texts: What does it actually mean by that a transducer has good dynamic response?

texts:
One of the basic requirements of a transducer is that it has good dynamic response. I am having trouble understanding the meaning.

My textbook says:

  The output of the transducer should be faithful to input when taken as a function of time. The effect is analysed as the frequency response.

I have confusion with the interpretation of the text. What does it exactly mean by output being faithful to input? And what does dynamic response actually mean?


texts: Can I use more than one of the taps on a transformer like this at the same time? If my total load (Amps) is with in the maximum that it can handle?


texts:
I have a fusible resistor

In some situation resistor will damaged.

How can I calculate the maximum current a resistor can handle with a safe limit?

is this resistor can handle inrush current from a ceiling fan motor ?


texts:
So the situation is the following:

I'm making half a dozen of my own electrical circuits which I would store in a long wooden box along with my micro ATX motherboard and the rest of my pc. The big wooden box is located on top of my room window on the inner side of wall, and was actually storage for outdoor (external) blinds.

I removed the blinds and used PUR foam to seal the gap trough which blinds would roll down. The gap is about 2 meters long and 1 cm wide. On both ends of the gap I left about 3-5 cm whole for cooling of my electronics. Now the winter came, I am afraid of moisture and condensation?

Will my electronics and PC get moisture and die off eventually?


texts: Connect two mobile power banks in series

texts:
I have two 20.000 mAh mobile power banks with two USB ports that can deliver 5V at 2.4A. I need a minimum of 9V at 2A in output.

I have 2 male USB connector cables and I want to connect the negative wire of one power bank port with positive wire of the other power bank port (not the same power bank port obviously.)

I have done a try, and it seems to work properly, I've powered a device with 10V by wiring in series two power banks.

I did another test, by connecting the two power banks in series, again, and switching off one of them.

Unexpectedly, the circuit was not interrupted, but I got 5V (instead of 10,) so in this way the current traverses the turned off power bank in reverse  (+ flow in - wire of the second power bank, and exit by + wire?)
Nothing was damaged, but can this be a problem?

I know that every current source can be wired in series to  get a higher voltage, and the maximum current can be the same as the lowest current generator.
Basically, every power bank has one or more 3,7V cells with a boost converter to convert 3,7V DC to 5V DC.

P.S. I know, I can simply use a QuickCharge power bank to trigger a higher voltage, but I can't in this case for some reasons.


texts:
Refering to this post, I changed mic5156 to mic5158 (datasheet) and
this mos.

I wired it several times as the datasheet shows but I can't get any regulated
voltage.
In order to understand what happens, I removed the mos and put a potentiometer
instead of the divider. The result is (IMHO) what it should: The gate voltage is
maximum when the divider is below the 1.235V reference voltage the goes to
"nearly zero" (in fact around 1 v) when the divider is above 1.235V.

Yellow: divider

Green: Vcp

Orange: Vgate

Then, I rebuild the circuit with the mos and did the following measurement:

Yellow: divider

Green: Vcp

Orange: Vgate

Light blue: Vgs

Starting with a 1A load, I raised it until 10A.

Some observations:

The output voltage goes from "too high" to "too low". The voltage is correct only when on marker 2 in the below capture.
The pump voltage falls to 0v on marker 1.

I definitely don't understand what happen.
Did I do a wrong choice with the mos?
Should I work around capacitors of the charge pump?
Is there a reason why the gate voltage in first test goes to "nearly 0v"
and not 0v?
Is it a regular behaviour that the charge pump voltage goes to 0? I supposed that It should stay always high, only the Vgs changes but may be I"m wrong.

A lot of interrogations...

[update]

Schematic:

Breadboard:

[Update]

I changed MOS for IRF610 (datasheet) and... It works! The specs does not fit my needs but the voltage is regulated with. Still wonder which characteristic makes the original mos unsuitable.


texts: Implementing dynamic frequency scaling on PIC32 by changing PLL multiplier/divider?

texts:
I read in the PIC32 Reference Manual that one can change the PLL multiplier and divider at run-time, provided that the input frequency is between 4 and 5 MHz and the resulting frequency does not exceed device specifications. Does this mean that one can use this to implement a dynamic frequency scaling scheme to save power (taking ino account PLL switching time and lock)

Thanks


texts: PIC when generating a PWM signal does the used timer throw a overflow interrupt flag?

texts:
I'm trying to make a 10kHz PWM signal with a PIC18f25k50. Which is generated like the following diagram. I configured timer2 at 750kHz which means if I set PR2 register to 75 the comparator should reset every 100 microseconds.

datasheet PIC18(l)f2x/45k50 p179

Now the part that I dont understand is what this means for the interrupt flag of timer2. Because the timer resets at TMR2 = PR2 (it says clear timer) does this mean the interrupts is never thrown because it constantly resets before it overflows. Or does this clear signal also trigger the overflow interrupt flag.

The reason I don't understand is that later in the datasheet(15.3.2) they suggest to wait for timer2 overflow interrup flag. But how is this possible if the timer resets before that?

datasheet pic18(l)f2x/45k50 p180


texts: Does ULN2803A need an Optocoupler Isolation

texts:
When using ULN2803A, is it really needed to isolate the MCU side using an optocoupler like PCF817? Any disadvantages of not using the same?

I am making a relay driver using the same, powered by 5 V.


texts: How does one calculate output voltage noise of a current output DAC?

texts:
I am using a current output DAC connected to a voltage reference and a transimpedance amplifier.

I know the noise characteristics of the voltage reference and the amplifier. The DAC simply lists "13 nV/rtHz output voltage noise density" in its datasheet.

How do I combine these three values to estimate the output voltage noise density of the entire system? I know the DAC must convert the voltage noise of the reference into current noise which is then gained up by the transimpedance amplifier, but how to actually do this calculation is a mystery to me.

The DAC is an LTC2757. I want to use it in the typical applications manner shown here:


texts: I have read from a vendor website. It mentions 3AG fuse block. What does 3AG mean?


texts:
This connector got damaged while repairing a device, and I've been unable to identify it to replace it.

The connector is SMD mounted with the circuit board underneath based on the image above. It is 1mm pitch and has (had) 5 pins. The cable connects/disconnects by lifting vertically away from the PCB.

Socket dimensions: 7.8mm x 4.5mm x 1.4mm, 1mm pitch, pins are 1mm long 0.2mm thick.

Plug dimensions; 7.1mm x 3.7mm x 1.2mm, the cable ends appear to be crimped.

Better image:

Cable end (the empty connection was always empty, the connector has space for five connections, only four are used):


texts: Quasi-elliptical vs pseudo-elliptical filters vs Chebyshev Type 2 filters

texts:
Are quasi-elliptical or pseudo-elliptical and Chebyshev Type 2 filters the same filter response?

Quasi-elliptical or pseudo-elliptical filters appear to be defined as "... filters with finite transmission zeros." The terms "quasi" and "pseudo" appear to be interchangeable, and most probably refer to the same type in the references I've seen. One reference tantalisingly close to what I'm looking for that I've seen referring to QE/PE filters is here, in Chapter 6, para 1 and 2, however the References section  at the end of the chapter is not included in the excerpt. I've found the reference in a local uni library, but won't get there for a few days to check it out.

If they are not, what do their gain, phase, return loss and delay responses look like in the wild? I know the responses for the Cheb type 2 and elliptical filters.

I've looked all over the internet, but the answers appear to be either proprietary or behind paywalls.


texts: Please help guide if my understanding is correct

texts: Please help check if my understanding is correct for the above circuits. As per my understanding the Voc=4v, since we have opened the circuit and there is no current flow. If that was not the case we would have applied the voltage divider to find the voltage in that branch.Kindly let me know if further explanation is required from my side.Thanks in advance.


texts: I have some carbon film resistors out of an electronics kit I got given and for a project I need 1/2 Watt of 4k7. Is there anyway I can test to see the power rating? I don't have any other resistors in stock atm so can't use 2 2k2 with 1/4 Watt.


texts: Which is a more accurate estimation of SOC between different versions of Kalman filter vs advanced Fuel gauge ICs such as the ones from Texas Instruments (Impedance Track algorithm) or Maxim Integrated (Model Guage algorithm)?


texts: Designing a circuit from a transfer function

texts:
I have this transfer function of a bandpass filter with 2 poles and 2 zeros:

$$
H(s)= 10^{-0.8} \frac{\left( \dfrac{s}{10} +1 \right) \left( \dfrac{s}{100.000} +1 \right)} {\left( \dfrac{s}{100} +1 \right) \left( \dfrac{s}{10.000} +1 \right)}
$$

I have a gain, 2 poles, 2 zeros and no idea how to design a circuit that has this transfer function.

Maybe it could be an active filter but it only can have 1 opamp (instructions) It could also be a passive filter. R, C and L can have any value.

How do I design a circuit from transfer function?


texts: STM32 starts timing out receiving data UART after reading 1 byte

texts:
I am having trouble using the UART on the STM32F103 where it stops receiving data, while not setting any of the error flags.

The UART device is an ESP8266 at 115,200 baud. I am sending it AT\r\n. The ESP8266 echoes back each byte I send -- I am able to receive these echoes. However, when it comes to reading the response after the echos (OK + some newlines), it times out after receiving one byte.

Here is the entire transaction, as seen on a logic analyzer.

STM32   sends: A  T \r  \n
ESP8266 sends:  A  T  \r  \r \n \r \n O K \r \n

In my code, I send one byte, then receive one byte until the payload is sent. Then, I'm attempting to listen for the remaining 7 bytes (\n \r \n O K \r \n) one-by-one. I receive the \n, then the communication times out after 5 seconds (using the debugger, I see it's waiting on the RXNE flag.)

When the timeout occurs, I see that none of the error flags (ORE NE FE PE) are set in the SR register.

If I attempt to read two bits at a time, the very first HAL_UART_Receive call times out.

The program creates some debugging info (below) as it sends each byte and received the echo, then attempts to receive the response. The code for the program is in a gist.

I've been banging my head against this for several hours. What could cause this behaviour?

Sending 4 bytes: AT(\r\n)
  Echo:
    Byte 0: sent 65, echo 65 (ORE 0) // A
    Byte 1: sent 84, echo 84 (ORE 0) // T
    Byte 2: sent 13, echo 13 (ORE 0) // \r
    Byte 3: sent 10, echo 13 (ORE 0) // \n, echo \r
  Receive:
    Recv 10  // \n
    Recv fail
    RXNE: 0 ORE: 0 NE: 0 FE: 0 PE: 0

Excerpt of code that attempts to read the bytes after the sending completes (full code):

while (1) {
    uint8_t recvChar;
    if (HAL_UART_Receive(&Device_UART_Handle, &recvChar, 1, 5000) != HAL_OK) {
        printf("    Recv fail\r\n");
        printf("    RXNE: %d ORE: %d NE: %d FE: %d PE: %d\r\n",
            __HAL_UART_GET_FLAG(&Device_UART_Handle, UART_FLAG_RXNE),
            __HAL_UART_GET_FLAG(&Device_UART_Handle, UART_FLAG_ORE),
            __HAL_UART_GET_FLAG(&Device_UART_Handle, UART_FLAG_NE),
            __HAL_UART_GET_FLAG(&Device_UART_Handle, UART_FLAG_FE),
            __HAL_UART_GET_FLAG(&Device_UART_Handle, UART_FLAG_PE));
        while(1) {}
    }
    printf("    Recv %d\r\n", recvChar);
}


texts: Switch current rating - actually current or really wattage rating?

texts:
I'm trying to build a dummy load for some power supply testing using some very large power resistors. Basically I will wire up the resistors in parallel and connect more if I want to decrease the resistance and therefore increase the current draw.

