texts: Concept of ground near negative terminal

texts:
What's the point of having the ground near the negative terminal when the electrons would just then flow out of the circuit into the ground?
Since there is already a potential difference between the positive and negative terminals, what's the point of a ground at all?

For example:

Why would ground be on the right? That means in technical current direction, the current would go to the ground and not to the negative terminal and there would be no potential between the ground and the negative terminal...


texts: Human perceived (relative) brightness of indicator LEDs

texts:
Humans looking at colored lights each at the same luminescence perceive yellow as the "brightest" color.  Green is somewhat dimmer, and red is very much dimmer.  Using a common formula for calculating mean luminance, 30% is red, 11% is blue, and 59% is green (R=645.16nm, G=526.32nm, B=444.44nm).

Theoretically, I should choose luminous intensities using ratios of Blue=90x, Red=33x, Green=17x, and I'm guessing, Yellow=15x.

Testing random LEDs from my junk box, a lux/fc meter with expired calibration, and two volunteers, Blue=152x, Red=143x, Green=23x, Yellow=15x.

  The application is for indicators easily distinguished under office lighting.  All will have the same package (T1,or T1.75), similar viewing angles (about 60 degrees), with the same lens (all clear/tinted, or all defused).  They will be driven based on the data sheet's test current and luminosity curve.

  I am assuming the all the other zillion factors like efficiency, encapsulation, geometry, orientation, etc. are specified constant (viewing angle, lens), or they are incorporated into the millicandelas (mcd) rating provided by the manufacturer.

1.  Anyone care to comment on these ratios, based on real life experience?

My experimental red number calls for 3 times more luminosity than the theoretical one.

2.  What mcd target values/colors would your experience suggest for LEDs viewed under office lighting?

My testing conditions can't give results in mcd, so my test data doesn't help.  Once I get a suggested mcd for a color, I'll use the ratios to get the other mcd values.  And of course, you can't buy exactly what the calculator says... so "rules of thumb" rule!

  Update...
  --->  Think of a traffic light.  What if drivers complained that the yellow lamp was too dim that the weren't sure when it was lit...?

  I don't want my users saying they can always tell if the color1 or color2 idiot light is on, but they are never sure about color3 without getting their eye next to the device.


texts: What determines the orientation of a coupling/blocking capacitor in an amplifier circuit?

texts:
"In analog circuits, a coupling capacitor is used to connect two circuits such that only the AC signal from the first circuit can pass through to the next while DC is blocked. This technique helps to isolate the DC bias settings of the two coupled circuits. Capacitive coupling is also known as AC coupling and the capacitor used for the purpose is also known as a DC-blocking capacitor."

Here is an example of use of it:

Below another example from a question on this website:

And here is an example from an electronics text book:

What determines the orientation of the coupling capacitors here?
Is that the Vcc voltage? But if so, the last example does not follow the first two. Which one is correct and why?

edit:

Below a polarized cap is used with an AC signal. There is no DC level.
As you see the voltage across the cap is alternating from +7V to arounf -7V?
Is this acceptable?


texts: I am using two 3.7V LiPo cells in series to power a device. The output of battery is converted to 12V using a dc-dc converter. I want to increase the capacity so that the device can run longer. Is it possible to used Li batteries in parallel? Because all the battery monitoring ICs I found are designed for cells in series.


texts: Is XADC synchronous in Artix 7 Series FPGA?

texts:
I was wondering if the output data of the XADC in the Basys 3 board is synchronous.

That is, can I use the EOC (End of conversion) flag as a clock for some other modules and expect it to be a periodic signal?

I'm in doubt because recently someone explained to me that for different voltages, the XADC can take longer to convert. But I don't know if the board handles that internally to get continuous synchronous output.


texts: RA4 of PIC16F648A output not as expected

texts:
In the original design of a timer RA4 is used as an output pin. The condition of the pin is set with BSF PORTA,OUTPUT or BCF PORTA,OUTPUT. OUTPUT being defined as D'4'. Bank selection unknown.

Since PORTA has it's own unique adress 05h i do not understand why the status does not change.
Although not understanding I experimented and selected Bank1 prior to changeing the status of RA4 and that works.

I can leave it that way. But i dont like the change if I do not understand why.

Some enlightment is required.

; Not working without bank1
BSF PORTA, OUTPUT or BCF PORTA, OUTPUT

; working
BSF STATUS,RP0 ; Bank1
BSF PORTA,OUTPUT or BCF PORTA, OUTPUT
BCF STATUS,RPO ; Bank0

From the datasheet PORTA is in Bank0 and not in Bank1 then why the selection of bank1 is working?

Not knowing the actual bank I could have saved the current STATUS but intend to do that when cleaning up after understanding.

Edit after comment. CMCON is set to 0x7.


texts: How do I connect the pickit 3 with PIC32MX795

texts:
I bought a USB 32-Bit Whacker - PIC32MX795 Development Board and a MPLAB PICkit 3 after working with some ATmega stuff in the past.

These are the 6 pins(on the pickit). I'm looking for them on the whacker board.  I can find

vpp
3.3v
gnd
pgd
pgc

in a row, but i'm wondering 2 things

is vdd the same as 3.3v?
where / what / do I need the LVP?


texts:
So Wi-Fi runs in the 2.4 GHz band, yeah (and the new ones 5 GHz)? Which means that every second, a Wi-Fi antenna outputs 2.4 billion square wave pulses, right?

So I was wondering, why can't it transmit data on every pulse, and be able to send data at 2.4 Gbit/s? Even if 50% of that was data encoding, then it would still be 1.2 Gbit/s.

Or have I got the concept of how Wi-Fi works wrong...?


texts: Basics physics question about calculating resistance

texts:
Why is the total resistance calculated differently when resistors are in parallel, compared to when they are in a series? For example, $$ \dfrac{1}{R_t} = \dfrac{1}{R_1} + \dfrac{1}{R_2} + \ldots + \dfrac{1}{R_n} $$

Also, if there is a set value for the amount of resistance for example a 50 ohm resistor and a 20 ohm resistor in parallel, why would this not equate to 70 ohms if the resistance that the electrons are encountering are the exact same (50 ohms and 20 ohms) as if it were a series? I get that since there are two paths, the electrons will split making it less resistance overall, i just don't quite understand how this could happen if it is set that they encounter 50 ohms and 20 ohms of resistance.


texts: Powering an old alarm clock LCD (need to invert DC to 3 V AC)

texts:
I'm tinkering with a cheap old alarm clock LCD screen. I think the LCD is multiplexed (there is only one row of connectors along the top of the screen, etched (or something) into the glass, and there doesn't appear to be any common ground or anything from the circuit board the LCD rests against). The clock itself is powered by a single AAA battery. There is no driver circuit board or anything directly attached to the LCD (as many hobbyist purpose-built ones seem to have), so I need to provide the current directly to the LCD. It appears that the screen itself receives about 3 V AC to activate a given region, as measured by a multimeter from the alarm clock circuit board.

So my question: how can I create this AC current from a DC source of around 1.5 V DC? Would it be possible to also do this from 5 V DC (provided by my Arduino)? I would like to avoid (if at all possible) up-converting to 110 V AC first (it seems to be a common recommendation from google searches). I have many basic components (resistors, caps, transistors, pots, diodes, etc) laying around in my 'nerd boxes' which I would prefer to use over specialized components, such as purpose-made inverters or the such, to do this.

As may be evident, I am somewhat new to electronics tinkering and as such may be way off with my expectations. I will respond to comments/answers, and can post pictures once I get home if it would help. I appreciate any help I can get on this :)


texts: RC circuit with pulse input voltage; finding the time constants

texts:
I've the following circuit:

  Question: What are the time constants of the voltage at node \$\text{Y}_2\$ when the up part of the puls comes and when the down part of the puls comes?

MY WORK:

The voltage at node \$\text{Y}_2\$ can by using the following analysis:

The input voltage (starts at \$t=0\$ at \$8\$ V and is high for \$\frac{1}{20}\$ seconds and turn than back to \$0\$) is given by (in the s-domain using the Lapalce transform):
$$\text{u}_\text{in}\left(\text{s}\right)=\int_0^\frac{1}{20}8e^{-\text{s}t}\space\text{d}t=8\cdot\frac{1-\exp\left(-\frac{\text{s}}{20}\right)}{\text{s}}\tag1$$
The relation between the voltage at node \$\text{Y}_2\$ and the input voltage is given by:
$$\frac{\text{u}_{\text{Y}_2}\left(\text{s}\right)}{\text{u}_\text{in}\left(\text{s}\right)}=\frac{600+\frac{1}{10^{-6}\text{s}}}{600+600+\frac{1}{10^{-6}\text{s}}}=\frac{5000+3\text{s}}{5000+6\text{s}}\tag2$$

So, the voltage at node \$\text{Y}_2\$ is given by:

$$\text{u}_{\text{Y}_2}\left(\text{s}\right)=8\cdot\frac{1-\exp\left(-\frac{\text{s}}{20}\right)}{\text{s}}\cdot\frac{5000+3\text{s}}{5000+6\text{s}}\tag3$$

Plotting the function (in the time domain gives):

So, for finding the time constant (\$\approx63\text{%}\$ of the maximum value) we need to solve:

$$8\cdot\left(1-\frac{1}{e}\right)=\mathcal{L}_\text{s}^{-1}\left[8\cdot\frac{1-\exp\left(-\frac{\text{s}}{20}\right)}{\text{s}}\cdot\frac{5000+3\text{s}}{5000+6\text{s}}\right]_{\left(t\right)}\space\Longleftrightarrow\space$$
$$t\approx0.368223\space\text{ms}\tag4$$

  Am I correct in my analysis or not? Because I also thought about using \$\tau=\text{R}\cdot\text{C}\$ so then we get \$\tau=(600+600)\cdot10^{-6}=1.2\$ miliseconds, is that right or is my previous analysis right? Because I got two different answers


texts: Node with two different voltages at the same time - Two branches (voltage source+resistor) in parallel - LTspice

texts:
I simulated the following circuit:

Why is Vu=7.5 V? I expect there to be an error because Vu=5=10 at the same time.

The current in the two branches is the same, thus (R1=R2):

$$Vu=R_1 i+V_1$$

$$Vu=R_1 i+V_2$$

$$V_1=5=V_2=10$$

Thank you in advance.


texts: Requesting the maximum available power from source

texts:
I’m trying to design my own battery pack. I want to use usb-c as one of the inputs. The goal is to draw as much power from the usb-c port as the source supports and to feed that into a boost converter to charge the cells.

I’m thinking about using the STUSB4500 (datasheet). The IC has 3 PDOs, PDO1 is fixed to 5v, PDO2 and 3 can be set to any voltage. A minimum required current can also be set for each PDO. Upon plugging into a charger, the IC will check whether any of the set voltages match the available voltages of the source, highest priority to PDO3, lowest to PDO1. If, for a common voltage, the source’s available current is greater or equal to the set current, it will agree on that voltage and allow power output.
There’s also a parameter you can set over i2c REQ_SRC_CURRENT. When set to 1, the IC will automatically select the highest available current, instead of the one set in the PDO.

