almost all flyback transformer data-sheets I've seen provide only the saturation current for the primary winding. The saturation value for the secondary is never given.

How can I ensure that my transformer's secondary is not saturating?


texts: body terminal of PMOS in transmission gate

texts: Why is the body terminal of PMOS in the transmission gate connected to VDD instead of its source? Why do we deliberately introduce body effect here?


texts: Why equal sign was used for limit outside of external conductor?

texts:
Why limit is r >= b when magnetic induction is zero instead of r > b?
Example: An air coaxial line made of copper (μ ~ μ0) is given. A constant current I flows through the inner conductor. The radius of the inner conductor is a and the outer conductor is of negligible thickness of radius b.


texts: P and N Channel MOSFET Pair? (Drain Tied Driver)

texts:
I have drain-tied two N-Channel MOSFETS because it is the only way to fit them in my (very) small circuit design. The source of the top one goes to VCC and the bottom goes to GND. The design works as it should electrically, but not as I intended. Because of the way MOSFETS work, I can switch on one of the fets to drive the line out high, but the other one then shorts it to GND because although it allows current to flow in both directions, it can only block in one.

My plan is to use a p-channel fet in place of the second one. Should it be enhancement or depletion? Basically all I want is to have one regular N-channel fet and the equivalent of one in exactly the same physical package, only the gate and source are swapped. This will allow me to drive the load both high and low, and my design can fit on the PCB.


texts: What fuse can I use to replace a Hitachi FN00373

texts:
I'm trying to replace a blown fuse from my stereo system.
The fuse has the following markings on one end: 125V 5A
and the following on the other: 51MS, an H with a circle around it (I'm assuming this means Hitachi), and some other symbols including the Underwriter Lab logo, an "SA" logo and an inverted triangle with a "T" inside (drawing below) and a line just above the T. It's 5mm x 20mm

The fuse has a wire, then a small blob of metal, then another wire (which, to my untrained eye seems a bit thicker).

I think this is an M Spot Fuse, as described by @Harry Weston in this answer: Slow Blow vs Fast Acting Fuse

As far as I can tell, this is a  Hitachi FN00373. Unfortunately this is a really rare fuse. I should also mention this stereo system is about 10-15 years old.

Is it possible/advisable to use a different fuse in its place (I'm not sure I can even get the Hitachi fuse anymore). Or, is it possible/advisable to use a slightly different fuse (e.g. one that isn't "M Spot" or has a slightly different voltage/current rating)? If you can recommend one, that would be ideal!


texts:
Which is the best way to convert Ac to DC , with maximum efficiency possible by using a transformer.
The required voltage is 5v and current is 1a .
I saw a circuit from my mobile phone charger they didn't use 7805 voltage regulator. They first convert Ac to DC using a bridge rectifier and then to transformer. Their circuit is complicated to understand. Can anyone post a link where I can find a circuit diagram.


texts: Trying to understand this table in a datasheet

texts:
I'm trying to understand this table in a datasheet:

Next to "Byte 2" there is a (5). What does that mean?


texts: Analyzing current-series negative feedback using voltage gain confusion

texts:
(I posted a similar question that shows a better understanding of the circuit here.)  I don't know if my reputation would suffer if I deleted this question.
I am learning the four negative feedback topologies.  I would like to reach a point where I will be able work my way from expressions like \$A_f={A_o\over(1+A_oB)}\$ through algebra to more concrete expressions using component values (resistors, e.g.). My first attempt was with voltage-series negative feedback circuits and a simple common collector.  I think I was quite successful.  I was able to find good expressions for \$A_o, A_f\$ and \$v_{out}, v_{in} \$.  From the expressions I derived I could see why we make approximations in analysis, such as \$v_{out}=v_s\$.
I arrived at the open-loop gain \$A_o={(\beta+1)g_mR_E\over\beta}\approx g_mR_E \$ and the closed-loop gain \$A_f={\frac{(\beta+1)}{\beta}g_mR_E\over1+\frac{(\beta+1)}{\beta}g_mR_E}\approx
{g_mR_E\over1+g_mR_E}\approx 1\$.
I was satisfied that my expressions for \$v_{out}\$ and \$v_{in}\$ were accurate enough when I was able to show the tiny amount that \$A_f\$ falls short of unity gain.  For example: \$v_{in}={v_s\over 1+\frac{(\beta+1)}{\beta}g_mR_E} \$ gave a good prediction of what appeared across \$v_{be}\$ in simulation and \$v_{out}=\frac{(\beta+1)}{\beta}g_mv_{in}R_E\$ gave a value of 9.95v for a 10v input signal at \$v_s\$.

simulate this circuit – Schematic created using CircuitLab
Then, I attempted to repeat the same process for current-series negative feedback, using a common emitter (with degeneration, not bypassed) as an example.  Here's what I came up with for open-loop gain:
\$A_o = {v_{out}\over v_{in}} = {g_mv_{in}R_C\over v_{in}} = g_mR_C\$
For closed-loop gain:
\$A_f = {v_{out}\over v_{s}} = {g_mv_{in}R_C\over v_{in}+v_f} = {g_mv_{in}R_C\over v_{in}-g_mv_{in}R_E}\$
\$A_f(v_{in}-g_mv_{in}R_E) = g_mv_{in}R_C\$
\$A_f(1-g_mR_E)=g_mR_C\$
\$A_f = {g_mR_C\over 1-g_mR_E}
\$
And for the feedback factor:
\$v_f = Bv_{out}\$
\$g_mv_{in}R_E=Bg_mv_{in}R_C\$
\$B = {g_mv_{in}R_E\over g_mv_{in}R_C} = {R_E \over R_C}\$
Everything looked good to me, and all my equations proved out in a simulator.  But then, disaster struck as I read more about the current-series negative feedback.  Must my work instead be based on this set of equations \$A_o = {i_o\over v_{in}}\$, \$A_f = {i_o\over v_{s}}\$, and \$B = {v_f\over i_{o}}\$?  I can see how using these equations as a starting point would make clear that I am looking at a transconductance amplifier, not a voltage amplifier, but if my equations work, does it matter which I use?  Is my understanding of current-series negative feedback sufficient?


texts: What is a conventional way to set a Modbus device address and baudrate?

texts:
What's a conventional way to set an address and baud-rate/parity on a Modbus device?

Is this supposed to be done using hardware switches or can be done through a software?

If done through a software, can this software be connected on the Modbus line or this has to be done through a separate diagnostics port?


texts: 220V/1ph/60Hz equipment to operate on 208V/3ph/60Hz

texts: Can an equipment built for 220V/1ph/60 Hz be connected to a 208V/3 ph/60Hz grid by using only two lines of the 110V each across the load?


texts:
I've been researching pullup and pulldown resistors after seeing them used in many digital circuits and while I understand what their purpose is, I haven't found any resource on how to determine the resistance values to use in such circuits and how these values affect the circuit's behaviour.

One of the examples I have is...

...which is an A/D converter circuit for a keypad input.  I have implemented this and it actually works very well but I can't quite pinpoint why a 1Mohm resistor was picked as the pullup and what exactly happens to it when one of the buttons are pressed - does it affect the voltage of the ADC input in such a small amount that it doesn't register or is it overridden somehow or...?

I know this is probably a very basic question but I can't seem to apply the thoery I have learned to this one.


texts: Measuring length of a circuit by signal attenuation (or of the like)

texts:
I'm pretty bad with electricity, so this might just be an ameture question, but here's my situation.

I'm wondering if I can, with any sort of accuracy, measure the length of a circuit using only the signal's information, and knowing what materials it's made of.

For example:

What would I need to do to measure the resistance of aluminum over distance x, thus sampling the distance?

Again, I'm bad with this sort of thing, so use small words and link resources please.


texts: How to get stall current from DC motor model

texts:
I'm studying the model of a dc motor from this link :

http://ctms.engin.umich.edu/CTMS/index.php?example=MotorSpeed&section=SystemModeling

The equations are:

\$\ s(Js+b)\theta(s)=K I(s)\$

\$\ (Ls+R)I(s)=V(s)-Ks\theta(s)\$

To calculate the Stall current I set the angular velocity to zero(since theta is the angle, the derivative is the angular velocity):

\$\ s \theta (s)=0 \$

but I get:

\$\ 0=K I(s)\$

\$\ (Ls+R)I(s)=V(s)\$

and then

\$\ I(s)=0\$

\$ I(s)=\frac{V(s)}{Ls+R}\$

The two results are different.To be equal, V(s)=0 but it is strange.How is possible that the stall current is zero?


texts: Replacing lightning connector with usb-c connector in lightning earphones

texts:
I have a lightning earphones, Sennheiser ambeo smart headset.
https://en-us.sennheiser.com/finalstop

The cables are yellowing, and I wanted to replace them, also I got tired of using this on my Iphone only, I wanted this to work with most modern devices with USB-C..

So I thought, could I just replace the whole thing with a 8-core cable with a usb-c connector?

If no, why. If yes, what most likely will fail? I feel like as long as I can connect the wires properly, then there would be no problem.


texts: Which of these board designs is more suitable for a high current circuit?

texts:
I'm creating a DC-DC switching buck regulator using the LM2596 5A regulator from texas instruments to convert 12V@3A to 5V upto 5A.

Since this is a high current circuit to feed servos, I've tried to keep the traces as thick as possible but since the size of the board is small and restricted by the mechanical dimensions of the enclosure, I've been concerned about trace width. I recently came across another approach of using polygons in Eagle to create thicker planes.