I want something to switch on each of these resistors. I thought maybe I could just buy some cheap wall switches but the ones I find are only 15-20A rated @ 125V AC but the testing I want to do could go to as much as 35A at 5V DC. I noticed that the switches would often be rated for 10A @ 240V and 20A @ 120V. Since I'm running such low voltage and only DC, could I run much higher than 20A?


texts: Can a household device limit consumption to avoid tripping circuit breaker?

texts:
A common problem for resistive loads, like household heating appliances, is that peak current is drawn on startup.

I have come across ICLs (inrush current limiters), which are cheap components.  Do they solve the peak cold-start problem?  If so, is there some other reason why they aren't frequently or always used in household resistive heating appliances?

Aside from the startup phase, I am wondering if "intelligent" (but still, household/countertop-level) appliances can be equipped with other countermeasures to overloading whatever circuit they're connected to.  For example: is it possible to sense or infer line load?  Perhaps based on voltage variations?  And if so are there any common current-limiting components that can be put on a 120V 15A device to modulate its load in response to circuit conditions?

Original question, closed presumably due to the distracting example, but left here so the previous comments and answers make sense:

I have a toaster and coffeemaker – two resistive loads – on the same kitchen circuit.  My old coffeemaker would trip the circuit if run together with the toaster.  A new coffeemaker heats water even faster but does not trip the circuit when run with the toaster.

So is there a way that such a household device can intelligently regulate its current consumption to avoid overloading a circuit?

E.g., is there some reliable line indication that it is being overloaded, like a drop in voltage?

And is there any other common current-limiting component that can be put on a 120V 15A device to react to any line feedback?


texts: Understanding this peak detector circuit

texts:
I think the circuit attached below is a peak detector because of the diode, resistor and capacitor at the op-amp's output. What I don't understand is the diodes on the input side. The input signal swings positive and negative. In the positive cycle, the signal goes through D2; what's the purpose of R2?

In the negative cycle the signal goes through D1 and R1. R3, C1, and R1 forms a low-pass filter network, right? Correct me if I'm wrong. I would appreciate any additional detail as to the operation of this circuit.


texts:
recently I've needed to buy a brushless motor, but because I couldn't find any motor with wanted characteristics, I've decided to make my own. I know that it's very precise job, but even if something goes wrong, I will enjoy just trying to construct motor. As perfectionist, first I must plan everything (if you aren't intrested in what I've already done, I suggest skipping to the end - there is my problem and question :P).

First I've tried to make a formula for calculating the number of turns on one coil (\$n\$). Maximal rotational speed in BLDC motor is the speed at which moving magnets induce voltage equal to negative voltage across the coil.

Faraday's law of induction: \$\varepsilon = -\frac{\Delta \phi}{\Delta t}\$

I have \$n\$ turns of wire, so:
$$\varepsilon = -n \frac{\Delta \phi}{\Delta t}$$

In my case \$\Delta t\$ is equal to time, in which next magnet "appear" next to given coil:
$$\Delta t = \frac{1}{K_{V} U m}$$
where:
\$K_{V}\$ - in my case it will be rotates per second per volt - not per minute
\$U\$ - voltage across one phase
\$m\$ - number of magnets in motor

\$\Delta \phi\$ is equal to change of magnetic flux during \$\Delta t\$. It means doubled magnetic flux of single magnet (\$\phi\$):
$$\Delta \phi = 2 \phi$$

That means:
$$\varepsilon = -\frac{2 \phi n}{\frac{1}{K_{V} U m}} = -2 \phi n K_{V} U m = - U_{c}$$
where:
\$U_{c} = \frac{U}{N}\$ - voltage across one coil
\$N\$ - number of coils per phase

Final effect:
$$n = \frac{1}{2 \phi K_{V} N m}$$

And at this moment I need your help. When I'm trying to estimate how many turns coil should have, I need to know magnetic flux of single magnet (in my case neodymium one). In the Internet you can find tables containing properties of the materials the magnets are made of, but there isn't magnetic flux (what is understandable).

My question is: is it possible (if yes, how?) to calculate magnetic flux of magnet with given dimensions, knowing remanence, coercivity and "energy density" (the product of B and H) of material the magnet is made of?

Sorry for all my English mistakes and thanks for answers.


texts:
When looking at a P type semiconductor band diagram, the acceptor level sits a little higher than the edge of the valence band, say Boron in Silicon.
i have learned that the acceptor level represents the energy needed for an adjacent silicon valence electron to jump to the incomplete covalent bond(frustrated silicon atom with 3 valence electrons) and thus forming a stronger covalent bond, since that electron now belongs to the no longer frustrated silicon atom and is not shared with any other adjacent atoms. If that is the case, that this incomplete covalent bond attracts a nearby electron, then the energy state of this new electron when stolen from the atom should be more convenient(nature tries to keep the energy of particles to the lowest levels), so the acceptor level should be BELOW the valence band edge.. ? I also read the acceptor level is something mathematically derived using the Hydrogen atom model analogy with modified permitivity and effective mass and the result puts the ionisation energy to that level. I am quite confused here :)


texts:
I ran this simulation in ltspice and my output voltage was -2.97V.  According to my calculations I should have roughly -10V when all sources are at 5V.
$$V_{out} = -V_{in}R_5  \left ( \frac{1}{R_1} + \frac{1}{R_2}+\frac{1}{R_3}+\frac{1}{R_4}\right )$$
I tried this same circuit on partsim's online simulator and got -9.97V.  Is there something missing in the LTSpice circuit?


texts: Want a USB mini-microphone array. Is it possible?

texts:
I have been learning a lot about adaptive beam-forming, and have been mucking around with various sims in MATLAB, etc.

But what better way to understand something - truly understand it - than to play with the entire system?

To this end, I would like to find (build?) a USB connected microphone array, with say, 5 mics or so. They would be able to acquire signals from the environment, (aka, wherever my laptop is), and I would then be able to take those signals and process them in MATLAB or whatever.

I would really rather not build the entire thing, so I am hoping someone has already used USB connected microphone arrays in the past, and can point in the right direction?

The microphones need not be anything fancy when it comes to bit resolutions of their A/D, etc. KISS microphones of respectable quality will do just fine.


texts:
I've always wondered the steps involved in designing a microcontroller.
Let's say one wanted to design a dedicated motion control chip, would this be "hard wired" into the chip? What kind of software is generally used for the design of these chips? And is this a lengthy, complex process which requires multiple PHDs?


texts:
I don't have much experience with power electronics but I'm trying to design a power supply with AC 220Vrms (311peak) to DC 1500V converter to charge a capacitor in 50 miliseconds (and keep charging it, since it'll discharge as soon as it reaches 1500V).
Conventional transformer + bridge rectifier dissipates a lot of power through the resistor needed to limit the current that charges the capacitor.
So, I'm thinking about using a bridge rectifier + a boost converter (with IGBT) to do that, like the following schematic:

Note that, with duty cycle of 60%, the voltage reaches 1500V in 50ms:

The problem here is the inductor, that using 5mH the current is too high:

I've found some 5mH inductors that can handle high currents like this but its purpose is for filtering and not store energy for switching.
Should I use another topology for the ac/dc converter? Any thoughts?


texts:
Hey all i am looking for some advice in how to go about my project with a Nest Protect gen 2.

In my home i have ran cat6 wire to all 3 locations that require a smoke detector. These cat6 cables are connected to a POE switch for powering the Nest Protect.

The version i picked up for the Nest Protect is the battery version. I am wanting to convert the battery to the POE in order to power it by POE instead of battery. The Nest Protect uses 6 x AA batteries that equal ~9vdc total.

I am converting the POE to 9vdc via a converter:

However my question is- do I need to wire up the 6 battery placers in parallel or series? It would seem that the Nest Protect AC version has only 3 x AA for power backup. Not sure if that matters in my case or not.


texts: What is the "positive charge" on a capacitor if only electrons and not protons flow through a circuit?

texts: Speaking in non-conventional current terminology, electrons should build up from the positive terminal of power supply to the top plate of a capacitor. What I don't get is, from an atomic perspective, how an electric field is created since the capacitor is given no "positive" charge from protons.


texts: Can't tell which pin is hot and which is ground on connector datasheet

texts:
I want to use the following bnc connector: 1-1634612-0 by TE Connectivity.
I am looking at the datasheet but I can't tell which pin goes to ground and which pin I connect to get an input. I linked the datasheet below the picture.

https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=1634612&DocType=Customer+Drawing&DocLang=English&PartCntxt=1-1634612-0&DocFormat=pdf


texts: Why can't I piggy back / Daisy chain surge protectors or a surge protector and an ups?

texts:
Assuming I don't exceed the wattage rating of the whole system then why can't a piggy back let say ups to a surge suppressor in order to let say increase the protection of my system.

Let's assume:
I have 1500va APS UPS that has built in surge suppressor and now I want to plug in a Tripp-Lite 6 outlet metal housed surge suppressor to single output of the battery side of the ups.  Everything else is connected to the Tripp lite and nothing else besides the Tripp lite is connected to the ups.
The total draw is let say 1500watts.

So what is negative about piggy backing surge suppressors?

Can I use the above setup without any detrimental effects.


texts: Adding external bluetooth antenna with U.FL connector

texts:
I want to use this Bluetooth Module inside a metal casing. So I need a U.FL connector to add an external antenna. All I know, is that the trace from the pad to the connector needs to have 50 Ohms. Other than that, I have almost no knowledge of RF design.
Can the trace be lower than 50 Ohms?
Are there more requirements for the trace from pad to connector than the impedance?


texts: LED display flickering when connected to an ESP8266

texts:
I'm building a simple clock using an ESP8266 chip and a 7 segment LED display which is driven by a HT16K33 chip. The ESP8266 uses 3.3V, the display can handle 5V. I want to use a simple USB cable as a power supply, so I've added a voltage regulator to get the correct voltage.

This all works fine, The problem I have is that the display is flickering when everything is connected to a single power source. During testing I connected the display and the ESP8266 to different power supplies and the flickering was gone. But obviously I don't want to use two USB cables for a single device.