So I was thinking, maybe I could enable this parameter and set the PDOs like this:

PDO3: 20v, 0.5A
PDO2: 12v, 0.5A
PDO1: 5v, 0.5A

Every charger will be able to output at least 0.5A, so by doing this, the IC will pick the highest voltage and then set the current to the highest available.
I think I could then get this maximum current using i2c, and limit the cell charging current to not exceed this.

Do you think this is a viable solution? One problem I’m thinking of is that if the charger would output for example 15v, this wouldn’t be a match and they would settle on 5v. Because there’s a limited amount of PDOs, I can’t set one for every common voltage.


texts: How to check if a device is compatible with a breadboard?

texts:
I am just in the process of purchasing components for a control systems project but I am having trouble selecting a barrel jack that is compatible with a breadboard layout. I'm not sure if there is a specific standard or code that would tell me if the device had the correct pin pitch to fit a standard breadboard (if standard breadboards exist).

I found this on digikey and thought it might work, can anyone confirm? https://www.cui.com/product/resource/pj-102a.pdf

Thanks!


texts: I want to design discrete boost converter with 5 volt input and 24 volt output with load current of 1 amp. How do I choose suitable input and output capacitor and inductor values; what formulas are used to select those values.


texts:
I wanted to ask what communication protocol arduino boards use exactly to communicate with pc?

How can the serial monitor work on such high baud rates through usb?

Will it be possible for using a dsPIC33 MCU to have such high speed communication with pc? (MCU having on-board usb on-the-go, USART modules)

I have heard that even though dsPIC MCU comes with USB 2.0 module capable of theoretical full speed(12Mbps), practically the speed acheivableis in kilobits not mega. Reason being the pc is also communicating with usb mouse, keyboard and other peripherals, and operating system busy doing other stuff, and MCU doing other stuff (not dedicated to just communication). This is the reason why usb drives transfer data in kilobytes not the theoretical speed of 12 Mbps. Is this all true?

If so, how can I optimize for best speed possible?

All this should be answered keeping in mind I am working on a portable oscilloscope using a dsPIC33 MCU. Sampling using the on board adc, transmitting the data to pc through a communication protocol to be decided (most probably usb), and displaying the data in gui software. Sampling speed of adc can be upto 1.1Msps where each sample is 10 bits. That make up alot of data to be transmitted and wondering whether usb will be able to such fast speeds.


texts: Replacing obsolete photodarlington with phototransistor

texts:
I've got an old circuit design I need to replicate, function wise, to fit into an existing larger design.  Logic I can usually handle,  anything with transistors starts to get me lost.  My strength is in DFM and manufacturing, not necessarily electrical design.  The original design functions as a simple on-off switch on a TTL logic circuit, with a separate IR LED source.  Top circuit is the original design, bottom is my proposed alternate.

D1 is a photodarlington, Motorola MRD370, long obsolete and difficult to find at a decent price.  Due to cost and availability I'd like to use a phototransistor instead of a photodarlington, but am concerned about enough gain.  Hence the 2nd schematic with an additional 2N3904.  Resistance value I haven't even tried to calculate yet.  The original circuit is a TTL logic circuit, just can't figure out how to show that in the schematic.   I have enough activity to post links now, so here's the original schematic I'm working from.  Identical circuit is duplicated a few more times on the board, each for an independent photodarlington.

Would my proposed circuit be completely off the mark here?  Photosensors are totally outside my practical experience.  Switching time really isn't a big concern here, as the circuit is detecting the presence/absence of a stationary object.   I added a 2nd proposed circuit, based on suggestions received.  Left the first one to hopefully avoid confusion with changes.

simulate this circuit – Schematic created using CircuitLab


texts: How to find the equivalent resistance of this circuit?

texts:
I know that finding the equivalent resistance depend on whether resistors are in serie (R1+R2+...+Rn) or parallel (1/Req=1/R1+1/R2+...+1/Rn), but i don't know how to apply that to find the equivalent resistance of this circuit (not including Ra):

simulate this circuit – Schematic created using CircuitLab

My solution:

simulate this circuit

R3, R1 and R2 are in parallel so:
1/Req=1/R3+1/R1+1/R2 so Req=3.299 Ohm.

I assumed that R3 isn't in parallel with R2 and R1, so I calculated Req in different ways:
Req=(R1//R2)+R3+
Or: Req=(R1//R3)+R2
Or: Req=(R3//R2)+R1

I know this may be the most ridiculous question you have seen today, but i'm very beginner in electronics. Any help would be apprieciated.

Thanks for reading my question.


texts: Designing a BJT transistor amplifier with a current gain greater than 1000?

texts: What would be an effective BJT transistor configuration for implementing an amplifier with a current gain of greater than 1000? This can be a multistage configuration, but it may only use BJT transistors. I was thinking of using a common-collector configuration for such a purpose. What would be appropriate biases for the resistors in the amplifiers (along with capacitor values if there any worth noting)?


texts:
I am beginner at programming uC's. I have read all the tutorials on what is I2C and how it works, but I couldnt find any help specific on how to create a connection between my sensor and ATTiny88 (ATTiny88 datasheet.

I use SHT21 sensor (SHT21 datasheet) and want to communicate with ATTiny88 (MUC sends command to getData, and then sensors sends to MUC back the data (temperature, humidity)) - can someone help me guide through?

Once you help me, I'll understand it for future, but I really need a jump start here.

Thanks!


texts:
Given:

Center Frequency f0 = 2.2KHz
Q factor = 5

The problem I'm facing is this: How do I calculate the 2 cutoff frequencies of this band pass filter? I'm confused because my question says "The cutoff frequency is not always the -3dB point. This is only the case for Q = 0.707".
I found a website that calculates the cutoff for a band pass, and the results were:
[F1 = 20KHz to F2= 2.4KHz].
But when I simulate the circuit in Multisim, I have a huge difference between the results:
[F1= 1kHz and F2=5kHz].
I need a way to calculate the two cutoff frequencies. The system functions are given at the end of the figures:

Copied from Wikipedia!


texts:
Recently I was working on a 5V switching power supply project and I found the best PCB for building it. But in the middle I got confused when I saw an IC with the letters ID2J.

It has 5 pins like an op-amp or an optoisolator SMD.  I searched for it and found nothing, no manufacturer and no datasheet. On the PCB silkscreen it's called IC1.

Does any one know what kind of IC is this?


texts: Interfacing an LVDS driver with an LVPECL receiver

texts:
I'm trying to understand how the below circuit allows interfacing LVDS levels with LVPECL levels.

Assuming:

Driver:

Voh = 1.4V, Vol = 1V, Vcm = 1.2V

Receiver:

VBB = 2V

After the transmission line, the AC coupling caps remove the DC common mode of the driver so that Voh = 0.2V and Vol = -0.2V, correct? I assume VBB sets the common mode of the receiver at 2V, so does that mean the inputs to the receiver are:

Vih = 2 + 0.2V and Vil = 2 - 0.2V?

And also is the bypass capacitor on VBB absolutely necessary?

Thanks


texts:
Pardon the possible simplicity of this question but I am incredibly new to antenna design. So, I settled on a simple loop antenna, made of 14awg copper and about 18inches circumference (tuned to 644Mhz) hooked to a Balun. I picked that size because that is the weakest channel I wish to receive. The antenna picks up a pile of other channels just fine but still gets no viable signal on that channel. I know that I cant just go about making things larger arbitrarily so how do I increase gain? Can I somehow add other loops (I think I saw a picture of this) and if so how do I chain these together?

N.B. I am height limited and this is stuck inside so the old advice of put it higher and remove obstructions is difficult.


texts: I'd like to count the number of vehicles traveling down a certain street. I'm reading about inductive loops, but that requires putting the loop into the pavement. I've also seen sensors that I imagine are magnetically based, like this one from Streetline. Is there a sensor component that I could hook up to an Arduino board to mimic that type of system?


texts: LM7812 power regulator 28v to 12 dc-dc converter wrong output

texts:
Hello I have an LM7812CT power regulator and I want to use it to convert a 28V dc to a 12V dc.

I am using the circuit provided in the data-sheet using 2 capacitors, one 0.33uF connected to the input voltage pin(1)and the ground ,and one 0.1uF connected to the ground and the output pin(3).

My problem is that I get output voltage 3.9-4.0 Volts.

I get this value even with 12V supply to input.

How can i fix it to get my 12V?

Where do you think am I wrong?
Is it burned??

Any ideas welcome

edit:: ok guys the LM7812ct was burned after all. I replaced it and everything worked ok!!
thnx and keep up the good work


texts:
I'm using an audio transformer SP-70 to isolate audio. (http://catalog.triadmagnetics.com/Asset/SP-70.pdf)
The question arises what is the maximum AC current allowed to operate the transformer without exceeding its ratings.
Driving audio parameters:

Vp-p =3V (or 1.125V rms)
Zsource=200 Ohm
AC coupled (DC is eliminated with a series capacitor)

Transformer output load:

Zload= design must survive short circuit

The datasheet states

Max. Ma DC Unbalance in Primary: 3mA (Am I correct to assume this is not applicable to me since I dont have DC?)
Power Level: 50 mW

Am I correct to assume that the last one is power dissipated by transformer? So If the output would be accidentally shorted the power dissipated would be (1.125V*1.125V)/200Ohm= 6.3mW?


texts: Fuel Injection Control through OBD port?

texts:
I am trying to implement remote control of a car, by connecting a GSM device to OBD port.

If someone is using my car, I need to remotely stop the vehicle by sending command.
Upon sending STOP command, GSM receiver & control logic in car connected to OBD port should send command to engine ECU to cut-off fuel injection.

Is that possible?


texts: Photodiode to Arduino interface for high lux measurement

texts:
I'm trying to create a photodiode interface for my Arduino Uno board that can measure very high lux values. This is to be part of my lightcontroller project for monitoring high wattage lamps (~1000w). I've made the following design to simulate this in Proteus, but since I don't own a lux-meter, I don't have a faintest clue how much current will go through the photodiode when exposed to a 1000w lamp.

Could I go with this approach in real-life?

Any suggestions/comments would be most appreciated!


texts: What is the difference between 960RGB and 1920RGB?

texts: In MIPI DSI display resolution, what is the difference between "960RGB * 1920" and "1920RGB * 960"?


texts:
How can a MOSFET cascode be explained (not calculated) intuitively?

Especiall I would like to know why it's output resistance is high and why the drain voltage of the lower MOSFET M2 is stabilized, i.e. changes very little when the ouput voltage (Out) is changed.

Would this be a correct explanation?