Which of the 2 layouts would be better:

Layout 1: Using regular traces. Most of the high current traces are atleast 100mil thick which according to a trace width calculator should be good for 5A.

Layout 2: Using larger polygons for planes. This also allows me to end neatly in pads that are much smaller than the trace and have small SMD decoupling caps connect to easily.

Which of these approaches is better and why? Or am I simply over engineering at this stage?

I'm using a 2 layer 1oz circuit board. 2oz board currently is not possible to use. Also I'm yet to add stitching vias.


texts: LED dimmer for high current applications

texts:
Hi Guys .. I am designing a few panels using LEDs for backlighting. Some of these panels have over 20 leds, using a 5v power source. So only one of these panels can draw around 500mA alone. I am planning on using the same PSU to power them all, but need a dimmer circuit to dim them all at once, but most of the dimmer circuits I have seen can only really do lower current draw, i.e. 2N2222 can only handle 800mA.

Any idea if this is possible with one high current dimmer, or do I have to build multiple dimmers ?


texts: Transistor Analysis of a Common Base(?) BJT

texts:
Hey. I am a biomedical engineering student focusing on the biomaterials side. However, my university makes me take a few electrical engineering classes as well. So I am not very good at this. I was hoping if anyone could help me out.

As of rn, I have tried to use DC bias to find Ie. But I feel that Ie should be just 1mA due to the current source and Ic should be 0.5mA.  But if I use Ic/alpha I get 505 microAmps. Could anyone point me in the right direction please?


texts:
I have just started to pre-program with the dsPIC33CK64MP102 and I want to turn on an LED that I have on the RA0 pin.
I have used mplabX's mmc to configure the pins and clock.
I have only activated the GPIO output of the RA0 and selected the Primary Oscillator at 8000KHz.
my code is the following:
#include "mcc_generated_files/system.h"
#include "mcc_generated_files/pin_manager.h"

int main(void)
{
  SYSTEM_Initialize();
  while (1)
  {
    LED_Toggle();
  }
return 1;
}

From what I have seen in the pin_manager.h file with LED_Toggle (); I should be able to turn on the led.
In principle when I debug with the PICKIT3 I don't have any errors.
Do I need to call any other instruction to be able to turn on the LED?
The clock configuration is correct?


texts: What causes the residual magnetic flux when the current is zero in an inductor hysteresis curve?

texts:
An inductor with hysteresis has the following current versus flux curve:

I marked the point in red where the current is reduced to zero but there is still flux on the above curve.

What really causes this permanent magnet like magnetic flux in the absence of any current?


texts: Which Raspberry Pi 3B+ GPIO pin is connected to which module in Adeept Motor Hat v2.0?

texts:
I need to find out which GPIO pin on the raspberry pi will be connected to which module when I fit the Adeept Motor Hat v2.0 on the 40 GPIO pins. I am attaching the image and the schematic of the motor hat.

Here is a link to the schematic.

Alternate link to the schematic

PS. Since I am new to this I am not sure if this can be figured out or not.
Thanks!


texts: Which tool is being used to create the following figure?

texts:
I am trying to determine the circuit drawing tool that is used to create figures in some papers I come across every once in a while. The tool is able to create some very slick-looking diagrams/schematics. Here is one example:

I like everything about the schematic above -- in particular, I really like the way the MOSFETs look and the ground symbol. Whenever I see schematics drawn with this tool in papers, I am always impressed with the way it looks in the paper (even if the author's interpretation of their results is not quite right).

In another similar question, xcircuit was given as a possibility, but the xcircuit drawn figures I've seen don't look anything at all like the example above.


texts: Equal rise time and fall time in CMOS circuits

texts: For the design of digital CMOS circuits, there is a need to ratio the PMOS and NMOS transistors so that the worst case rise time and fall time on the output are equal. Why is this a crucial requirement?


texts: Getting rid of charge injection click and hum sound on this switch I have designed

texts:
I have designed this 4 stereo channel TRS switch.

You have 4 channel stereo input and 1 stereo channel out. You press a button and you switch which channel you want to send to the output. Once the input is selected by the flip-flop and the MAX359 it is amplified by a IC TEA2025B.

The power supply works like this: it is a virtual ground. It receives +15VDC from an external adapter and converts it to +7.5VDC / 0V / -7.5VDC, needed by the switch in order to keep the signal on the middle of the rail.

It is working almost wonderfully but I have two problems:

when I press the switch to select the input channel I hear a click/pop noise on the output. Like a transient.
I have hum noise all over the place. I am already with the whole thing assembled on a breadboard. I have no shielding anywhere. What should I shield when I have it on a PCB or what can I change to remove this noise.

What can I do, change or improve to fix both problems?

Thanks in advance.

NOTE: The diagram shows +5V and -5V. The voltages are in fact 7.5VDC and -7.5VDC.


texts: Differentiator circuit - can output be larger than input?

texts:
I have a question regarding differentiator circuits, and whether or not their output voltage can be greater than their input voltage.

The voltage across the resistor in such a circuit corresponds to the derivative of the input signal:

$$V_{out} = RC \frac{dV_{in}}{dt}$$

I think this means that a high frequency input signal, which has a large rate of change of gradient produces a larger output signal than a low frequency signal, but I am unsure of whether or not it can exceed the input voltage.

What do I need to consider to understand this?


texts: Acquisition time of sample & hold circuit

texts:
What determines the acquisition time of a sample and hold circuit?

For example if I had wanted to design a circuit that samples at every 0.1 second intervals what would limit and affect the desired acquisition time?

Would it just be how long the capacitor  takes to charge? Or are other factors involved


texts: What use is a Zener diode's leakage current spec?

texts: Consider this datasheet for a family of Zener diodes. All of the parts 3V and under have their leakage current rated as some current at 1V. I've seen this is multiple family datasheets, but it really doesn't make sense. There is no relationship between the test voltage and Zener voltage. I could see a spec such Zener voltage at 1uA having utility. At least the test condition would remain consistent and have the same meaning for each part in the family. Why are Zeners spec'd the way they are?


texts: How to get 3.3 output voltage in PC817 opto coupler?

texts:
I am using PC817 opto coupler.  I want a 3.3 output voltage. In its 1st pin I am giving 12volt and 2nd pin is gnd. I have connected a pull down resistor on 3rd pin. But i am confused because when I am giving 3.3volt on 4th pin, and I am checking output from 3rd pin which is 1.5volt. How can I get 3.0 - 3.3volt output on 3rd pin.

I have tested it with 5 volt, means when I was giving 5 volt on 4th pin and when I was checking voltage on 3rd pin it was 4.7-4.8v which is I think correct. But I dont know what is happening in case of 3.3volt. PLease help.

Thanks

EDIT : i have attached a screenshot of proteus simulation. I actually didnt find the PC817 opto coupler but I got the similar opto coupler. I am getting an output voltage of 3.22. Please tell me that is this connection good. I mean if I make this connection in real, will this work?


texts: DC Shunt Generation Ascending/Descending Terminal voltage Saturation Curve help?

texts: In a DC Shunt Generator we increased Field Current from 0 to 2.0 and calculated the Terminal Voltage, we then decreased field current from 2.0 to 0 and collected our field current again. When plotting the data of ascending and descending field voltage on a saturation curve why does the descending portion of the curve lie above the ascending portion?


texts: What is the point of the pull-up resistors for rows on this schematic?

texts:
I am looking through a schematic of a keyboard. It for some reason has pull-up resistors on row lines. Meantime the firmware it uses suppose to iterate over rows by bringing them up from the ICs own GPIO pins.

Wouldn't having pull-up resistors here defeat that logic by having those lines always high which in turn would cause issues with keyboard?


texts: What's the best way to detect zero crossing in this design?

texts:
The design that I am talking about:

I want to be able to detect the zero point with an MCU of which pin can withstand only 3.3 V. I'll forgo optocoupler because A. I want everything to be as cheap as possible and B. I want everything as simple as possible.

As you probably have guessed no, I don't have a 100% understanding of the schematic, so this design could very well have featured a zero-crossing detecting mechanism yet I failed to find it completely but I doubt it.

The incoming voltage max will be 110V. I want to detect the zero-crossing so I can turn on and off Q1 and Q2 alternatively on a regular cycle to make the throttling of power possible.

So my questions:

How do I do the zero crossing detection?

My knuckle-dragging plan: attach one pin to a resistor 500K to limit the current, then attach the resistor to the center point surrounded by L1, Q1 and Q2 and D13, yes, that point attached to the K pin of Q1 and Q2, negative pole of D13 and one side of L1. I'll keep sampling it with ADC and decide when the zero point has arrived, at which point I'll make the switch.