What can I do to prevent the flickering? Since the problem doesn't exist with two power supplies I ruled out a software problem on the ESP8266 (I've written a relatively simple Arduino sketch using existing libraries for a connection to the WiFi, handling the time including NTP and updating the display). The display is updated once a second by the code, but the flickering is distinct higher.

Some more specs, as requested in the comments:

The voltage regulator is an LF33CV (TO220). It outputs up to 500 mA

The ESP8266 module is one of the ESP-01 type. I measured ~70 mA while it is running.

The HT16K33 module is an Adafruit LED Matrix Backpack. It is controlled by the ESP8266 via I2C. It draws around 20mA (including the LEDs).

For the electrolytic capacitor C3 I tried:

47 µF
100 µF

for the other capacitors C1 and C2:

0.01 µF
0.1 µF

It is difficult for me to find out what capacitors I need for this.

Both capacitors are as close to the modules as possible on the breadboard.


texts: How can I build a composite video to scart converter?

texts:
I'm interested in building a composite to scart adapter.

How can I?


texts: How to fast charge capacitor 2200uF/400v in fewer seconds?

texts:
I have a problem to charge a capacitor 2200uF/400v. It takes 30 second to reach 300v. I hope can reach 300v in 10 seconds. thanks :)

This my schematic:
![the capacitor its on output (cn2)
 i use transformer toroid inner diameter = 5cm, outside diameter = 8cm, high = 3cm , for secondary 350 turn (0.7mm) for primary 14 turn (1.8mm)]2


texts:
I have designed a board with an AD7616 chip on, connected to a microcontroller. The AD7616 chip is configured in software mode and with SPI interface (one MISO and one MOSI wire). I have read the whole datasheet, and believe that the connections are okay. This is my schematic:

These are my findings:

1. SPI doesn't function
The first problem I encounter is the nonfunctional SPI connection. I attempt to write the CONFIGURATION_REG at address 0b00010, and read it out again to verify if the value really changed. I read out only zeros. The MISO pin (master in, slave out) remains low.
In short - the SPI connection doesn't work. I've checked the signals with my oscilloscope. The microcontroller outputs the expected waveforms. The AD7616 remains dead.

2. All power supplies are connected
I have checked the presence of 3.3V and 5V on all the power-pins of the AD7616. The power supplies to the chip are okay. So the problem is not related to wrong or missing power levels.

3. No voltage on the REFCAP pin
All the following pins should have a specific voltage: REFCAP, REFINOUT, REGCAPD and REGCAP. They are all okay, except REFCAP. This pin should output 4.096V, but I don't measure any voltage.

What could be wrong?


texts:
We're using this kind of solder sponge made of brass in our electronics course:

One kid told me that he had seen this before. I wondered a bit, because they are all new to soldering. Finally he brought that thing into the class and it turned out to be steel wool, used in the kitchen.

Is it ok to use that instead? If not, why not?


texts: Powering multiple DC gadget(Routers, switches, RPis etc) using a single smps will be efficient than multiple power supply?

texts:
I have multiple DC gadgets (Routers, switches, RPis etc) so obviously multiple DC adapters too. I have two spare ATX SMPS. So I was thinking to modify one SMPS so that I can replace all those adapters with the single SMPS to run all my gadgets.
So my question is will it be worthy? I'm considering worthiness corresponding to the power efficiency. Will the single SMPS be more power efficient than running multiple adapters?


texts:
Is is possible to transmit power using magnetic resonance coupling at 50Hz? Assuming I have no constraints on the minimum distance between the primary and the secondary coil. However, the coils are to be Air Cored.

Most of the examples available use high frequencies such as 12KHz for the Primary coil, but can the same be achieved for an Input of 50 Hz? What could the drawbacks be?

My Primary Coil would be supplied with 220V, 50Hz AC Supply. On the secondary side, I require anywhere between 5-12V rms.


texts: Configuration of XBee network with multiple end devices

texts:
How do I configure an xbee network with multiple end devices (each connected to sensor and microcontroller) and one coordinator (connected to the PC)?

Do I use AT mode or API mode? What is main difference between them?

In this type of network, when two end devices transmit data will there be interference between them? If so, how to avoid?

Some one told me the XBee sleep mode is used for this type of network but how do I do this?


texts: A light dependent current astable multivibrator

texts: i have basic knowledge about multivibrators and how a photodiode is operated but i'm having trouble trying to combine them into one circuit. Suppose if i am to operate the photodiode on the circuit as shown am i not suppose to get a rectangular wave with a longer period ?


texts:
Does anybody know the impedance of the Tektronix A622 current probe? I don't find it neither on the datasheet, nor in the user manual...

EDIT: As requested, here is some extra info: I need the output impedance of the probe, for proper impedance matching with the scope. And no, it's not printed on the label of the probe.


texts: need a schematic or info for wiring for a T35696-HP cooling fan motor

texts:
I have two T35696-HP cooling fan motors from an HP C7000 server rack.  I am going to use the motor/fan with a DC source outside of the normal capacity as a cooling fan for a server.  Therefore, I am not going to be using the existing circuit board that controls the motor.

I have not been able to find any schematic for the circuit board for this cooling fan.  Because of this I am having difficulty knowing what wires coming out of the fan motor do what.  There are only three (3) wires coming out of the fan motor.  Blue, Yellow, Red.  I am assuming the Red wire would be power but I would expect to see a Black wire for ground.  There is not one.

Since the fan is wired to the circuit board and the board is plugged into a computer slot, I am running under the assumption the ground was somehow handled within the circuit board itself.  If that is so, could I simply ground the motor housing if running directly to a power supply?

I plan to wire this motor up to an external 12 V power supply and a controller that will control the speed of the fan.  I would like to know what wires to use for 'power', 'ground', 'control'.


texts: Set rules for net connected to specific component in Altium

texts:
I'm using Altium 17.1. I'm trying to set a clearance rule for my PCB. Some of my components have tight pads and thus I need to set a low value for that component. I set the pad to pad clearance with InComponent query to skip pad to pad check. Now I'm trying to define a clearance rule for all nets connected to a specific component. I don't want to set individual rule for nets one by one. I tried to use this query but didn't work:

  InNetClass('All Nets')  and InComponent('U5')

Actually, I'm trying to use Autoroute But I want to set low clearance for specific components that their pad is very tight compared to other parts.
EDIT:
I'm trying to say that the green clearance is fine and for the red circle is violate. Suppose clearance between these pair nets is the same.


texts: Determining how to make 7-wire AC motor run without wiring diagram

texts:
I acquired a blower assembly from an old air handling system, with the intention of using it as an exhaust fan in my workshop.

It came as an assembled unit of blower and motor on a subframe. The wires had been cut prior to my arrival.

I have Googled "7-wire motor," "AC motor wiring," "brushless AC motor wiring," and many more ways of trying to describe what I have in-hand. I have been unsuccessful in finding useful information about how to wire this up.

I have found a couple of things that appeared to describe how to figure out what wires do what - one of which takes me through testing for continuity and says I should find two separate groups. I don't.

ALL wires have continuity to each other. Verified by using a 12v battery and a light bulb, + to each wire and - to others for each of the colors. Bulb lights up every which way.

Motor label info:
493 (probably a part number i guess)
1PHASE
TYPE CA0514D-R SANSO
POLES 4
OUTPUT 85 W
VOLT 220-240 V
HZ 50
07.08.28 KC

Wires:
Black, Red, Yellow, Blue, Orange, Grey, White

What I want to do:

1) Make it run, using any built-in speed differences that may be a part of the existing setup.

2) Alternately, just make it run, full on.

I sorta thought this would just be simple, but I guess not. Don't want to feed power to any wires until I can tell what is what. Need help. Below are pics of the lot.


texts: Wiggle in the current source of an emittter follower amplifier

texts: This has been bugging me for days. I still don't understand why the book says the current I through Q1 remains constant when there is a varying input signal at the base of  Q1. Some peeps here also say that it is constant. I understand that Q2 is like a constant current source but when I try simulating it in LTspice the current through Q2 is not constant. Take note that the simulation is for RL open.


texts: Using sub 1GHz 6LoWPAN, which development kits are available?

texts:
I need to create a network with 6LoWPAN, or maybe some others supporting IPv6, and are looking for development kits.

The ones I found are

Texas Instruments using Sensinode’s NanoStack
NIVIS

I would also like input on projects available that I can get some inspiration from.
Thank you!


texts: Can I use this rf module with HT12E and HT12D?

texts:
I have recently made RC car using HT12E and HT12D connected to a cheap ASK RF module of 433 MHz frequency,but it's range is not good only a few meters and also so prone to electrical noise generated from DC motors,I have tried every solution like covering motor with metal chasis which is connected to ground and low pass filter....but nothing works so finally decided to change frequency,found this
but unlike normal module,it has 6 pins,I know it's transreceiver so I will buy two pcs but how to use them with HT12E and HT12D,what are PROG and CTS pins and how to use them?


texts: RGB led each color on at a specific voltage

texts: My set up is a small solar panel(10W) charges battery's in my camper, the old led showing that it was charging no longer works, The old led had epoxy around it with 3 diodes in it as well,being a older camper replacement lights are not readily available, I wanted to put in a RGB led with the Blue coming on at approx 11.8 volts and the green at 12.6 and the red at 13.6, they can overlap in or just change from one to the other, I would like to keep it as simple as possible, I have some room so it doesn't have to be tiny, The led specs are Forward current 30mA(green/blue) 50mA(red) supply 3.5v-4.0 max(green/blue) 2.0v-2.6 max(red) any help would be appreciated,


texts:
I'm confused about how N-channel MOSFETs operate in BLDC circuits.
Say we had MOSFETs that are being driven with Vg = 10V, and DC+ is 36V. Say we have Q1 and Q4 on at some instance (Through phase A and C). What would be the voltage at the source of Q1 (and drain of Q4)? From my understanding, due to the nature of mosfets Vgs > Vth, so would the source voltage be at most 8V (with the assumption Vth = 2V)?
The broader question is I'm confused how higher voltage is resulting in higher current draw/spins faster when it seems like Vgs is the limiting factor. (I know I'm probably wrong, but am confused).


texts: I was going through  http://papilio.cc/index.php?n=Papilio.Hardware and realized that they mention ZPUino Soft Processor but I am unsure of what this is exactly. I know that it is an soc according to http://www.alvie.com/zpuino/downloads/zpuino-1.0.pdf but what exactly is its role on the fpga-board ? Why do we have a separate ide for it (ZPDuino). I thought we have to write everything for an fpga in verilog or vhdl. What is this c like syntax? Even in the quick start guide for papilio they genrate a bit file using c like syntax(http://papilio.cc/index.php?n=Papilio.P1QuickstartSketch). So what exactly is it and what does it do?


texts: Connecting led IP65 strip from a wall socket to an adaptor/psu

texts:
I have no electrical background, so I have very basic knowledge about this, but this is what I can gather. So I'm trying to set up an led IP65 white strip, but I know that it needs certain components. Just to clarify, from the AC 220V wall socket, I have to connect it to the PSU/Adaptor (I have no idea which to use) first in order to change AC to DC, which then connects to the switch, then connects to the LED strip?