VG2 voltage determines the current going into the drain of M2. This current has to be the same for M1.
Gate-source voltage of M1 (= VG1 - drain voltage of M2) is adjusted so that the drain current of M1 is equal to the drain current of M2.
If output voltage (Out) is changed, the drain current of M1 would change due to the channel-length modulation of M1. But as the current of M1 has to be the same as the current of M2, the drain voltage of M2 (and thus the gate-source-voltage of M2) changes so that the currents are equal again. And this change is very small because the I_drain(U_drain_source) curve of a MOSFET is relatively flat and the I_drain(U_Gate_Source)-curve of a MOSFET is very steep. Therefore a big change of the Out voltage causes a very small change of the drain voltage of M2 (voltage is stabalized here). Therefore the current changes not much and the output resistance of the cascode is very high.


texts: about the high voltage capacitor found in charger circuit

texts:
A while ago i have opened an electronic balance charger for a reason to try understanding how the circuit works so I've drawn the entire circuit for that purpose but i no longer have the drawing, but i remember the place of high capacitor voltage in that circuit so i only drew the part where the capacitor is present, to illustrate
and which i would to know is the capacitor role in that circuit, According to what I understood is that capacitor role is Cut down an amount of voltage by acting as closed circuit During capacitor charging,
so my qeustion is that correct? and if is correct i would to know about the others lines connected with capacitor positive line does current will flow to them during capacitor charging a cause of high voltage? because i know in low voltage no current will flow to any line with resistance until capacitor fully charged,
notice : the power source is 220 V
and thank you all for any help.


texts: How can I use USB output (5V DC) to power a fan 12V DC load?

texts:
I would like to power a 5V DC/0.23A fan (beside another device such as 12V LED lamp, and 12V DC water pump). The only possible power source is using USB output, either from computer, mobile phone's charger, and most possible from power bank, which their output are 5V. I was trying to think to use BJT/MOSFET/IGBT, but seems are not possible, as the maximum voltage coming to the drain (in the case of N-channel MOSFET including to cascade the MOSFET, and IGBT) is 5V only, and BJT is not amplify the voltage.

So, how can I do it? What component should I use? Is anyway to do that? Appreciate any helps with design.


texts:
I want to use diode on 240V because I do not want current to flow in reverse direction. I use it and everything is ok except voltage drop. Actually diode drop voltage from 240V to 120V. How  can I get 240V by using a diode?
Thanks for answer. Because actually I have three toilet on my job and client want to use sencer for light and toilet fan to work. All three toilet have big one fan. So problem is when one sensor work other 2 toilet light goes on. Because all switch live combined in fan. That's why I want to use diode so when fan work no light goes on in another 2 toilet. Please do you have any other idea


texts: Building a “if” statement circuit where i can control different light diodes

texts:
I want to design a circuit to react in different ways depending if a microphone picks up one frequency and in different way if it picks up the some other frequency.
I want different lights to shine depending on what signal is coming from the microphone.
The circuit will only be analog.
The frequencies will be fairly far apart from each other, one of the sounds has around 0,5 seconds of pause time between beeps and the other has a couple seconds.


texts: What is the minimum electric field strength,that the induced electrical tester led begins to turn-on?

texts:
On the follow photo you may see the standard induced tester,which the led(not neon) inside
turns-on when you hold the metal tip of the screwdriver and move the other side of it close to sockets,
hot AC electric wire,etc,which have a voltage of 220V 50hz.This tester,as far as i know,detects only electric
field.

My
 question is:what is the minimum electric field strength(v/m),that,usually make the led to start turn-on?(the sensitivity)?
Thanks.


texts: Pull-up and pull-down resistors for RS-485 TTL I/O pins

texts:
I'm Using a THVD1451 for full-duplex RS-485 communication.
In Datasheet, for transient protection against surge transients, it's recommended to use the circuit below:

In this circuit, there is a pull-up resistor for 'receiver output' (R) pin, and also a pull-down resistor for 'driver enable' (DE) pin.
I have two issues here.
First, why there is no push-up/down resistor for 'driver input' (D) pin?
And the second one is that how to choose between pull-down and pull-up resistors for such pins?


texts: normally open or normally closed OptoMos

texts:
In the following OptoMos datasheet the OptoMos is defined as Normally closed, when there is no input the output is closed.
But in other OptoMos like the SFH618A-2 i can't find if the OptoMos is NO or NC.


texts: Heating element for Air Conditioner thermostat

texts:
I currently have a series of thermostats that are connected to a window air conditioner, one is used to check room temperature the other is to trick the AC to run to a lower temperature by switching on/off a heating element connected (taped to) to the AC thermostat.
The heating element that I am using is a night light bulb, which works fine except they are no longer making them (except for LEDs which don't put out enough heat) and they last about 2 or 4 months.
I found on eBay "12V-220V Constant Temperature PTC Heater Element Thermostat Heating Plate Tablet" which is rated to heat to about 200C at 110V.

Voltage: AC DC 12V          12V dry burning table temperature: 80℃ / 120℃ / 220℃ ± 10 ° C

Voltage: AC DC 24V          24V dry burning table temperature: 70℃ / 110℃ / 220℃ ± 10 ° C
Voltage: AC DC 36V          36V dry burning table temperature: 220℃ ± 10 ° C
Voltage: AC DC 48V          48V dry burning table temperature: 220℃ ± 10 ° C
Voltage: AC DC 110V        110V dry burning table temperature: 230℃ ± 10℃
I only need a temperature of about 40 degrees C /100F, so is there some way I can wire in one of the thermostats with a resistor/transformer, etc. or something?
I don't want to melt everything!
Thanks?


texts: If I know that the Ideal Diode only allows current to flow once V > 0, how would I go about implementing the two resistors into the IV graph? How do I analyse the circuit as a whole IV graph?


texts: My formula is v(t)=10cos(30pit). My theory is that Vmax is the 10 which means Vpp is 10V and -10V. Since the formula for v(t) = vmcos(w*t+theta)


texts: AC voltage on the outside surface of micro USB charger cable

texts:
My micro USB mobile charge cable is having about 98V AC voltage on the outside surface. (PFA measurement image. The black probe is connected to the Power socket Ground port. I could not take the whole picture with one hand) The DC voltage is about 0.02V w.r.t. the Ground.

Online QA websites suggested that this may be due to a faulty charging adapter. But I have inserted another micro USB cable into the same adapter and it showed only about 1.5V AC on the surface.

Then, I took another charging adapter and the same thing happened. The first cable showed about 47V AC and the second one only 1.3V.

Thus, it seems that it is not the fault of the charging adapter. My electrical knowledge is not very good. Can someone explain why is this happening?

Edit: Just to clear the confusion I created with the example of 2 wires, actually the AC voltage is always there at the adapter output. I have put my multimeter probe on the metal just inside the adapter (without touching any of the 4 wires inside). and the inside was about 98V AC. the 2nd cable's both bare end metals were not continuous. so, the voltage didn't appear on the micro USB end.

So, my question is, why is the AC voltage appearing and does this mean that the adapter has gone bad?


texts: How to have arduino only turn on when enough power has been collected?

texts:
There was recently an article in the Christian Science Monitor about the launch of a cracker-size satellite. The article says that the satellite has, "power storage in capacitors, and switching circuitry to turn on the microprocessor when the stored energy is enough to create a single radio-frequency emission — a digital beep." The power is collected from a solar cell.

I'm interested in creating an earth-based device which would do just that, collect power from a solar cell and only turn on the device to transmit when it's got enough power. I recently purchased an arduino, but have little experience with this kind of engineering. Any suggestions about how to get started? Thanks!


texts:
I have an outdoor electronics project which is running 5V DC through 12 AWG wire to power strands of LEDs through 24 AWG wires. The strands are powered in parallel like so:

5V/GND --------------------------------------- ...
          |     |     |     |     |     |
          |     |     |     |     |     |
          |     |     |     |     |     |      ...
          |     |     |     |     |     |
        LED1  LED2  LED3  LED4  LED5  LED6

My first try to get them connected was to use weather proof wire nuts to connect the wires together (so each nut has two 12AWG wires and one 24AWG wire). However, I don't think this is a good solution as these wires will need to be able to move with environmental events (wind, rain, etc.) and it seems like the gross mismatch in the wire gauges will cause the LED power and ground wires to be pulled loose.

I can't make the gauge of the power supply wires smaller since they run over about 50 feet and I don't want to suffer a large voltage drop, and I can't directly make the LED power wires thicker.

So, are there other any good connectors I can use, taking into account the large difference in wire gauges I'm working with?


texts: Resonance condition in series RLC circuit

texts:
While going through a book, I came across a statement "The magnitude of  transfer function is minimum during resonance".
What I did not understand is that transfer function means a ration of output to input, so across which terminal is the output taken?
Does it not matter, that is, is it minimum irrespective of the component across which we take output?


texts: I am designing a prototyping platform called evive. It is a learning cum prototyping platform for students and makers. Since many times we requires debugging of our circuits, so I thought to include some testing points in PCB. I came across this image: It is used in Dr.Duino (debugging shield). Can anybody explain what it is? Or any other idea about how to give test points in PCB for users, such that user can easily attach the alligator (crocodile) clips or Banana multimeter cable tips.


texts: How to measure headphone impedance for a target cut off frequency?

texts:
Lets say I have an audio signal with a DC offset and I want to use my earplugs to listen it clearly. Since I'm a human my hearing range is 20Hz to 20kHz. It means I need to filter very low frequency components i.e where f<20Hz. It means the cutoff frequency for the simple high pass filter circuit in my figure must be such that 1/2*piRC=20Hz. Here I need to know the impedance of the head phone (shown as R in the figure) to choose a proper capacitor.

At this point I'm confused:

My question is how can I measure this impedance? By simply using an ohmmeter? But what if it has different impedances in different
frequencies? Should I apply an ac signal at a particular frequency and measure its impedance? Is headphone impedance pure resistive?


texts: Battery charging questions Parallel charging and battery balancing of LiPos

texts:
I'm having a long discussion on an RC board regarding LiPo parallel charging.

The basic crux is that my understanding of how charging works is something like this:

Charger Line voltage of x(8.4v in this case) @ y amps (5.0) with 4 batteries connected.  The battery capacities are listed as 2x1000mah and 2x1200mah.

Each battery internal voltage will rise as current is soaked into the battery.  As each battery approaches 8.4v it will naturally soak less current up until the whole battery bank is approaching 8.4v at which point the peak current will drop low enough that the charger shuts off.

My assumption is that each battery will increase in voltage at more or less the same speed given that the battery bank is wired in parallel... That means the 1200mah batteries are soaking proportionally more current than the 1000mah batteries...

Or am I drinking too much moonshine?

The second part of the question regards balancing, my understanding is that the individual cells (2) are wired in series, this means that those cells have the potential to charge at different rates.  Therefore balancing is recommended, but probably not mandatory all the time?