Please offer help! Appreciated!


texts: why and how do I use a capacitor in a switch circuit？

texts:
I have seen many designs of switch circuit:

I know that a capacitor will help anti-shake but I realy do not know how i can anti-shake. Does it work like a decoupling capacitor or a low-pass RC filter?
and then I want design another switch circuit but do not know how to add a capacitor:


texts: How to change the top directory in LTspice for Mac?

texts:
As LTspice on MacOS - empty library points out, there doesn't seem to be any way to change the top directory in LTspice for Mac.
How to change the top directory in LTspice? shows a screen with a control panel tab to change the search paths on a PC, but that tab is missing from the Mac version:

I tried adding a symbolic link from the Mac LTspice Library folder to my folder, but LTspice doesn't seem to understand symbolic links.
Is there any way to change the top directory on LTspice for Mac? Or to have LTspice search my directory as well as its own library?
I'm especially interested in LTspice finding the autogenerated symbols for my own hierarchical schematics. Thanks!


texts: Control the duty cycle of my square oscillator

texts:
I Would like to know how i can control the duty cycle of my circuit.

simulate this circuit – Schematic created using CircuitLab

What is the best way to control the duty cycle ( from 1 to 99%) of my circuit?


texts:
I recently switched from Mentor Graphics Expedition to Altium 14. I really like a lot of Altiums features but efficient routing still eludes me.

In mentor my typical workflow was:

Place components roughly where I want them
Route priority nets, and rearrange as necessary
Route lower priority items rearranging as necessary

The issue I'm having is that Mentor would automatically shift traces (while keeping the same general shape) when I dragged a component that was already routed. As a result, I could move something without needed to fix the traces (for the most part). In altium if I want to nudge a component even a few millimeters I need to rip up the traces and reroute them so that they don't end up crossing over and shorting or having little nubs left over in the process of moving a part.

Is there something I'm missing? Can such a feature be enabled in Altium, or is there a better workflow I should be following?

I appreciate any suggestions, this is really killing my productivity with Altium.


texts: Is it possible to have a non-integer multiple of minimum length in MOSFET technology?

texts: I need to design an OTA with 0.25 \$\mu m\$ CMOS technology. Can I choose to have a transistor with a channel length of 0.60 \$\mu m\$? I don't know if 0.25 is the resolution of our technology process and so it means that each transistor must have a channel length (or the width) that is an integer multiple of 0.25.


texts: Debouncing/Stabilizing power supply rocker switch?

texts:
I'm having trouble with the power signal out of my Rocker Switch (https://www.sparkfun.com/products/8837 for reference).

My PIC18F4550 + 16x2 character LCD screen project was running fine until I added a Rocker switch to break the +5V line. Now, 50% of the times the LCD screen backlight will turn ON, but no message will display. This does not happen when I leave the Rocker switch in it's bridging position and plug/unplug the DC barrel jack directly (which has much fewer bouncing problems due to it's mechanism).

I do have a Power ON timer configured in my PIC program, which should give me around 60ms before going into the program, but apparently it isn't enough. It's also worth noting that whenever I press the Rocker switch VERY SLOWLY, I don't get the problem (thus, pointing to bouncing problem again).

Concept:

Do you guys think it's a debouncing problem? How do you recommend me tackling this? Hopefully, if it's indeed a bouncing problem, we can fix it with caps and resistors only.

PS: The TO_PIC line on the picture not only goes to the PIC voltage pins, but it also goes to a LD33V Chip

Bit more complete circuit:


texts:
I've been having a common reoccurring issue when I write VHDL code. I end up writing code similar to this (as an example):

ENTITY registerfile IS
    PORT(VX : OUT STD_LOGIC_VECTOR(7 DOWNTO 0);
         RS1: IN  STD_LOGIC_VECTOR(3 DOWNTO 0));
END registerfile;

ARCHITECTURE rtl OF registerfile IS
    TYPE FeedbackSignal IS ARRAY(15 DOWNTO 0) OF STD_LOGIC_VECTOR(7 DOWNTO 0);
    SIGNAL V_F : FeedbackSignal;
BEGIN
    PROCESS(RS1, V_F)
    BEGIN
        CASE RS1 IS
            WHEN "0000" =>
                VX <= V_F(0);
            WHEN "0001" =>
                VX <= V_F(1);
            WHEN "0010" =>
                VX <= V_F(2);
            WHEN "0011" =>
                VX <= V_F(3);
            WHEN "0100" =>
                VX <= V_F(4);
            WHEN "0101" =>
                VX <= V_F(5);
            WHEN "0110" =>
                VX <= V_F(6);
            WHEN "0111" =>
                VX <= V_F(7);
            WHEN "1000" =>
                VX <= V_F(8);
            WHEN "1001" =>
                VX <= V_F(9);
            WHEN "1010" =>
                VX <= V_F(10);
            WHEN "1011" =>
                VX <= V_F(11);
            WHEN "1100" =>
                VX <= V_F(12);
            WHEN "1101" =>
                VX <= V_F(13);
            WHEN "1110" =>
                VX <= V_F(14);
            WHEN "1111" =>
                VX <= V_F(15);
            WHEN OTHERS =>
                VX <= (OTHERS => 'Z');
        END CASE;
    END PROCESS;
END rtl;

Assume V_F is connected to an internal register or something similar.
I feel like this is extremely repetitive, and I can't seem to figure out a better way. Is there a more concise way similar to something like:

VX <= V_F(RS1);


texts:
I am attempting to write some code for a PIC24FJ64GB002 using X16. I am not a software developer, so very much a "noob" here.

I am trying to make RB0 (pin 4) go low on an event using the code:

        if(joyd.x_axis < 127)
        {output_low(PIN_B0);} else{output_high(PIN_B0);} //if LEFT pressed

This gives a warning:

implicit declaration of function 'output_low'

and an error:

error: 'PIN_B0' undeclared (first use in this function)

I have been googling all morning to no avail. Can anyone point me in the right direction to resolve these two issues please?


texts: Precision battery voltage meter, Auto adjustment by R-2R

texts:
For a more precise measurement of a battery voltage I'd like to apply auto adjustment. The input voltage ranges from 2.5V-4.2V (single cell) to 20V-72V (module). At the moment the input voltage is divided by ~30 with a differential OpAmp and fed into a 24bit/512kSPS ADC (ADS127L01).

Since the voltage for single cells does only use a fraction of the full scale range I'd like to adjust the circuit. During my research I found a rather promising solution:
http://www.electronicdesign.com/test-measurement/optimize-high-voltage-measurements-self-adjusting-attenuator

I built the schematic with LTspice and simulated the desired output voltage which looks quite good. Nevertheless, I'm not quite sure because the diodes are not simulated correctly. Can anybody explain how this should work? As soon the corresponding OpAmp saturates (eg. -5V), the voltage at the negativ input pin increases and can cause damage to the OpAmp as it exceeds the positiv voltage supply. How should this be avoided by the two diodes in parallel to the resistor?

How about accuracy? I also run a noise analysis in spice but as I said, I highly doubt the results are correct. The result would be around 10nV/sqrt(Hz) for the sample rate of ~500kSPS. Is it recommended to apply aditional differential filters, also to match with the differential inputs of the ADS127L01?

Furthermore, I have a question on extending this circuit for even higher voltages up to 1000 V. If I use R4 (eg. 10Meg) and adjust all other resistors so that the stages match with ranges of eg. 100V-300V, 300V-600V and 600V-1000V this should work as well?

simulate this circuit – Schematic created using CircuitLab

I'm looking forward to your replies!


texts: Why use DC motors for driving elevators?

texts:
This New York Times article says that on November 14, 2007 Consolidated Edison Company was going to end supplying direct current to the remaining several buildings that used those to run elevators.

I don't get why there would be DC-powered elevators.

Yes, at the end of 19th or the beginning of 20th century DC equipment was rather popular, but it's unlikely that an elevator would last a century and all the elevators I could find information for now run on AC.

Also DC is typically preferred for easier RPM control (like in trains, tramcars, etc) but this is not a problem for elevators - they typically use two-speed three-phase AC motors and speeds are changed by switching the number of poles.

Why would there still be elevators running on DC?


texts: How does the data rate of a CAN bus affect the value of the capacitor used in a split termination scheme?

texts:
I'm helping to redesign the CAN bus of an electric car, and we're interested in achieving higher data rates of up to 8 Mbit/s. We have a transceiver selected, a CMC to reduce inductively coupled noise, and we are now looking at termination schemes as the next step.

We came across the split termination scheme which, according to section 4.5.2 of this TI document and various other sources, can help stabilize the common-mode bus voltage and filter out high frequency noise. A typical value for the center tap capacitor is listed as 4.7 nF for a data rate of 1 Mbit/s if I'm understanding correctly. Is the relationship as simple as solving for the capacitance with the given equation? If so a value of 620 pF would be suitable for 8 Mbit/s, but the common-mode voltage itself shouldn't be changing at such a high frequency should it? Would this value work?


texts: MEMS microphone different output voltage at the same dB

texts:
I am trying to measure noise using the ADMP401 (MEMS) sensor.

In the dynamic sound (applause, the sound of hitting the desk, etc.,) a sensor output of + -200mV is obtained. However, for the sound of a cell phone at the same dB, it gets about + -50mV.

The upper waveform is the sound of a mobile phone, and the lower waveform is the sound of a mobile phone similar to the dB of the dynamic sound.

I used a high pass filter, weighting filter, preamp, etc. to solve this, but it still has a lot of change in dynamic sound. And if the sensor recognizes the dynamic sound, clipping occurs in the negative direction. Both sounds are around 100dB.

The circuit diagram is as follows. The XPG1 part was used instead of the ADMP401 sensor.

I experimented with preamp and weighting filter circuit in front of C1, but the problem mentioned above is not caught. I've spent a lot of time trying to solve it, but it didn't work.

Can you help me solve it?

This is part of the sensor datasheet. Even if I interpret it, I am not sure where the problem is. Do I need to change the sensor or use a different filter? How to get a constant output in dB regardless of the type of sound?