These are the lights I would like to use: LEDs

Requirements from the page: 12V, 7.4W per Meter.


texts: What does make difference between a WTHD and a THD from practical point of view? Where and when the WTHD is more prevalent than THD?


texts:
As far as I understood from here, phase margin means the amount of phase that needs to be added in order to coincide with 0 db gain and -180 degrees phase. Likewise for the gain margin it means means the amount of gain that needs to be added in order to coincide with 0 db gain and -180 degrees phase. But i don't understand why do they both necessarily have to be positive for stable systems?

Re-stating my question. I want to know: Why gain crossover frequency must be lower than phase crossover frequency for stable systems?

Relevant: Can a phase margin become bigger than 180° and is this bad?


texts: How to generate heat using a battery and a wire

texts: If i connect the positive and the negative terminal of the battery with a wire, the wire will turn red and generate heat.This creates a short circuit.This can damage or explode the battery?Is there any safe way to do it?


texts: Help identifying pneumatically activated switch with possible BMS

texts:
Some decent googling has yielded me no results.
Attached are pictures of a component that allows power from a 3-5v power supply to flow when positive pressure is applied to one side or negative pressure on the opposing side. It also has a voltage cutoff. The internal diode has the text "C912 AYCeY".
I am also interested in figuring out how the sensor (unidirectionally!) detects the pressure difference.
Thank you!


texts: What's this length-tunned shape in this circuit?

texts:
Here is an image of an LNB circuit:

Probably you heard something about length-tunned traces that they use in high-frequencies PCBs. There is something similar to the length-tunned traces in the PCB(blue circle) but it's not length-tunned trace because they are cutted-out. What could be they?


texts: When is noise a factor in basic analog circuits?

texts:
I have a good understanding of circuit theory, but only a few large projects under my belt.  In practical applications, at what voltage level does noise really become an issue.

Is there any 'typical' white noise level in circuits (e.g. 100mVpp can be expected in most circuits).

I am building a current sensor circuit with just a basic series resistor.  I am going to measure the voltage drop across it to determine the current.  Let's say I was going to measure 150V supply current.  If I use a 0.1 ohm resistor in-line, and expect 10 Amps, that would be a 1V drop and 10W dissipated power.  If I use a 0.01 resistor, I get only 1W of dissipated power, but now my signal is at 100mV.  Will noise become an issue at the 100mV range?  Will a simple capacitor filter out enough noise for me to reliably measure current?

EDIT:

I am interested in noise for analog circuits specifically.  I realize that in digital circuits, there are many noise generators due to switching.  If I have a 100mV signal in a purely analog board in an aluminum box, is there typically enough noise to make the measurement unreliable (let's say +/- 15%).  Are any filtering techniques required, and if so, what are some options?

What if that same signal was 0-100 uV?


texts: i'm trying to build a small power bank flashlight

texts:
I am wanting to make a power bank with two 18650 batteries and an led flashlight combination. I have this free light , https://www.amazon.com/Ultra-Bright-Portable-Worklight-Flashlight/dp/B08189KYCG/ref=asc_df_B08189KYCG/?tag=hyprod-20&linkCode=df0&hvadid=416958783560&hvpos=&hvnetw=g&hvrand=13539993788906158846&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9024398&hvtargid=pla-870946458439&psc=1&tag=&ref=&adgrpid=89137678690&hvpone=&hvptwo=&hvadid=416958783560&hvpos=&hvnetw=g&hvrand=13539993788906158846&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9024398&hvtargid=pla-870946458439 , It would fit the two 18650 batteries and I have a maker power
bank module , https://www.amazon.com/Mobile-Battery-Charger-Module-Protection/dp/B07D6M2LCS/ref=pd_bxgy_img_3/134-5433051-3166302?_encoding=UTF8&pd_rd_i=B07D6M2LCS&pd_rd_r=8e86fb08-aa54-4b74-b1c9-62c0e164e869&pd_rd_w=2AgsA&pd_rd_wg=5hKkz&pf_rd_p=f325d01c-4658-4593-be83-3e12ca663f0e&pf_rd_r=EKF7Z42MYMPEBNHW0A5X&psc=1&refRID=EKF7Z42MYMPEBNHW0A5X The light is 3AAA batteries and I'm wondering if I should step up .5to.8v directly from the 2x18650 battery to the lights directly, that I plan to leave in the flashlight, and how i would go about that, or if i should use resistance from the output on the power bank module to step down the voltage for the light circuit and or how to do this.
any tips would be very appreciated.
ps. I am very new to this but electrical engineering has always been something I wished to learn well and I now have the time to start learning and want to start small and am so appreciative I found this site today. :)


texts: The circuit with 74HC138 is working, but with 74LS138 it is not, why?

texts:
I used 74HC138 in the first circuit and 74LS138 in the second circuit.
Only the one with the 74HC138 is working.
Why?


texts: How to implement a soft power switch controllable by microcontroller?

texts:
I want to design a circuit such that the microcontroller can toggle a GPIO pin and shut the whole system (including microcontroller itself) down. And when the user presses a momentary button, the power is brought back up again.

Is this possible?


texts:
I broke the motherboard of an old Acer notebook, and as a part of my fiddling, I managed to get the screen (+webcam) off the rest of the body.

It looks like this :

Now, I have two cables going out on the right side (photo 1), and on the left one cable (photo 2) + many very very small ones in a sheath (photo 3) :

Is there any way I can use it without dismounting it completely and using an LVDS controller ?


texts: How to simulate a mosfet from a datasheet in ngspice

texts:
First of all, I'm pretty new to the simulation side of engineering. I'm using gschem to draw simple circuits and I'm using ngspice from the commandline to run the simulation and plot the results.

So far I've succesfully done a simulation with a simple voltage source, and resistor. Just to get used to the basic workflow.

Now the next thing I would like to accomplish, is to use a Mosfet in my simulation.

This generates the following netlist:

* gnetlist -g spice-sdb -o sim1.ckt sim1.sch
*********************************************************
* Spice file generated by gnetlist                      *
* spice-sdb version 4.28.2007 by SDB --                 *
* provides advanced spice netlisting capability.        *
* Documentation at http://www.brorson.com/gEDA/SPICE/   *
*********************************************************
*==============  Begin SPICE netlist of main design ============
M1 drain 1 0 unconnected_pin-1 STN2NF10
V1 Vcc 0 DC 12V
R1 drain Vcc 250
.tran 1ms 100ms
V2 1 0 pulse(0 5 0s 2ns 2ns 1ms 10ms)
.end

Now when I try to run this I get the following error:

Error on line 9 : m1 drain 1 0 unconnected_pin-1 stn2nf10
  Unable to find definition of model stn2nf10 - default assumed

Which is not realy a supprise, after all, how should ngspice know the characterics of all components in the digikey catalogue.

So I understand that I have to specify the charcteristics of this mosfet. This is where I get stuck. I've read the part of the ngspice manual (p. 127, sorry not enough reputation to post 2 links: ngspice.sourceforge.net/docs/ngspice-manual.pdf) about mosfets, it says the general form to define a mosfet is as follows:

MXXXXXXX nd ng ns nb mname <m=val> <l=val> <w=val>
+ <ad=val> <as=val> <pd=val> <ps=val> <nrd=val>
+ <nrs=val> <off> <ic=vds,vgs,vbs> <temp=t>

The 'm' parameter is for multiplicity, I understeand this one.
Now the 'l' and 'w' parameters, these are the length and width of the channel. How on earth should I be able to know these? They are not in the datasheet for sure. Same for the 'ad' and 'as' parameters these are the drain and source 'diffusions'.

Why can't we just enter the characteristics as meantioned in the datasheet: STN2NF10. Vdss, Idss, Igss, Vgs, Rds, etc.

I believe there is a good reason why it's the way it is, I'm probably just missing or misunderstanding something.

The question:

How do I simulate a circuit containing a Mosfet, and transform the values in the datasheet of the mosfet into ngspice.

PS. The same question is of course applicable to other parts then mosfets, I would just like to keep to the mosfets for now, in order to keep thins simple and practicle.


texts: LTspice output of a bjt amplifier is offsetted

texts:
If I choose "start external DC supply voltages at 0" from transient simulation settings, the output is centered at 4.55 Volts. The amplification and gain is OK, but the output is not centered at 0.

However, If I don't choose that option "start external DC supply voltages at 0", then output is also centered at 0 volts.

Is it related to charging of C27? But output offset is also not likely to drop towards 0. It continues oscillating around 4.55 volts.

If someone can explain me what is the difference between those two options and how to solve offset problem, it will be nice.


texts:
I saw two different IV characteristics of thyristor on the net.

First:

Second:

So far I know, that when the voltage reaches breakdown value, the avalanche breakdown happens in the thyristor structure and as follows the voltage across the thyristor drops to some low value.
For me, the first IV characteristic seems to make more sense.
However, I don't know if the first characteristic is correct.


texts: Why does reciprocating compressor's motor starting winding have high voltage than running winding

texts:
I want to know why the starting winding of (2 ton) reciprocating compressor's motor have high voltage than running winding? I have attached the voltage that I have captured from oscilloscope.
This reciprocating compressor has potential relay with start capacitor and also have run capacitor. Start capacitor provide the start torque, but what is the purpose of running capacitor?
I could see that, starting winding have high starting current. But when the starting capacitor is disconnected from potential relay, the voltage at starting winding to common become 275 V, which is very high but the point that is triggering the start winding current. Start winding current reduced to 0.1 A or more less.
Why and how this can that the is high but current is almost zero?

In this picture, you can see that the yellow is the starting voltage which is high. Blue the running voltage with respect to common. RMS voltage of starting winding is 276 V and RMS voltage of running winding is 226 V.

In this picture, yellow is the running winding current and blue is the starting winding current.
The current through starting is 0.1 A and the current through running winding is 12 A.


texts: Connecting strain gauge output terminals to an instrumentaiton amplifier

texts:
Before posing the question the figures are about as follows:

In Figure 1 a strain gauge's outputs v1 and v2 is connected to an instrumentation amplifier’s inputs. For simplicity buffering part is not drawn and I'm assuming the signals are balanced with equal line impedance. Let’s say I measure v1 and v2 with respect to ground such as: v2=0.390mV and v1=0.400mV. So that v1-v2=0.005mV. If the inamp is not ideal and obtaining common-mode voltage vcm = (v1+v2)/2= 0.395mV will affect the output voltage since every non-ideal amplifier has common mode gain.

In Figure 2 the same outputs from the same strain gauge goes into a mysterious circuit called M which converts v1 and v2 to v1’ and v2’ such as v1’= (v1-v2)/v and v2’=-(v1-v2)/2. So that v1’= 0.0025mV and v2'=-0.0025mV so that again v1-v2=0.005mV. But in this case obtaining common-mode voltage vcm = (v1+v2)/2= 0mV will not affect the output voltage since it is zero.

