texts: What is 2 layerd circles component in this circuit?

texts: What is the 2 layered circles symbol in this circuit? What does it do?


texts:
I want a MOSFET for my project which is a motor driver. But after going through the datasheet I got confused what to look for.

My current rating for the motor is 21 A. So I want a MOSFET which can handle around 25-30 A. The lithium polymer battery voltage is 11.1 V.

Microcontroller voltage = 5 volts
Brushless motor rating = 21 A
Lithium polymer batteries - 11.1 volts


texts: How do I achieve 50Hz using an astable multivibrator?

texts:
Based on the \$f=1/1.38RC\$ equation I came up with the conclusion that \$R\$ must be 69000 ohms and \$C\$ must be 1000uF, is this correct?
I have a side question:
If I am charging a capacitor without a series resistor, is the only resistance I should include in the \$RC\$ calculation the internal resistance of the power source, maybe with the internal resistance of the capacitor?
I need to know if I charge a 1000uF capacitor without a series resistor, would it take 5000uS (because of the the x5 constant, so 1000uF x 5 = 5000uS or 5ms) or would it be less time assuming the internal resistances total to 0.5ohms, would that mean half the time? 2500uS or 2.5ms?


texts:
I wanted to know if it was possible to dynamically regulate voltage with, for example, a potentiometer which allows me to select output voltage and some kind of voltage regulator.

Suppose that I have a solar panel connected to this hypotethical voltage regulator; I want to be able to choose the output voltage of my regulator in 'real time' so that I can recharge for example batteries with different voltages.


texts: How to connect a W25Q64 3.3 SPI Flash to a 5V Arduino Mega?

texts:
I need memory to read from, for my project. I first intended to use an SD card, but I now found out a W25Q64/128 SPI Flash is more practical, since I don't need to write data.

However, this W25QXX Flash works with 3.3V SPI and the Arduino Mega has a 5V SPI.

By searching around, I find many solutions, but two that work which are quite different:

Using a voltage divider, which has the advantage of a simple circuit, but has problems that too less current is passed. However according to this link, in the end, someone fixed it easily by using much smaller resistor values.
Using a buffer circuit, which has the advantage of probably being more secure, but means some quite big ICs to be added. A circuit is mentioned in this link; credits to Steve Marple.

Question: Why should I (or shouldn't I) use this SPI Flash with a 5V using small resistor divider voltages?

(It seems that if I only want to add only this single 3.3V SPI Flash on the SPI bus, I can use the voltage divider using small resistors).

UPDATE

After Marcus Müller's answer, I found the following page that gives a lot of backgrounds (his solution is indeed the one with the most advantages):
how-to-interface-a-5v-output-to-a-3-3v-input


texts:
I found some youtube vids on Ultrasonic Cleaning, and thought it would be a cool DIY project. On eBay I found this. Some other transducers in the same range requires 400-800V supply. Anyone have any idea how to drive this thing? What kind of signal does it need? My guess is a 40kHz sine wave in the voltage supply range.

I was thinking a sine wave generator, and stepping it up to 400V++, mabye change the Watt/voltage with a potmeter.

The same seller on eBay also sells the driver board, but I want to make it myself. The images seems to include trafos, something three-legged that needs coolig and some passive components.


texts: What sealing type for cable/tube enter casing for outdoor use?

texts:
I build an electronic device which is used outdoors. A bundle of cables enter the device in a small 30mm diameter tube. This tube should be sealed so no dust/water/moisture enters the casing. It should be possible to remove tube easily for maintenance without damaging the sealing, tube or casing.

See the illustration below:

Illustration legend:

Orange: Casing
Green: Sealing
Blue: Tube

I assume there are common solutions for this problem and I am searching for either the correct term for this kind of sealing.

The illustration of the green sealing is just an assumption from my part how a such sealing could look like. It does not have to look and work this way. For me, the requirements for the sealing are:

Seals against dust, water and moisture.
For tube/cable with 30mm diameter.
Removable for maintenance without damaging tube, sealing or casing.

What standard solutions exist for this case?

What is the correct term for this kind of sealing?


texts:
I recently learned about ADSL and its modulation method DMT.

I know the frequency spectrum is split up into a number of orthoganally spaced bins:
Voice(PSTN) - Guard Band - Upstream - Downstream

Seeing as these bins are orthoganally spaced to prevent inter-bin interference, what is the use of the guard band between the PSTN frequencies and the upstream frequencies? The same goes for the small guard bin between the upstream and downstream.

I am by no means an expert in this area, so my apologies if I made a fundamental mistake at understanding this method.

Thank you in advance


texts: Voltage step up module and if I am using it correctly

texts:
I am making a "simple" bluetooth speaker and have followed instructions from a Youtube video on  how to assemble the components I have bought.

However... I am finding that the rechargeable li-po battery that I am using for power in conjunction with a protection circuit and voltage boost module doesn't seem to want to do so...

Could somebody tell me what would be the best way forwards?

This is the module I am using, and this the battery.

The battery is rated for 3.7V as written on the side of it, but when connected to this battery protection circuit it seems to drop to 3.4V (assuming for protection purposes?).

Given that I am working with 3.4V at FULL charge, I charge up an then switch the circuit on and adjust the boost module to output a steady 6.5V as per the Youtube video. I assume this is done such that as the battery is drained and the voltage reduces, the boost will remain above the 4.5V required to power this bluetooth amp board...

Could somebody please inform me if I am wrong about this?

Just FYI, the speaker works perfectly when I am powering through the micro-USB cable connected to a wall charger.

I am new to the world of hobbyist electronics, so my knowledge is limited.

Update (more info)
I just had a quick test of the voltages throughout the system with my multimeter.

Battery terminals: 3.2V
Protection board output: 2.5V
Booster V-in: 2.5V
Booster V-out: Varying unstably between 3.5 and 4.2V (I did not have a capacitor connected across the V-out terminals at this time)

I have drawn a very rudimentary diagram to hopefully explain my layout:


texts: Need to find the component with marking 500

texts:
I am having hard time in finding what this component is . It has 8 pins and a marking on it says 500.  It has 2 pins on bottom on each side and two on each top side.

On the board 2 pins on left bottom are as inputs and two on the right are used as outputs.

I searched for it on SMD codeBook as well as this site but couldn't find anything.

I hope some one can help here. It is part of a rs485 circuitry on a board. There is another Sot23 marked W216j I couldn't find this also. This is how they are connected. Please ignore the pin names on SOT23/IC1

**UPDTAE""

I have got the product and its the exact one by help provided by @Tom and @jp314
This is the product that was marked 500, The SOT package is quite lear but still I couldn't get the exact one.


texts:
TL;DR : I want to use a darlington transistor model(BD679&BD680) within LTspice. Can I do that by using default symbols npn or pnp from component selector menu?

I have done it with TIP41C & TIP42C, the downloaded file for them were like this:

******
* Spice Model
* Item: TIP41C
* Date: 8/11/10
* Revision History: A
* ==========================================================
* This model was developed by:
* Central Semiconductor Corp.
* 145 Adams Avenue
* Hauppauge, NY 11788
*
* These models are subject to change without notice.
* Users may not directly or indirectly re-sell or
* re-distribute this model. This model may not
* be modified, or altered without the consent of Central Semiconductor Corp.
*
* For more information on this model contact
* Central Semiconductor Corp. at:
* (631) 435-1110 or Engineering@centralsemi.com
* http://www.centralsemi.com
* ==========================================================
******
*SRC=TIP41C;TIP41C;BJTs NPN; Si;100.0V  3.00A  3MHz   Central Semi Central Semi

.MODEL TIP41C  NPN (
+ IS=290.83E-15
+ BF=113.55
+ VAF=100
+ IKF=1.9905
+ ISE=1.3946E-12
+ NE=1.4763
+ BR=.1001
+ VAR=100
+ IKR=10.010E-3
+ ISC=320.65E-12
+ NC=1.8994
+ NK=.58929
+ RB=.71129
+ CJE=348.44E-12
+ VJE=.78228
+ MJE=.42865
+ CJC=184.26E-12
+ VJC=.47897
+ MJC=.40458
+ TF=36.381E-9
+ XTF=100.32
+ VTF=21.563
+ ITF=28.791
+ TR=10.000E-9 )

I have just copied and added .MODEL part to the end of  standard.bjt file. And I was able to choose it from "pick new transistor" menu. So, I now downloaded the library file for BD680 darlington transistor but it is more complicated than the former TIP41C case.

**************************************
*      Model Generated by MODPEX     *
*Copyright(c) Symmetry Design Systems*
*         All Rights Reserved        *
*    UNPUBLISHED LICENSED SOFTWARE   *
*   Contains Proprietary Information *
*      Which is The Property of      *
*     SYMMETRY OR ITS LICENSORS      *
*    Modeling services provided by   *
* Interface Technologies www.i-t.com *
**************************************
.SUBCKT bd680 1 2 3
* Model generated on Feb 14, 2004
* Model format: PSpice
* Darlington macro model
* External node designations
* Node 1 -> Collect
* Node 2 -> Base
* Node 3 -> Emitter
Q1 1 2 4 qmodel
Q2 1 4 3 q1model 2.46191
D1 1 3 dmodel
R1 2 4 8000
R2 4 3 120
* Default values used in dmodel
*   EG=1.11 TT=0 BV=infinite
.MODEL dmodel d
+IS=1e-12 RS=10 N=1 XTI=3
+CJO=0 VJ=0.75 M=0.33 FC=0.5
.MODEL qmodel pnp
+IS=2.23835e-12 BF=149.682 NF=1.2 VAF=59.0895
+IKF=0.118079 ISE=9.09119e-14 NE=1.42175 BR=0.587475
+NR=0.75 VAR=100.388 IKR=0.0934405 ISC=9.09118e-14
+NC=2 RB=15.5445 IRB=0.450416 RBM=12.8364
+RE=0.0939759 RC=2.76027 XTB=0.497353 XTI=2.9942 EG=1.05
+CJE=1e-11 VJE=0.75 MJE=0.33 TF=1e-09
+XTF=1 VTF=10 ITF=0.01 CJC=1e-11
+VJC=0.75 MJC=0.33 XCJC=0.9 FC=0.5
+TR=1e-07 PTF=0 KF=0 AF=1
.MODEL q1model pnp
+IS=2.23835e-12 BF=149.682 NF=1.2 VAF=59.0895
+IKF=0.118079 ISE=9.09119e-14 NE=1.42175 BR=0.587475
+NR=0.75 VAR=100.388 IKR=0.0934405 ISC=9.09118e-14
+NC=2 RB=15.5445 IRB=0.450416 RBM=12.8364
+RE=0.0939759 RC=2.76027 XTB=0.497353 XTI=2.9942 EG=1.05
+CJE=1e-11 VJE=0.75 MJE=0.33 TF=1e-09
+XTF=1 VTF=10 ITF=0.01 CJC=0
+VJC=0.75 MJC=0.33 XCJC=0.9 FC=0.5
+TR=1e-07 PTF=0 KF=0 AF=1
.ENDS

So I assume I cannot just copy this into standart.bjt file.