As the dynamic sound mentioned above has a large change in dB in the low frequency band, a weighting filter is used to catch the low frequency.


texts: Unexpected huge MOSFETs power consumption

texts:
I have 2 MOSFETs :

NMOS -->
     Ref :BSZ520
  Rds_on : 52 mohms

PMOS -->
     Ref :IRF9640
  Rds_on : 500 mohms

My load (Cact1) is drawing around +/- 250 mA. I calculated the power dissipation with P= R*I² which gives me the following results :
BSZ520  -->
       P = 3 mW

IRF9640 -->
       P = 31 mW

Then why when I use ALT+right click, LTspice gives me hundreds of watts? I hope it's not relevant.


texts:
I am building a microSD to USB adapter using the Microchip USB2244 IC. The device is in a miniPCIe form factor and communicates via USB to the host which is an embedded platform that runs on batteries.

I found that when idle (no SD access), the device's battery life went from 4hr 53min to 3hr 51min. It seems strange to me that my adapter uses so much battery life when idle, so I was wondering if anyone knows if there's something I can do to improve the power usage.

Update: I did some more tests. The device has a 2210mAh battery. With a generic USB microSD adapter connected, the difference in 2 hours of idle (screen on, no activity) use gave a difference of 75mAh in remaining battery. That means there's an average difference of 38mA with and without the USB device.

With my adapter though, the difference was about 121mA so I think that the host does not support USB suspend mode--the USB2244 uses 110mA while active in full speed and I think the generic USB adapter uses a chip that's more power efficient.

But what's strange is that in another test, I made sure the device is completely powered off (the host keeps the USB port powered even if the device is off) and found that 528mAh was used in a span of 8 hours. Since normally the host can last months powered off, this means the average of 66mA was completely due to my adapter. I know there's no USB activity when the device is powered on, so it should be in suspend mode, right?

If it helps, I've attached the schematics below.


texts:
I recently got an et-3400a and there is no model for it online,  there is one for the et-3400 though,  I was wondering what the spots marked AA, AB, ST1, ST2,  etc.. do or just the raindrop shaped holes in general,  I look at the picture and it seems like there is something soldered underneath but I have no idea what and don't have the proper manual for the 3400a.

http://s16.postimg.org/ukyjhwo6d/1453053782049_592525063.jpg

It didn't come with a manual.

It's probably a stupid question as I am very new to soldering.


texts: Connecting 4 dev boards (5V) in series to 20V power supply

texts:
What will happen if I connect 4 identical Orange Pi One boards (which require 5V @ 2A) in series to a 20V @ 2A power supply? The reason I want to do this instead of using four 5V power supplies or one 5V @ 8A in parallel, is because the 20V one is much cheaper.
The boards are identical but my understanding is that they draw different current depending on the load (I don't know how much current they draw).


texts: Electromagnetic actuator – extension of field beyond coils?

texts:
In an electromagnet with an iron or similar core, how far down that core, beyond the coil, will the rod be magnetic when the coil is energized?

I'm wondering if I can create an actuator for an object inside a sealed container. The rod would enter the container, with an electromagnet outside the container. A magnetic sleeve on the rod, inside the container, could then be moved toward or away from the end of the container by energizing the electromagnet, if the magnetic force extended a sufficient distance down the rod.

This obviously depends on how far down the rod (core) the magnetic effect extends.


texts: Identify unmarked leads on a 9 lead motor

texts:
How would I go about identifying unmarked leads on a 9 lead motor ?
I also need to establish wheather this is wires delta or Y.


texts: Laplace vs Fourier Transforms in Transmission Lines

texts:
Consider an electric transmission line with transient equations
$$\frac{\partial v}{\partial x} =-Ri -L\frac{\partial i}{\partial t}, \qquad
\frac{\partial i}{\partial x} =-Gv -C\frac{\partial v}{\partial t},$$
zero initial conditions
$$ v(x,0)=0, \qquad i(x,0)=0, \qquad x\in [0,L],$$
and sending end boundary conditions
$$ v(0,t)=v_s(t), \qquad i(0,t)=i_s(t), \qquad t\in [0,\infty).$$
I am studying wave attenuation by using the Fourier transform and ABCD matrix representation.  If I were to take the inverse Fourier transform of the solution, I may not obtain the correct initial condition.  If I use the Laplace transform instead, does the single-sided Laplace transform provide the same attenuation analysis by simply evaluating the complex Laplace variable on the imaginary axis?  Is there another way to fix the ambiguity of the initial condition using Fourier transforms?
I hope my questions are clear.  Any thoughts on this matter would be helpful.  Thank you.


texts: What are the basics I need to know to power LEDs with RF at a range of 30 feet?

texts:
I would like to light up a path in the woods with hundreds of LEDs using RF. The idea is that I would carry a RF transmitter powerful enough to light LEDs. As I approach the LEDs would get brighter, showing the path, and fade out as I pass out of range. Similar to the effect of carrying a lantern. I would like the LEDs to become noticeable, though dim, at 15 to 30 feet.

Is this possible?

I have never attempted anything like this before and I would really appreciate any tips or help with this project.

Update*
Parameters:

Transmitter weight as heavy as 20 lbs

Forward voltage up to 3v

No solar pannels

No long wires linking LEDs

Passive LEDs (no battery)

Parabolic dish if necessary

Also, is safety an issue when holding a transmitter so close?


texts:
I designed a PCB to fit inside the case of a parallel port connector cable. It will be soldered, internally, to the pins of the cable connector. I already did a first version, I printed it on paper in order to better see the results. Below, there is a picture of it:

(click small image above for larger image)

But I'm afraid to design it to fit exactly into the case, because this way, it will fit only to the type of case that I measured and, maybe, it would not be a good choice. So, I was concerned about two points:

If it does not fit exactly, if it is smaller, it could swing inside the case and it can break the soldering between the PCB and the connector pins.
If it does fit exactly, I will be a "prisoner" of this case format. If, for some reason, this format of case became unavailable, I would need to redesign the PCB.

What do you think about it, does anyone have any advice?


texts:
In the LM311 circuit below that is used as a comparator, how does voltage at the reference (- Input), affect the output?

For a sine wave, would having a higher voltage at the reference increase or decrease the duty cycle of the output?

And finally, is there a way to calculate this duty cycle, based on the resistor values of the voltage divider at the reference input?

NOTE: The circuit above is just for reference. The application I am using an LM311 for is something else.


texts: Why do devices plugged into the wall not take in all 120v?

texts:
It's an odd question, but every search online routes me to articles about leaving chargers plugged in using energy.

What I'm asking, is if I plug my a 5V 2A USB hub into a normal wall outlet, why is it not forced to take in all 120-ish volts when it's plugged in?


texts:
I have been using a Spartan 6 where  the TX/RX pins are multiplexed with the IO pins, I can't find any dedicated TX/RX pins on the Xilinx Zynq Soc, is it a Xilinx thing to multiplex TX/RX with IO pins? I not able to find any thing in the data sheet.

EDIT:

Its using the Arm Cortex A9 processor, I presume the TX/RX pins would be the same as on the a9? would I be correct in thinking so?


texts: Boost converter for High Output voltage and High Output current

texts:
I want to design a variable power supply.
I need to get output voltage from 7.5 to 30 V and output current of 0-40 A.

One of the above values will be fixed while the other changes. This is for resistive load (chlorinator cell whose load changes with the salinity of water and temperature).
I bought this boost converter from ebay.

They provide 400 watt power.
Input voltage DC 8.5-50 V
Current: 15 A max
Output Voltage: 10-60 V (nearly meeting my
expectation).
Output Current : 0.2-12 A (I want up to 40 A).

On eBay, they say we can connect them in parall to get higher power but they have mentioned that only for the 1200 W model.
Is there any way I can achieve my goal by using these boost models or is there any other ways besides boost model to get these outputs values?
I thought about using voltage selector on primary side of the transformer but the problem is the high output current on the load side.


texts: On a VGA connector, there are numerous 'ground' pins. Three of these are Red return, Green return and Blue return; But why does each color component have its own ground pin?


texts: TPS60312 charge pump severely drops zinc-air coin cell voltage at higher output currents

texts:
I'm trying step up the voltage of a size 675 Duracell Zinc Air button cell battery: http://www.microbattery.com/microbat/pdf/duracell/duracell-hearing-aid-battery-008-2014.pdf

from its nominal 1.4 V to 3.3 V using the charge pump TPS60312: http://www.ti.com/lit/ds/symlink/tps60311.pdf

while continuously drawing a current of ~12-14 mA from it. The charge pump should be able to supply 20 mA at 3.3V from its OUT2 pin.

First I checked if the cell is capable of supplying that current by creating a simple circuit with only the cell and a load of a 100 Ohms. The circuit stabilized with the voltage of the cell dropping down to ~1.2V with a current of ~11.5 mA going through the circuit.

Next I connected it to the charge pump, as shown in the schematic on the bottom left of the first page of the charge pumps data sheet linked above (using five size 0402 ceramic 1 uF capacitors, and no resistors as PG is not required), plus applying the same 100 Ohm load to the output as before. Doing this results in the voltage severely dropping across the battery down to ~0.7V, which is below the operating input voltage (0.9V) of the charge pump. The charge pump still generates an output but its below 1V.