Now my question is: Which way is used in real life? If exists what is the mysterious circuit M in my Figure 2 which gets rid of the the common-mode voltage?  I’m asking this question because we are using instrumentation amplifiers often for strain gauges.


texts:
I have a DC stepper motor that appears to be powered by 75V supply voltage (I measured this). However after connecting the motor to the controller (supply), I measured the voltage across the coil (while the motor was running) to be only 1.2V with a multimeter in DC mode. Is this because of the back EMF generated by the motor coil? My guess is that since the average DC inductor (coil) voltage is zero, this cannot be measured by the multimeter. However, shouldn't the voltage at the supply terminals still read 75V?

What exactly is going on? I am trying to power a solenoid by connecting it in parallel with one of the motor coils.


texts:
I have the answer. But i'm not sure how the input of the adder is derived.

Why is it a,b,1,1 for x and 0,a,b,0 for y?

Been searching multiple sources but i'm stuck. Trying to study for my exams.


texts: Why is Vtyp less than Vmin on a CMOS chip

texts:
Regarding the chip 74HC08

On the table describing Static Characteristics (Section 9). Why is the typical VIH lower than the minimum value.
And vice versa for VIL


texts:
Is insulation standard or does it vary? If I have a wire with 2 14-gauge wires inside a second plastic sheath will it handle higher voltage than the technical rating of 110V? I want to use it in a 220V country.

Please note that this is just a set of lamp sockets and the bulbs will be local ones rated at the same power for our voltage, therefore neither power not current will be an issue as power remains the same and current is half at the double voltage. So I am only asking about the insulation.


texts: E-I transformer vs ring transformer applied to isolation transformer in audio

texts:
Most higher-end audio systems have an isolation transformer between mains electricity and DAC/AMP(audio system.)

I know ring transformers havr higher efficiency than E-I transformers.

But noise after through transformer I'm noy sure.
(Audio system desires good sinusoid power input.)

I'd like to know which is better suited in an isolation transformer on an audio system.


texts:
I would like to create a module that can change the value of a register passed to it (+/- 1) using an inout port. I wrote this:

module tune(
    input clk,
    input read,
    input [15:0] x,
    inout [15:0] y,
    input plus,
    input minus
);

reg [15:0] a;
reg [15:0] b;

assign y = read ? a:'bz;

always@(posedge clk) begin
    b<=y;
    a<=x;
    if (plus) b<=b+1;
end

endmodule

When read is HIGH, I expect y to be initialized to the value of x.
When read is LOW, I expect to output the value of b (which can be decremented or incremented by using minus or plus).
Currently however, plus does not do anything, and read toggles y between 0xFFFF and 2 (when I pass 2'd42 to x).

I admit I do not have a good grasp of non-blocking assignments. What should I change to make my code work, or is there a better way to implement the desired behavior?


texts: How to implement a delay OPTOcoupler input there by the circuit remain on for the next 1 second

texts:
I have another new project, the project is simple one when a call lands to the mobile an ac machine is triggered and it turns off when the mobile ring stop, for that I have used this circuit

The issue is that I have looped out the connection from vibrator of an old cell phone to this circuit , I need to turn this ac machine continually till the call rings , I have no other option other than the vibrator output , let me know how to modify the circuit thereby the circuit remains on till the call ends

  here the vibrator outputs  0---2.1 ---0----2.1----0------2.1 volts and
  the interval is around 1sec; so I need to implement another
  modification that the optocoupler will remain in ON state for 1sec,
  then the circuit will probably remain on for a time of 180 sec from the start of the call.

  > My requirement is when the 2.1v comes across the vibrator output the
  circuit must be turned on and it must persist in the On state for 180
  or (180 x 2 )seconds after that turns off automatically


texts: Node Voltage Method, how to resolve with Voltage and Current sources?

texts:
Here is the circuit.

simulate this circuit – Schematic created using CircuitLab

What I have to do when there are 2 different sources?

Find all the voltages in the resistors.

Supposing every current going out of the nodes, here are the equations:

NODE1) \$V1=-15\$

NODE2) \$V2/R2+(V2-V3)/R3-I1=0\$

NODE3) \$(V3-V1)/R1+(V3-V2)/R3-I2=0\$

-Don't know if the first equation is right, or it has to be:
$$-15+(V1-V3)/R1+I1=0$$
-Don't know what am I supposed to do with the \$V1\$ in the NODE3's equation, using -15 instead of \$V1\$ or simply don't put it. (?)

Considering only the NODE2 and NODE3 equations:
$$G*V=I$$
I have to find \$G^-1\$:
$$G^-1=1/detG*(G^a)^T$$
\$G^a\$ = matrix composed by algebraic complements, \$G^T\$ = transposed.

By doing that I find wrong results.

I know there are many ways to resolve this problem, but I have to practice the node voltage method.
Also it can be that I did some algebra or numbers wrong, I'm trying again meanwhile.


texts: What is the term for resistance to change in current and what is its correct formula?

texts:
In all the texts I read, including online tutorials, "reactance" is defined as the resistance to alternating current and they always base the equation off the assumption that the voltage is continuously changing.  The equation is X(L) = 2piFL

But as far as I can tell, this doesn't seem to hold up right when you're talking about a coil's reaction to applied DC where you apply a steady ON voltage and then wait for the current to reach maximum amplitude.

As far as I can tell the inductive resistance to a 50% duty cycle square wave is actually just 2x the circuit's DC resistance if the pulses are timed to exactly 1/4 the inductor's natural frequency.  The current will rise and fall steadily at the start and end of every pulse.  During the transition period, it will always move from zero Amps to maximum Amps assuming you are always cutting the voltage input right when the maximum current amplitude is reached.  So the result is you're getting approximately half the current you'd get if it were just a continuous flow DC circuit.

Can anyone clear this up if I'm missing something here.  And if I DO understand it right, then is there some special term for what I'm describing?

Here is a diagram of what I'm talking about:

It appears to me that the average current is just a matter of computing the average amplitude of a parabola, which I don't know how to do.  LOL   I can go research that, but I'm just trying to see what some of the other folks have to say about this.


texts: Reprogram / modify existing products containing microcontrollers

texts:
Is it possible to reprogram a device containing a microcontroller if I know the name of the microcontroller and have the necessary equipment to program a clean microcontroller of the same type?

To be more specific, I'm wondering if one could manipulate the software of a scientific calculator and what know-how you need to have for this.


texts:
I'm trying to connect raspberry pi with stm32f103 over SPI where stm is a slave.

I'm not really like SPL and also I found awesome cmsis drivers
 for peripheral from Keil so I decided to use them.

Well, the problem is that I can't send any data to RPi. Reading works nice: everything I send from RPi is caught by STM but nothing is on the MISO line.

Here is my SPI initialization and some used definitions:

#define FRAME_START_POS             0
#define FRAME_TYPE_POS              1
#define FRAME_DATA_POS              2

#define FRAME_START_BYTE            0x1B
#define FRAME_TYPE_START            0x01
#define FRAME_TYPE_DATA             0x02

#define FRAME_HEADER_SIZE           2

#define RPI_SPI                     Driver_SPI2

void SpiInit(void)
{
    out_data[FRAME_START_POS] = FRAME_START_BYTE;
    out_data[FRAME_TYPE_POS] = FRAME_TYPE_DATA;

    if(RPI_SPI.Initialize(RpiSpiCb) != 0)
    {
        LOGGING_Error("Can not initialize SPI");
    }

    if(RPI_SPI.PowerControl(ARM_POWER_FULL) != 0)
    {
        LOGGING_Error("Can't set SPI power");
    }

    int status = RPI_SPI.Control(ARM_SPI_MODE_SLAVE    |
                                 ARM_SPI_SS_SLAVE_HW   |
                                 ARM_SPI_CPOL0_CPHA0   |
                                 ARM_SPI_DATA_BITS(8U) |
                                 ARM_SPI_MSB_LSB,       RPI_SPI_BUS_SPEED);

    if(status == -1)
    {
        System_ErrorLedOn();
        LOGGING_Error("Can't set SPI control");
    }
}

static void transfer_headers(void)
{
    /*
     * out_data[0] and out_data[1] are never seen
     *  on the MISO line but in_data is filled.
     */
    if(RPI_SPI.Transfer((void*)out_data, (void*)in_data, FRAME_HEADER_SIZE) != 0)
    {
        LOGGING_Error("Can't transfer data over SPI");
    }

    state = READ_HEADER;
}

I can't find out what I'm missing here. Maybe sending data when you are a slave is tricky but I haven't found anything about that?

P.S. Using RPI_SPI.Send() instead of Transfer() also does not work.

UPDATE

Here is function that is used to send data from RPi:

def __send_data(self, data):
    ans = self.stm.xfer2(data)

    if ((ans[FRAME_START_POS] != FRAME_START_BYTE) or
       (ans[FRAME_TYPE_POS] != FRAME_TYPE_DATA)):

        raise IOError("Wrong bytes in header from stm: 0x%02x 0x%02x" %
                      (ans[FRAME_START_POS], ans[FRAME_TYPE_POS]))

    if len(ans) > FRAME_HEADER_SIZE:
        return ans[FRAME_HEADER_SIZE:]

    return []


texts: Measuring temperature using resistance termometer Pt100

texts:
Given:

voltage source \$U_0\$ = 1.2 V
\$R_i = 1000 \Omega\$
\$Pt_{100}\$ is described by \$\Delta\delta=T-T_0=0°C\$ with \$R_0 =100  \Omega\$ at \$0°C\$
\$R_1 = 500 \Omega, R_2 = 50 \Omega\$

Asked:

Calculate the \$I_{out}\$ at the amplifier for \$0°C\$ and \$100°C\$

\$R = {\rho L \over A} = 50 \Omega = R_{L1} = R_{L2} = R_{L3}\$

\$R_{0°C}=R_i+R_{L1}+R_{Pt0°C}+R_{L3}=1200\Omega\$

\$I_{0°C}={U_0\over R_{0°C}}=1mA\$

\$Uc_{0°C} = I_{0°C} (R_{Pt0°C}+R_{L3})= 0.15 A\$

\$I_{out} = {U_c\over R_{L2}}=3mA\$

Calculate the general transfer characteristic - thus, the \$I_{out}\$ of the amplifier as a function of temperature.

I've found the solution for 0°C, but I don't know how to calculate it at \$100°C\$ (because I don't know the \$R_0\$ at \$100°C\$).

Many thanks for your help.


texts: How to use a Phototransistor and photodiode?

texts: I don't expect my parents to spend the money required to get a ballistics chronometer for me so I decided it would be easier to make one from parts laying around in my room. I have the general plans worked out for a basic setup, which would be having the phototransistor/IR LEDs from two old computer mice set up in a linear configuration, spaced about a foot apart. Each assembly would be mounted on a breadboard connected to an Arduino, connected to my PC or a small LCD display. I have one problem though: This is my first time using a phototransistor. I know how a regular transistor works though. Can anybody give me a bit on insight on how this thing is to be used?


texts:
I want to build a portable device (handheld) that receives and transmits Morse code in the form of Radio Frequency. I want the antenna length to be  8 inches or less and would also like a range of up to a half a mile, including inside a building with many rooms.