When I was also trying to use LM741, I added its library file in form of .sub file to the /sub folder of LTspice and I was able to use .lib LM741.sub. I have been choosing opamp2 from component selector menu and just renaming its name to LM741 was sufficient. But this method did not work for BD680 darlington. I assume opamp2 for intended to be used with sub models however pnp is not. But I am not sure.

So what can I do?

update: I think dragging the library file into LTspice and creating a new symbol can be one of the solutions. I have just figured it out. So, you can provide better solutions if you have any.


texts: How to calculate Input backoff per carrier of a satellite

texts:
I was trying to calculate the sizing of SSPA in my satcom network where input backoff per carrier is required to calculate Power flux density.
My current network configuration in C band is
Total carriers=15
SFD of satellite=-85dbW/m2

Please help me how to calculate input backoff per carrier.


texts:
I have recently started learning to use pic micro controller. I am using pic16f887 mc and for programing using mplabx with xc8 compiler. My micro controller is getting reading from switch and turning on led when I use any digital i/o pin except rb0-rb5.  I don't know why those pins are not working. I made the circuit in proteus also.It is giving me the same result. Can anybody tell me why this is happening? Here are codes and schematic where I used rc7 for input and that works perfectly.

void main(void) {
OSCCON=0x76;
TRISC7 = 1; //RC7 as INPUT PIN
TRISD1 = 0; //RD0 as OUTPUT PIN

RD1 = 0; //LED Off

while(1)
{
 if(RC7 == 0) //If Switch Pressed
 {
    __delay_ms(100);
    if(RC7==0)
    {
        RD1 = 1; //LED ON
        __delay_ms(3000); //3 Second Delay
          RD1 = 0; //LED OFF

      }

    }
  }
 return;
}


texts: Why does the cascode current mirror have a lower output capacitance?

texts:
Fig 1

Fig 2
Comparing Fig 1, a normal current mirror, with Fig 2, a cascode current mirror, why is the output capacitance at the drain of Q3 in Fig 2 lower than that at the drain of Q2 in Fig 1?


texts:
I'm trying to find an efficient way of calculating an inverse on an AVR (or approximating it).

I'm trying to calculate the pulse period for a stepper motor so that I can vary the speed linearly. The period is proportional to the inverse of the speed (p = K/v), but I can't think of a good way of calculating this on the fly.

My formula is

p = 202/v + 298; // p in us; v varies from 1->100

Testing on the Arduino, the division seems to be ignored completely leaving p fixed at 298 (though perhaps this would be different in avr-gcc). I've also tried summing v in a loop until it exceeds 202, and counting the loops, but this is quite slow.

I could generate a lookup table and store it in flash, but I was wondering if there was another way.

Edit: Maybe the title should be "efficient divide"...

Update: As pingswept points out, my formula for mapping period to velocity is incorrect. But the main problem is the divide operation.

Edit 2: On further investigation, divide is working on the arduino, the problem was due to both the incorrect formula above and an int overflow elsewhere.


texts:
I've been thinking about this for a while.
Now that we have means to generating electricity in DC, what would it take to do a DC wiring for an house to work along the traditional AC wiring.

Specifically, I would be very interested in understanding the formulas to compute dissipation, and get advise on how high should be the voltage for distribution to avoid wasting too much power due to omh's law.
It is fair to assume that every outlet will be no further away than 30 meters (90 feet) from the source.
Also, worth assuming that the outlets would be anything from a 5v usb, to a USB-c that can negotiate up to 20v.

Power wise, each outlet will need to support from 10w to up to 100w.
What would be the formula for computing resource waste of the buck conversion? DC Solar (13v) -> DC (distribution) -> DC Outlet.

I think the final question boils down to: can this be more efficient than a system that has to do DC -> AC -> DC conversion (which I believe has a 89% energy efficiency).


texts:
I have a suspected bad transformer in a board that has come out of a treadmill which I'm trying to use for another project. I suspect the transformer as I have removed all connectors and replaced one by one until from the main switch back until the the RCD trips and it's when the transformer is connected that I start to get the problem, so this is my first point of investigation.

The transformer is set up like this:

The transformer has 2 connectors sharing 6 wires which I have identified as per the diagram on the transformer as 2 red (240v), 2 yellow (22v), 2 black (10v).

I'm trying to confirm the transformer is the problem and have done the following:
Tested continuity across all combinations:

Yellow wires have continuity with each other
Black wires have continuity with each other
Red wires have no continuity.
No continuity on any other combinations (i.e. blacks to yellows to reds etc)

I've also measured the voltage coming out of each coloured wire pair when putting the transformer near another working transformer (technique I found on a youtube video) and had the following outputs which relative to the diagram seem fine.

Red - 0.55v
Yellow - 0.055v
Black - 0.001v

Question 1 - given that yellow and black wire pairs have continuity, should the red wires have continuity too. It seems weird that winding would have a voltage when near another transformer if it doesn't have continuity.

Question 2 - is there any other tests I can do to check if this transformer is the problem or if it's further into the circuit.


texts:
I'm currently in the process of designing a simple CPU in VHDL using Xilinx ISE and ISIM. The design portion is going remarkably well, but I can't seem to figure out a way to do verification in a consistent  manner.

Right now I have a VHDL test bench that I update to test the function I'm working on at any particular moment. This is very ad-hoc, and it does not help me to catch regressions and cannot be used to verify compliance with specification/instruction set.

I've thought about developing an extensive test suite, but the problem is that the potential state of a general purpose part as a CPU is huge compared less generic components.

I am looking for a method that allows me to perform design and testing in a more controlled manner. Some sort of "hardware TDD" if you will. Does such a thing exist? Can it be applies relatively easily to general purpose parts such as a CPU?


texts:
Can anyone explain how Rgd is obtained? I plugged both Ix into Rgd expression but did not get the correct result.

here is my attempt

I cannot proceed. What did I do wrong? How can I get rid of Vx ?


texts: Is a 600+Hz R/C Servo/ESC refresh rate possible?

texts:
In the R/C multirotor scene, the trend at the moment is to have very high refresh rates on your ESCs (speed controllers).

My understanding of how servos/ESCs are driven is a 1-2ms pulse is sent to the servo/ESC. at the standard rate this happens every 20ms giving a 50Hz refresh rate.
More here: WikiPedia article on Servo Control

I can understand how this happens up to 500Hz, where full throttle (or full lock on a servo) would mean the line is just pulled high (one 2ms pulse ends at exactly the same time as the next one begins), and 0 throttle (or full lock the other way on a servo) would be a 50% duty cycle signal with a period of 2ms.

I have just seen this: HobbyWing X-Rotor 20A OPTO ESC For Multirotor Applications which is an ESC that states: "supports a signal frequency of up to 621Hz." How is that possible? By my calculations the pulses would overlap at full throttle.


texts: Why do three series connected 1.2 V NiMH batteries read 4.16 V when charged?

texts:
I have a 7.2 V Dremel.  The old battery pack was dead, so I had to replace the six rechargeable batteries inside.  The originals were 1.2 V 700 mAH AA; I could only find 1.2 V 1100 mAH NiMH AA batteries.

The pack design has three of the batteries grouped together, with nickel strips (shown in blue) connecting them in series:

There are two groups of these three-packs inside, but the two battery groups are not connected to each other.  So the pack exposes four terminals, two plus and two minus.

The Dremel dedicated charger is marked as outputting DC 9 V at 0.20 A and indicates a 3 hr charge time (but does not shut off by itself).

I figured that since the original batteries were 700 mAH and I replaced them with ones rated 1100 mAH, I would need to charge them about 1.57 times longer.  So, I charged them for 4 hours and 45 minutes.  (At the end of this period, both the charger and the pack got really warm.)

When I checked the battery pack connections with a multi-meter, it read 4.16 V and 4.18 V, for each of the two groups.

My questions:

1) Shouldn’t each battery group read 3.6 V (i.e. 1.2 V per battery x 3 batteries in series)? Why am I seeing 4.16 V and 4.18 V instead?

2) Why is the charger output marked as 9 V? Wouldn’t this voltage damage the batteries? Or is the 9 V divided into two and each group gets 4.5 V?  Even so, 4.5 V is still greater than the series-sum of 3.6 V.

3) Is my duration calculation correct?  If not, and since the charger is rated at 0.20 A, how long should I be charging the battery pack?

EDIT PER winny's SUGGESTION:


texts: Why is there a short between my VCC and GND in this circuit?

texts:
I am doing a project where I am using a FPGA board which connects to a circuit I designed. It has a quad Comparator (LM339N), a few resistors and an LDR; two distance sensors (GP2Y0A51SK0F) are connected to it by wires, and the circuit gets it's voltage from the FPGA board (DE0-Nano, 4.80V). The comparators are also powered by the 4.80V from the board.

This is the schematic:

As you can see, the output of each distance sensor (this sensor only has 3 pins, I couldn't make the fourth hidden) goes to a comparator. The point was to turn the distance sensor into a proximity sensor and output '0' when it sees something at a certain distance. The FPGA then receives that '0' and acts. Somewhat the same with the LDR.

I can confirm everything worked when I used two different voltages supply when I tested this - one being 5V that goes into the distance sensor and one 3.3V that goes to the comparators. Both 3.3V and 5V came from a DC power supply.

Now, I'm using the DE0-Nano to supply power, the only source being one pin of 4.8V and one pin of GND. As you can see from the schematic, everything has one single power supply.

My problem - things are not working with the distance sensors; Trying to measure voltage at the output of each of the sensors I just get 0V, so obviously the comparators output nothing as well. I'm using a multimeter to try and check what the problem is, and when I tried to check for shorts (with a mode called continuity, I think), one of the following may happen (or together):

A short between VCC and GND - but there is no physical connection between them, I check that with resistance mode.
A short between the VCC and GND pins of the LM339N

1 and 2 will never happen at the same time.

A short between one of the outputs of the comparators (U1 or U2) and VCC. When this happens, The 3K pull-up resistors are also a short.

Like I said, there is no physical connection between VCC and GND so I assume that the short the multimeter is seeing is due to pins having the same potential?
Is it possible that the pull-up resistors are too small and that is why this problem happens?
Is it possible that I fried the distance sensors?

Thank you for your help, I have been testing this for days and trying to figure out what the problem is.

Edit - here are a few screen shots from scope:

This is the power pin:

This  is the power pin, zoomed:

This is the sensor's output:

The output stays like this no matter what, so it doesn't really seem like it is working. maybe the amplitude is increasing but I don't think it matters (it could also be the other sensor and I don't remember).