I tried some different resistor values and the circuits seems stable with a steady 3.3 V output for lower current draws, but once it goes above ~5 mA the cell voltage starts to drastically drop.

I also tested the charge pump with a power supply instead of a cell, and the same thing happens, the displayed voltage on the power supply drops down to 0.68V once the 100 Ohm resistor is placed into the circuit.

What could be the cause of the severe voltage drop?
The data sheet mentions one alkaline, NiCd, or NiMH batteries as
typical uses for the charge pump, but there is no mention of zinc air
batteries. Could this be an issue?
I also used physically smaller capacitors (0402) than recommended in
the data sheet (0805). Does this matter, and how much does the
capacitor physical size actually matter in cases like this (assuming
the other properties are the same)?


texts: Will placing inductors near each other have adverse effects?

texts:
I want to place two inductors next to each other on my PCB, will the fields interact in a way that would adversely affect each other?

If it's important they are 1mH each, with a 8V peak to peak, 800KHz signal running through them.


texts:
A circuit i made using opamps and transistors causes lots of oscillations (parasitic maybe ?), a solution to that which i find very reasonable is to limit the bandwidth of my main driving opamp so any oscillations are attenuated/removed. .

Update : adding a 100uF cap between pin 14 and ground removed about 99% of the oscillations , but instead i got this voltage spike that occurs when i drive the motor with a square wave ( the spike appears with every falling edge)


texts: MSP430G2553 and LDO ADP162: Is an external pull-down necessary?

texts:
I need to control the 'IN' (enable) pin of this LDO Voltage regulator (ADP162) with a microcontroller (MSP430G2553). In the datasheet of the LDO, I couldn't find whether or not it has an internal pull-down resistance.

Is it necessary to put an external one or can you directly connect the GPIO pin of the MSP430 and the EN pin? I really use two LDOs: one to power one LCD and the other LDO to power one RF module. In the data sheet, in figure 39 you can see that the start-up time is almost 1 second, so I think it would give plenty of time for the microcontroller to set the appropriate value on the GPIO pin that controls the EN pin of the LDO.

Therefore, I think it is not necessary to use a pull-down. It is right?


texts: reduce from 12 to 7.5 volts and can carry 4 ampere

texts:
i have 2 servos operating at 7.5  which each of them consume 4 ampere at stall and i have battery 12 volts.i want to make a circuit, buy a circuit or even know if it i possible to make or buy something to reduce 12 to 7.5 or 8.5 even (it is the same for me) and can carry 4 ampere without burning it.
thanks in advance.


texts:
so I configured the adc(ad7689) using lpc1768,and here is what i get:(a few conversions of each for the same voltage)

VDD=5v,vref=4.096v
4bcf>> v=1.2129
4bdf>> v=1.2139
4b8f>> v=1.2089

but

VDD=5v,vref=2.5v
8007>>1.2502
8004>>1.2501
800f>>1.2505

i cant find where the source of this issue is,any help is appreciated.


texts: Why does electrical phase vary with element length?

texts: In a reflectarray antenna, each element on the antenna aperture requires a different electrical phase due to different distances from the antenna feed.  One way to achieve this phase variation is to vary the size of the elements on the reflectarray.  What I do not understand is: why does changing the element dimension change the electrical phase of the element?  I am looking for answers with a qualitative explanation in addition to any maths that may be necessary.  Thank you!


texts: What is the continous power consumption in milliwatts of this circuit?

texts: Also, I want to add a button switch to it. Can I also remove the microphone?  I just need to deliver a signal basically like a car key except in a room with several walls (should be strong enough?) I have never assembled anything analog that is why I am asking.


texts:
Many sources say that composite video input should be AC-coupled. Voltage levels for blank, black and white signal are also specified. How is it possible to detect these voltage levels after AC coupling (aka dc-blocking capacitor)?

Doesn't the DC-component (average) of the signal vary wildly depending if the content is all black (0V-0.3V) or all white (0V-1V)?


texts:
After using Stackexchange for several years now for solving all my Python, LaTeX, math, electronics, engineering and life questions, I have finally come up with a problem I cannot find an answer to. I hope you can point me in the right direction.

My problem is as follows: I bought two diy dimmer sets for 230VAC, max. 100W (like the one in the picture). Because the Halogen light I want to control is 100W I replaced the triac that came with the package with a BT139 (just to be on the safe side). After putting them both together I noticed that one of the two starts flickering below, say, 50%. I have tried switching the bulbs, switching the wiring order, I measured the potmeters resistance (which is fine), I measured the voltage drop across MT1 and gate (0.412V, which is about the same ass the other triacs), all soldering and wire connections are fine (<1 Ohm).
Unfortunately, that is about as far as my knowledge goes.

For understanding the circuit, I found a scheme of exact this dimmer here on Stackexchange (the Diac is a 30V one, the triac is a BT139):

Can you guys give me some hints of what I can do?

Thank you!

P.S. I only have a multimeter, I don't have a oscilloscope at my disposal...

Thanks for all the help guys! It appears the solution was really simple: I tried reversed the wiring of the dimmer (again) and miraculously it now stopped blinking...
Can anyone of you come up with a theoretical explanation? It would be great to say I did not waste all those hours fooling around, but I actually learned something(:


texts:
I have looked at many DC connector types but still couldn't find what type is the following connector. It's not XLR or Power DIN. Any ideas?
It's similar to GX16-4 4-Pin 16mm Aviation Pug but it's not the same


texts: What exactly is prepreg and core in a PCB?

texts:
I am trying to wrap my head around the structure of a multilayer PCB, and while I can understand many things, I am not able to grasp the concept of "prepreg" and "core". What do they exactly do? I have attached a reference stackup below.

Only thing I understand about them is that they are used to glue the layers together. But why both, why not only "prepreg" or "core"? How do they differentiate from each other?

Could you please demystify these things for me?

Any good reference to understand this and how the layer stackup is determined is also appreciated.


texts:
I'm a software engineer dipping my toe into hardware. I am trying to interface an LM335 temperature sensor to an XBee radio device. The XBee has an ADC built in. The XBee pins are:

1 = VCC = 3.3V
10 = GND
14 = VREF
19 = ADC

The specifications on the XBee say that VREF "must be between 2.6V and VCC".

The LM335 has (-) and (+) and (adj) pins, see LMx35, LMx35A Precision Temperature Sensors.

Could someone give me some guidance on what circuit I would need to make this work? Or at least a reference where I could learn more?


texts: Inverter not cutting off before deep cycle danger level?

texts:
The documentation for my 400 watt inverter says the *inverter will shut down if the input voltage drops below 9.5V+/-0.3V

In the Deep Cycle Battery faq listed here:
http://www.windsun.com/Batteries/Battery_FAQ.htm (under "State of Charge")

it shows that my unsealed 85AH Costco deep cycle battery would be completely depleted at 10 volts, which is when  my inverter would shut off. If this is correct, it would obviously harm the battery.

Does this mean I need to constantly monitor the voltage of the battery and cut it off manually? Get a better inverter where I can specify a cutoff voltage? Or is there some kind of extra cutoff attachment I can add to my setup? Please let me know if my logic is correct and what the best approach here to saving the life of my battery. Thanks!

*The inverter will operate from input voltage ranging from 10 volts to 15 volts. Optimum performance will occur when the voltage is between 12 volts and 14 volts.
If the voltage drops below 10.5V+/-0.3V, an audible low battery warning will sound. The inverter will shut down if the input voltage drops below 9.5V+/-0.3V. This protects
the battery from being over-discharged.


texts: How to determine the value for the gate resistor (Rg) of a MOSFET in low side configuration?

texts:
Once the FSR is pressed the output of the comparator should go high. This, will drive the MOSFET ON which has a DC motor on its drain terminal. I was wondering how can I determine the value in ohms of the gate resistor? should it use one at all? Thanks.

Comparators' data sheet: https://www.onsemi.com/pub/Collateral/NCS2250-D.PDF


texts: Photodiode sensing circuit with inverted output

texts:
I want to build a photodiode light sensing circuit so that the output voltage is inversely proportional to the light intensity going to the photodiode. I.e less light equals more voltage.

I'm thinking of a circuit like this:

simulate this circuit – Schematic created using CircuitLab

As the light intensifies the current in the circuit get higher and there is more voltage drop in the resistor. That's what I'm thinking.

I have a few questions: Would this work? What should the resistor value be? Do I need an amplifier?


texts: Serial communication and reading byte arrays with Arduino

texts:
I am establishing a serial connection with my Arduino. In order to get data from it I have to send data in the form of byte arrays. I am able to send the command and read the ACK. But I can't figure out how to get the data after the ACK.

The developer documentation for the protocol I am using says it goes:
command to access data -> ACK REPONSE ->DATA

I can't figure out how to get the data after the ack response. It should be a byte array of 14 hex values.