I want a simple button to transmit Morse. I also want a knob to change the pitch it transmits Morse at. I want the Morse to be heard when you receive it from someone else as well as when you transmit through a speaker.

I'd like to power this with 6 volt maximum, and 3 volt minimum. (I will be using AAA batteries). I don't really care about the frequency, but my friend has an amateur license and I will be getting one soon, so I can transmit on those frequencies.


texts: Taking 5v and converting it to 3.3v for Raspberry Pi GPIO?

texts:
Raspberry Pi 3b.

For some reason I am having a hard time conceptualizing what I need to do to bring a 5v reading down to 3.3v so I can sense it with my Pi (without damaging it due to the Pi not liking 5v signals).

Scenario:

I have a fan that when it is on there is a 5v potential between the fan + and - terminals when the fan is ON, and of course it is 0v when the fan is off.

There is no way for me to get a current reading due to the fan PCB layout not really having anywhere to put the probe in series to get the amps. So I am just going to say that I would like to know how to reduce the voltage out of curiosity and if it helps protect my Pi that is even better.

I would like to be able to read that 5v into a GPIO pin so I can determine if the fan is ON or OFF.

My code works right now reading the 5v into the GPIO pin. A stated I am just concerned about put 5v on a GPIO pin.

The wiring flow is that I have a ground wire connecting the - (ground) terminal on the Fan to the Pi ground terminal and the + (hot) terminal on the fan plugged into a GPIO pin that is set to READ mode.

What resistors can I place in between the Fan (+) terminal and the GPIO pin to reduce the voltage down to 3.3v or steps I can take to reduce the potential damage to the Pi.


texts: How to make a split-supply from a single supply by using two linear regulators like LM7812 & LM7912?

texts:
I want to obtain +-12VDC supply from a 24VDC supply where the total load will driver 100mA max. I tried using two power supplies but one of them blew up. I need the split supply for excitation voltage which I mentioned in my previous question. So I decided to make a spit supply from a 24VDC supply. I have some many LM7812, LM7912 or equivalent. I tried the following circuit:

But instead of +-12VDC I'm getting the following output:

These are the only components I have at the moment.How can I use them in a way to obtain +-12VDC?

edit:

Regarding @Trveor's answer:

edit2:

Discrete solution(?):


texts: Calculating Thevenin voltage and Norton current for complicated circuit

texts:
I asked this question before in relation to calculating power before but it seems I might have not been clear enough. I'll draw the original circuit and then the circuits for calculating Thevenin and Norton:

Original:

simulate this circuit – Schematic created using CircuitLab

Here's how I would go about writing the circuit to find I short circuit or I Norton (EDIT: just noticed, is my arrow for Isc backward given V0? BTW, this isn't my main trouble for this problem):

simulate this circuit

Here's what I would do for V open circuit or V Thevenin:

simulate this circuit

I could calculate the open circuit voltage and the short circuit current easy if I had more independent sources but the dependent sources make these calculations harder.

I'm not sure how or where to use source transformation, mesh or nodal analysis, etc on this circuit. Each time I try one I end up in a spot that I can't figure out how to use it or I get equations that don't give me values.

For example, If I try to find I short circuit by using mesh analysis, I do not have any resistors that will give me a current for I short circuit. I can't solve the system of equations for I short circuit after getting the other meshes. I could try and find the other currents and then apply KCL at one of the nodes that I short is going into or out of, but I can't ever find the correct equations for the other currents in the other meshes.

For V open circuit, I just don't know where to start with that one.

This circuit seems impossible to solve and I have been looking at it for hours now. If someone could please give me some guidance/solution you will save my sanity. Thank you.


texts: Grounding Shielded Panel-Mount Connectors

texts: I'm building an amplifier in a conductive metal chassis. The general grounding plan is to have an audio ground, a power ground, and a digital ground that converge at a single point on the chassis. However, my audio connectors are all panel-mount, so the shield of the connectors get grounded by contact when mounted. Technically, should I insulate them from the back panel and wire the ground connection? Practically, does it matter whether I insulate them or not?


texts: MCP 23018/23S18 for LED and Switch control

texts:
I'm working on a project that involves about 200 LEDs and about 120 Switches. I'd like to use several MCP23S18 DIP chips across 2-3 buses to control everything. I'm a CS guy and just want to make sure I've got a decent idea of how this is supposed to come together.

The MCP23S18 datasheet.

Some general fact checking and advice on better ways to do this are all appreciated, I'm very new at this (for the record, this is not for class, just fun).

1) I've got LEDs for 2.2v at 20ma draw. I plan on using them in serial pairs, so the voltage drop should be 4.4 and the draw should be 20ma for each pair right?

2) According to the MCP23S18 datasheet (pg 33) the max Vin current draw is 125ma, and the max Vout is 400ma. This means I can safely power 6 pairs of LEDs with an approximate 4.4v chip input right? This means I should be able to use the remaining 11 pins an inputs as long as they are in the open drain configuration, thus avoiding significant draws right? Will it be safe to run all LEDs and have all switches open at the same time (assuming ample power supply)? What is the difference between "current sunk" and "clamp current"?

3) Does anyone have any ideas for a better alternative way to drive multiple leds? I know for some areas of the project that have groups of LEDs it will probably be easier to make a few cheap drivers so I can use all 16 pins as LED control. I've also considered using shift registers for this because I've found some with a 500ma Vin max, I could drive several easily this way. Perhaps a combination of the two, controlling the SR via an IO expander?


texts: Will this optocoupler circuit work for sensor and DC motor?

texts:
I am working on a project in which I need to operate a DC motor and some ultrasonic sensors.
I want to operate the motor using motor driver DRV 8871 by giving logic signals and read sensor value on controller pin.
I also need to maintain isolation between my motor and microcontroller and same with the sensors.
I tried to prepare circuit with optocouplers for isolation, but I am very confused between sink and source circuit for the optocoupler.
Will this circuit work ?

Datasheet Optocoupler PC817
Ultrasonic sensor NPN and normally open, Operating voltage (10-30VDC)
DC motor supply voltage is +24 V
Motor driver data sheet
5.Microcontroller Ti CC1350


texts:
Regarding state estimation in electrical power grid, does the voltage phasor magnitude at each bus(P-Q bus and P-V bus) considered as a static state variable or a dynamic state? I am a little bit confused about it.
If we consider those bus voltages as static state, can we use dynamic state estimation techniques to get an estimation of those voltage or we only use static state estimation?.
If I want to plot the magnitude and phase angle at each bus over time, are there network dynamic models I can use to do so? For example a differential equation of the voltage with parameters such as reactive, real power etc...

(I am working on a summer project on state estimation using phasor measurement units -PMU-)


texts: Can I replace a 33uF 100v Electrolytic Capacitor with a 47uF 400v Electrolytic Capacitor?

texts:
I'm -Extremely- new in the DIY Electrics. So go easy on me as I have 0 Electrical Engineering background. Handle me like a 5yo, haha.

I recently decided to give self-repairing the old electronics I have lying around a try. Mainly my old LCD/LED Monitor. Which seems to have power issues.

Symptoms:
When plugged in the Monitor LED (Power Indicator) appears to turn on then off after a couple secs.

On a good day it turns on, and remains on and functions normally for a day or 2 then randomly shuts off during use then it would refuse to power on again showing no power LED until after a day or 2 of rest.

Which "LED" me here, haha.

I read that with age (8 year old monitor) the electrolytic capacitors can be the culprit. So I did a tear down and found 2 electrolytic caps on the base (The rest appears to be solid caps). One rated at 33uF/100v and the other 220uF/25v.

Now where I live there are no Frys/ or Radio shacks. So I only have found caps rated at 47uf/400v and 220uF/35v.

I'm hoping the monitor is just a simple case of replacing the caps.

Additional Note:
My monitor uses an external power brick (I've tried a different brick, same symptoms). The Capacitors I'm talking about are in the base of the monitor where the power brick connects. The monitor is an HP x2301.

Image Link (Capacitors in RED Outline):


texts:
I have a question regarding reading import and export energy from an electricity meter, the system has a solar array fixed allowing power to be exported to the energy grid when there is excess power.

The link to the energy meter I am interested in (CL model), is below:
https://www.accuenergy.com/files/acuvim-l/Acuvim-L-Power-Meter-Brochure-1030E1210.pdf

On page 2 the real time energy functions are listed, this should all be available over MOD bus.
I believe all I need to read to obtain import power is Power P1,P2,P3,Psum?
I believe all I need to read to obtain export power is Reactive Power Q1,Q2,Q3,Qsum?

The functions Energy and Reactive Energy see more appropriate but share the same parameters.

Could someone please clarify if this is correct or provide what parameters are required to read and calculate the exported power?


texts: How does the Store Word(SW) and Load Word(LW) instructions work, MIPS

texts:
The SW and LW instructions are defined as:

     sw $t, offset($s)  : 1010 11ss ssst tttt iiii iiii iiii iiii
     lw $t, offset($s)  : 1000 11ss ssst tttt iiii iiii iiii iiii

SW performs the operation MEM[$s + offset] = $t, but in the data-path it looks like they have performed the operation MEM[Data($s)+ offset] = $t , because instead of taking the value $s as an input into the ALU it took in the data stored in $s.

LW performs the operation $t = MEM[$s + offset], but looking at the datapath it looks like it is performing $t = MEM[Data($s) + offset].

Another thing I don't understand is why we use sign extend instead of just moving the sign to the 32nd bit and filling the rest of the data with zeros.If you have defined an offset is

0x8fff : 1000 1111 1111 1111

it will be sign extended to 0xffff8fff : 1111 1111 1111 1111 1000 1111 1111 1111 , which is a completely different number from the offset, the number we really need is 0x80008ffff.


texts: Amplifying Signal From Electret Microphone

texts: My project requires me to use an electret microphone and I am having a lot of trouble getting any decent-sized signal out of it. I currently have it configured with a 100Kohm pullup resistor and a 47uF capacitor. The signal is so weak that even if I put it through an amp with 200V/V gain, I only get an output whenever I tap the microphone or blare music straight into it with my earphones. Is there a trick to using the microphone right or do I just have a crappy one? I don't know the model because my professor didn't provide it, but 54LO is printed on the top.


texts:
I'm trying to get UART working on a STM32F0 part and can't figure out the interrupts. According to the reference manual

Bit 7 TXE: Transmit data register empty
This bit is set by hardware when the content of the USARTx_TDR register has been
transferred into the shift register. It is cleared by a write to the USARTx_TDR register.
An interrupt is generated if the TXEIE bit =1 in the USARTx_CR1 register.