Those screen shots are from one sensor only - the other shows different results, but when checking their output, none seems to actually respond.


texts: State-transition diagram for a Mealy machine

texts: I created a state-transition diagram for the Mealy machine below. but I wasn't sure if it was correct. The part that confused me was that s1 has no edges.


texts:
I am trying to work out how to match a current source coupled with a capacitor to a 50 Ω load for maximum power transfer. Specifically I have a 6pf PIN photodiode which driven by a 2.5 ghz optical signal. At 2.5 Ghz the PIN diode has an impedance of -10j Ωs.

$$\begin{align}
Z_c &= \frac{1}{jwC}\\
 &= \frac{1}{j2\pi f C} \\
 &= \frac{1}{j2{\pi}2.5 \cdot 10^9 \cdot 6 \cdot 10^{-12}}\\
&\approx -10j ~ \Omega
\end{align}$$

simulate this circuit – Schematic created using CircuitLab

I have seen impedance matching but usually they are matching a non reactive source impedance, e.g. 50 Ω, to some complex load. In this case the source has a purely complex impedance of -10j and I want to match this to 50 Ω by using some transformer method (Single stub, 1/4 wave or combination or what ever). One conceptual problem I have is that that the load and sources should be complex conjugates of each other and If I manage this then I would end up with a purely inductive impedance and the circuit load and source would be a simple LC resonator and no power transfer would occur ? I haven't done this for quite a while and would appreciate some guidance.

I have seen some approaches which match a mixed complex load with real and imaginary parts, but not a matching a purely complex generator to a purely real load, ie 50 Ω.


texts: I'm trying to light a series of LED's at different voltages. Ranging from 1 to 10 volts (hand crank generator). So for example at 1 volt the first LED lights up, at 2 volts both the first and second LED's light up and so on. I think an LM3914 in bar mode is ideal. But I'm not sure if I understand how to set the dividers. Is it as simple as grounding the ref low (pin 4) and just running 10 volt to ref high (pin 6)?


texts: Atmel and coil close on a board - is interference an issue?

texts:
I'm going to build a circuit which uses AVR uC (probably ATmega8 or some ATtiny) and a coil with iron powder ring core. The coil has 330uH and will be working under current of approx. 6A.

I'd like to make the PCB as compact as possible. Is there a danger that coil would interfere with uC? Yes, I'll be doing analog measurements with the controller.


texts:
A conductor in case 1 has two separate uniform magnetic fields   \$B_1\$ & \$B_2\$:

The magnetic fields(the blue rectangles are the field regions parallel to the conductor, while X's are the field lines going into the page) both changing at the same rate over the same duration of time, inducing an EMF(\$\epsilon\$) on each part with respect to their magnetic fields.However, \$B_1\$'s change is in a way that it's induced \$\epsilon\$ opposes the other:

Now it's quite simple to solve, since this is not a closed loop(only focusing on EMF) the net EMF would be (A) $$ V_n = V_2 - V_1 = 0$$

However, what if I changed things in case 2, by changing the region of the magnetic field of \$B_1\$ , yet made the rate of change between the two fields the same, so that their induced EMF's are both the same:

What is the end result here? I don't know how this affects the induced EMF's cancelling each other; they are still the same and opposing one another:

With that change, is this expression still true?

(B)$$ V_n = V_2 - V_1 = 0$$

If not, why?

NOTE: This is an open circuit, focusing only on the behavior of the opposing voltages, it the sake of understanding.


texts: Inter Device Expandable Network Protocol?

texts:
Currently I am working on a project where I need to install several peripheral devices in the network along with a master. This total system have some industrial application. I need to have the network expandable as there might be device addition or subtraction from the network. The device might gets faulty so will need to replace. All the peripheral devices are fairly big and will cover around 2ft X 3ft area, leaving behind the minimum communication port to port distance at least of 3 ft.
Now, I have thought of SPI, I2C, CAN Bus, LAN networking. I have some doubts in my mind to select between them. Please consider me newbie in the field of communication and help me to select the best one.

SPI: I have already rejected the protocol as my requirement is off-board / inter-device communication. Also I need 2 way communication, which might flood the master device with bunch of CS/SS wiring and make it messy in every aspect.

I2C: It seems promising to me, but if you consider the length of the network I doubt It will work proficiently. The speed of the network is not the big criteria till it drops bellow 100 kBPS.

CAN Bus: Totally confused and didn't have found much of documentation w.r.t. AVR MCUs. I seek your help on this seriously.

Wired LAN: Good option, can be implemented where the systems are closely maintained. but when it comes to a scenario where you don't have any control over the number of devices, that makes difficult to provide service. Mainly maintaining the IP records when you replace the device will be the headache to the operator.

I have already have implemented WiFi communication between industrial devices for my last project, but that have problem of random disconnection due to hardware limits.

I am expecting here some guidance for selecting the protocol.

BTW: The heart of all of my peripherals is ATmega32U4 MCU and the Master device will be a PC.


texts: Why does output impedance behaves this way

texts: Why does the output impedance(Ro) of a common emitter amplifier is considered in parallel with the collector resistance(Rc)...as according to the KVL--->Vcc=IcRc+Vce+IeRe  they seems to be in series....??


texts: Some questions about antistatic wrist strap

texts:
The photo below shows an antistatic wrist strap grounded to the chassis of a PC through its alligator clip:

I have three basic questions:

If the chassis above is not earth grounded, does it make no sense to connect the alligator clip to the chassis? In other words should the alligator clip of the wrap always be grounded to the mains earth in a way?
Is this type of wearing antistatic wrist strap aiming to protect the human from ESD shock or sensitive electronic circuits in general?
Is this wrap also used to protect from 230V AC line hazards or used only for ESD?


texts: PNP too big of a voltage drop accross Collector Emitter

texts:
I have a rather simple circuit that acts as an overvoltage protection switch with an input control signal to enable/disable the output.On the final output I am driving a motor that consumes around 2A in the startup phase for 200-300ms and around 500mA constant. My input voltage is in the region of 12-30V

The issue is that I have a very large voltage drop across the transistor when the motor starts to spin up, but according to the datasheet this transistor should be able to handle large current. main pnp datasheet

Does anybody know why the drop across my FZT956 PNP transistor is so high? I need to reduce it because the motor is used in a pulsed fashion so I need to minimise the heating in this period.


texts: Who is the CPU or FPGA maker in this picture?

texts:
For the life of me I am unable to find or determine who makes the chip with the label shown in the image:

HLi, HL Inc, KLi?


texts: We all know that in a battery, there is no current flowing but why is that in the instant that you connect a wire, current will now flow? How about if the wire is connected to a light bulb and you connected it to a battery, is there a difference between the speed of the current flow as compared in the former setup (wire alone)?


texts: What will happen if I don't use RS232 driver for UART?

texts:
I already read some topics about the difference between UART and RS232, but I still didn't get it.

I read that UART is kind of logical interface, and RS232 is physical interface. But I don't understand that.

We usually use a RS232 driver for UART. Because the driver will make a link between the logical and the physical interface.
To really understand that, I'm asking what will happen if we don't use it.
Is this driver kind of buffer? So we need it?
What will this driver do?

(We will suppose we have the same level (3.3 V on both side)

Thanks


texts: How to add thermal model on SOAtherm-Nmos block in LTspice

texts:
I would like to analyze the junction temperature of a SCT3022AL MOSFET during switching operation on LTspice.

Followint the Spice model and the thermal model of the MOSFET:

https://www.rohm.com/products/sic-power-devices/sic-mosfet/sct3022al-product/documents

I'm going to use SOAtherm-Nmos block.

Unfortunately the thermal model of SCT3022AL is not alredy inserted inside the block.

How can I add the thermal model given in the above link into this block?

Thank You.


texts:
I'm using the MC9S12DP512, Motorola's microcontroller. I was executing a service and ,at the end, I put low logic level at the pins PS4, PS5 and PS6, then after that, I configured these pins as inputs.

However, after put these pins as inputs, they present high logic level . Why it happens ?

In the datasheet says:

  Port S Pull Device Enable Register (PERS)

  This register configures whether a pull-up or a pull-down device is
  activated, if the port is used as input or as output in wired-or (open
  drain) mode. This bit has no effect if the port is used as push-pull
  output. Out of reset a pull-up device is enabled.

  PERS[7:0] — Pull Device Enable Port S

  1 = Either a pull-up or pull-down device is enabled.

  0 = Pull-up or pull-down device is disabled.

I thought that a pull-up would be enabled, but it not happens in my code, so I checked up the motorola driver's code to verify if it is a pull-up by default. And there it is the motorola's code :

/*** PERS - Port S Pull Device Enable Register; 0x0000024C ***/
    typedef union {
      byte Byte;
      struct {
        byte PERS0       :1;                                       /* Pull Device Enable Port S Bit 0 */
        byte PERS1       :1;                                       /* Pull Device Enable Port S Bit 1 */
        byte PERS2       :1;                                       /* Pull Device Enable Port S Bit 2 */
        byte PERS3       :1;                                       /* Pull Device Enable Port S Bit 3 */
        byte PERS4       :1;                                       /* Pull Device Enable Port S Bit 4 */
        byte PERS5       :1;                                       /* Pull Device Enable Port S Bit 5 */
        byte PERS6       :1;                                       /* Pull Device Enable Port S Bit 6 */
        byte PERS7       :1;                                       /* Pull Device Enable Port S Bit 7 */
      } Bits;
      struct {
        byte grpPERS :8;
      } MergedBits;
    } PERSSTR;
    extern volatile PERSSTR _PERS @(REG_BASE + 0x0000024C);
    #define PERS _PERS.Byte
    #define PERS_PERS0 _PERS.Bits.PERS0
    #define PERS_PERS1 _PERS.Bits.PERS1
    #define PERS_PERS2 _PERS.Bits.PERS2
    #define PERS_PERS3 _PERS.Bits.PERS3
    #define PERS_PERS4 _PERS.Bits.PERS4
    #define PERS_PERS5 _PERS.Bits.PERS5
    #define PERS_PERS6 _PERS.Bits.PERS6
    #define PERS_PERS7 _PERS.Bits.PERS7
    #define PERS_PERS _PERS.MergedBits.grpPERS

I didn't understand very well this passage below:

byte PERS0       :1;                                       /* Pull Device Enable Port S Bit 0 */

The ":" is doing exactly what ? The motorola driver's code that I put here is doing a pull-up by default ?

[edited]

I want to put the pins at low logic, and after that, as input, because I don't want they stay energized at the end of the procedure.


texts: dsPIC 33EP128MC506 will not read RB8, appears to be software problem

texts:
I'm using a dsPIC 33EP128MC506. I have two PCBs with this chip, both displaying the same symptoms, implying it's not one-off damage. RB8 is definitely being driven to 3.3 volts, confirmed with a multimeter and a scope. I've updated MPLAB X and the XC16 compiler to the latest versions, without effect. If I try to read RB8 immediately after setting the TRISB register, before any peripherals are enabled, I still get zero. Nothing in the errata seems to be relevant, but I could have missed something.