Thank you for your time.


texts: Checking maximum current provided by charger, how?

texts:
Using only an entry-level multimeter (and an assortment of common discrete PTH components, say on a breadboard), what could be a reliable way to check the maximum current that a switched-mode AC-DC adapter can supply ?

The adapter in question is a typical mobile phone AC-DC adapter that is rated for 5VDC @ 800mA output, with 220-240VAC input. However, this is an el-cheapo east-asian generic, so hopefully one understand my reasons, to check if this can really source 800mA @5VDC or not.


texts: How to know about multiplexed inputs/outputs

texts:
I am working on AM3352 processor, and i need to know, which of the input/output pins are multiplexed. How to do this using datasheet, it may sound simple thing, but i am new to the  processors. Please Help.

Link to datasheet of AM3352


texts: if you have a control circuit of 120V on the secondary side of a transformer which you have fused at 1.5 A since you are using a 150VA dry type and you connect a wall outlet plug in that 120V circuit and the device's ac/dc power adapter has an input rating of up to 1.5A on from 100-240V then won't potentially blow your secondary fuse on the transformer since it is pulling 1.5As?


texts:
I am using NXP's LPC1768 development board and I came across the User Manual for this part and page 67/849 section 4.10 descusses the External Clock Output. I couldn't figure out which pin out of the 40 pinouts on the board is this clock out sitting on. By Googling around, I found this code that is supposed to output 10MHz:

/* clkout of 10mhz on 1.27 */
LPC_PINCON->PINSEL3 &=~(3<<22);
LPC_PINCON->PINSEL3 |= (1<<22);
LPC_SC->CLKOUTCFG = (1<<8)|(14<<4); //enable and divide by 12

But again, I am not sure which of the board pins this clock is coming out from? Or do I have to solder a connection to somewhere on the board?

UPDATE
I have tested the code that Nils Pipenbrinck provided. It works. But I am not sure if there are limitations on that clock output and its accuracy. Here are screenshots for frequencies 10MHz, 5MHz, 1MHz: - it seems to degrade as you we go higher. Any input on how to improve the signal's shape and accuracy?


texts: How to solder wires on to this power barrel plug?

texts:
I got this power barrel plug.
http://www.digikey.ca/product-detail/en/PP3-002A/CP3-1000-ND/992136

It doesn't have any hole for me to put a wire through. The wire just goes into the hole for approximately 0.5cm. How am I suppose to solder this? I also tried crimping it, but it flatten the tube and causes the centre pin to touch the bottom pin.

Also I found it really hard to solder even on the bottom pin as the solder doesn't really stick to it.

I wonder if anyone could give me some suggestion on how I can attach wires onto this barrel plug.


texts: How to get a 1 clock period pulse from a constant signal clock input on every 64 clocks?

texts:
I would like to "extract" a one period pulse from a constant clock signal on every 64 clocks. This pulse signal is to be used for reset. What kind of logic circuit should I be looking for?
Thank you.


texts: Inconsistency in a simulation using Multisim

texts:
After simulating the following circuit in Multisim :

I got these timing diagrams (1 ms/Div and 5 V/Div) :

I think that the output Q is inconsistent , shouldn't it look like this instead  ? :


texts: Superheterodyne receiver channel selectivity

texts:
I am new to RF so I have quite simple question about topology of superheterodyne.
I am facing with adjacent channel selectivity problem.

The problem is that I can't obtain selectivity more than 40 dB.
F.e. when wanted channel frequency signal had ampl. level 1 dBuV and adjacent channel frequency ampl. have more than 40 dBuV receiving process is broken. Both frequencies are provided to antenna circuit by sumator.
Similar problem - 20 dBuV (wanted freq.) and 60 dBuV adjacent freq.

It is not a issue of IF filters stage - problem doesnt't occur when IF frequencies are directly modulated and provided to IF stage skipping first mixer and LNA stage. Then almost 85 db selectivity is obtained.

The problem is VCO (to first mixer) frequency reference from crystal.
Due to phase noises output frequency (from VCO) to first stage mixer have only 40 dB difference of amplitude between center frequency and + / - 20 kHz.

So, if any adjacent channel frequency have amplitude 40 dB bigger than wanted freq. channel it's mixed with phase noises from crystal / VCO and have higher amplitude than wanted frequency (so it is totally corrupted).

The question:
Is there any topologies or f.e. limiters / attentuators at the RF antenna signal stage to limit unwanted signal without limiting wanted 40 db lower signal?

Thanks for any answers.


texts: Working display connected by GPIO pins to microcontroller?

texts:
Would it be possible to add a normal HDMI port or a display to any microcontroller with the GPIO pins?

(I didn't buy anything yet, I'm just getting information before I buy...)

EDIT: Thanks for all the information guys, a moderator should probably close this discussion now...


texts: Estimate current draw for battery replacement

texts:
Trying to revive an old electronic keyboard.  It is labelled to take 9-12V and I have an appropriate connector, but don't have an idea of how much current to allow for.

It can also be powered by 6 D cells, and presuming that they should last for some non-trivial length of time, that should give some kind of reasonable approximation, but I don't know the calculation to do.

So, if I want to use a wall-wart or line-lump transformer of big enough but not overkill from my junk box, how to reasonably estimate from the 6-D batteries to how much current to allow for?


texts: what is the difference between coin battery and alkaline battery

texts: i'm quite curious with coin battery and alkaline battery. I have submerge 2 coin battery into the water and the battery short circuit and damaged after a while. While i put 2 alkaline battery into the water, but they still can perform well. i wonder why both type of battery is short circuit, but only coin battery will damage. Does anyone know why?


texts: Making complex boolean circuits that give true as output only for a specific combination of boolean inputs

texts:
This is my first question on a stack exchange website so please bear with me.
I am making challenges for a jeopardy style capture the flag event in my college and I had come across the minetest challenge in the hardware section of google CTF qualifier conducted last year. A clean and organized solution to this problem has been provided by liveoverflow.

I would like to design a simpler version of this problem for my college's CTF event but I am unable to design a complex circuit that gives true output only for a specific combination of inputs. I know that a circuit with this functionality is not very difficult to implement and just needs to represent the following logic:

trueinput1 AND trueinput2 AND ... NOT falseinput1 AND NOT falseinput2 ...

However I want it to be vast and complicated so that participants cannot decode its functionality just by doing a visual analysis. Is there any technique to complicate the boolean logic above and to design a corresponding circuit that looks ugly even for a small number of inputs(32/64).


texts: Why battery chargers take a pair of batteries and not one?

texts:
I have a number of AA- and AAA-sized NiMH rechargeable batteries ('accumulators'). All the chargers I encountered allow to charge 2 (4, 6, 8,..) such batteries at a time, but never a single battery.

Is there a good engineering reason for this?


texts: How to make 5 volts PWM form 3 volts on stm32?

texts: I am generating PWM on the transistor with help STM32, PWM voltage of 3 volts, but the transistor is "fully open" somewhere on the 5 volts. How to make PWM voltage 5 volts, or are there transistors which can be opened fully at 3 volts and capable of flowing a current of about 20-25A current and 50 volts? Maybe there are another solutions to my problems that I will be very glad to hear it.


texts: How to prevent large inrush current without a reset-fuse

texts:
In another question (DC-DC booster fails with lead-acid battery source) I described a problem with a DC-DC booster that destroyed itself by dragging a large current when its output was disconnected.

This did not happend when the power source was a sw-mode (maybe due to its overload circuit), but when a Lead-acid battery was used who could deliver large burst current (>40A).

Apparantly this is a consequence of the DC-booster design. So I need some shut-off circuit which could be a resettable fuse, but I think that this is somewhat a primitive solution.

Maybe its possible to use some power FET, but im not much into how to design control a shut-off state at, say at 8A - and certainly not to make it well working.


texts:
I'm a beginner in electronics, so I just have an idea in my head and don't know how to actually make it. I want to make a countdown circuit, for an event in next 5 month. The display format is like this:

DDD HH MM SS

Days have 3 digits, hours, minutes and seconds have 2 digits and I want to show the numbers on 7-segment displays. I just want to show remained time to a specific time, some day in October. I want to make it with a PIC or anything that you suggest.
I googled it, but just found a MM:SS countdown circuit. I can't expand it for solving my question. How can I do that?


texts: the relationship of amps to rpms in an induction motor

texts: when searching for a 2000 watt induction motor online the rpms seems to range from 3450-3600  Why? if you wanted to double rpms to say 7000 ,is that possible and if you are using 3 phase 220 V line, how would amps be effected. where can I study about this? I am a novice


texts: Time scale comparison between fast-fading and path-loss in wireless communications channels

texts: As I know, when receiving mobile users move, the fast-fading channels between transmitter and receivers may vary very quickly as wavelengths change, e.g., every 2.5 ms. On the other hand, when we model users' distribution as PPP, we have path-loss changes as well, e.g., 1 m displacement in 6 ms if 60km/h. However I am wondering how significant path-loss changes compared to wireless fading channels changes. Do they (fading and path-loss) have different time-scales for changes? if so how  do we get rough idea on those changing time scales?


texts:
I have already read a few EE texts where a sine wave is often seen.

Why is the sine wave often used as a test function for a circuit or a system? Why don't we use any other signal instead of sine?

Do we use sine waves as test signal because of the fact that they are common, (for example, AC power)?


texts: Multiplexing 24V signals to DC load generator

texts:
(Electronics beginner)
I have a DC load generator (TENMA 72-13210 a rebrand of Korad KEL103).

I want to use if for testing a custom board designed in-house with 30 outputs each capable of driving 10A loads at 24V. The output signal is either 0V/24V or a PWM signal. The board measures the current produced on each output. I want to verify how well the boards measurements matches the actual load reported from the load generator.
My DC load only supports one input so I can only test one output at a time. It would be great if I could create a gadget that let me remotely switch between which output is connected to the DC load. Something that I can control from my PC via some means.
I view it as a spare-time learning project (but that will be useful for me in my work now that I'm forced to work from home during the pandemic). Ideally I would want the ability to test several outputs at once, but I want to make the gadget simple enough so that I will be able to finish it. By reusing the DC load I get rid of the complexity from implementing my own DC load.
I guess I'm thinking of something similar to a Multiplexer Switch but much simpler and cheaper - a weekend project.

How can I do "time-divided multiplexing" of the output signal to the board? Do I need to create a tree of power transistors that I control from a microcontroller or SBC (raspberrypi/beaglebone black/...) or are there ready made components to achieve what I want?

Do I need to worry about one output back-powering another? If so, how prevent it? Diodes? Is break-before-make the term used here?
What are the trade-offs between using relays; discrete MOSFETs; or integrated Load Switches?
How much will the switching mechanism affect the readings? How much load will they add?