However, I can never see the TXE flag clear. Here is what I have in my IRQ Handler:

  if(USART_GetITStatus(EVAL_COM1, USART_IT_TXE) != RESET)
  {
    /* Write one byte to the transmit data register */
    if (TxBuffer[TxCount] != '\0')
    {
      USART_SendData(EVAL_COM1, TxBuffer[TxCount++]);
    }
    //else{
    //  USART_ITConfig(EVAL_COM1, USART_IT_TXE, DISABLE);
    //}
  }

Unless I uncomment the else statement, the send interrupt keeps triggering endlessly even after I stop sending bytes to the TDR.
Is there a way to stop the interrupts without disabling them? Or do I need to re-enable every time I want to send something?


texts: Parallel current limiters, ballast resistors and transistor matching

texts:
Are ballast resistors (R17, R8 and R5) required when using parallel current limiters as show below?

I found it hard to find working examples on the internet with values already present to tweek around with.

So here is a link to the full circuit in LTspice XVII: https://pastebin.com/NakdA45N Just download the file and remove the .txt at the end, or copy the content to a .asc file.


texts: The motor I saw has 14 brushes spaced around a commutator that is about two feet in diameter, and is used to move a large antenna. What is the advantage of having so many brushes and is the commutator wired any differently then normal.


texts: Arduino is not getting power from adapter or Vin

texts:
Hi I am very much new to electronics, specially micro controllers and stuff. I am a Java/Android programmer by profession. I am currently creating a autonomous robot but I am stuck due to a problem.

The problem is that I have been using my Arduino UNO with a motor shield L293D this http://i.ebayimg.com/00/s/MTYwMFgxNjAw/z/70EAAOSwvzRXw-s7/$_12.JPG  and a Bluetooth module HC05  Everything was good when I connected my shield to arduino, I checked my code using four extra small motors (2.5-3.7V). My arduino was functioning well with my code I was able to operate all the motors with it on my signal.

After all check when I added my all 4 motors to the shield in  M1, M2, M3,M4 with my 12V battery of  1 AMP. There was sudden buzz and one IC L293D on motor shield got fried. Don't know this was because of some wire mess because wires that time not very tight and very neat. After that the gold thing on my arduino middle between USB and DC connector is getting very hot without even any usage. (I have replaced my ICs with new one). Now when I connected everything back all seems to be ok and my robot working fine but arduino last time drawing the power from the shield itself (12V battery pack). and now arduino is not taking power hence I am giving power to it from USB but I can't keep usb connected. So tried it with DC connector jack. It is not working too. Vin socket not working for power too. Ony usb is working. I also tried to connect my 9V battery to the 5V pin near Vin and it worked but after that HC05 stopped working but it is working fine with USB.

My Questions -

Why that gold thing is so hot (It wasn't happening earlier as per my memory).
Is my arduino got some problem if yes than can I solve it?
If arduino is really got fried what precautions shall I take to protect my next arduino.

Please help me with it. Thanks a lot.


texts: How much current can I draw from the Arduino's pins?

texts: What's the maximum amount of current which I can draw from each of the Arduino's pins without tripping any of the internal fuses? Is there a limit per pin as well as an overall limit for the whole board?


texts: Safely detecting presence of 12v applied via exposed terminals for use with microcontroller

texts:
I have a board which contains a microcontroller and a 10k NTC thermistor (B57421V2103J62) wired to two external terminals, one of which is common with the board ground plane. The terminals are exposed on the outside of the case and, when the case is docked with a host device, the thermistor is connected to 12v via a 10k series resistor (on the host side). Apart from it being common with VSS the thermistor is not otherwise wired into the logic on the board.

I want to use the presence of voltage across the thermistor to detect when the case is docked (as there's no other reliable means of doing so). Within the operating temperature range of the hardware the voltage I would normally see on the thermistor contact could be in the range of roughly 10v down to 3v.

What I need to do is pull a 2.5v line either high or low (doesn't matter which) when the above voltage is applied and hand that to the micro. In the process of doing so I cannot pull any meaningful current from the thermistor circuit as doing so would alter its behavior.

I expect this is pretty straightforward with a FET but given the terminals are exposed (can be touched for example) I need to ensure it's properly protected, and I'm unsure about the most appropriate approach.

I was thinking of using an e.g. BSS138 with S tied to VSS, D to the 2.5v rail via a 1M series resistor and a 10k resistor in series with the gate which is then tied to the thermistor.

Does this sound reasonable? If so is there anything else I could/should do (such as add a zener?)

Edit: The micro is a PIC24H running at 2.5v. Speed isn't an issue.


texts: CMOS: Why is an nMOS transistor a bad conductor of high logic, but a good conductor of low?

texts: I can't find an answer that addresses this and makes sense to me. I know that V_t is subtracted from the 'output', but I don't understand why.


texts: Copper wire in municipal water piping foam insulation?

texts: A couple years ago the municipality upgraded the water piping in part of the town. I couldn't help but notice while walking nearby that the new pipes had small gauge, insulated, solid core copper wires (similar to the ones in CAT5 cables) coming out the foam insulation, likely attached to some kind of sensor. I'm very curious what those are for. I mean pipes of this kind:


texts: How are PMOS equations different than NMOS's?

texts:
I have been googling about it and I see lots of different ways such as only flipping the signs (< becomes >) and switching variables (VGS becomes VSG). Some people even say just put absolute value without changing anything and putting absolute for threshold voltage. Which one is most accurate and easy to remember?

I know that the current ID goes from source to drain so we have to flip the AC model also.

I just need an easy hint of altering the NMOS equations for PMOS to keep in mind for my exam.


texts: Minimum design for controlling 2 LEDs to light either one or both?

texts:
I am an absolute beginner in electronics. So far I have created a circuit with 2 LEDs and 2 SPST pushbuttons, each controlling a different LED. Very simple, you should get the idea without me drawing a circuit.

I've been trying to figure out how to add a third pushbutton, which would control both two LEDs at the same time, without altering the functionality of the two existing two pushbuttons.

Is it even possible to achieve this with 3 SPST pushbuttons, without adding any other components? If not, I am interested in learning what would be the simplest design to achieve this. Thank you.


texts: Why do many electronics operate on 5 AND 3.3 Volts?

texts:
Many modern appliances use a 5V Power connection. Internally they are working with 3.3V. Wouldn't it be easier to have 5V everywhere?

Examples are many USB devices or Routers (they use 5V for power but 3.3V for serial communication).


texts: Is there a theoretical possibility of having a full computer on a silicon wafer instead of a motherboard?

texts:
I have not seen a single reference where a whole computer is built inside a chip itself instead of modularizing and spreading it on a board.
I acknowledge that having modular parts enable versatility, but can big silicon companies such as Intel, AMD produce a whole computer with cpu, chipset, RAM, memory controllers, all in a microchip?
I am familiar the concept of SoC but havent seen ALL the components inside single chip.


texts:
For the sake of understanding, I shall refer to voltage as a "pushing force that causes electrons to move and hence generate current."

Now, I know that this force is "built up" and does not flow(unlike current). But what do people mean when they voltage is "transmitted" in transmission cables. Are they talking about the movement of voltage from one point to another?


texts: Is there a way of conditionally triggering a compile-time error in verilog?

texts:
I have a parameterised module in verilog, where the parameters are a clock rate and refresh rate, which is used to calculate how many cycles of inactivity are inserted between instances of a repeating operation.  However, it is very easy to set parameters that cannot be attained (because the operation takes a non-trivial length of time, so the repeat would have to occur before it had completed), and at the moment the design does not give any feedback on this.

I was wondering if there was some way I could trigger an error during synthesis (or compilation prior to simulation) if the conditions cannot be met (i.e. if one localparam is less than another)?  Some equivalent of the popular C/C++ compile-time-assert hack, perhaps.


texts:
I'm designing a pcb which contains HF circuits and mounting this in a conducting enclosure.

To minimize EMI/EMC should the pcb ground always be connected to the enclosure?

Or is this not always the way to go?


texts: A minor confusion with calculation of the total thermal resistance

texts:
For a voltage regulator without a heatsink, the temperature change ΔT is calculated by using the electrical power P by the regulator which is basically roughly P=Iin*(Vin-Vout) and the total thermal resistance θ_total. For example a data-sheet for a linear regulator mentions:

  Thermal resistance of the TO-220 package (T) is typically 4°C/W
  junction to case and 50°C/W case to ambient.

So one can write down the following:

θ_JC = 4

θ_CA = 50

θ_total_no_heatsink = 54

If I'm not wrong, as you see above the total thermal resistance θ_total_no_heatsink is easily found from the data-sheet.

But what happens to the total thermal resistance when the regulator is used with a heatsink with a thermal resistance θ_H°C/W? Would the total thermal resistance be θ_total = θ_JC+θ_H or only θ_H? And why? There are examples they take into account resistance from the case to the heatsink ect. So I'm not sure if in the case of heatsink what should be added to the thermal resistance of the heatsink itself.


texts:
I'm trying to figure out how dense of a strip to buy for my project. Everybody knows that the white LED cobs in bulbs are far more efficient than  incandescent bulbs but I'm having a hard time finding information specific to the RGB LEDs in strips.

The closest I came was looking at this data sheet for WS2812B: http://www.seeedstudio.com/document/pdf/WS2812B%20Datasheet.pdf which states an approximate 2.1cd of luminous intensity for its combined RGB output.

Assuming I get 5m of 30LED/m strip, that would be 315cd total. Trying to compare it to a bulb, I assumed its sri to be 180 degrees which would make it ~2000lm total for 45W.

The approximate average output of a 10W white LED bulb is 900lm so 45W worth would be 4050lm. That would mean that the RGB strip is less than half as efficient as its cousin white LED cob.

Is this conclusion anywhere near correct?


texts: I have never used a relay before but am now in urgent need for one. The only relay I have on hand is called the EC2-3NU, which is a pretty obscure and undocumented part. I have found datasheets and a pinout for the relay but fail to understand it. I am able to pass DC current through the coil pins but not through the normally open (no) pins (4, and 5) which should be, well, normally open. Is it because I DC does not goes through a relay? Am I misunderstanding the pinout? I am really lost here. Datasheet: https://www.alliedelec.com/m/d/5699b9c7dad5da7825ac67f49bc95255.pdf


texts:
I have the Freetronics Eleven, which is 100% compatible with Arduino Uno. Ultimately, I want to make a foot pedal switch that connects to a digital pin on the arduino so that a LOW is read when the pedal is pressed, and a HIGH is read when the pedal is released, or vice versa.

At the moment I'm just trying to test making a switch of the same behavior by sticking wires in the pins and connecting them together. I've tried connecting and disconnecting pin 2 and gnd, pin 2 and 5v, pin 2 and pin 12 etc. with pin 2 set to input.

What is the correct setup to make a basic switch? Which pin do I connect to which to make it so when the pins are connected one reads low instead of high, or vice versa?