I've confirmed via serial output that TRISB<8> is set. TRISB is set to 0xFFFF, so one related problem where the wrong bit controls the direction seems to be inapplicable. RB9 also works fine as an input, so it doesn't appear that the upper half of PORTB is consumed by JTAG as others have reported. There are no writes to PORTB in the code, and there are no writes to LATB<8>. RB7 works fine as an input, as does RC13 (the physically adjacent pin). Peripherals that share the RB8 pin are:

T4CK, Timer 4 external clock input; unused and explicitly disconnected (T4CONbits.TCS = 0, confirmed by serial output)
TCK is JTAG test clock input pin; _FICD configuration word sets JTAGEN_OFF
ASCL1 is Alternate synchronous serial clock input/output for I2C1; _FICD configuration word sets ALTI2C1_OFF, and I2C is not used
RP40 is remappable peripheral 40; RPOR3 is 0x0000, confirmed by serial output, and the bit code for RP40 is never referenced in the program in decimal, hex, or binary
CVREF10 is Op amp/comparator voltage reference output; explicitly disconnected (CVRCONbits.CVR1OE = 0, confirmed by serial output)

I'm out of ideas.


texts: How frequency generator in telephone works

texts:
I was doing some research, on how telephone works, and I found that when user, click numbers they are converted to frequency and passed to wire. I want to know how the frequency generator work, what is it's official known as and what frequency range it work under?

One more thing, when user click number does it convert to signal and send to wire or when 10 digits are pressed then that group is converted to signal and passed to wire?


texts: Which way does current flow in (automotive) spark-plug wires?

texts:
Every modern gasoline engine, that I'm aware of, uses an ignition coil to generate "spark".  Usually, a current is introduced into the primary of the ignition coil and then interrupted (by a solid-state switch of some sort) causing a spike in voltage at the secondary of the ignition coil.  Depending on how the secondary winding is connected to the spark-plug wires (through the distributor), the resultant current could presumably be in either direction.

Is there a good reason for current to flow "towards" the spark plug versus "away" from the spark plug?  Is it the same way on all vehicles?  How about
small engines (lawnmowers, snowblowers, chainsaws, outboards)?

All of this is significant because the cost of automotive timing lights is largely due to the cost of the inductive (clamp on) pickup.  A positive or negative "edge" from the inductive pickup fires a Xenon flash tube which illuminates the timing marks.  Some alternate way of developing an edge (relative to chassis ground) could be significant.


texts: How can I make nichrome wire perform more consistent heating in liquids?

texts:
Was told to ask this here from chat.

I have 32AWG nichrome water that I want to use to heat liquids. I submerged it into water and noticed that the part outside of water is glowing red, but the part submerged is not. This is expected as the water will bring down the temperature of the submerged part.

I'm thinking of putting the wire inside something that has high heat transfer, but low conductivity so that the wire can heat more evenly inside and also provide protection from accidental contact. My questions are:

What is the best material to use?
Is there a better method?


texts: while proving flatband voltage, I can`t understand what is different between Pie(s) and Pie(s0)

texts:
The picture above is proof of the flat band voltage formula by gate voltage formula.
I can`t understand what is different between Vox and Vox0 and also Pie(s) and Pie(s0). Could you explain what do they refer to in the energy band diagram, please? Then I think I can understand the next step "= Vox+Pie(s)+Pie(ms)"


texts: ULN2803 not working like I expect, or at all

texts:
I am a total electronics noob trying to build a simple circuit for a jukebox that I'm making using a Raspberry Pi and an old jukebox wallbox.  I'm a computer systems engineer by trade.  And it's my first time asking a question on SE, So please go easy :)
I am integrating a Raspberry Pi with a 3 digit LED display.  Each of the numbers uses a single ground across all 7 segments, and each segment is tied together on the numbers.  (IE, the top segment is a common input across all three digits, and if I wanted to light it up on the first digit only I would connect the ground on the first digit only.)  The Pi is capable of lighting up all 7 segments at a time on a single digit using GPIO, but that would be too much current to sink with a single ground GPIO on the Pi.  I saw somewhere a recommendation that a ULN2803 could be used for switching common connections.  By taking a GPIO high on the Pi it would connect the corresponding pin on the ULN2803 to common, completing the circuit.  Basically acting as a solid state relay.  So I got a small breadboard and some ULN2803APG and tried building the circuit with an LED. I have common from the breadboard bus connected to pin 9, and common from the LED going to pin 18, and the LED connected to the + bus.  My understanding of how this should work is that when I take ULN2803 pin 1 high by connecting it to the power supply positive lead the LED should light because the ULN2803 is connecting the negative lead.  But that doesn't happen.  If I move the LED connection from ULN2803 pin 18 to common the LED will light, so I know the LED is good.  But I have no idea why this isn't working.  Do I have the wrong idea of how this should work?  Or do I have the wrong ULN2803?  Or am I too low voltage?  Or am I doing something else wrong here?
For a ULN2803 pinout I'll reference this drawing:
https://components101.com/asset/sites/default/files/component_pin/ULN2803-IC-Pinout.png
Hopefully I've explained everything well enough.  The LED and keyboard work the same way with common grounds so I have to figure this out to be able to integrate with them.  Altering them is out of the question, nothing good will come from trying to alter 40 year old PCB.  Thanks for your help.
Here's my breadboard circut:

The eventual LED matrix that I need to integrate with:

EDIT-- So I was partially mistaken... the LED does light, but it's so faint that unless you're looking straight on at it (IE, not from the side) you can't see it.  Not sure what that means.


texts: Falstads circuit simulator : capacitors have initial voltage?

texts:
I started playing with Paul Falstad's circuit simulator applet to see if it would be useful for my intro physics students. However, I'm running into a quirk regarding capacitors which I don't really understand. Namely it appears that capacitors start with a voltage difference of 1 mV, with the positive terminal being whichever endpoint was chosen first. Is there an obvious way to eliminate this behavior? I would much prefer that capacitors start with no initial voltage, i.e., uncharged. (I can 'hack' a solution as such: create two capacitors of capacitance 2C and connect their positive terminals. This creates an effective capacitance of C and ensures no voltage difference across the two negative terminals. But such a procedure seems tedious to do repeatedly.)

(Link to example circuit)


texts: Output of op-amp getting as a constant voltage of 500 mV in PROTEUS

texts: Earlier i tried generating a +5V to -5V square wave using an op-amp as an astable multivibrator . The wave had a frequency of 1 kHz. The op-amp was given +Vcc of 5.5V and -VCC of -5.5V. I got the desired square wave at the output. Now i want to generate 0 to 5V square wave using the same circuit. However when I tried simulating the circuit taking -Vcc as 0V im getting a constant voltage of 500mV. Can you please help me to troubleshoot the circuit. The op-amp I have used is an LM324.


texts: Why doesn't this Colpitts oscillator design work?

texts:
falstad schematic link

My setup:

I made many attempts at building a Colpitts oscillator, and this one by far supposed to be the most advanced and with high chance of success.

Yet, it's still not enough. I tested voltages on the amplifier and they all seem to be as I predicted in calculations, so the amplifier should be fine. I researched the air gap problem on cylinder rod cores and used this calculator to verify that this solenoid of around 300 turns, 0.1 mm wire, 10 mm diameter, 94 mm rod length, 100 initial permeability (for carbon steel) should have around 25 effective permeability and so inductance is from 5 to 7 mH, which should give around 9 to 11 kHz frequency. Yet all this huge effort that I put into this thing seems like a waste now.

Theory does not work in practice.

What could be the reason?


texts: How to estimate the maximum current provided by a transformer?

texts:
I have a transformer that outputs 14.3V (AC of course) and the current in short-circuit is about 13A (made a beautiful spark when I measured it :) ). Can I guesstimate from here what is the 'normal' current that I can get from this transformer without overheating it? I need 1.3A.

Other data:

Input voltage: 230V
Output 1: 14.3V
Output 2: 18V
Transformer's iron core: 4.5 x 5.5 x 3 cm.
It is written on the transformer that it has an internal thermal fuse.
Transformer name: transformer SF-57E/11B/18A
From an music player (tape, cd, pickup, radio) with speakers of about (2x) 4-8W.


texts: Determine the number of bits before receiver misses a bit

texts:
A transmitter sends 100 bits per second but the receiver's clock runs too slowly causing it to measure once every 0.0107 seconds.  How many bits are measured in a row before the receiver misses a bit?

I have considered r=100bps and t_miss= 0.0107 and compute the time as 1-t_miss in order to determine the number of bits before a receiver misses a bit. Can anyone clarify me about this?


texts: What electronic design considerations relating to peak accelerations experienced, should be taken into account?

texts:
When designing the layout of an electronic circuit for a smartphone, are there any ways in which the electronics can be designed to be able to withstand larger accelerations/shocks.

To aid the above design, I am also trying to determine the maximum acceleration the electronics within a typical smartphone can withstand.

I have found this IEEE paper:
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=1644050&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D1644050

It seems to say that cell phones can withstand up to 2000 G for several milliseconds before experiencing damage to their solder connections. However this is an old paper, and thus very different to today's smartphones.


texts:
I am currently using LTC2311 as ADC with CMOS setting in my circuit. However, I cannot seem to get any output out in the microcontroller (I use the STM32 Nucleo development board).
My question is that

In the datasheet, it is mentioned that to start the conversion the CNV pin needs to be triggered by a low jitter pulse of 38.1ns to achieve the maximum rate of conversion.

What is the most effective way to send the CNV signal ? should it be done by the usual GPIO pin or with the pin specially assigned for chip select

For the clock signal, it is mentioned that

The falling edge of this clock shifts the conversion result MSB first onto the SDO pins. A 105MHz external clock must be applied at the SCK pin to achieve 5Msps throughput.

I am currently using the microcontroller's internal clock of 48MHz. Does this affect the data that is sent? I am aware that this changes the data sampling rate, but apart from that is there any effect on the output?
is there any better way to generate a clock signal for the output? if so, how?

Thank you so much for your help, It will help with my thesis so much.


texts:
I know what torque is but I find difficult to understand what Torque: 3kgcm means ?

I am not sure, how much weight that motor can carry, and I want to know how I can calculate that.

Please give me some hints :)


texts: Switch Debounce Topology for Rotary Encoder

texts:
I'm looking to debounce the output of a rotary encoder I'm using as a switch to ground with a pull-up. Looking online I saw the debouncing circuit in Figure 2 and read about it here. However, I also saw the first image below and read about it here. Is one better than the other for my application? According to the datasheet, the GPIO of the imx6sl I'm using has a Schmitt trigger and input hysteresis, so I'm assuming having a capacitor connected to it is okay.