Sorry for the vague question. I'll try to fill in details as I learn about the proper terms.


texts: What technique is applied to a traffic light system to make sure it is still safe even when errors occur?

texts: From time to time traffic lights stop operating properly - and so instead of directing the traffic they start flashing yellow and someone from the traffic maintenance must show up to fix them. Does anyone know what  technique is applied to a traffic light system to make sure it is still safe for us even when errors occur?


texts:
I recently bought a SFP fiber transceiver module to play around with. My idea was to connect the transmitter pins to a waveform generator, loop the optical output to the optical input with a fiber cable and then look at the receiver pins on an oscilloscope.

What I saw on the oscilloscope was an ugly 100MHz sine wave, but I only have 100MHz bandwidth on my scope so I assume the measurement is not valid at all.

Anyway, this got me thinking... Is it possible to transmit, let's say, a 1MHz, 50% duty cycle signal using a fiber transceiver rated at 1.063Gb/s, or do you have to transmit and receive at the rated value always?


texts: How to sink current to drive 7-segment LED using a 4026 chip?

texts:
Am referring to this project here;
http://electronicsclub.info/p_random.htm

with a schematic like so;

Key points:

Resistors are not required for the LEDs because the 4026 IC limits the current to about 5mA for each LED
Outputs of the 4000 series chips can sink and source only about 1mA

I am now actually connecting a 7-segment (single digit) LED which going by the circuit shown, needs to be a common anode component, however i ended up getting a common cathode version and am now wondering how i should reroute the circuit accordingly.

My guess is it's not quite as simple as reversing the above schematic and connecting the LED (single anodes) up to the 9V rail, with the single common cathode down to GND.

Do i now need current-limiting resistors for the 7-segment LEDs ? Would it be one for each (anode) pin out of the 7-segment LED or would just one suffice, ie. on the common cathode before connecting down to GND.


texts: How to amplify the 0-60mV voltage drop of a current (sense) shunt to 0-10V?

texts:
I want to measure the current of my system with a shunt.
My system has a maximum current of 10 A.
How can I change the 0-60mV signal from the shunt to a 0-10V signal for my PLC?


texts: what's that symbol in the attiny13a I/O schematic?

texts: I was reading the ATtiny13A datasheet and I can't figure out what's that symbol in the general digital I/O schematic. I've circled it the figure below.


texts:
Suppose I have a digital signal, or at least a signal that is gnd referenced.  Like a NTSC video signal for instance like this:

Then I have a single supply opamp, and I want to amplify this by 2x say.  I think that if I just input this to a simple opamp circuit with 2x gain that my signal will clip because it will be amplified around my virtual GND.

So then instead I have to add a DC offset probably equal to my virtual gnd voltage so I can amplify without clipping?  I think I understand that to be true but maybe my understanding is wrong.

Then my last question is after I've done this and amplified the signal the output is going to be centered around my virtual gnd voltage.   So how do I get my signal back to DC (assuming my receiver is not AC coupled and he expects levels referenced to 0V DC).  I can't just subtract the DC offset, since my signal amplitude will vary I don't know the right amount to subtract.

I've read a little bit about DC restoration circuits, but I'm not sure if I'm on the right path or not.


texts:
I'm designing a project that I need to save data logs into Tags. I've chosen NFC because it has high capacity tags compared with RFID. I've checked the Mifare 8KB cards like this one.

I have two questions about these, first how much user space I get for an 8KB tag, and second how much it takes to read and write the full capacity? I haven't got my hands on these but I was wondering if anyone had a similar experience.

Also, I found that there are many types out there and I was wondering what are the main differences between those besides capacity.


texts:
I need to design a LED chaser that expands as you add modules, modules are daisy chained to each other over long distance.

I was thinking of using a master and N number of slaves, my first though is to use UART as I can transmit commands from one module to the other. But how do I transmit the number of connected modules in the system to the master. The master will be a MCU that will control the pattern of activation and timings. The slaves can also either be small cheap MCUs or some LED drivers or something else.

Here is an illustration.


texts: LPC1768 Power Supply Design (an unknown symbol)

texts:
I have a question about power supply design for a board which use an LPC1768. Below image is taken from http://www.nxp.com/documents/other/IAR_LPC1768_Eval_Board_Schematic.pdf document.

There is a symbol in this schematic named "CLOSE". I want to be clear about what it is. My guess; it's the bridge connection between power planes for analog and digital. But I want to be sure before I start to do my design.

Please help, thank you.


texts: Route multiple analog (audio) signals using a single switch

texts:
I'm working on a guitar wiring project (=> I'm confined by space and I'm working with high impedance, low voltage & current signal) - it's a router for pickup wires (there will be 5 "banks" that will connect the pickups in a certain way). There are 10 wires from the pickups + 2 (ground and hot lead from output jack).

These 12 wires will need to be switched by a 5-way switch (in each position, they will be connected to a single bank) - essentially, I need a 12 pole 5-way switch.

It doesn't seem like it's possible to buy these anywhere (for understandable reasons) - I was thinking about using a set of multiplexers - that would, however, require power source which I'd like to avoid.

What are some other possibilities? Does multiplexer work with analog signals without introducing delay or distortion?


texts: I have a Radio Shack DMM (Cat #2200811).  I'm trying to test a 100uf 16v electrolytic capacitor on the auto range capacitance setting.  I tried it with a 30uf 160v cap. and it worked (measured as 29uf) so I assume the meter works.  But with the 100uf cap. I keep getting readings that are all over, such as .198nf then jumping to 50uf then O.F.  To do the test, I've stuck the cap. leads into a piece of cardboard and I hold the meter leads to it.  I think I have the polarity correct. I've tried 2 of these caps. and gotten the same results.  Do I just have 2 bad caps or am I doing something wrong?


texts:
Dip meters are no more manufactured (and old ones are no more calibrated). These devices were thought to be very useful to a large game of ham radio and electrical engineers.

Usually, when a device disappears, this is because there are cheaper or more powerful devices on the market.
Yet, it is not obvious what has actually replaced dip meters.

My question is:
What is the modern replacement for dip meters?

or, to put in a more practical way, when you have to measure the resonance frequency of a circuit (without connecting it physically to a measurement device), what do you do?


texts: What does "run a panel" mean in the context of PCB/PCBA fabrication?

texts: A design engineer told me our PCB prototypes would be completed soon and then he would have his assembler "run a panel". Does anyone know what that means?


texts: Do multimeters take into account their own internal resistance?

texts:
When considering sources of error for an experiment measuring the resistivity of a length of wire, the internal resistance of the multimeter I used to measure the resistance came to mind. Would this be accounted for by the multimeter or be a legitimate source of error?
Any help is much appreciated. Thanks a lot.


texts:
I'm trying to figure out the best way to build a small "wall" of 20 different OBD-2 connectors which would be use to initialize a set of OBD-2 compatible devices.  The situation is that I need to be able to have a user plug in a set of these devices and just walk away and come back later and they have all been initialized.

I've tried dealing with the signaling (and level conversion) necessary to emulate one of the OBD-2 protocols and have given up main due to lack of time.  So I'm looking at using one of these OBD-2 simulator boards, e.g. http://www.ebay.com/itm/like/152464135531

My question is electrically what is the "normal" mechanism for connecting a series of circuits from one pathway to the next? I think only need 4 wires for each device to make this work (a bus plus and minus, an overall 12v+ and overall ground - probably can combine bus minus and overall ground).  But the idea would be to use a Raspberry Pi or Parallax Propeller board to connect the simulator device to the first physical port, wait 2 minutes, then connect it to the second, etc. and so on.

If I use a transistor to trigger the pathway (from 3.3v on the microcontroller to whatever the higher voltage is - 5v for the bus or 12v for the overall power) the flow is essentially one-way, which works for power but not for an actual data wire which is being driven and sensed alternately from both ends.

Is there some normal way this is done?  Perhaps some inexpensive piece of hardware that does this sort of thing that I should be looking at?


texts:
I have a circuit with 2 PNP transistors, probably one of these is broken. One of these tested gives me a diode between Collector(+) and Base(-) while open circuit if I change the polarity of the test.
The second PNP instead gives me a diode in both direction so I guess this is the broken one, am I right?
And what exactly means "broken"? What happened?
PNP here


texts:
I built a prototype of a frequency-to-voltage converter using a LM2917 following exactly the "Minimum Component Tachometer Diagram" example schematic - just to play a bit and understand how it works.

It happens the IC draws too much current, and without limitation it will burn in a while. I checked several time my breadboard and seems ok.

To exclude any error, given a new IC I connected pin 6 to +12V and pin 8 to 0V and nothing else. Even in this case the behavior is the same.

Is there something obvious I'm missing? I can accept my circuit is wrong, but why I can't just power the IC using pin 6 and 8?


texts: 18/4 connector for repeated plugging and unplugging?

texts:
I'm designing a device for off-grid DC power delivery. Because this is a fairly specialized system that wants to minimize complexity and whatnot, the plan is for the power supply and load to be decoupled, with a bare minimum of circuitry on the load side. Accordingly, the plan is to connect the two with 18/4 (18 AWG, four wires) wiring which can be plugged in and unplugged as needed.
Requirements:

Suitable for 18/4 wire
Rated for at least 1000 plug/unplug cycles
Rated for at least 12 V / ~2 W (~200 mA)
Ideally neither the inner nor outer insulation jackets are exposed ("looks finished")
Should be "easy" to plug and unplug (screwing on is okay — "easy" doesn't have to mean "quick" — but having to struggle to get it to let go is undesirable)
Mechanical (not just solder) connection between the plug and wires would be preferred
Ideally can be flush-mounted to a housing
Optionally dust-proof; does not need to be waterproof

Possibilities:

Molex Mate-n-Lok
Molex Mini-Fit Jr.
SATA
"Kycon"
XLR
GX16/GX20/GM21/GM21
NMEA 2000

Would any of these be suitable? Mate-n-Lok are a PITA and I've heard Mini-Fit Jr. isn't suitable for repeated plugging and unplugging, plus neither of them would look "finished". I'm not very familiar with the others.


texts: How do you output whole number voltages (1-4V) from an Arduino/5V source using only digital pins and passive components?

texts: I would like to output whole number voltages 0V,1V,2V,3V and 4V from two digital pins on an arduino/5V source. A simple r2r ladder doesn't seem like it would work because it would split its definition across the whole 0-5V range. Is there a way to lower the 5V output to 4V and then feed it into a 2 bit r2r ladder?


texts:
I have currently built a buck-boost converter using LTC3780 on a breadboard following this deisgn.

The circuit is calculated and designed to accommodate the input voltage given in the schematic. I have checked countless times and ensure that there is no mistakes in the connections. However the output that I am getting is only a noisy 6V. The switching signals that I observed on the oscilloscope is also fairly noisy. Can someone enlighten me how to troubleshoot this converter?

Thank You


texts: Constant Current Source using Fixed Voltage Regulator

texts:
I was in the process of building a 2W laser diode driver and I realized after some debugging that I had a 3.3V constant voltage LM1086 chip instead of an adjustable voltage regulator. I intended to build a constant current source that is adjustable up to 1000mA. The following circuit replicates what I put together on the bench using an LM1086 for regulation. Ignore the LM317, I didn't have an TI LM1086 chip to insert into the simulation.