This is my code

byte GetData[] = {0x02,0x12,0x00}
byte GetDataACK[] = {0x02,0x06,0x06,0x06,0x06,0x06};

void setup(){

  Serial.begin(9600);
  Serial.write(GetData,sizeof(GetData)); //Send the byte array
  delay(200);
  if(Serial.available() > 5) {
    for(int i=0;i<6;i++){
      if(ackmodule[i]!=Serial.read()){
        // Do something
      }
    }
  }

}

void loop(){

}


texts:
I need a power supply that delivers 12v with an input between 8v and 35v. That's the reason I bought a couple of TPS55165Q1 from Texas instruments. I've made 3 different PCBs with a similar circuit. All of them works great in buck mode, delivering 12v up to 500mA. When I change to boost mode, It does not deliver neither the current or voltage it was calculated.
When I switch to low-power mode, it works just as expected in buck and boost mode. That's why I conclude that there is a protection thats working (in Low Power mode, all protections are disabled).
I've tried to emulate as close as possible the circuit of Figure 3 of its evaluation board: http://www.ti.com/lit/ug/slvuay1/slvuay1.pdf

I show you

I've chosen SRU1048-4R7 inductor from Digikey and take special care of its Rdc and peak current. All capacitors are ceramic except for the 100uF. Can you give me some advice in order to get it work?
Thanks!

** EDIT **
I attach some oscillograms. It was taken with a Vin of 14.8v (Step-up mode)


texts: Transistor Switch for my Raspberry Pi 3 FAN

texts:
Update 1 :

After some help and advices from nice people here i'm going to use this circuit :
http://everycircuit.com/circuit/5857347480322048

the 25 ohm resistance being the fan.

I'm requesting your help for a little electronic circuit, a simple transistor switch. I need help because i don't know how to choose the right transistor or the right resistance for my circuit. I need advice for adding a protective diode.

I explain myself :

it's a circuit that switch a 5v 0.2A dc fan to cool my raspberry pi because i use it intensively.

here is the circuit i designed :

updated (look up)

the online link to it : Updated to new link (look up)
(the 25ohm resistance is the fan's resistance, i didn't know how to modelise it).

I use the 5v pin to power the fan and a gpio pin (3.3V 16mA) to turn the transistor on/off by a python code i will do myself later.

is the resistance choosen ok ? how can i choose the right transistor after it's specs ?

if i get to make the circuit work fine, i will then use the PWM pin of the RPI to make it's speed variable with the temperature of the CPU, but that's after.

i hope my question is complete,
What do you guys think ?


texts:
I am part of my company's work to become more environmentally friendly and sustainable. On a high level for the company that means pursuing ISO certifications (such as ISO 14001) and working according to other standards. But I'm trying to figure out what this should mean for me, as a electronics developer?
So far I'm looking into switching PCB manufacturer to a company that regularly produces sustainability reports that I think are transparent and good, adapting PCB designs to minimize waste materials, improving the recycling/waste sorting in our lab, and perhaps using OSP instead of ENGI as surface finish. But what else is there that I can do as a developer? Are there components I should stop using in my designs, standards/certifications that are suitable to follow as a developer, or anything else that you have done yourself or could recommend me to look into?


texts: Does a zero-recovery diode really have literally zero recovery time? If so, how?

texts: Some diodes are advertised as "zero recovery". Is this true? Or is it marketing speak for "so fast you couldn't possibly care"? If it's true, what makes a zero-recovery diode fundamentally different than others?


texts: How to find the Common Mode Rejection Ratio of this circuit?

texts:
My attempt was like,
by using the formula,

I can get, \$CMMR=\frac{\sqrt{2\cdot4\cdot8\cdot5\cdot10^{-6}}\cdot44000\cdot2}{x}\$

For the denominator, I used both 10% and 20%, but all the finals were wrong.

For 10%, CMRR=15741.92, For 20%, CMRR=7870.96.

Did I approach this question properly? What did I do wrong here?

Thank you!


texts: Does coil require extra resistor before connecting mains?

texts:
I am planning to build diaphragm air pump. For this instead of using an AC motor, I am planning to connect an aluminium rod to diaphragm, and put a permanent magnet on it that will be pulled and pushed continuously by the magnetic force of two coils.

These coils will be connected to grid (220VAC, 50Hz) in reverse direction. My expectation is that the rod will move back and forth continuously between two coils while the current changing direction, thereby the diaphragm will do pumping.

Since I do not have any this type practical experience with mains, I have a question to ask.

Since mains follow sine wave, when the current reaches to peak points, change
on current will be very small, and reactance of coils will be at its lowest,
and the impedance as well. Ignoring general impedance that is to be calculated based on frequency of mains, impedance of coils is expected to be changing based on delta t.

My question is that considering the above situation, should I be putting
a resistor before coils to prevent current getting too high due to low
impedance? As far as I see in electric DC motors, coils are directly connected.

Another related question is what I should do about flyback to prevent arcs? DC motors don't have anything on them and disconnected without a problem.


texts: STM32F7 discovery USB device CDC using CubeMX

texts:
The thing I want to do is sending some bytes with STM32F7 discovery to my laptop, through USB (HS or FS). I tested the virtual com example provided by keil microvision so the hardware is OK, but I need to do it using STM32CubeMX. The libraries are different and the best luck I had, was seeing Virtual Com Port in device manager. but Hyperterminal or Putty cannot detect it and there is no sending or receiving data. I have attached my sample code link and clock config, so I appreciate if anyone could help and tell me what the problem is.

My Sample Code


texts:
I want to drive servo motor with PWM signal.Servo motor rotation angle changes with the ratio of the duty cycle.Generally , servo motor rotation angle  according to PWM  can be seen in figure below.

Suppose that

I apply duty cycle with 1ms  but Vmax=12V and V min =-12V
I apply same duty cycle but Vmax=12V and Vmin=0V .

In both cases ,will I obtain same rotation angle on the servo motor?If not ,Is there spesific Vmax and Vmin voltage to rotate servo like in figure above?


texts: Do some microcontrollers require data to be loaded in temporary memory before programming?

texts:
When I programmed the AT89Cx051 series of microcontrollers, I didn't have to use special memory to program the data, but now even though I'm following the instructions in the datasheet (found from http://futurlec.com/Atmel/AT89LP4052-20PU.shtml) to the best of my ability, I still can't get the damn chip to run even when running it with a 555 timer at low speed as a clock.

But the new chip manual states theres a "load code page buffer" function and a "write code page" function. After (attempting to) erase the chip using the proper commands, I went straight to the "write code page" function and inserted the binary of the following code:

mov P1,#0A5h
sjmp $

When the chip runs correctly, the outputs of alternating port pins from P1 (starting with the lowest) should be logic high and the rest should be logic low, yet all I get is everything as logic high.

This is how I attempted to program 6 bytes in detail after erasure:

Make VPP 12V
set CS to low
Set P1 to AAh
Set XTAL to high then to low
Set P1 to 50h
Set XTAL to high then to low
Set P1 to 0h because high address is 0.
Set XTAL to high then to low
Set P1 to 0h because low address is 0. we start from byte 1.
Set XTAL to high then to low
Set P1 to 75h (the MOV instruction)
Set XTAL to high then to low
Set P1 to 90h (the P1 address)
Set XTAL to high then to low
Set P1 to 0A5h (the value)
Set XTAL to high then to low
Set P1 to 080h (for sjmp)
Set XTAL to high then to low
Set P1 to 0FEh (to stall)
Set XTAL to high then to low
Set P1 to 0h (padding)
set CS to high
wait for busy to reset

I think I'm doing everything right? but is it mandatory to execute the load code page buffer before writing the buffer? I'm confused.

The microcontroller in question here that I have difficulty with is AT89LP4052


texts: Maximising sensitivity of AC voltage measurement on top of DC voltage with Arduino ADC

texts:
I have:

Single supply rail voltage (3.3)
current sensing transformer that outputs an 1v pk-pk value at is max rated sensing current (10A). The Transformer biased at 1v DC in order to ensure that the input signal never falls below 0v (i.e. on the negative cycle of the transformer, output will be 1v -1v =0, and on the +ve cycle it will be 1v+1v = 2V
An arduino with and ADC input. its a 10bit ADC
The Arduino ADC can use the internal voltage ref of 1v or the supply of 3v3 which will equate the max value of the ADC (1023) to this ref.

My problem.
How can I maximise the sensitivity of my ADC reading. My current circuit has the following constraints

I would like to use as much of the ADC range to measure the variation in the AC signal and remove the common mode bias of 1v
My current circuit means that an max output voltage of 2v is possible and hence I need to use the supply (3v3) as the ADC reference. This means that 1/3rd of the ADC rangne is never used
I spend a lot of time measuring the DC value of 1v, when all I am interested in is the AC

Is it possible to convert this signal to a 0v to 1v (FSD) that I could feed directly into the ADC and then use the whole 10bits to represent the 0 to 1v range (hence a resolution of approx 1mv) by using the internal 1v reference?
I can only afford to use the lower end components so AC to RMS converter chips are out of my budget... LM358 are in my budget :)
Thanks


texts: How does increasing voltage to a motor affect the power and current usage?

texts:
Using this motor as an example, which is rated for 7.4 to 14.8 volts.
When the voltage is increased (from 7.4 to 14.8) to the motor, how does this affect the power and current usage?
My understanding/guess is:

Torque increases
Power consumption increases
Current stays relatively similar

Using the performance data in the image below (performance data for the same example motor given above, which is data at 11.1v), is it possible to calculate how much the motor would perform at a different voltage?


texts: Figuring out ATX Power Supply max output

texts:
I have a Delta DPS-400AB-17B power supply, and I am planning to change over some of the connectors to different ones. I want to make sure I don't overload any of the 12v 18awg wires, so I am figuring out how to disperse the load evenly across the available 12v wires (keeping rails in mind). The power supply has 12 12v terminating wires (2x for 24 Pin, 4x for one EPS 12v connector, 4x for another EPS 12v connector, and 2x for 2 SATA), however many of these 12v wires "share" a connection to the PSU's PCB, as such:

My initial thought was that this would possibly be a thicker wire, but it is 18awg just like the others. Should I be concerned about this small (roughly 2") section of wire heating up too much because it is carrying twice as much current as any of the other single 12v wires, or does the fact that it is only a very small run change the wire's ampacity at all?


texts: How to build a precise voltage controlled resistive heater?

texts:
I have been tasked to build a heater for an industrial application. The heater uses resistance to heat the liquid and the application needs very precise control of temperature (+/- 1 degree). Existing system uses simple ON/OFF control, I am thinking of implementing a better control algorithm (using existing hardware) and take the hardware to the next level and control the current on the resistance to further improve the precision of the temperature later.