Figure 1

Figure 2


texts:
I am designing high pass RL filter. R is 550 [Ohm], L is 220 [uH]. I calculated that time constant is therefore 0.0000004 [s] and -3 dB pulsation 2 500 000 and frequency 397 887 [Hz]. I put this on the breadboard and connected JDS 6600 signal generator and Rigol DS1054Z oscilloscope to test it. For testing I apply sine signal of 5 [V] (Vpp, amplitude) and varying frequency. As expected I observe decreased amplitudes of the signal at the output for low frequencies and increasing amplitudes for signals of increasing frequency. Using transfer function

|H(j omega)| = 1 / sqrt(1 + (1 / (omega tau)^2))

I calculated that 0.95 signal attenuation should happen at 1 210 781 Hz (|H(f=1210781)|=0.95) and that would mean that I should see about 4.75 V at this freq, but in practice I get this value at about 1 MHz.

Why do I see such a big difference?

simulate this circuit – Schematic created using CircuitLab


texts: A/D conversion improvement through Arduino

texts:
I have a certain analog signal v(t) which varies from 0 to 2V, which I want to be read by Arduino.

I know that Arduino can read it through the function AnalogRead, and the result will be a sequence of numbers from 0 to 1023. Now, I have some doubts:

The input range 0 - 5V is mapped to 0 - 1023. Therefore, if I get the result X and I want to find the original input voltage V, I have to apply the formula: V = X * 5 V /1023. Correct?
The output range is 0 - 1023: this means that Arduino uses 10 bit for the A/D conversion. If I am correct, this means that the Arduino resolution is equal to 5V/1024 = 4.88 mV. But my signal varies from 0 to 2V, so there is a waste of bits. I think the conversion might be better. For instance, if all 10 bits were used for the range 0 - 2V, we would get a resolution of 2V/1024 = 2mV. Any solution? Moreover, what does it happen if I decide to amplify my voltage with a gain = 2.5? Is there a benefit?


texts: Pot Power calculations is a searching process to determine the peak power (75- 99 % of linear pot). Why is this not normally discussed?

texts: Here are the math relationships involved.  The maximum theoretical power requires a searching process.  It is important because the user may park the pot in that position.


texts: SMPS stability near and above switching frequency

texts:
I am simulating in LTSpice a switched-mode power supply (LT3845) at a frequency of 150kHz. I am measuring the loop gain at the feedback node according to this article.
The way I understand it, the simulated loop gain is only meaningful up to around ~1/10 of the converter switching frequency. Any frequencies higher than that and the converter can't react fast enough and the waveforms stop behaving in the linear region (cosine in, cosine out). Intuitively this says to me that the converter should be inherently stable from this point onwards to higher frequencies because it shouldn't be possible to be driven to instability when the converter itself cannot react to the speed of the disturbance (and instead settles for the average).
But then I look to a number of papers/articles that appear to measure real hardware loop gains using network analyzers into the MHz range. Why? I would expect the data to be meaningless above a certain point.
Edit: I did find one paper here that suggest I am approximately correct, see pg. 33.


texts: How to determine wattages on an applications note schematic?

texts:
Specifically, I refer to Fig 18 on Page 14 of this datasheet for dual supplies.

Really nice, really "simple" to use 2x40W power amp I want to try out. Unfortunately, I'm a newbie and their schematic doesn't list any wattages or voltages. I assume with a max +/- 35V supply, if I get 50V caps I should be safe; but what about the resistors?

I imagine that the 4.7ohm ones would need to be large, but how large? 5W? How do I determine that? What about the others?

I'm not quite so foolish I want to just throw 1/4Ws everywhere and see what blows, but I'm also not skilled enough to be able to fully figure out how much amperage is flowing where.

I've tried finding similar problems but maybe I'm not good at research, I turned up empty. Any help or direction is really appreciated since I also don't want to make an amp out of 10W resistors. Not yet anyway.


texts: Switch to stop battery from discharging step up

texts:
I have a problem with this circuit.
The circuit works fine with the LDO, step up and battery management.
However, when the step up still remains on when the SHDN is set to zero.
Effectively, I would need to have a switch just before the step up to ensure that the battery does not discharge when the circuit is not in use.
What ways can I make a switch that does not involve a physical button or a physical switch? A relay is too big for the circuit. Any ideas?


texts: I was wondering if there are any common household devices from which I can get a small DC motor (I have a 9V battery...) to use with a breadboard? It'd take me a long time to buy one so I was hoping to just extract one from somewhere instead...


texts: Identifying a broken Rotary Encoder on guitar foot pedal

texts:
I have a guitar foot pedal, "EHX Stereo Memory Man with Hazarai", with a rotary encoder that broke off. Here is a picture of the knob in question:

Also, here is a picture of the circuit board, where the board is labelled 'ENC1' :

I have removed the rotary encoder but the shaft is snapped and deformed preventing me from testing its ability to be a push button. There are no part numbers on the part at all, and I emailed the manufacturer asking for the part number but was told only to send it in. There are 3 pins on one side of it and two on the other. If you like I'll upload some pics of just the encoder.

Update: I so here is a photo of the underside with a strange H8 marking. I think I found a suitable replacement part to try out show in pic 4:

That last one is a product i found at a company called Seeed and is titled a 'Rotary Encoder with Switch' for $3.70


texts: What's the name of the type of button that you have to press and hold for current to pass through it?

texts: I want to build a LED toy gun that lights up when the trigger is pressed. I need a button or switch that only allows current to pass through it only when the button is pressed and held down. What is the name of the type of switch/button I need to help me with this project?


texts:
I need to shift ±2.5 V signal into 0 V to 5 V for my A/D converter.

I found several designs, most of them using either voltage divider or an opamp.

I wonder, why not to use just a single reference to shift the voltage? It works on the breadboard so far... What are things I should be concerned with? Noise? Dynamic characteristics?

simulate this circuit – Schematic created using CircuitLab

PS: The Signal comes from opamp and is connected directly to ADC


texts: Cheap 12V to 5V DC-DC converter for PCB?

texts:
I want to clarify: I understand there have been many questions on this site regarding this same voltage conversion; however, what I am asking is not simply how to convert 12V to 5V but how to do it in a simple way I can integrate into a PCB.

My situation is that I am trying to create a 'smart' RGB light strip controller. The strip runs off 12V and the NodeMCU board controlling it runs off 5V (usually via USB). This is the guide I am following. Currently, I have the circuit wired up using jumper cables and I am using a USB car charger to convert 12V to 5V for the NodeMCU, and the whole circuit works perfectly.

However, I am now looking to design my own PCB which negates the need for all this wiring, as I am looking to use this circuit more permanently. Thus, what would be ideal is to simply plug in a 12V plug to the PCB, have that feed the strip and also be converted down to 5V and offered on a pin so that I can attach to the NodeMCU's Vin pin via a jumper wire.

My question is: What is the cheapest (requires the least parts) and best way of converting 12V down to 5V with through-hole components on a PCB? Other guides recommend using an 7805 converter due to its simplicity; however, I understand that this is extremely inefficient and can pose serious problems due to excess heat, which would not be appropriate considering that I am looking to have this circuit permanently on. If someone would be able to attach a schematic of a circuit which solves this problem reliably, I would be very grateful.

Thank you in advance for any help.

P.S. Is it be worth just simply copying the circuit inside the USB car charger, as this seems to work perfectly with barely any heat? If so, which components are required?

P.S. As for the current requirements of the NodeMCU, I am unsure exactly what the maximum draw could be, as I couldn't seem to find a straight answer online. However, I assume that it must be way under the possible current of even the most basic USB ports, as it is such a small device.


texts:
I am preparing for an exam. I found this problem :

I am trying to use the properties then use a pre-transformed function from the table but I couldn't find one.
I saw a solution on web :

I think he has a mistake since he forgot the t's ( each tau should be t)
Is he right or am I missing something?


texts: Do we need the CE certification for test series in quantity of 100pcs

texts:
We are developing a multimedia application WiFi + Audio out + Mic Input + and few buttons), which we plan to produce in the number of 100 pieces and half of that sell to our aquaintances and the rest from site bu using pre-order mechanism button.
In this way we could geather feedback about the device and then re-think is there is future for such device and if there is sence to produce it in bigger series
So the question is:
How can we bypass the CE certification as there is no need in it for a small series.
We would like to know how would be correct law-wise or maybe in somehow through the agreement state this point and aknowledge the customers
about such approach? Has this been practiced by anyone before and is this possible theoretically?

Originally all the components( WiFi module etc) inside the device are certified, incoming parameter are: input voltage  5V, current consumption 800mA, charger is not included.


texts: How to differentiate between multiple different connections connecting to a common socket?

texts:
I'm working on a project that involves 9 female connections on the top of a box, and 4 male connections coming from the front of the box. The requirements of the project involves connecting these male connections to the female connections, however I need to be able to differentiate between these male connections. How do i differentiate between them?

I'm using an arduino as the "brains" of the project. My initial plan was to use 2 4051 multiplexers to extend the number of analog pins on an Arduino Uno to 9, and then use different signal strength on the male connectors to differentiate between them. Through talking to some colleagues, I've also thought of using logic gates.

I'm a novice when it comes to electronics, I apologize in advance if this question is confusing. I've attached an illustration to try to clarify things.


texts: Why do you use a buffer when the whole point of op amp is to amplify signal?

texts:
This might sound like a dumb question but I just learned about buffers and learned that they have same Vin and Vout from the amplifier providing nearly identical Voltage source value to the next op amp or sensor. But I don't understand why we use this in the first place.

If you want to amplify your signal in the first place why don't you directly hook up a non inverting or inverting amplifier to directly amplify the signal right away?

Why do you have to put a buffer and then pass down your signal to the next opamp to amplify signal? Wouldn't it make more sense to directly use the non buffer amp hooked to a source that you want to measure and directly amplify the signal?


texts: My LED strip arduino setup doesn't use a resistor. Is that okay?

texts:
Very beginner with this.

I am powering an analog LED strip (10 sections, total 12 V, 200 mA required). I'm using a N-MOSFET and an arduino to fade in/out the lights. From my calculations I don't need a resistor, but I feel weird about this (I haven't seen a schematic without a resistor). Is it okay to not have a resistor?

There is 11V coming from the VIN pin on my arduino, and since I need a max of 12V then I wouldn't need a resistor? And you don't use a resistor for amps, since the device will only pull what it needs.

Here is a picture of my setup ( which works, I'm just worried there is something I'm missing)

Any advice would be tops!


texts: What are the best old electrical appliances to extract electronic components from?

texts:
I would like to build some simple drones and robots which I will be controlling using a microcontroller. Instead of buying expensive brand new components, I prefer to look for old electrical appliances at home or on the internet, and then extract what I need myself (small electrical motors, capacitors, resistors...)