My wrong chip selection made me wonder, can you use a fixed regulator to create a constant current source or do you need an adjustable one?

As an aside question is this approach in general a good method of driving a 2W laser diode or are there better circuit architectures?


texts: heating a 5 ohm resistance with a 9V Battery

texts:
Hi I am working on a project which involves heating a resistor with a 9v battery. I am heating resistance because I want to increase the temperature of a temperature sensor so that I can do something with arduino after the sensor reaches a specific temperature.

But when I connect the resistance across the battery the voltage drop comes out to be 0.5 volts instead of 9v. And the resistor is not heating up.


texts: Building an electromagnet to work over an air gap

texts:
I am currently working on a project where I am building an electromagnet that works over an air gap. Specifically a gap of about 0.3 inches. The electromagnet type was selected because I need to be able to turn it on and off based on input sensors to my micro-controller. Also all of my design work has been done in solid works using their Emag plugin.

How for the real grit. The essential problem I am having is that to make the electromagnet strong enough, I have to increase the size to a point where it is becoming too heavy for my project (too heavy is roughly over 3 lbs). Also the magnets should have a pulling force of about 50 lbs over the air gap from before. Furthermore I have dabbled into designing electro-permanent magnets but they, one also become to heavy, and two do not entirely turn off.

So here is my questions for you all:

Has anyone had experience making electromagnets that work over air gaps that could give me pointers?
Or has anyone had experience making electro-permanent-magnets that work over air gaps that could give me pointers?

EDITS:

The magnetomotive force required is calculated below.  It takes into account the reluctance of the core, the air gap, and the material it is attracting. The material is 1008 12 guage steel.  The core is either Vacoflux 27, which is 27% cobolt and 73% iron, or we may use high purity Iron, around 99.98% purity.  Currently we have been using SolidWorks EMS plug in to do FEA analysis of the magnetic fields instead of using equations.
N=number of turns;
I=current;
F=desired physical force;
Lm=length of magnet;
Lp=length of plate;
Z=length of airgap;
Uo=permiability of air;
Up=permiability of plate material;
Um=permiability of core material;
Sm=cross sectional area of magnet core;
Sp=cross sectional area of plate;


texts: Transmission (TX) halts using FTDI 232RL with ATmega328-PU

texts:
FTDI seems to be a popular forum topic, but I can't seem to find an answer to a confounding issue I have. I'll try to give as many details as I can, since I can't seem to narrow down the issue.

I am using an ATmega328-PU (the cheaper problem-child for ArduinoISP users) with an FTDI 232-RL Breakout Board. I was able to burn the Arduino bootloader using the breakout board with no problem, as well as load the sketch I am using.

Now, I am trying to use the FTDI serial com port from my PC to interface with the 328. The only pins I am running from the breakout board to my board are the TX, RX and GND pins. I am using a Baud Rate from my serial port of 115200.

Symptoms: the RX indicator flashes consistently, so it's getting lots of happy bits from the PC. The TX indicator flashes for about 1 second, then quits. No happy bits from FTDI to ATmega328.

I have no reset button on my 328 circuit, just a resistor to +5V. I have a 16MHz external clock in my circuit. I have attached my sketch's setup code for additional reference.

Now, the questions:

1) Do I need to do anything with the CTS and DTR pins coming from the breakout board?

2) Is there an internal clock still on the ATmega328 that's screwing me up (even after the bootloader? If so, how would I go about disabling it?

3) Is there a need for a reset button in my circuit if the sketch is already loaded?

Hopefully someone can shed some light onto my issue. Much appreciated!

Here's the setup code (after declaring pins on 328):

void setup()
{
  DDRB |= (1<<1)  | (1<<2)  | (1<<3) | (1<<5) ; // BLANK, SS, MOSI, SCLK as OUTPUTS
  DDRD |= (1<<3)  | (1<<4) |  (1<<6) | (1<<7) ; // VPRG, XLAT, GSCLK, Debug as OUTPUTS
  DDRC = 255;

  XLAT_Low;
  BLANK_High;
  VPRG_Low;
  Debug_Low;

  //Timer 1 (16bit)
  TCCR1A  = (1<<WGM11) | (0<<WGM10);            // Fast PWM with ICR1 as top
  TCCR1B  = (1<<WGM13) | (1<<WGM12);            // Fast PWM with ICR1 as top
  TCCR1B |= (1<<CS12)  | (1<<CS11) | (1<<CS10); // external clock (T1) on rising egde
  TIMSK1 |= (1<<TOIE1);                         // enable overflow interupt
  ICR1    = Gray_Scale_Depth;                   // Grey scale depth for TLC-PW

  //Timer 0 (8bit)
  TCCR0A  = (1<<WGM01) | (0<<WGM00);            // CTC
  TCCR0A |= (0<<COM0A1) | (1<<COM0A0);          // Toggle on Compare Match
  TCCR0B  = (0<<CS02) | (0<<CS01) | (1<<CS00);  // No Prescaler
  OCR0A   = 0;                                  // f(OCR) = F_CPU/2/Prescaler

  //UART Initialisation
  UCSR0A |= (1<<U2X0);                                 // Double up UART
  UCSR0B |= (1<<RXEN0)  | (1<<TXEN0) | (1<<RXCIE0);    // UART RX, TX und RX Interrupt enable
  UCSR0C |= (1<<UCSZ01) | (1<<UCSZ00)             ;    // Asynchrous 8N1
  UBRR0H = 0;
  UBRR0L = 1; //Baud Rate 1 MBit   --> 0% Error at 16MHz

  //Enable global interrupts
  sei();

  //Configure SPI
  SPCR = (1<<SPE)|(1<<MSTR);
  SPSR = B00000000;

  ptr=display_buffer;

}


texts: How to prevent a battery powered microcontroller(ESP32) from reseting when motors start running?

texts: I am working on a brushed motor quadcopter. It is powered by a 3.7V LiPo Battery. I have an ESP32 microcontroller which sends PPM signal to a SP Racing F3 EVO Brushed flight controller. The 3.3V to the ESP32 are provided by a LDO regulator(MCP-1700-330) and the flight controller board is powered directly by the same battery. The issue I am facing is that when the brushed coreless motors start running the ESP32 resets(via Brownout Detection). I read similar threads which suggested using large valued capacitors at the regulator input/output else using separate power supplies. In my case I did try large capacitors(470uF) at the input of the regulator but the ESP32 still reseted. And it is not possible for me to use a separate power supply. Please help me as to how I may solve the issue.


texts: Starved thermal on GND or starved thermal on power

texts: These errors can make me a short circuit in my PCB which consists of 4 layers (top, power, GND, bottom.)


texts:
I'm making experiments with simple SA602 (formerly NE602) chip to educate myself build radio circuits. I started with local oscillator circuit. I used a 10 Mhz crystal. It oscillates at that frequency. But it is not stable at its khz digits. I assumed it should have been 1000000 Hz.

Is this oscillation normal or should it be a fixed value?


texts:
I am having a weird issue with the enc28j60 controller and atemga8. I am trying to build this circuit:

I am using this schematic to power up the circuit with a 9V battery:

  (all the capacitors are actually 10uF)

The enc should respond to ping but I have to plug in/plug out the battery a few times before it works. Also it seems that when I add a new battery it doesn't work at all. Only when I use a slightly older 9V battery (multimeter tells me it's 7V) it works from time to time.

Any idea why is this happening since both lm accept a wide voltage range ?


texts:
I am trying to measure the temperature of a battery pack using Zener diodes.
I want to use Energus's Tiny BMS 30A. In their battery modules they use Zener diodes to measure the temperature of the pack like this:

I want to copy their design, as it is very elegant and simple. But I need a Zener diode which can match the voltage curve of the ones used in their design, sadly they don't specify the diode.
I am having a hard time wrapping my head around voltage temperature coefficients.
I can't find a graph showing the relation between temperature and voltage for Zener diodes I looked at.
I also a bit package constrained, to SOD-323, SOD-523, SOD-723. The supply voltage is +5VDC.
Help would be greatly appreciated.


texts: PIC18F25K80 can transmit over CAN but can't receive

texts:
I've built a prototype circuit on a solder breadboard. I've connected the PIC18F25K80 to MCP2551 as shown in the schematic for this demo board. I'm running the example code from Microchip's website for CAN Mode 0 and CAN Mode 2 on PIC18, only modified to use PORT A rather than PORT D, as PIC18F25K80 does not have PORT D.

I have a 120 ohm termination resistor between CAN_H and CAN_L on the MCP2551.

The system is connected to my PC via a sysWORXX CANmodul1 CAN-to-USB adapter. Using PCANView, I can receive a message on my PC when sent from my circuit. However, I can not get the microcontroller to receive a message sent from PCANview. If I scope the CAN_H and CAN_L pins, or the CAN_RX pin, I can clearly see a digital signal traveling through the circuit and into CAN_RX.

I have tried disabling filters via changing RXM1 in RXB0CON and RXB1CON, but it doesn't seem to help.

How can I fix this problem?

EDIT1: I've been fiddling around with it a bit more, and I've noticed that RXB1D<7:0> holds the data I transmit after transmitting. The operational mode at the time IS normal (not loopback), so should the message ever be getting to the buffer? I currently have all filters and masks off.

Also, I'm using B0 through B4 as additional Rx buffers in Mode 2 (FIFO), and B5 as a Tx buffer with auto-RTR.

For reference, I'm using MPLAB X 1.80, C18 v3.46, and a PICkit 3 set up for in-circuit debugging.

PIC18F25K80 datasheet for reference:
http://ww1.microchip.com/downloads/en/DeviceDoc/39977f.pdf


texts:
This is the circuit that I built: (desired voltage levels are described next to the circuit)

simulate this circuit – Schematic created using CircuitLab

I tried to make proper bias conditions for this circuit, but failed (I tried many different similar examples before). The problem is that there is too high Vbe on Q2 and Q3, but the Vbe of Q1 is actually negative; Q2 and Q3 are saturated; Q1 and Q2 are unbalanced, of course.

You may be wondering why Rc* and Rc** are not the same - I tried to make a voltage divider for Q3 (to properly set Q-point) with Rc*, so I would be making another divider for Q3 (one resistor less).

R4 and R5 were meant for a negative feedback for later on AC experimentation, but already failed at biasing point.

Something is very wrong in this circuit but I cannot find what would that be. Can anyone spot and describe mistakes I made?


texts:
I, like many others, am playing with a DVD drive stepper motor. I ordered some L298N driver boards, hooked everything up and got movement, but it's choppy. I've tried every orientation of the motor wires. I have identified my coil pairs, but I don't know which is considered A+ and A- or B+ and B-. I've got the arduino set up to run the stepper at 120 rpm and I've determined that the motor itself is a 20 step-per-revolution one. I can tell it to move clockwise and it does, as well as counter-clockwise, but as I said it's quite jerky, and both the heatsink on the L298N chip, as well as the motor itself, get quite hot.