I have built voltage controlled DC current sources using opamps and mosfets but not for AC. What is a a good architecture I can use with a 8 bit micro-controller that has a DAC. The mains voltage is 220V.


texts:
I want to attenuate an incoming signal (16 bit signed number between -1 and 1) by a certain amount (let's say 0.8), i.e.,

incoming = incoming * 0.8

Where incoming is a signal:

signal incoming : std_logic_vector(15 downto 0);

But I'm having trouble getting this to work. Inside a process block:

variable temp : std_logic_vector(31 downto 0);
variable scale_factor : std_logic_vector(15 downto 0) := x"6666";

begin

incoming_raw <= data_in;
temp := incoming_raw * scale_factor;
incoming <= temp(31 downto 16);

end process;

ModelSim doesn't like this and gives me:

# ** Error: /home/blah/blah.vhd(254): No feasible entries for infix operator "*".
# ** Error: /home/blah/blah.vhd(254): Bad right hand side (infix expression) in variable assignment.

Why can't the * operator do this when both operands are 16 bit std_logic_vectors?


texts: Interlacing Verilog and schematic in a FSM

texts:
I'm a noobee to HDL based design.

I've built a Simple Dual Port memory using the fpga's IP tools and instantiated it in a schematic.

I'm implementing a custom external cpu interface (with hand shake) with the fpga and one of the operations is to write a byte of data to the fpga memory cell defined above

I am attempting to write, in verilog, a FSM that will control operations on the "Write" side of the memory.

Question -- Memory is instantiated in a schematic along with it's associated address register/counter.

For a specific state in the FSM, I want to write data (coming from the fpga input - identified as a bus) to the memory (memory data is a  bus) and increment the address counter associated with the memory.

So -- incoming data (bus),  memory data in (bus), and memory address register/counter are all external to the verilog FSM and all defined in a schematic

How can I make the FSM (verilog) aware of these schematic related components and have the verilog code work with them -- especially the increment memory address counter operation.

I hope I've explained this well.

All the documents I have found on verilog/FSM/FSMD don't speak to controlling registers/busses external to the FSM code.

Thanks


texts: DCF77 antenna preamplifier from available components

texts:
I plan to build a DCF77 receiver, which includes an active antenna. When I was looking for inspiration to design an antenna preamplifier, I came across a scheme that I liked. Here is the link. When I wanted to buy the BF256B, I found out that it was no longer in production. The same goes for the BC550B. Therefore, I was wondering if anyone would help me to design a similar circuit diagram but with the difference that transistors can be obtained.
Thank you in advance.


texts: Has anyone else had issues using an LT1761 regulator?

texts:
I've designed a circuit and I needed to use low noise regulators. The regulator that I chose for my positive rail is the LT1761-5, the 5V fixed output version of the regulator. I put 6V in and I haven't been able to get the 5V out. I generally get somewhere between 4.2 and 4.6 V. I've tried increasing my Vin in case it was a headroom issue but that hasn't changed anything. I milled a board just to test the regulator (in case my circuit was causing the issues) and I'm still having the same issues. I'm attaching the schematic and the PCB here. If anyone has any ideas of what this could be please let me know.

Thanks!!


texts:
I have designed a PCIE to USB3 converter device that is based to VIA LABS VL805  Q6 Chip.
My problem that I can't recognize the VL805 chip in Linux, using the command "lspci":

here is the schematic for the design VL805. Wherever there is the world "NEW" its something that doesn't exist in the current board version and I want to make a revision for it.
on the first version of the board, I mistakenly connected TX of the PCI (from CPU) to the TX of the device, and also connected the RX's together. then I made an ECO for several boards in order to see if this can solve the problem before sending a request for board revision.
Unfortunately, this didn't solve the problem. (in the current PDF the TX signals are connected to RX signals in the right way, as they should be)
Notes:

There is an External SPI flash that should include a firmware that VIA labs sent me. I already flashed it with the firmware on previous board but that didn't help. on the current validation boards I didn't flash this SPI. I think that at least I should be able to recognize the device even before it having firmware.
all the voltages for the device are provided (checked in DVM), but I didn't check if the power up sequence is in the right order that VIA LABS suggested in their design notes:

Questions:

Is this SPI critical for the Device Identification process?

could the power up sequence be the cause of the reason? they didn't provide any specification about the time difference between the different signals.

I didn't place series capacitors to the TX pin outputs as in the picture:
, could this be really the source of the
problem?

Update: after replacing the ECO for the TX and RX wires fix with thinner wires and adding 100nf series capacitors to the VL805 pins, and externally flashing the SPI, the chip was recognized and functioned correctly. the PCIE to USB3 device works and is in a good shape. right now I'm doing validation tests.


texts:
How does voltage bias affect a photovoltaic cell? I'm receiving conflicting opinions online, with some saying that photovoltaic mode is entered only with forward bias, some saying reverse bias, and some saying no bias. Furthermore, is there a breakdown voltage for photovoltaic cells? The Shockley equation as I understand it (\$I = I_0(e^{(eV/k_BT)} – 1) – I_p\$) physically cannot tend to negative infinity as it's an exponential equation.

Thanks!


texts:
I'm trying to implement a sim-card reader for my own. I followed step by step the guide on www.ladyada.net site but it does not work as it would be. My PC and softwares i used to read/write data from/to sim-card could't recognize my sim-card reader. Have someone successfully made this sim-card reader circuit? Pls help me with some ideas or show me where i went wrong. Thanks so much.
P/s: this is the circuit schematic in .png

And this is the site i followed:
Reference Link


texts: I have been planning on building a rain water collection system for my parents to be used for watering their dogs outside. I thought it would be a cool project to automate the watering process. Basically, it should be gravity fed so there will be no real need for a pump. I need a simple way to remotely start and stop water flow. I have very limited experience with this sort of thing so you may need to break it down for me as if I were 5. I was thinking of maybe using an Arduino, however if anyone has some other suggestions, I am going into this with an open mind. I am also not picky about how the valve will be remotely accessed and any suggestion regarding the best way to power this device would be greatly appreciated. I am hoping to use this as a learning experience.


texts:
Greetings from a physics student.

I have to do an activity which aim is to design a filter in frequency. To do so, I need a transfer function (gain, poles and zeros) that must meet the following conditions:

The frequency response must pursue a specific functionality (high pass, low pass, band pass, band deleted, double band pass, etc.).
The frequencies of the transfer function factors (poles and zeros) should be chosen as appropriate for that frequency response.
The total order of poles plus zeros shall be a minimum of 5 and a maximum of 7.
There may be poles at the origin or zeros at the origin (not both at the same time), with a maximum of 2.
There must be at least one quadratic factor in the transfer function.

Then I have to do Bode's plots but I control that part.
I am struggling with the choice of the function because we lost a lot of classes due to COVID-19 so I came here for a bit help.

Thanks!


texts: 3.3V Voltage Regulator for LiPol battery

texts:
I'm looking for a low drop voltage regulator to use in a 600mA – 1000mA (peak) 3.3v system that can be powered either through a singe-cell LiPol battery or USB (so a max drop of ~0.4V).

So far the AP2112K seems like a good choice and is moderately priced, but I would like to know of alternatives. This is intended for hobbyist usage, so industrial-level quality is not required.

Any recommendations?


texts:
I'm trying to understand the circuit below (from the Apollo Guidance Computer), which is two S-R latches connected together. The top input resets the output and the bottom input sets the output. But there's more going on than a plain S-R latch, maybe the bottom input is edge-triggered?

I'm trying to analyze this circuit by drawing out the states, but I keep getting messed up. Is there a strategy for understanding this sort of circuit?


texts: Connecting four wires to and from SMT PCB

texts:
I have a strange situation where I need to modify a signal through my own PCB board and then output it through a new set of connectors / wires. The problem is i am a self-taught electrical engineer, and I don't know the word for some of these products, so I am having trouble doing research on them.

The PCB I am building is a bit like a DIY / maker product. So the options I choose here can't be one-off (it's not just something for personal use). But they should also be easy enough to assemble in-house. In other words, the products that I choose need to be available in bulk, ideally, and as cheap / quick to assemble as possible. Later I will describe my research on Digikey.

Input signal: My first problem is connecting 4 existing wires to my PCB. I know that I can just solder these wires to my board, but I'm not sure if soldering is the best solution. Solder frequently breaks and it might not be the fastest, easiest, or most reliable solution. I have seen some 3D printer companies use some type of screw system to attach wires to their product. You stick the wire into the housing, screw each wire in, then move on. What are these called, and are they easier than soldering? Are there 4-pin options available for SMT assembly?