I am really new in this field (I did some basics at university) but never did anything myself. I would like to ask the experts if they have any suggestions as to what are the best cheap appliances from which I can extract some parts easily and will cost only a few euros (or dollars)?


texts: Design 8X1 MUX with enable using three state buffers and any logic blocks you need

texts:
I have no idea where to start.
I know how to create a MUX but how can I create it using three state buffers ?


texts: Information-Freezing values in data registers of compass module?

texts:
I am working on a compass module. This module provides the information through 6 registers. In fact, there are 3 pairs of registers.Each register pertaining to one coordinate (X,Y and Z).  In each pair, there is a MSB register and a LSB register. Data of the MSB register, shift 8 times and its logical OR with the LSB register is computed.
 The strange thing I observe is when I rotate the Module, in some degrees of rotation, some data show up in these registers but after a certain point it is frozen on a value like 3c. It goes like this, from 00 to 3c the value changes, but after exceeding 3c, only 3c is read out and I have to reset the module.
 By the way, the Module is HMC5883L.

I wonder Where is my mistake?
Is there any further assumptions that I am not considering?
Have I messed up with computations?

I'm doing as stated in Datashed

  Write CRA (00) – send 0x3C 0x00 0x70 (8-average, 15 Hz default or
  any other rate, normal measurement)
  2.  Write CRB (01) – send 0x3C 0x01 0xA0 (Gain=5, or any other desired gain)
  3.  For each measurement query: Write Mode (02) – send 0x3C 0x02 0x01 (Single-measurement mode) Wait 6 ms or monitor status register  Send
  0x3D 0x06 (Read all 6 bytes. If gain is changed then this data set is
  using previous gain) Convert three 16-bit 2’s compliment hex values to
  decimal values and assign to X, Z, Y, respectively.

I suspect this part :

  Send 0x3D 0x06 (Read all 6 bytes)

What does it mean exactly?

and the other thing is, do we have to provide address of the every register that intended to be read? Or we only need to provide the first register address and the I2C takes care of the next registers?

Is there an simplified example code?


texts: What are ADC channel "map," "max," and "amount" used for on a Microchip ATSAML21 ARM MCU?

texts:
I'm working with a Microchip ATSAML21J18B ARM microcontroller and learning how to set up an ADC input. Coming from the AVR world, things are rather more complicated.

The ADC features (datasheet pg 1030, §42.4) indicate that there are up to 20 analog inputs. Examining the I/O multiplexing section (pg 29-30, §7.1), I can see that there are 20 AIN[xx] designations in the ADC column of the pin function table. I believe I correctly understand that some of these pins reference VDDANA, VDDIO, or VSWOUT based on the values in the Supply column.

I understand that you can also combine channels for various reasons that I'm not familiar with.

Using Atmel "Start", it has generated the following ADC init method:

int32_t adc_async_init(struct adc_async_descriptor *const descr,
    void *const hw,
    uint8_t *channel_map,
    uint8_t channel_max,
    uint8_t channel_amount,
    struct adc_async_channel_descriptor *const descr_ch,
    void *const func)
{
    int32_t init_status;
    struct _adc_async_device *device;
    ASSERT(descr && hw && channel_map && channel_amount && descr_ch);
    ASSERT(channel_amount &lt= (channel_max + 1));

    device = &descr->device;

    for (uint8_t i = 0; i <= channel_max; i++)
        channel_map[i] = 0xFF;

    descr->channel_map    = channel_map;
    descr->channel_max    = channel_max;
    descr->channel_amount = channel_amount;
    descr->descr_ch       = descr_ch;
    init_status           = _adc_async_init(device, hw);

    if (init_status)
        return init_status;

    device->adc_async_ch_cb.convert_done = adc_async_channel_conversion_done;
    device->adc_async_cb.window_cb       = adc_async_window_threshold_reached;
    device->adc_async_cb.error_cb        = adc_async_error_occured;

    return ERR_NONE;
}

My question is, what are the arguments map, max, and amount for?

The generated example shows the call to this method as so:

// Definitions preceding main()
#define ADC_0_CH_AMOUNT 1
#define ADC_0_CH_MAX 0
struct adc_async_descriptor         ADC_0;
struct adc_async_channel_descriptor ADC_0_ch[ADC_0_CH_AMOUNT];
static uint8_t                      ADC_0_map[ADC_0_CH_MAX + 1];

// ADC init
adc_async_init(&ADC_0,
    ADC,
    ADC_0_map,
    ADC_0_CH_MAX,
    ADC_0_CH_AMOUNT,
    &ADC_0_ch[0],
    (void *)NULL);

I assume these have something to do with combining channels, but I admit I'm very confused about how to set up a single channel just to do a basic 8-bit conversion.

Perhaps a better question title would be, "Explain Microchip/Atmel's ADC implementation on ATSAML21 like I'm 5!" There are so many extra features and options that I'm completely lost.


texts:
I began to read up on transistors, which led me to this post on electronics stackexchange.

At the end of the original post, the question asks "the voltage at the base would be a sine wave with the DC bias as the baseline, correct?"

I understand the V2 with the two resistors in series is a voltage divider.

I am struggling to see how at the node connected to the base, the voltage is going to be simply the sum of V1 and V2, resulting in the AC signal superimposed on the DC signal from V2.

I think I can best express my confusion in the form of the second image below.

The voltage between the capacitor and GND is ground no matter the input oscillating voltage before the capacitor.

Then why should the first case be the sum of the AC from source 1 and DC from source 2 ?

-----p.s.------

Also, I remember playing with small batteries as a child. When I put hooked up those batteries of the same voltage in parallel, the voltage output was the same as having a single battery, which I believe is kind of like the first case. (So why should it be the sum of the two voltage sources in the case of the first image?)


texts:
It is not uncommon to see people asking about how to balance a quadricopter using MPU-6050. It's also common to see people answering that a PID controller is needed. However, people doesn't say how.

In my case, I've already managed to combine data of accelerometer and gyroscope with a complementary filter. Also, I've already studied about PID in college. What I don't get is:

The input is voltage signal to the motors, the output is quadricopter's tilt angle and the setpoint is 0 (no tilt angle), right? The error operated by the PID is the difference between setpoint and output. So, how will my system know how to operate in the motor in order to make tilt angle closer to zero? I guess I have to implement my own logic to speed up some motors and slow down others, according to the error. But, if I have to do so, I don't see why PID is necessary. If I haven't, I don't get how motor is balanced according to the error. Could someone clarify how PID could work or share another solutions?


texts: What are some of the more compelling use cases for plug computers?

texts:
Are plug computers useful for anything besides network-attached storage?

I know that you can hang a bunch of drives off them, maybe set up your own web server.  But those uses have limited attractiveness in a home environment, and in a corporate environment, I suspect that ordinary servers would be used.  I could see them used in an industrial environment, perhaps as environmental controllers or energy management devices, but the lack of I/O (keyboard and display) appears to limit their usefulness.

Am I missing something?  Or do I simply lack imagination?  Do you envision a way to use these in a home environment, other than as a media server/poor man's Tivo?


texts: Managing Peak Motor Currents with Capacitors

texts: I'm currently working on a project involving three 90V 5A DC stepper motors controlled by G320 Geckodrives and powered using a single 90VDC 13.5A power supply. I'm working with a mentor who suggested I use a rack of 250V electrolytic capacitors to manage the peak currents drawn by the motors. I imagine that these capacitors would be placed across the power terminals of the Geckodrives and I understand that in this configuration at full charge the capacitors would maintain a constant 90V but I'm not sure how they would help manage current. If anyone has an explanation to this concept or can steer me in the right direction that would be greatly appreciated. I also wanted to ask what is a typical charge time for the capacitors to design for?


texts:
I'm using a Freescale MC9S08DZ60 microcontroller, and Ive written the code for applying PWM on a specific pin.'This is an attempt for Breathing Effect of LED, a question i had already asked - LED Breathing Effect. Even Though the advice was sound, it just made the LED blink at random intervals. I changed my approach.

Default Setting: SET OUT TO COMPARE(Fade ON). Increment the Channel Value Register by the value of i. Checks for the value of Channel Value Register,then switch to CLEAR OUTPUT ON COMPARE(Fade OUT), update the value of i as before onto the Channel value Register.

BUT, when the code is flashed, It SWITCHES between the options(FADE ON & FADE OUT) only ONCE. That is after the first switch between options, it remains to FADE OUT option.

Default Settings:
Modulo Counter = 65535.

Period = 4.096ms.

Edge Aligned.

On Channel 1.

PWM out action: Set OUtput on Compare.

Channel Duty = 4.095ms.

How is it possible to switch between these two PWM options?

Is the number of Timer 'TICKS' an attribute that i am overlooking?

Thanks in advance.

for(;;)
{

 TPM1C2SC &= 0b11110011; //TO SET OUTPUT ON COMPARE.
 TPM1C2SC |= 0b00000100;

 TPM1C2VL =~ (i<<1);
 TPM1C2VH += TPM1C2VL;

 if(TPM1C2V == 255 )
  {
   TPM1C2SC &= 0b11110011; // CLEAR OUTPUT ON COMPARE.
   TPM1C2SC |= 0b00001000;

   TPM1C2VL =~ (i>>1);
   TPM1C2VH += TPM1C2VL;
   i=0;
  }

}


texts:
I have a rail of unidentified SOIC-8 ICs with marking

501
115

Nothing else. No manufaturers logo, no nothing. Does anybody know what this could be?

edit
(picture added)
At 3mm they're quite high for SOIC-8, so they could be optocouplers or so?

Grid is 5mm. (Yes, I know the devices aren't properly aligned, but I did this on my scanner with a sheet of paper over the devices...:-))

update/conclusion
It's almost certainly an Agilent HCPL-0501. The marking matches completely: the 501 refers to the type number, the 115 means week 15 of the year 2001. And the date code appears below the type number (which was a problem with the TR115).
Also diode tests all pass. The 5-6 test which passed was an error; I probably held the testprobe on pin 6 and 7 simultaneously, and 5-7 is the transistor's base-emitter diode.
Thanks for all the replies.


texts:
In any CMOS circuit like an inverter or an n-input NOR or NAND gate, where the pMOS network is connected at the top to Vdd source terminal and nMOS network is connected at the bottom to the ground terminal, can any node voltage (junction where two transistors connect) be negative?
In almost all the sources I read it is assumed that the node voltages are always in the range [Vdd, 0]. Of course, this assumption is quite reasonable and intuitive and not worth talking about; but how to 'prove' it logically and through reasoning?
Without this assumption, how to reason/understand, in a CMOS network, which terminal is the source and which terminal is drain for any transistor?
In a network consisting of only capacitors and resistors it is easy to see what the exact voltage of each node is because those devices have simple clearly defined relationship between their voltages and currents/charge across them. How to similarly reason the conclusions about the polarity of each terminal voltage in a transistor network when some transistors are in cutoff and some are conducting?


texts: Measuring surface and volume resistance of a cylinder with a multimeter

texts:
I'm trying to measure the surface and volumetric resistance of a cylinder shaped object using a multimeter.