I'm not sure what other information would be useful, I can post a schematic or drawing of my wiring. The code I'm using is just the stepper_oneRevolution example in the arduino IDE. Is the choppiness due to driving it by full steps, or at low speed? Any help would be appreciated!


texts: Auto snap to the selected component when press "M,S" in Altium

texts:
In Altium schematic editor, select one component, and press "M", then "S" (move the selected object), when you press the mouse button now(anywhere on the sheet, even not on the component), the cursor will snap to the component automatically. But in PCB editor, the cursor won't snap automatically, is there any "settings" to make it behave the same in the schematic editor?

Update:

Let me explain in details. Actually, I'm using two displays, one show the schematic, another show the PCB, and I check the "Cross Select Mode" under the "Tools" menu. So, when I select one component on the schematic, the component with same designator will be selected on in the PCB editor, but the selected component may not be visible on current screen, such as if you don't zoom the board to fit to your screen. Now when I press "M,S" in the PCB editor, I want the mouse snap to the selected component without navigating to it manually. This will make the component placement more easy.


texts: Beef up inverter by adding more mosfets?

texts:
I have a 120 V, 500 W halogen work light that needs more power than my inverter can handle. It is one of those generic 120 W continuous power inverters you find in those jump starter multi tools.
Opening the inverter up, there are two MOSFETs inside. If I got more of the same MOSFETs, could I just add two more in parallel on each side (6 total) for more output power or is it not as simple as that?


texts:
What is the full code name of this electronic device?
This is an electronic device on the mainboard of a Samsung laptop.
Only "6GT" is written on the surface.

The ball pen is visible at the bottom side on pictures.. it is small size.

Length 2mm Width 2mm side device


texts: Second-Order Low Pass Filter Configuration

texts:
Can someone explain why this is a second order filter, and what both sets of resistors and capacitors do?

Also, I read somewhere that both sets are low-pass filters. If that's true, why do we need two sets? I know it attenuates it at -4odB/decade, but how does having two sets of low-pass filters make it do that?


texts: Replacing li-ion cells in handheld drill battery

texts:
I am considering to replace the 18650 battery cells in a 3S1P 11.1V cordless drill battery pack rated at 1300mAh, with three 2200mAh cells from a salvaged laptop battery pack.

One of the four cells in the laptop battery pack was bad (0V), but each of the other three had a nice 4.1 volt charge.

Should I consider all the cells from the laptop battery pack bad?

Is it likely that the charger for the 1300mAh pack can't handle charging a 2200mAh pack?


texts:
How much variability is there in the thickness of a standard PCB?

Let's say I order a 1.6mm FR-4 board. Will the actual thickness range 1.5mm-1.7mm? 1.4mm-1.8mm? 1.59mm-1.61mm? What is the (approximate) value of x in "1.6mm ± x%"?

What if the board is ordered thinner? (say 0.8mm)

How does controlled impedance affect this range? It's supposed to specify that the dielectric thickness must be controlled, but how much does it actually reduce the variance?

I'm assuming this all varies somewhat by manufacturer, I'm just looking for some reasonable guidelines for what to expect.


texts: Is there a circuit like a flip flop but with 1 input and 4 outputs

texts: I've searched online and can't find anything other than sequential circuits but I'm an amateur just trying to do my thing and don't understand anything. I need a circuit with lets say inputs X and outputs A B C and D when I push a button to pulse X, it will activate A. When I push it again it will activate B and deactivate A. So on and so forth. Any help would be appreciated, thanks!


texts: What do these numbers represent in this schematic diagram?

texts:
What are those 1 4 and 2 3 on both sides of the button? They look like having connected to same places at both ends, it looks like redundant cable to me.

So, what are they representing?


texts: Remove DC offset from op-amp output to allow increase in gain

texts:
I have the following circuit which amplifies a 50 KHz signal and works ok. I would like to increase the gain of the second stage (by making R3 smaller), but when I do the output of the second stage is pulled upto 5V.

There appears to be a small DC voltage being amplified. I though the 680pF capacitor would filter this out, so only the AC component was amplified, the 680pF doesn't seem to help.

Is there a better was I can remove any DC offset at the input to the second stage?

Thanks

UPDATE: First op-amp output distortion

I have attached two scope images which are both of the output of the first amplifier while experimenting with R3/R4 values. The distorted signal is when the gain of the second amplifier is set to 75 (R3 = 6.8K, R4 = 510K), the clean signal is with a gain of 5 (R3 = 100K, R4 = 510K).

How would the operation of the second op-amp at different gains effect the input signal?

Thanks for the responses all. I have found that adding a 10uF ceramic capacitor in parallel with R6 has improved the circuit massively in my case. This has stabilised the DC offset that is used by both op-amps.


texts: How to solve this RLC circuit for when the switch is closed?

texts:
In texts I see the example for RLC series circuits which is more straightforward, but how can I set the equations for the following circuit to find its response either in time or s domain and reach the response for the inductor current?

If I apply KVL there is two KVL. Should KCL be used here? I'm confused about how to approach this.


texts:
Background

Consider the following technologies:

100 lm/W OLED (2008, source)
303 lm/W LED (2014, source)
94 lm/W LEP (2015, source)

For growing food, the preferred measurement is Photosynthetically Active Radiation (PAR), given in μmol/s-m2 (PPFD). Finding equivalent PAR measurements across various lights can be difficult (due to various ways PAR can be measured)--plus manufacturers don't always list the value.

Problem

From what I've read, LEP is being touted as superior to LED for growing plants, for a few reasons:

Less power consumption
Less heat, which has numerous benefits
Emits UV, which can inhibit mildew growth

Questions

I am wondering:

How can a device that operates at 94 lm/W be superior (i.e., use less wattage) to a device that operates at 303 lm/W (for growing plants)?
Is it because of the devices have drastically different PPFD values?
What is the highest theoretical lm/W that a LEP device can generate?

I understand that converting from lm/W to PAR doesn't make sense (as PAR is more concerned with wavelengths and lm/W is about brightness).

Addendum

See also:

http://www.lrc.rpi.edu/programs/nlpip/lightingAnswers/plasma/output.asp


texts: Prototyping with ATMEGA328P-PU (DIP-28) for ATMEGA328P-AU (TQFP-32)

texts: My schematic will use internal oscillator, but will not require precise timing. It will be produced using surface-mounted ATMEGA328P-AU (in TQFP-32 package). However this is not convenient for prototyping, so I'd like to prototype using ATMEGA328P-PU (in DIP-28 packaging). Will this work in this scenario?


texts: Why is a resistor put before the gate of a transistor?

texts:
In most of the H-bridge driver circuits I've come across so far, there's a resistor in the path of the signal to the gate/base of the mosfets/BJTs, like in the images below

why is it put there ? wouldn't it drop the signal voltage level to somewhat lower value ? Especially in case of power mosfets, the value of instantaneous current flowing into the gate can reach up to 3-4Amps(at high frequencies) and this resistor would dissipate much energy, so would it be okay if I apply signal directly to the gate without putting the resistor? and If it's not possible to get rid of it then what value resistor should I use and upon what factors does its value depend? I'll be using tl494 to generate the signal at about frequency of 50KHz and ir2113 to drive the H-bridge.


texts: Is there a way to make a edge to edge connection only using external magnets and gold fingers?

texts:
This question might sound pretty stupid, but I have been searching for solutions for a few days, so all of your new ideas are highly approsciated.
I am on a hunt for a solution for modularly connecting magnetic blocks (for example cubes with a connection on 4 sides out of 6).
The solution needs to be pretty cheap (let´s say max 1 dollar for the four sides), I want it to connect just by a few magnets snapping together. The connection is needed for 4 pins - 2 for power, 2 for data. Let´s say max 5V 0.5A on the power lines and I2C data on the other two.
The connection is straight forward (+ to +, SCL to SCL, SDA to SDA, GND to GND).
I was thinking about using pogo pins with external magnets in my enclosure, but there is always a female and male side.
I was wondering if you have a suggestion, how to make "hermaphroditic" board to board connection on the cheap.

If there was a way to make something like this using only PCBs and magnets in some kind of an enlosure it would be perfect.
Also is there some way to connect two PCBs just by force pressing two pads together.
If you´d like me to clarify something, please tell me.


texts: Are all T flip flops master-slave JK flip flops?

texts:
I'm busy learning about flip flops. It's my understanding that JK flip flops toggle when JK are both 1. However without a master slave arrangement this will lead to a race condition, so the master slave arrangement creates negative edge triggered behaviour that stabilizes the output. Makes sense.

I also understand that T flip flops are just JK flip flops with the same input to J and K. This makes sense. But surely, for this to be any use, the JK flip flop must always be in a master slave arrangement else the T flip flop will just be in race around when T is high?

And yet I can't find a single reference confirming that my assumption is true. Am I missing something?


texts: Astable multivibrator using op amps - why does it start?

texts:
I'm new to electronics and I'm learning some circuits with op amps. Now I have been shown this astable multivibrator.

I understand how it works.

The op amp is saturated at one side or the other
Voltage is divided and a portion of it goes to non-inverting input.
Voltage also charges the capacitor until it gets equal to the voltage on the non-inverting output
At that point the op amp swaps its output to the other saturation point.

Why is the op amp saturated at point 1 to begin with?
If I remove the capacitor (either shorting it, opening it or replacing it with a resistance), the op amp will sit at zero volts, since both inputs are zero, and that is totally what I would expect.

Why, by plugging in an uncharged capacitor, does the op amp suddenly decides to saturate?
The uncharged capacitor should not create any change in the difference of voltage between inverting and non inverting inputs that the op amp could amplify, so I would expect that in a perfect simulation this circuit would not start oscillating in the first place unless the capacitor does hold a tiny bit of charge.
Why does it start oscillating?
EDIT: so it turns out that in the simulator the capacitor actually had an initial voltage, and indeed if I set it to zero then the simulation will not oscillate.


texts:
As I understand, GPS is supposed to work because :

You have 4 (or more, but let's say 4) satellites whose clocks are extremely highly synchronized (through atomic onboard clocks)
You have a receiver that receives 4 pings / messages from these satellites, each containing a timestamp of date of emission wrt to the "GPS time"
Supposing the receiver time / clock only has a bias wrt to GPS time (ie, a fixed, constant error), you can from these 4 signals and the map of satellites position, deduce your 3 cartesian coordinates + the time bias error of your receiver clock wrt to GPS time.