EDIT: Thanks for telling me about the pull-up resistor. I have since discovered via google that the arduino pins have built-in pull-up resistors. For others who come along this problem, this is how you enable them:

pinMode(10, INPUT); // set pin 10 for input
digitalWrite(10, HIGH); // set pull-up resistor on pin 10

then to use:

if (digitalRead(10) == LOW) // pin 10 is connected to gnd
    doSomething();
else // pin 10 is not connected to gnd
    doSomethingElse();


texts:
I am trying to repair a very expensive manlift joystick.
It has 4 pins total, three like a normal rotary potentiometer and then a fourth across from the other three pins.
It is PEO 284-04378 Type EJ pot. It has another number stamped "5k 1342"
The company not produce it more and I'm looking if there is something similar to do the same work I was looking for P271-DS21BR10K but is 10K would that affect?


texts: Modifiying variable inside of Interrupt vector. AVR

texts:
My question is again about modifying variables inside the ISR. If the variable used only inside of ISR, I don't have to declare it as volatile, right? After some researching, I figured out that variable need to be declared as static, and inside of ISR function. But it also didn't help.
I'm using Arduino Ide, so don't have many debugging options. I'm using an LED indicator for checking if the variable has incremented, as you can see below:

ISR(TIMER2_COMPA_vect) {
  static  unsigned int count20ms = 0;
  count20ms += 5;
  PORTD ^= (1 << PD6);        // Indicates that ISR executes
  if (count20ms == 10) {
     PORTD ^= (1 << PD7);      // Indicates that counter incremented
     count20ms = 0;
  }
}

I can observe that ISR executes through a blinking LED on PD6. But Condition count20ms == 10 is never true . And thus, the LED connected to the PD7 never blinks.
How should a static variable behave ?


texts:
I was simulating the following RC circuit to know the behavior of current through various components.

I got the following plots..

To satisfy the KVL at t=0+ voltage across capacitors will indeed change to 1V and because of that there will be impulse current t=0+. But from the plot I can see that there is impulse at t=0+ but also current starts at 0.5mA for C11, -0.5mA for C12 and -1mA for R10.

I am not able to understand  how current is the getting distributed in RC components after impulse current(t>0+).

Please give intuitive explanation for this.

Edit- There is a one mistake in the plot -I(R10) points in clockwise direction.
So the direction is as follows....
I(C11)--Clockwise
-I(C12)--Clockwise
-I(R10)--Clockwise


texts: Strange PCB Connector I haven't Seen Before - What is it?

texts:
I'm trying to determine what connector this guy is, but I've never seen it before.

It has two rows of seven pins, and they are offset a bit.

More importantly, does anyone have any tips on matching sockets? Trying to navigate through the sixty million parts / black and white pictures of sockets is really challenging.


texts:
I'm trying to prototype a hobby project on a breadbaord.
I'm using an electret microphone + opamp to feed MCU ADC with audio signal.
When I'm using a regulated power supply  I get good signal with relatively low noise.

Now I wanted to power it with battery using a step up boost converter - but got a serious noise problem on the amplified signal.
Since it's a hobby project I don't have the equipment (scope) to find the exact characteristis of this noise, I only know it's bad enough to completely ruin my audio input, and that it comes from the boost converter since I don't get it when I use regulated power supply or when connecting the circuit directly to batteries.
Tried to add decoupling caps, but it didn't help much. I even tried adding another low dropout regulator (s81230ag) before the opamp and adc analog power but the noise is still there.

How would you recommend to proceed?

Is there a simple way (small number of components, on a breadboard) to filter this noise with the existing components this and this?
Should I try a differnt boost converter, perhaps with switching frequence high enough so it could be filtered by the mic amplified circuit?
Pehaps I should use a differnt amplifying circuit for the mic which is less susceptible to power supply noise?


texts: Is one of the inputs in this discrete H-bridge driver schematic inverted?

texts: I'm writing some firmware for somebody else's board and would like to check in advance so I don't fry anything - could someone please confirm if the following h-bridge driver would operate with either H_BRIDGE_HI or H_BRIDGE_LO being driven logic high causing there respective MOSFET to conduct (one at a time obviously) or is one of the inputs meant to be driven with inverted logic?


texts: Why passive component has better drift characteristics than active components had?

texts:
I came across this paragraph in the classic reference Op Amps For Everyone by Ron Mancini where it says on the first page:

Many attempts has been made to make a stable amplifier, but temperature changes and power supply voltage extremes experienced on phone lines caused uncontrollable gain drift. Passive components had much better drift characteristics than active components had, thus if an amplifier's gain could be made dependent on passive components, the
program would be solved.

I don't quite get what that means. I'm going to take a few assumptions here and hope someone can confirm or correct my understanding.

Say when there's a voltage applied across a passive resistor, its resistance changes within some specified tolerance as it heats up overtime by the current. Is that why we see or what we call the drift in the input voltage vs. output current?

Let's take a BJT as the active component. Be it configured in common collector, emitter or base amplifier, the only variable in any of the gain equations that is not passive is the \$ \beta \$ or the Hfe. (e.g. \$ A_v = {R_E \over {\alpha r_m + R_E + {R_B \over {\beta + 1}} }} \$ for C.C.). So the volatility or stability of \$ \beta \$ is essentially the main indicator for the drift?

Because the \$ \beta \$ is more unpredictable than heating does to a resistor's resistance, hence the drift characteristic in a passive component is better than an active component?


texts:
I am using a STM8S105C6T6 in one of my application and I am facing problem while programming it.
Software used: STVD version 4.3.12
Compiler: Cosmic CXSTM8 Special Edition 4.5.1 (Free 1yr License version)
I have build my application and when I click on ''start Debug'' in STVD, below error comes

Debug Session:

Starting debug session...
-> Emulator reset (usb://usb)...
done.
Opening application
C:\Users\Micro\Desktop\STM8\STM8S105\led\Debug\led.elf...
-> failed to download application: error: swim prog error [42004]:
memory write error
Application closed.
Debug session closed.

Using Light Programmer
When I am Trying to Program using STVD in-built Programmer, it is showing below error:

''STVD > Tools > Programmer'' or using STVP.
Programming...
PROGRAM MEMORY:
Blank Check not feasible Programming Error : Programming failed Error
: Problem while trying to Reset swim and device. Apply a Power On
Reset

The interesting thing is, sometimes the MCU is getting programmed (LEDs are blinking as per requirement) but the software is showing same error message as above.
I don't understand why I am getting this error. My hardware connection and the SWIM communication are OK because I am able to program my other MCU i.e. STM8103F3P6 bare minimum blue board using same settings in STVD
How can I solve this error ?


texts: Building memory system adresses with decoders

texts:
Well I got the following (multiple choice) question. Even with the result given I have 0 idea how they could come to the conclusion..

  With 64 memory elements of size 1Mx4 and several 2-input decoder chips an as large as possible memory system with words of 16 bits is being built.
  How many decoder chips are needed for this system?

From what I understand this means you have a total of 64 * 1M * 4 = 256M bits memory. Which have to divided into words of 16 bits, so 16M addressable locations. This means that the memory-adress-size  needs to be at least 24 bits. (So far it is correct right?)

To access it there are 2-input decoder chips (so 4-outputs on each chip). These can be build like a tree to allow for more bits of adresses. Now the problem is, this easily gets very large.

The answer that was correct was "5".
I have no idea how that answer is found: a sytem with 5 2 input decoders consists of 2 layers, and has 16-output lines. What do I understand wrongly here?


texts:
I've been playing around with this circuit. It's a minimum parts AB class amp.

I've managed to get it to work but I still don't understand how should I optimally adjust resistor values and corresponding currents for the given amplifier to work best. I know that the given circuit is not best in itself performance-wise but it's simple enough to understand.

To add, I know that this circuit is not the best or even safest (for output transistors). What i am really interested in is how to balance it to give the best possible results. What are the trade offs in distortion and power? How much negative fedback, voltage gain  is good? How does saturation come into play? These sorts of things. This amp is intended to amplify sound if it isn't obvious. Maybe someone knows of a good site or blog where these things are thought through. Please don't take too hard on me, as I am only beginner learning on example.


texts: If I get the transformer equivalent circuit of the above circuit did I really get a purely resistive circuit with a resistance of n 2 times RLoad . I am asking because I realized that in the oscilloscope screen there is delay(phase shift) between input voltage and input current. If I could not get purely resistive circuit why this equivalent circuit fails?


texts: Base-emitter reverse breakdown and current

texts:
I have a circuit as follows,

simulate this circuit – Schematic created using CircuitLab
which provides a control current to an OTA as \$i_\mathrm{abc} = (3.27\mathrm{V} - V_\mathrm{in})/R1\$. The reason for the reference voltage being 3.27V is that I want to make sure I can completely turn off the OTA, even after accounting for various offsets. Of course, the problem here is that when \$V_\mathrm{in} > 3.27\mathrm{V}\$, the op-amp tries to push current in the reverse direction, which it can't do, and therefore saturates at around 11.5V. In this case, the BJT has about 8.5V of reverse voltage, which is in excess of the datasheet absolute maximum reverse voltage of 5V.
There's of course the standard solution of throwing in a diode in the reverse direction to protect the BJT and satisfy the op-amp, but as the board has already been routed and prototyped without the diode and it's really cramped, avoiding the diodes would be really nice. The board does work at least this far, so the transistor does not fail immediately (or in about half a year time span).
So my question is: considering that I'm breaking the absolute maximums here, what is the danger of the transistor actually breaking/degrading significantly? Note that even if it goes to reverse breakdown, the reverse current will be at most about \$0.03V/3.3k\Omega \approx 9\mu \mathrm{A}\$, i.e. the power will be correspondingly small. Measured from the prototype, the actual values are \$4\mu \mathrm{A}\$ and \$33\mu\mathrm{W}\$. The product will be manufactured in quantities of some hundreds of pieces, and there's 10 circuit blocks such as above per board, so lifetime failure probabilities on the order of one in a few thousand are likely to manifest themselves.


texts:
I have ready made working electronic product. I am applying reverse engineering on it. The WiFi module is connected to micro-controller via UART( RX & TX). The android app sends command to WiFi and micro-controller works as per the command. I have attached a USB to TTL cable on RX and TX also command ground as well of WiFi module. The cable is connected to serial monitor on PC. When the app send data to WiFi, the serial monitor shows Indecipherable value. I have checked every baud rate possible. Instead of USB to TTL cable, I also used HC05 Bluetooth module. But it shows Indecipherable data. How can I get the readable values on my serial monitor. Do i need to disconnect micro controller from WiFi?

No RS232 is used in whole design.

The first two images has similar data but with different baud rate. First image data is set at 4800 and second one at 9600 with No parity, 8 bit data, stop bit 1. "0D" is just enter command( For readability).


texts: Does a circuit graph say anything about controllability of its currents?

texts:
Graph of an exemplary circuit can be found below.

Based on this graph, can anything be said about controllability of the edge currents ED, AN, BN and CN if the edges DA, DB, DC, AE, BE and CE comprise controlled voltage sources?

Thank you!