At what points should I place the probes, and what formulas should I be using to calculate the above values respectively?

I have looked at "Standard Test Methods for DC Resistance or Conductance of Insulating Materials" (ASTM-D257) but it does not cover electrodes which are pointed (like those in a multimeter) nor does it cover cylindrical shaped objects (like an oil drum)

The cylinder I'm trying to measure is plastic, so it is likely to be in the insulating range.


texts: Does Bluetooth range increase with lower baud rate?

texts:
I am using two Bluetooth dongles for an Arduino project of mine.  I am only sending a single int over the connection so it does not need to have a high baud rate.

If I use a baud rate of 1200 will I be able to have more range than if I were to use something such as 115200?


texts: Calculating the ripple voltage from a standard wall adapter power supply

texts:
I've come across a formula for calculating the ripple voltage from a wall adapter AC to DC power supply, which uses a step down transformer, fed to a rectifier, with the rectifier output connected to a ripple smoothing capacitor in parallel with the load.

The formula would be:
V(ripple)=V(DC)/(RL* C*f).
Going by this formula, if the load is not purely resistive, can the resistance (RL) be replaced by impedance magnitude?


texts:
How do you auto correlate the following Barker code? I tried to use the formula on Wikipedia's page but it did not make sense to me.

+1, +1, -1, +1


texts: configuration of a SPI bus with different slave devices

texts:
I need to make an on-board SPI bus with one master and a few slave devices(microSD card, Gyroscope, magnetic field sensor). Since it is the first time for me to use more than one slave device, I wanted to know what I should be careful about.

From my understanding of the SPI interface, it is okay that the slaves have different clock polarity/phase, different data frame format(LSB/MSB first, bit-width). It would be also fine that one uses SS signal pulse in between packets, while others don't use that. Here I assumed that the master device(a MCU) changes its configuration before starting the communication with each of the slaves. Also the switching between the slaves does not have to be fast.

As far as I determine the logic level, number of lines(full-duplex/half-duplex), then I don't have to worry about other parameters in the bus configuration. Could one please confirm if this is correct?


texts: Autoelectrics: Testing components off 12v battery

texts:
I'm quite good with mechanics and am just starting to learn more about electrics specifically applicable to automotive. One thing I am still yet to get the grasp of is the way electricity behaves. It seems some things I read say 'a device will only use (draw from the circuit) as much power as it needs', but other learnings contradict this. So this question is about overloading components / component protection.

When playing with little electronic kits and building a simple LED light circuit one of the steps is to add a resistor so that the LED doesn't blow out.

This got me thinking; this weekend I was having trouble starting one of my classic motorcycles using it's electric starter and I was able to isolate the problem to the starter solenoid. My process of elimination was to jump across the solenoid to check that the starter motor engaged which it did. I then disconnected the solenoid and measured the voltage for the two wires going into it (which complete the circuit of the starter switch). I got ~12v when pressing the switch so that part works fine. The problem must be the starter solenoid.

The next test I did (which wasn't really necessary but I was interested to see the result) was to check for continuity across the main terminals (which go from the battery to the starter motor) by applying the two wires (which would otherwise come from the starter switch circuit) directly to the battery. The solenoid clicked as it was doing before but no continuity was found, which if it worked I should have.

My question is, if this relay was good. Would applying it directly to the battery damage the relay? My basic understanding is that the starter switch wires are on the main 10A fused electrics circuit, and the battery > starter motor is a 30A fused circuit.

Depending on the answers above, what about doing this with other components? Could you use jumpers to hook the headlight up to the battery without damaging?

If the answers are yes, why isn't a resistor required like in the basic electronics kit?

Thanks, and sorry if this is a very basic question.


texts: Problem in understanding bridge rectifier

texts:
Why does electricity not flow from the other two diodes after it has been through the load in a full wave bridge rectifier?
I'd asked this question on Physics SE but was told to ask it here.


texts:
My book introduces a divider design:

It said that if the divisor is n-length number, we need n+1 steps to finish the division.

For example: 7 / 2 (0111 / 0010) demands 5 steps. I don't quite get why it requires us to do 1 more step? It can automatically shift the divisor at the beginning.

This is the steps described closely:


texts:
I'm trying to build the below function with CMOS, is my implementation correct?

$$ F =  ABC + (\overline{B+C})D $$

I am having trouble with the $$(\overline{B+C})$$ in all of the examples I've seen the function is in the form $$F = \overline{blablabla}$$ (the inverse of the whole expression).
I gave it a try but I'm not sure if it's correct, for example is it ok to have ~A as input to a PMOS (I don't see why not).

The correct layout after Dave Tweed pointed out the missing connections on the N-block.
(The added connections are marked with pink)


texts: Designing a Diode Clamp Current Source with calculations

texts: I have an assignment for our analog electronics module for the university to design a polygraph circuit using a Transimpeadance circuit, coupled with a Diode voltage-clamp current source to give the constant required reference voltage. I'm not going to lie this year I have not been productive being that covid has made work very busy and being a part-time student is very hard, and with the uni's  VLE (their online databases storing all the required course notes and videos) being hacked over the Xmas holidays most of the class is dangerously behind. If anyone can take their time and explain how to do this problem you will have saved the course for not only me but for all the other students. I have attached the section I am having problems with here, the whole circuit has to be simulated in LT spice as well


texts: Audio amp causing microcontroller glitching - how to better decouple?

texts:
Complete schematic is at https://cdn.hackaday.io/files/1667667134916544/Evil%20Simon%20v1_2_1.pdf

This is a little game with a DAC output being used as a digital audio playback system. The DAC output goes into an LM4871 amplifier. As shown in the schematic, the same 3.3v boost converter (It's a XC9142B33, not a 9140) powers both the logic system and the audio amp. In this configuration, playing audio (the speaker is an 8Ω 1" magnetic loudspeaker) causes the controller to reset, presumably because the transient load overwhelms the boost converter's transient response abilities and browns-out the controller.

I've broken the trace that feeds power to the amp so that I can experiment with alternatives. What I at first attempted to do is add a decoupling inductor from the 3.3v rail followed by extra capacitance. The values I've tried are 47 µH and 47 µF (tantalum). That seemed to make things a little better, but not good enough. Upping the capacitance to 120 µF (electrolytic) didn't make things any better.

Am I barking up the wrong tree with this idea? Or do I just need to crank up the inductance until the thing stops browning out?

Another thing I tried is connecting the inductor up to the drain of the soft-power MOSFET. This works, but I am concerned that the audio amp is going to get an inconsistent voltage as the batteries age. I'd prefer the power be well regulated until the boost converter can't deal anymore and drops out.

EDIT: Someone asked to see the layout. Not shown in this (partial) screenshot is a ground flood on both sides of the board. Power to everything except the audio amp is on the blue line going down to the left. On the prototype the short trace from pin 6 of IC3 to the nearby via has been cut and a through-hole inductor tacked on to the + side of the nearby bypass cap. The other end has at various times been tacked directly to the bottom of C5 or the drain of Q8.


texts:
I am interfacing a 5V system to a 3.3V using the SN74LVT125 to shift down TTL voltage to 3.3V

My problem or my question is, Some of the input pins (the A ones) are being triggered by a 5V signal that comes directly from a phototransistor optocoupler. I couldn't find (or dont know where it is) how much current is the maximum allowed to send through the inputs of the SN74LVT125, or can I just put the 5V directly into the input pin without any resistor?

I tried searching the web but couldn't find any helpful information, I hope somebody can help me.


texts:
I saw this project: http://diyhacking.com/arduino-lamp-dimmer/ which I'm interessted to(except that I will have to use some 24V, still enough to hurt the Raspberry Pi).

There is several things that I'm not sure to understand:

The optocoupler is used to isolate the 5V from the 230V(24V in my case), ok
The MOSFET is used to normaly used to command an higher voltage with a lower voltage.

So what I don't understand is why we need the MOSFET since the optocoupler already receive some 230V(24V)?

Thank you


texts: What is the equation for capacitance with aysmmetric plates?

texts:
The general equation for capacitance:

\$C = \frac{\varepsilon_0 \ * A }{d} \$

C capacitance
\$\varepsilon_0\$ permitivity of free space
A area of equally sized plates
d seperation distance between plates

I cant seem to find an equation whereby the equation features two areas i.e A1 and A2 (representative areas of each plate)

Does such an equation exist (I'm sure it does, somewhere)?

Failing that how reasonable a result would I expect to find if assuming A as the smallest area of the two plates?

Background:
Working on implementing my own proximity sensor whereby the first plate is the sensor head itself, but the second plate is the object the sensor detects i.e. the object is bigger than the sensor head.


texts: How necessary is ESD protection, really?

texts:
I'm not asking about manufacturing. I'm asking about designing electronics to survive normal use in the field. I want to figure out just how necessary it is to include TVS diodes in my design.

As I mentioned in my previous question, rarely did anyone bother in the 80s and 90s to include any ESD protection on I/O lines. These devices seem to survive OK.

I imagine it will depend on what type of ICs the I/O lines are connected to. In the 80s and 90s, they were generally NMOS VLSIs, early CMOS VLSIs, CMOS and TTL gates.

Are modern 5V MCUs more vulnerable than 74HC gates, warranting the inclusion of TVS diodes on the I/O pins?

Does the type of connector dictate the degree of ESD protection required? I can see a female D-sub connector being reasonably safe without any ESD protection - unless the cable itself is charged.

If I do need TVS diodes, then do I also need series resistors? I looked at the datasheet for a suitable 5V TVS, it specifies a maximum voltage drop of 24V when shunting a 20 amp ESD spike. If I connect the TVS directly to the I/O pin, the ESD diode inside the IC will conduct. 24V is much greater than the 0.3V ESD diode drop.

I could put a 33 ohm series resistor between the TVS and the I/O pin. This limits the current to less than an amp through the internal ESD diode which it can probably withstand. But is it really necessary? I have a lot of I/O pins and I'd rather avoid the resistor. Can I rely on the ESD diode having a sufficiently high dynamic resistance that the TVS will take the bulk of the discharge?

simulate this circuit – Schematic created using CircuitLab


texts:
I am looking to idiot proof some connectors I use, which are not intended to be hot plugged, but of course they are..

The typical problematic case is with a standard 4 pole connector I use where the pins are:

20V
GND
SDA (I2C)
SCL (I2C)

I am using a 2mm pitch, 4 pole, JST connector (B4B-PH-K-S), where all pins are the same length so there is no certainty in order of connection, thus the hot plug issues.

I have no issues with these connectors when they are safely plugged/unplugged from the system when it is off. But they consistently have failed during unintended hot swapping.

I know many common hot plug interfaces (such as USB) have extended power pins to guarantee contact order of pins, in order to prevent damage.

I guess my question is, are there any low cost, small form factor, similar to the JST connector I am using that has this sort of feature?