Output signal: In the "first problem" I am using existing wires -- I don't have a choice, I basically have to use the raw wires that were given to me. But in the "second" problem, I am creating my own output to new wires. In this situation, I can take advantage of something like a JST connector. But I would really like the smallest, easiest 4-wire connector that can be used on SMT. Is there something else other than a JST connector that can be used here?

I have tried to look up connectors for this on Digikey, but I am only finding board-to-board connectors. I need a female connector that can be soldered to SMT, with with a male connector that has ~four 6 inch wires running from it, and ideally it would be cheap / able to be ordered in bulk like from Digikey.


texts:
We use Orcad and we want to update our libraries. When we place a part and want to rotate it,we don't like the layout of the labels(names,values etc) and thus have to manually reposition them. It's not a big deal but it gets annoying after a while.

To solve this issue, we came with two solutions:

-Create for one component two parts(an horizontal and a vertical one)

-Create a symbol with the convert option which allows us to choose in a click

Does anyone here have any suggestion on what would be best ? I'm leaning towards the convert option because it seems faster and we have less components, but my supervisor would like to know what people in the industry do. I've linked some images to clarify what I mean.
Thank you very much, and even if you don't use Orcad,if you have an informed opinion, I would still like to hear it

https://imgur.com/a/iVTt5eW


texts: How can a circuit be unexpectedly affected by change in light levels?

texts:
I have (or rather, had) a completely functioning circuit the monitored input from a button to toggle an integrated LED on and off.

Much to my surprise, the circuit has very suddenly become finicky with light levels.
I have a lamp where I work and, when I block the light shining down on the button and its connections, the button's LED goes on the fritz.
Why could this be happening?

I have double-checked to make sure that I don't have any short circuits.
Is there anything physical that could be causing this, or is this purely a software issue?

simulate this circuit – Schematic created using CircuitLab


texts: Looking for a temperature probe connector

texts:
I have a temperature probe I need to connect to a PCB in a housing and I am looking for a good connector that require my needs.

The temperature probe has 3 wires of 26 AWG (0.1288 mm²).

Ideally I need something like a surface mount terminal block connector in which I don't need to physically join the wires. The connector ideally should have a height smaller then 5.00 mm due to the casing. It should be RoHS compliant and not too expensive (less than €1).

Can I possibly just use a crimp connection or will this affect the signal quality of the probe?

I have looked on all the big electronic component sites (Mouser, Farnell, Molex, ...) but with no luck so far.


texts: Will the temperature of a resistor converge to a predetermined value assuming ideal conditions?

texts:
This is a two-part question I haven't been able to get off my mind:

Given a resistor in a vacuum chamber (to ideally eliminate heat loss due to air), assume you apply a constant voltage across it. The temperature of the resistor will rise - now, assuming heat lost to radiation and conduction to the wires is negligible, will the temperature of the resistor rise indefinitely? Or will the temperature max out at a certain value (and is there a way to calculate this value assuming you know the value of every property of the resistor and the voltage source)?

Finally, if there is a value the temperature will max out at, how consistent a temperature would this be if, for example, it maxes out at about 330 K?


texts: How can I calculate the input resistance of this BJT Differential Amplifier circuit

texts:
I have a table of \$V_{out}\$ values for different source resistance values.  Using this data, how can I calculate the effective input resistance of this circuit?
My attempted solution was using KCL around the base-emitter loop:
$$\frac{V_s - I_bR_s-V_{be}}{I_b}=R_{in}$$
and $$ \frac{I_c}{\beta}=I_b$$
this doesn't appear to be correct, my values are varying with \$R_s\$ and I'm even getting negative values.  What am I missing here?


texts: Relay always damaged in switching circuit

texts:
I have a simple relay switching circuit which is used to turn off/on the power supply to a laptop.
SPDT Relay is 8A , 440AC part number--> G2RL-24DC.
The relay always gets get damaged - the contacts do not movr at all.
Either the contacts are permanently closed or common pin is not and at all moving. Can you suggest a solution to resolve the issue? I see no physical damage like coils burned or contacts burned.
A laptop charger with 230V/3A is connected to this relay. I am switching the AC power with the relay
Simple circuit with transistor relay on/off:


texts:
I am making Autonomous Quad.
I am programming my IMU using ADXL335 -3 Axis analog Accelerometer & L3G4200D 3-axis digital Gyro.
I am using ARM Cortex M4F based TI's stellaris launchpad LM4F120XL.

I've a problem while implementing IMU.
Here is my algorithm of IMU...

By ADC I am getting reading of accelerometer in Dx, Dy & Dz.
Now as I've 12bit ADC I am using the following formula to get the readings in "g"

Rx = [(Dx*(3.3/4095) - Tx] / 0.3
Ry = [(Dy*(3.3/4095) - Ty] / 0.3
Rz = [(Dz*(3.3/4095) - Tz] / 0.3

In stable condition I've checked the Tx, Ty, Tz:

Tx = 1.630820
Ty = 1.658477
Tz = 1.997728

For Gyro (at 250 dps with 8.75 mdps/digit)

To get reading in dps I am using following formula

X = Gx*8.75/1000
Y = Gy*8.75/1000
Z = Gz*8.75/1000

(Here Gx, Gy & Gz are data from gyro... I've checked them- they are signed values and also accurate (min. noise) )

I want to measure angles with respect to all axis (pitch, roll & yaw). For that I am doing as per following

Th = 5;
T = 0.05; // approx. 5ms I've checked it using counter
c = 180/3.14;

while (1) {
  // initial values of Rxe, Rye, Rze are same as Rx, Ry, Rz
  Xd = atan2(Rxe, sqrt( (Rze*Rze) + (Rye*Rye) ));
  Yd = atan2(Rye, sqrt( (Rze*Rze) + (Rxe*Rxe) ));
  Zd = atan2(Rze, sqrt( (Rye*Rye) + (Rxe*Rxe) ));

  // To calculate Xavg, Yavg, Zavg from two consecutive X, Y, Z values respectively
  gyro();

  if ((Xavg >= Th) || (Xavg <= Th)) {
    Xd = Xd + (Xavg*T);
  }
  if ((Yavg >= Th) || (Yavg <= Th)) {
    Yd = Yd + (Yavg*T);
  }
  if ((Zavg >= Th) || (Zavg <= Th)) {
    Zd = Zd + (Zavg*T);
  }

  Rxg = sin(Yd) / (sqrt(1 + ((cos(Yd) * cos(Yd)) * (tan(Xd) * tan(Xd)))));
  Ryg = sin(Xd) / (sqrt(1 + ((cos(Xd) * cos(Xd)) * (tan(Yd) * tan(Yd)))));
  Rzg = ((Rzg > 0) ? 1 : ((Rzg < 0) ? -1 : 1))*(sqrt(1 - (Rxg*Rxg)-(Ryg*Ryg)));

  get_accl_data();            // To get ADC values
  accelerometer();            // To convert ADC valuse in "g" - Rx, Ry, Rz

  Rxe = (Rx*0.015)+(Rxg*0.985);      // weighted average
  Rye = (Ry*0.015)+(Ryg*0.985);
  Rze = (Rz*0.015)+(Rzg*0.985);

  Xd *= c;     // converting in degree
  Yd *= c;
  Zd *= c;

  Print(Xd);
  Print(Xd);
  Print(Xd);

  Xd /*=c;    // converting in radians again
  Yd /*=c;
  Zd /*=c;
}

I am printing Xd, Yd, Zd... It is okay while satble or within +/- 10 degree...
But for more than 10 degree I am just getting fault values. I mean It is informing whether the device is satable or not OR whether it is moving on positive side(counter clock wise) or negative side (clockwise) BUT not giving the exact +/- 40 degree output while it is actually on 40 angle with respect to ground!

What I am missing? Please help me ...
I've done it by referring some docs and blogs.

// al variables type are taken proper (as per my knowledge).

One more question : Do I really need to know these angles? or can I use the current values also to make my quad stable ?
What else data I'll require to make my quad stable?


texts:
I am having trouble solving the following exercise.

I am having trouble with the damping constant as you can see. It is giving me a gain less than 1. I am following my course notes but can't solve this question. Any help would be great!

"Design a 2nd Order SK HP filter with f_c = 3KHz and zeta = 1.3. Use C=10nF and R2 = 10kOhms. I used zeta = 0.5*(3-G) to find gain, which gave me 0.4. Since it's a non-inv amp this isn't possible and hence why i'm stuck


texts:
This is a computer architecture question given in our college syllabus and i was finding difficulty in solving it.
Calculate the range of a 16-bit 2's complement number system for representing both signed and unsigned integers.
Please guide me.


texts: Is it safe to splice an output extension onto an AC Power Adapter?

texts:
(first post, trying my best to follow the rules :D)

I recently bought a Cintiq 27qHD tablet, and an Ergotron arm (with an extra arm segment) to mount it.
The intended way to do this is to run the output cable from the adapter inside the hollow ergo arm.
Unfortunately, the output cable is not long enough to comfortably run the full length and make the turns it needs to.

The connector type is apparently a type of DC connector known as a "power-DIN" or a Kycon KPPX-4P. It's similar to a DIN and Mini-DIN but not quite.

the adapter is rated 24v and 5A, if that helps. The manuafacturer is "Adapter Tech".

If anyone has a better idea other than splicing in an extension between the adapter and the connector, I'm very open to suggestions!

Cheers,

-Garrett