That's all fine in theory, but in practice :

The timing accuracy we are looking for is in nanoseconds (as there is c involved and the goal is to achieve metric-like accuracy on pseudo-ranges)
So is it technologically "easy" to ensure that the actual "sending" of the signal by the GPS satellites is at the actual timestamp of the atomic clocks ? I mean, it's going through an electronic system, then a real-world, physical, analog antenna. I'm not talking about adding a known delay (which is not a problem as it can be accounted for as long as it is known), but what about unknown delay / jitter ? For example, is it "easy" to ensure that the analog antenna's emission date is within requirements / specs ?
Same question with the antenna / circuitry of the receiver ?
Additionally, on the receiving end, there is also problem of jitter / repeatability of the "time bias" wrt to the GPS clock. Since we're actually looking for nanoseconds, this seems not obvious. I get / guess the receiver has a well-known stable quartz (or similar) low frequency clock and a jittering VCO for nanoseconds granularities ? And the jitter of this VCO is low enough to allow ignoring it when solving the GPS equation system supposing a fixed biais ?

Of course, feel free to move the question elsewhere if Electrical Engineering is not the adequate community (in the end the question is I think more about pure circuitry than aeronautics, so I chose to ask it here, but I may be wrong).


texts:
I have a circuit that drives a 240Vac line to line power to a resistive load. I am testing for radiated and conducted emissions. Radiated emissions went fine but conducted emissions failed with "broad band noise" on the power line (L1) in the 150Khz to 600Khz region.

The SCR switches at zero crossing point at 400Hz a 20A load, and I have input power filtering for EMI with some caps and common mode and differential mode inductance, as well as lightning protection.

While trying some limited changes based on component availability I increased the capacitance across the lines, and the emissions got worse. Due to the 20A load, the highest differential mode inductors are 4.7uH. The input power goes to the SCRs and to a transformer that drives a 5V linear regulator.

What are things I can try to improve the conducted emissions?

UPDATE 1:
I create a simulation on LTSpice XVII to compare the FFT response to the 15 ohm resistor across all the inductors. I noticed quite a difference, and I would imagine it would have an impact but could I realistically correlate this oversimplification using FFT on all nodes? The numbers I played with were:
-replaced inductors from 4.7uH to 15uH
-added and removed 15 ohm resistor across all inductors

Since I do not have a way to physically measure without paying a lab, I would like to get a good indication that this could work. It seems changing to a 15uH and 15 ohm resistor created the cleanest FFT. Am I in the correct path?


texts: What is crystal, resonator, crystal resonator, crystal oscillator?

texts:
After browsing different online electronic stores, I got a little bit confused with crystals...

What's the proper name for this:

Crystal? Quartz crystal? Resonator? Quartz crystal resonator? Oscillator? Crystal Oscillator?
This one have the same function as what I posted on #1 but less accuracy and stability?

Is it called Resonator? Ceramic resonator? Ceramic crystal? Oscillator?
This is the same as #2 but have two ceramic capacitors built in?

So what do you call it?
What do you call these:

This is the schematic symbol for #1?

What about for #2, #3 and #4?
This is a crystal oscillator? Can I replace The "Crystal" with #2/#3/#4??


texts: I am building an FMCW radar that has a bandwidth of 1 GHz. The IF frequency is up to 1 MHz. Would the ADC requirements simply be that it has to b 2 times the IF frequency of 1 MHz? If that's the case can I simply put an ADC of 5 MHz and not worry about anything else? What are some things a should look at for DSP requirements? I'm not so clear on how range, velocity, and resolution affect the requirements. Thanks for any help. I expect editing this question as I am sure I left some parts unclear. Thanks


texts: I have built the above circuit. The relay switches once, but then stops. Why does this not oscillate, as the current is broken every time it connects?


texts:
I'm trying to get the transfer function of a simple passive pi low pass filter, but I'm a little bit confused about the result.

It comes out that it is a second order filter, but it should be a first order filter. What I'm doing wrong? How should I proceed?
I know that I could find the transfer function just by putting the two impedances of the capacitor and the inductor equals, but I would like to find it using another method. Thank you.


texts: Does a dc generator need a flyback diode?

texts:
From what I've read and understand, it makes sense that a dc motor needs a flyback diode to protect the rest of the circuit. I have a much harder time finding an answer about whether or not a dc generator needs one...

I'm doing some experiments that are similar to those I saw online where a model steam engine, driving a dc generator, is used to power an Arduino. So far, I measured that the dc generator can output from 0 to about 11 Vdc. The circuit containing the Arduino that I intend to power with this dynamo draws around 40 mA.


texts: Measurement system with MATLAB real-time windows target and NI PCI boards

texts:
I'm setting up an experiment which employs MATLAB real-time windows target and NI PCI-6229 and carrier SC-2345 board while I'm wondering about the hardware's compatibility

It's given from here  (MATLAB support page) that PCI-6229 is supported. However, in my setup, SC-2345 signal conditioning board is put between my PC and PCI-6229 board. Therefore, I'm afraid it won't work

Any relevant experience about similar system is a big help. Thank you!


texts: Why is frequency not measured in db in bode's plot?

texts: While drawing bode's graph paper where Y axis is gain given in db while the X axis is frequency given in absolute value but scale used is log. I think the reason for log scale on X axis is to increase frequency range over which plot can be drawn. But can't same advantage be achieved if frequency is represented in db and scale used is linear for both X as well as Y axis.


texts: I do want to run a motor under kerosene, before to that I want to know that will it be dangerous or not?


texts: Semiconductor switching device with extremely low leakage current in off state

texts:
I would like to use a semiconductor device that acts like an ideal relay, that is, with very low leakage current in the off state. By very low, I mean at least 100 pA per volt (like a 10GOhm resistor), and preferably 10pA per volt. Relays are good but they use too much current for my application. I don't think that the Mosfets I know do that. Any idea?

EDIT (for my particular application):

supply voltage: preferably 3V, may be 5V
switching frequency range: I need only very low frequencies 20-500 Hz is a good range
current to switch: at most 1A, probably much less
voltage to switch: very low, between 0.1V and 10V
resistance in the on state: may be relatively high, even 1kOhm is probably good.


texts: First-Order Circuit that Looks like a Second-Order Circuit

texts:
The image attached is a first-order circuit because the two branches of the circuit are uncoupled, but I'm struggling to show that mathematically. From the diagram, we can immediately write two equations from KVL (each loop containing the independent source) that are first order ODEs in the two different capacitors. But I can't think of a relation between the two capacitors.

If anyone can explicitly show why this must be a first-order circuit I would really appreciate it.


texts: Increasing sensitivity for voltage measurement

texts:
I am trying to differentiate between two kind of marbles.  I am using the marbles as a second resistor in a voltage divider and measuring the voltage drop on it. Theoretically there must be a difference in the voltage drop since the materials are different but the resistances of the marbles are too small to be measured (multi-meter gives 0 voltage for the each marble ) . My goal is to amplify the voltage difference across each marble , so I can connect them to a microcontroller that can differentiate the material of the marbles according to the value of the voltage.
Thank you .

UPDATE: The two marbles (sphere balls) are of materials brass and steel both having diameter 20mm.Resitance of brass:1.003* 10^-6 , resistance of steel : 1.1 * 10^-5  The voltage drop on the marbles will be connected to a microcontroller that should differentiate between the material of the balls and control a gate (opens it or not depending on which material).

Measuring setup:
A ball will be moving on a track and two contacts will be provided by thin aluminum sheets covering the inner track


texts: Increasing AC frequency vs increasing number of phases

texts:
An AC signal has a certain frequency which according to my understanding is the switches between the two extremes of the voltage per second. While my outlets around here typically seem to have a single signal of that form (1 live, 1 neutral, maybe 1 ground) I have read about systems that overlay multiple signals with a phase offset (i.e 3 phase AC output).
Picturing two phases it seems that you will no longer have a alternating voltage between -xV and +xV but by switching between phases you can get a voltage alternating between +xV and 0V at twice the frequency.
Consider the following image:

If you switch between red and blue vs neutral at the right interval you will alternate between +xV and 0V (at twice the frequency of each of the phases).
I was wondering, can you theoretically achieve a similar result by increasing the frequency of a single phase?


texts:
how can I detect signals edges in ABEL language?

In other words, there is an equivalent of 'event (VHDL) in ABEL?
Thanks for your help!


texts: How do I increase the voltage of a circuit that powers and transmits data to an led

texts:
I am a noob, but I managed to make a TV-B-Gone out of an Arduino UNO and some parts (I used this tutorial: http://www.instructables.com/id/Arduino-TV-B-Gone/). It only does one led, but I want it to do more than one. How can I increase the voltage without compromising the integrity of the data in the circuit so i can do more than one?

A note: I know that it has some thing to do with transistors, but the method of doing this doesn't seem to be popular.

Another note: that the schematic didn't work on the page above.


texts: Solenoid switched by TIP120 transistor stopped working after two weeks

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I have no kind of knowledge about these things. I just copied some instructions from different projects and now my project died.

I have this 12V 0.8A solenoid that switched for about two weeks. Now the switch gives 2mV to the solenoid.

I measured a new transistor between base and emitter and I got 5.5kOhms. The one that is inside the circuit gives 12.5kOhms. The resistor is still 10k.

I am thinking maybe the 10k resistor was too much or the transistor had too much heat.

The thing is I have a headache from all the reading and would appreciate if someone would help. How do I solve it?

Edit1: If I measure the power supply alone I get 30V, but if I measure it while powering the solenoid directly it's just 14V and it works.
Edit3: It turns out (after the discussion) that the signal should have been (and was and is again) 5V. I thought the problem was that I overloaded something but is not. Now that I know I need a higher current at the base I know what to measure in the future. So my problem was the 2mV current I measured when someone asked me.

simulate this circuit – Schematic created using CircuitLab

Thank you.


texts: Why did the liquid tin evaporate off my board when soldering?

texts:
On the weekend I designed and etched a tiny little 12V booster circuit for an OLED. To prevent the traces from oxidising in the future, I removed the leftover ink after etching and placed the board in MG Chemicals’ Liquid tin straight away - so the copper was fresh. I left it for about 2 minutes.
Upon soldering though, some of the tin evaporated off the traces. I was just wondering how this is possible? I thought it “plated” the traces, or chemically bonded to the copper.
Soldering was done at 350 degrees celsius and I just used a standard electronics no-clean flux pen.
Here’s what the board looked like before and after soldering. I’ve placed two arrows at notable spots where the tin has evaporated.
Dodgy soldering aside, the circuit works great FYI.

Just wondering why this happened, and how to prevent it in the future.


texts: 5 band resistor - value, watt and tolerance

texts: my 700 watts EVGA power supply has stopped working.  I think a resistor has gone bad. The resistor has 5 bands - Brown, Green, Grey/Silver, Gold, Green.  I would appreciate if someone can tell me its ohm, watt and tolerance.  Thank you in advance.


texts: Can I output a HDMI signal with an Arduino?

texts: There's various articles online detailing how to use an Arduino to output a VGA signal, but can I use it to output a HDMI signal or is it simply not fast enough? It would only be used to display some basic text, nothing in the way of fancy graphics.