Other ideas on solutions are welcome as well!


texts: Every so often when I'm looking through industrial supply websites looking at various fractional hp electric motors there appears to be a class of motors that are referred to as "hubless".  Attempts to find diagrams or explanations of these types of motors only yields references to various 2-wheeled conveyences with large open wheels.  So, what is the defining characteristic and operating principal of a hubless electric motor, and where are they used?


texts:
I got 40 DC solenoids (12 V, 2 A) and each solenoid may be turned on for max. 5 seconds every couple of minutes or even more. Does this implementation require that an overheat protection should be provided for each solenoid? if any, what do you suggest, please? a heatsink or a fan? and how many fans could be used for the 40 solenoids?
Moreover, does a simple microncontroller circuit (including relays) require a fan or a heatsink?
In addition, I read that a flyback diode should be connected backward in parallel with each solenoid to prevent back EMF from flowing back to the circuit; what kind of diode do you recommend, please?
Is 1n4007 good enough?


texts: Driving a 35V PMOS circuit from a Grounded/Floating input

texts:
I have an application where I need to switch a contactor on and off using a spare output of an off the shelf Battery Management System (BMS)

The input is the signal coming from the BMS, while the output is the signal going to the contactor

Input/Output

When the input is FLOATING, the output should be OFF
When the input is GROUNDED, the output should be ON

The manufacturer of the BMS provided the following circuit diagram to follow:

Constraints

BMS output must not sink more than 175mA
BMS output must not have more than 24V across it

The main supply of this circuit is a battery which will have a maximum operating voltage of 35V. Looking through the P MOSFETS available in my country, I can only find a max Vgs of -20V. I have looked at gate voltage protection circuits and tried to adapt the following circuit to work:

The circuit I have derived is the following:

Zener diode: BZX85C22V
PMOS: Vishay IRF9540PB

My logic is that the 10K resistor acts as the pull-up when the BMS input is floating. When the input is grounded, then the Zener starts conducting and clamps the gate to 22V. Therefore Vgs is -13V (well under the -20V maximum). Iz looks to be about 22mA for the zener to conduct, so I assume let 25mA flow. so then

R2 = (35-22)/0.025 = 520R. Choose 470R, which gives 28mA. Resistor power dissipation is P = I^2 * R = 0.36W (Choosing 0.6W resistors)

Zener dissipation = V * I = 22 * 0.025 = 0.55W (Under the maximum of 1.3W).

My question is that will this circuit work reliably? I am not experienced with circuit design, so your feedback would be very appreciated.


texts: Is it a good idea to have a power plane and route power selectively?

texts:
Hopefully not too general of a question but: in a 4 layer design with the following stackup:
Top
GND (solid plane)
Power (solid plane)
Bottom
Is it a bad idea, given the above, to ever route power traces on the top (rather than tapping it with a via close to the component?) This is given the power plane is used for some components, just not all.
And by bad idea I mean: are there technical disadvantages?


texts: Combining pins of a GX-12/GX-16 (aviation) connector

texts:
I'm intending to use LED strips and use GX-12 or GX-16 connectors.
Depending on the number of pins and GX-12 or GX-16 type there is a max current allowed (liked 3A).
Can I safely combine two or three pins to get 10A (for the VCC and GND connection to the led strip(s), assuming the current will be (kind of) evenly split between the two or three pins?
(so when I would use an 8 pin connector, to get 9A when I use 3 pins for VCC and 3 pins for GND).
As additional question, does it matter if I connect the 4 or 6 pins to two separate LED strips (of different sizes)? (I assume not).


texts: Driving high-powered LED with demanding requirements

texts:
I have just purchased this impressive looking 100W "7-band" LED multichip, apparently it's the latest innovation. My problem is the chip's voltage demands are far lower than what ordinary 100W drivers operate at; this chip requires 22-26V/3.5A, while 100W drivers almost exclusively run at 30-36V/3.0A.

I asked the creator and he said it would not work and would most probably blink constantly. So since constant current drivers look out of the question, would it be possible to use a power supply with some kind of buck regulator with an adjustable voltage/current potentiometer such as this?

I also have a digital ammeter/voltmeter display which could be connected between the two would make potentiometer adjustments accurate, and I have a friend who can wire all the above up for me.


texts: My analog sensor outputs .5 to 4.5VDC. How do you convert to analog 0-10VDC?

texts:
My analog sensor outputs .5 to 4.5VDC. How do you convert to  analog 0-10VDC or
1-9VDC?


texts: How to control a motor with a photoresistor

texts: I have a little 2 to 5 volt hobby motor that I would like to control with a photoresistor aka photocell.  What is the simplest way to control the circuit?  Is there a photo resistor with enough range to be the only element inthe battery motor series circuit?  So that I can just turn off the motor by the photoresistor resistance going high enough?  Or do I need a voltage divider with the motor in parallel with the larger resistor, so that the photoresistor can take voltage away form the larger resistor as the photoresistor resistance approaches the larger resistor?  This is for a project for my kids school, so I want it to be really simple.  Does a motor have a resistance when on or off?


texts: Have current feedback op amps gone out of fashion?

texts:
Or have they perhaps always been a bit of a niche product?

I've been working with op amp circuits on nights and weekends for about a year now. It was a fair amount of time before I encountered a current feedback op amp (CFA) even by mention, and only now that I come across one in an actual circuit I'm studying (LT1210 on page 3).

I was looking around for a nice jellybean CFA I could use to experiment around with a bit and notice:

There are way fewer CFA's out there, at least at the places I looked
All the CFAs offered by TI are OPAx models, I believe indicating they came along with their Burr Brown acquisition, implying TI didn't make any itself before or since. Roughly half of those are now obsolete.
CFAs are generally "pricey" compared to the voltage feedback op amp (VFA) options that are out there. Say $5 to $10 compared to plenty of VFAs for around $1.

So I was wondering, did CFAs arise to meet a market need that perhaps has largely passed? Or were they kind of always a niche device; perhaps a compromise for when output speed and current were design priorities?

In short, how might one characterize the market life-cycle trajectory of CFAs? Are they something to be avoided (or substituted with something newer and better) for new designs? Or are they maybe a continuing good option for special cases and just don't have the volume to drive their price point lower?


texts: Why aren't components in DIP package shipped with straight pins?

texts:
I've noticed that all DIP packaged devices have pins which are at an angle other than \$90^{\circ}\$ and need to be bent so that the angle is right for insertion into holes on the PCB or wherever.

Is there any reason other than tradition for that? I imagine that in most cases components are machine-inserted into their sockets or PCB holes, but why would it matter to the machine if the pins are bent or straight.


texts: How could I evaluate the signals from the audio input so that it acts as a switch to turn on my Bluetooth Speaker?


texts: DIY PWM Fan Controller; Speed changing too fast

texts:
I couldn't think of a way to explain all this in one line, so apologies for the slightly vague title.

I've built a PWM Fan Controller for a DIY Laptop Cooling Pad Project. It theoretically works, and I am able to vary the duty cycle and achieve a change in fan speed from about  10% to a 100%.

However, the fan speed only changes when I rotate my Linear 100K Potentiometer to the half-way mark, and it increases really rapidly afterward. Changing which components, if any, would help make the change in speed slower and smoother?

I built this taking reference from an Overclockers.com forum thread about the same thing:
http://www.overclockers.com/forums/showthread.php/641111-Building-PWM-Controller-for-4-wires-PWM-fan?p=6473318&viewfull=1#post6473318


texts: Simplest possible I/O for Homebrew 8-bit CPU

texts:
I am working on designing an 8 bit cpu as a personal project for no real reason. I am using mostly 74HC series chips and am generally focusing on ease of programming over performance.

I am using various projects on the internet as inspiration, and I feel I have a pretty good grasp on how the basics will work, including the alu, registers, and the basic memory path.

The one thing I don't have a clue about is Input and output. I am not really interested in anything super fancy, like tcp/ip or uarts, but I would like to have a keyboard and a basic text output to a monitor of some kind. I really have no idea what hardware to use, or what instructions to make to use it.

I could squeeze a few more specialized instructions out of my ISA to access specialized hardware, but if I could do it all with some kind of memory mapping scheme that could be even better. I am planning on using a 64K ram chip, but maybe certain addresses could get diverted to other hardware or something.

I don't really want to implement interrupts, but I don't want to lose keyboard data either. Does that means I need some kind of queuing buffer chip for my keyboard? I don't even know where to start looking for a video chip, or how I would interface with it.

Any tips would be greatly appreciated. Again, I don't need anything fancy, a simple getChar and putChar would suffice. Pixel level control of graphics could be cool, but not absolutely required. I think I just need to be pointed in the right direction.


texts: I want to measure the temperature with PT100. At the first stage the resistance is converted to voltage (ca in range 1.5-2 V for 0°C 100°C). How can i scale this voltage to range 0-3.3V with the second opamp (red box)? I want to have 0.3V for 0°C  and 3V for 100°C.


texts: DS1307 timekeeping date significance (leap seconds?)

texts:
As part as a hobby project I built a relatively simple BCD binary LED clock using a PIC micro controller and a DS1307 RTC. Upon battery power loss the DS1307 resets back to 01/01/00 00:00:00 which makes sense. However, since the user is only able to see hours, minutes and seconds on my clock it makes no sense to set the date.

My question is, what is the relevance of setting the date in a DS1307 in relation to timekeeping. As far as i know the only relationship between time and date is a leap second correction every few years which i doubt the DS1307 implements.

Is it okay to let the date remain 01/01/00? I would assume it wouldn't make the time drift a lot but maybe i am missing something.

Either way, it's just a hobby clock, accuracy isn't mission critical, I'm merely asking out of curiosity.

Thanks in advance!


texts:
I want a fading effect on a 12V led strip when power is turned on/off. I want to keep it simple and efficient, so I choose an Attiny45. The problem is that for the Attiny to work, I would first need to step down 12v to 5v and then step up 5v to 12v.

Are there any better alternative led drivers? If not what circuit should I use in conjuction with the Attiny to accomplish the task?


texts: Can Cortex-A series ARM processors remap the physical address of DRAM via the Memory Controller?

texts:
Many ARM SoCs have memory as MMIO. However, I have seen other ARM processors that support (like x86, et. al.) the ability to program the memory controller and move this mapping.

Is this a SoC-dependent feature? Or is the ability linked with a particular ARM core IP? The the ability linked with a certain ARM core tier and above (for instance, all Cortex-A)? Or is it up to the SoC vendor to decide if remapping is supported in their Memory Controller?

Specifically, because I am working with A series:

Is memory remapping supported on Cortex-A and later?

I want to run some firmware that has memory mapped into a location that is not supported by the specific SoC I have, so I was curious to see if it can be moved.

Edit:

Fundamentally, I think the question I am asking is whether or not the presence of an MMU/Memory Controller implies the ability to remap the physical addresses of DRAM like you can on x86 hardware.